This paper presents fabrication, measurement and modelling results for a
metal-dielectric-metal metasurface absorber for solar thermal applications. The
structure uses amorphous carbon as an inter-layer between thin gold films with
the upper film patterned with a 2D periodic array using focused ion beam
etching. The patterned has been optimised to give high absorptance from
400-1200nm and low absorptance above this wavelength range to minimise thermal
radiation and hence obtain higher temperature performance. Wide angle
absorptance results are shown and detailed modelling of a realistic
nanostructured upper layer results in excellent agreement between measured and
modelled results. The use of gold in this paper is a first step towards a high
temperature metasurface where gold can be replaced by other refractory metals
such as tungsten or chrome.

Due to the lower cost, natural dye molecules are good alternatives for the ruthenium based sensitizers in the dye-sensitized solar cells. In this article, we have reported the natural sensitizer based dye-sensitized solar cells fabricated using TiO2 nanorods. Rutile phase TiO2 nanorods have been synthesized by template free hydrothermal method which results in TiO2 nanorods in the form of acropora corals. These TiO2 nanorods have been sensitized by flowers of Sesbania grandiflora, leaves of Camellia sinensis and roots of Rubia tinctorum. The maximum conversion efficiency of 1.53% has been obtained for TiO2 nanorods based solar cells sensitized with the leaves of Camellia sinensis.The flowers of Sesbania grandiflora and roots of Rubia tinctorum sensitized TiO2 nanorods based solar cells exhibited an efficiency of 0.65% and 1.28% respectively

The efficiency of solar cell is generally defined at standard test conditions. However, wind direction, wind velocity, tilt angle of panel and solar radiation during operation differ from those at standard test conditions. The effects of operating conditions on the temperature and efficiency of silicon solar cells are widely analysed in literature. In the current work, the thermal performance of perovskite and dye-sensitized solar cells in operating conditions has been analysed and compared with monocrystalline silicon solar cell. The effects of wind direction (wind azimuth angle), wind velocity, tilt angle of panel and solar radiation on the temperature and efficiency of the cells have been analysed. The results show that as wind azimuth angle increases from 0° to 90°, the temperature of the cell increases from 51.8°C to 58.2°C for monocrystalline silicon, from 45.5°C to 50.7°C for perovskite and from 48.4°C to 53.9°C for dye-sensitized solar cell and the corresponding efficiency of the cell decreases from 22.3% to 21.5% for monocrystalline silicon, from 20.1% to 19.5% for perovskite and from 11.8% to 11.7% for dye-sensitized solar cell.

The stability of perovskite solar cells (PSC) is often compromised by the organic hole transport materials (HTMs). We report here the effect of WO3 as an inorganic HTM for carbon electrodes for improved stability in PSCs which are made under ambient conditions. Sequential fabrication of the PSC was performed under ambient conditions with mesoporous TiO2/Al2O3/CH3NH3PbI3 layers and, on the top of these layers, the nanoparticles embedded carbon electrode was used. Different concentrations of WO3 nanoparticles as HTM incorporated in carbon counter electrodes were tested, which varied the stability of the cell under ambient conditions. The addition of 7.5% WO3 (by volume) led to a maximum power conversion efficiency of 10.5%, whereas the stability of the cells under ambient condition was ~350 h, maintaining ~80% of the initial efficiency under light illumination. At the same time, the higher WO3 concentration exhibited a high efficiency of 9.5%, which was stable up to ~500 h with a loss of only ~15% of the initial efficiency under normal atmospheric conditions and light illumination. This work demonstrates an effective way to improve the stability of carbon based perovskite solar cells without affecting the efficiency for future applications.

This paper provides an analysis of the benefits of passive cooling for High Concentrator Photovoltaic (HCPV) systems in terms of costs and kWh annual energy yields. For the first time, the performance of the heat sinks has been related to the calculated energy yield of a standard triple-junction GaInP/GaAs/Ge HCPV cell in a system deployed at several suitable locations across the globe. Copper and aluminium heat sinks have been considered and their merits have been compared. The finite element analysis software package COMSOL was employed to gain insights regarding a simple flat plate heat sink. The cell temperature was found to have a linear dependence on the geometric concentration with a characteristic slope that increases with cell size (ranging from 10 - 0.25 mm). The results show the advantages of miniaturization, and that the cooling of smaller cells can be accomplished using flat heat sinks. Within the considered range of geometric concentration ratios (up to 1000×), aluminium heat sinks are, in general, found to be preferred over copper, because of their lower densities and costs for the same thermal management. Closed-form thermal models based on the Least-Material (LM) approach have been utilized to design more complex finned heat sinks (operated under natural convection) that yield the best compromise between thermal performance and weight. For a 60 °C cell operating temperature, a greater kWh output is obtained, but a LM heat sink designed for a cell temperature of 80 °C has a material cost per unit energy that is between 50 % and 70 % less than the one designed for 60 °C. Heat sink costs between $0.1-0.9 per Wp were estimated for a geometric concentration above 500 suns, depending on the cell’s temperature and size. There are strong reductions in HCPV installation costs by limiting the dimensions of the cooling system at high concentrations

Concentrating photovoltaic-thermal (CPVT) technology harnesses solar energy by increasing the solar density upon cells using optical concentrators. CPVT systems are the focus of ongoing research and improvements to achieve the highest potential for energy harnessing and utilization. Increasing the concentration ratio for high energy generation raises many advances and limitations in the CPVT design. This article highlights the influence of the temperature with an increasing concentration ratio on CPVT components in terms of single-/multi-junction semiconductor materials, primary and secondary optical concentrator materials, and thermal receiver design. To achieve this, the theory of single- and multi-junction solar cell electrical characteristics (V ,I ,FF and η) is first explained to understand their dependence on the temperature and concentration ratio. An extensive literature review discussing the advantages, disadvantages, and potential of current CPVT research is given. This includes graphical and tabular summaries of many of the various CPVT design performances. In this review, it has been ascertained that higher concentration ratios raise the temperature at which the performance, operation and reliability of CPVT system are affected. Also, this review indicates that the temperature elevation of the CPVT components is significantly impacted by the optical configuration and their material types and reflectance. A thermal receiver is illustrated as three components: solar cell (heat source), heat spreader (substrates) and its different types, and cooling mechanism. In addition, the article addresses the thermomechanical stress created with intensified illumination, especially with secondary optics, where the optical materials and optical tolerance need to be carefully explored. The economic implications of a high concentration ratio level are briefly considered, addressing the reduction in system cost by enhancing the system efficiency. Suggestions are made throughout the review as to possible improvements in system performance. oc sc

High concentrated photovoltaic systems (HCPV) have demonstrated the potential to achieve high conversion power over conventional photovoltaic panels (PV) especially for areas with high solar irradiance. However, the multi-junction (MJ) solar cells may be subjected to damage if the temperature exceeds 110 °C as recommended by the manufacturer. Hence, in this paper, the overall performance of a 1cm. MJ solar cell with a mini-channel heat sink subjected to high concentration ratio (500×to2000×) is investigated to find improved method of reducing the cell temperature. The impact of using water, Al O /water, and SiO /water on the effectiveness of heat transfer, temperature distribution on the MJ solar cell, and performance evaluation criteria are studied. Also, the evaluation of the HCPVT system performance is presented. A 3D computational modelling is performed and the experimental measurements for the thermal conductivity are constructed for the different fluids and entered in the simulation. Nanofluids maintain the maximum solar cell temperature at 95.25 °C and 67.1 °C at Reynolds number (Re) of 8.25 and 82.5 respectively and a concentration ratio of 2000×. The overall efficiency of the system increases by 3.82% at Re of 8.25 and a concentration ratio of 500× by using SiO /water at 5%. 2 2 3 2 2

Low concentrating photovoltaic (LCPV) system has been studied extensively, which showed excellent potential for the building integration application. However, such a system suffers from higher operating temperatures due to the concentrated light exposed into the solar cell. In this work, two different methods have been used to regulate the operating temperature of the solar cell without the interference of any other external mechanism. Two concepts were used to study the operating temperature of the solar cells are: i) use of Argon gas within the concentrator element, ii) incorporation of polymer-dispersed liquid crystal films (PDLC) on top of the module. In both cases, the power was improved by 37 mW–47 mW when temperature was reduced by 10 °C and 4 °C for the Argon gas-filled module and PDLC integrated module, respectively. In addition, the temperature effect of the PDLC integrated module showed a unique nature of reduction of the short circuit current due to the orientation of the liquid crystal particle, which increased at a higher temperature. The current study, therefore, shows the greater potential of improving the operating efficiency and reduction of solar cell temperature, without the need for additional pumping power such as needed for photovoltaic thermal application.

For low/high concentration, when the distribution of solar radiation is non-uniform over the surface of the solar cell, it gets heated up non-uniformly which affects the cell efficiency. Thus, in the present work, three dimensional analysis of the solar cells is carried out under non-uniform solar flux. It involves partial differential equations. For silicon cells, studies are available that use numerical techniques (involving iterations) to solve the differential equations. However, if the differential equations can be solved analytically, one can get an analytical expression for three dimensional non-uniform temperature distribution of the cell. The current work aims at it. Dye-sensitized (DSSC), perovskite and mono-Si cells are investigated. The effects of wind direction, its speed, inclination and solar irradiance on the three dimensional temperature distribution, heat losses and cell efficiency have been investigated. It is concluded that with increase in wind azimuthal from 0° to 90°, the efficiency decreases from 22.1% to 21.3% for mono-Si, 19.0% to 18.0% for perovskite and 12.0% to 11.9% for DSSC.

Dye-sensitized solar cells based on a poly(styrene-co-acrylonitrile) based gel electrolyte gave a photo conversion efficiency of 6.72%.

Integrating photovoltaics into windows provides the possibility of including an additional function of energy production to a conventional building fenestration component. There is no doubt that electrical power can be generated on-site. However, the effect of PV windows on the indoor luminous environment of the space served by them has not been comprehensively researched. This paper investigated the daylight performance of integrating four types of photovoltaics (semi-transparent thin film Cadmium telluride (CdTe) solar cells with 10% and 50% transparency, crystalline silicon solar cells with and without crossed compound parabolic concentrators (CCPC)) to a window of a typical south-facing office under different Window-to-Wall Ratios (WWRs). Annual useful daylight illuminance (UDI), daylight uniformity ratio (UR) and daylight glare probability (DGP) have been analysed based on dynamic simulation using RADIANCE. The simulation results show that windows integrated with crystalline silicon cells and CCPC optics have the potential to provide best daylight availability when compared with standard double glazed windows and other tested PV window prototypes, if it is applied to rooms with large WWRs (e.g. 60% or 75% WWR) at high latitudes (e.g. city of Harbin). Its application also improves the uniformity of daylight spatial distribution and eliminates the risk of glare. Semi-transparent CdTe PV window with 10% transparency can also improve the percentage of working hours that fall into UDI. range, however, it will result in the most sharp illuminance contrasts within the room. Applying all of these tested PV windows can effectively reduce the possibility of glare. 500–2000lux

In this work, carbon counter electrode perovskite was developed at the laboratory environment and building integrated photovoltaic (BIPV) window application using this material was investigated. At 1 sun (1000 W/m2) continuous incident solar radiation from an indoor simulator, this particular type of perovskite had 8.13% efficiency. Average solar and visible transmittance of this perovskite BIPV window was 30% and 20% respectively. Solar heat gain for different incident angle was evaluated for this perovskite glazing. For the University of Exeter, Penryn (50.16° N, 5.10° W) UK location, solar heat gain coefficient (SHGC) or solar factor (SF) varied from 0.14 to 0.33 at the highest and lowest incident angle respectively. Overall heat transfer coefficient (U-value) of 5.6 W/m K was realized for this glazing while calculation was performed by window performance analysis programme, WINDOW 6.0. Daylight glare control potential of this glazing was investigated using subjective rating methods and comfortable daylight penetrated through glazing in a typical cloudy condition. Colour properties of this material showed that 20% visible transmittance is threshold limit, and below this value colour or visual comfort using this glazing is not achievable. 2

In this paper, a two-stage square parabolic concentrating photovoltaic (CPV) receiver dish with an overall geometric concentration ratio of 500 suns is designed to provide a uniform intensity distribution on high-efficiency triple-junction solar CPV cell module. The system comprises of a square parabolic dish with an aperture area of 9 m. as a primary concentrator and an array of the compound parabolic concentrator integrated optical homogenizer of 0.27 × 0.27 m. as a secondary concentrator in tandem with the dish. The CPV module consists of an array of 12 × 12 triple junction CPV cells with each cell connected in parallel or series combination and integrated CPC homogenizer dedicated to each cell. The homogenizer length is selected based on the peak to average ratio of concentrated flux with the aim to maximize the optical and electrical performance of the CPV system. Monte Carlo ray-tracing model is used to predict the flux distribution. The predicted solar flux distribution on individual CPV cells are used as input to determine the electrical performances of the CPV module with three different cell interconnections. For optimized homogenizer length of 0.005 m and receiver height of 3.7 m, the maximum optical and CPV module efficiencies are obtained as 68.30% and 32.03% respectively. A year-round electrical power output of developed CPV system is 2.19 MWh which is up to 33.54% higher as compared to conventional CPV system. The proposed novel geometric design could accommodate the bypass diode for each cell, effectively reducing the current mismatch effects. 2 2

The accumulation of dust on photovoltaic (PV) devices has an adverse impact by degrading their performance. In this work, a review of the effects of dust accumulation on PV module performance and measures to mitigate them have been provided. Energy losses from PV due to dust is an issue which cannot be ignored and can be an obstacle to achieving renewable energy targets in Nigeria. However, this paper presents a number of mitigation techniques which are available to maintain a certain level of performance. There is a need for further conduct comprehensive research on the effects of dust in all geopolitical regions in Nigeria to acquire data that can be used for designing the PV module system considering the most suitable technique in reducing or preventing the effects of soiling in each specific area.

It is well known that increasing the concentration ratio of concentrator photovoltaics has a positive impact on the power output of the system but can reduce the solar cells performance due to the heightened temperatures. In this paper, we introduce the impact of using an infrared (IR) filter on the performance of a silicon solar cell as a preliminary investigation for an ultra-high concentrator photovoltaic system. The investigation is carried out in terms of the optical characterization of the Fresnel lens and the IR filter. Besides, the performance of the system has been introduced in this paper. The results show that although the IR filter protects the solar cell from damage near the tabbing wire, it reduces the experimental power output of the cell by 46.08% due to the low transmittance of the filter while the cell efficiency increased by 183.3%.

A steady, three-dimensional model considering all the layers of a solar photovoltaic-thermal collector with sheet and tube heat exchanger is developed. The model takes the solar heat loading as the thermal input to estimate the temperature distribution in the collector for variation in incident radiation, ambient temperature, wind velocity, flow rate and inlet water temperature. Based on the numerical results, the parameter that highly influences collector performance is the coolant mass flow rate. For the range of flow rates considered, a maximum efficiency of 93.01% is obtained for 44 LPH. Further, a techno-economic comparison of the photovoltaic-thermal system is made with a photovoltaic system and a flat plate thermal system. The increase in electrical efficiency of the photovoltaic-thermal system is only marginal to that of the photovoltaic system but the overall efficiency of the former is high. The annual cost of energy that the photovoltaic-thermal system can supply is found to be 0.13 USD/kWh from economic analysis.

Natural source derived carbon materials make them ideally suited alternative to costly Pt counter electrode for their good catalytic activity, resistance to iodine corrosion, and high stability of the device. Apart from the extensively acclaimed photoanode TiO2, BaSnO3 (BSO) has been projected as an efficient alternative to it. In this study, remarkable efforts have been endeavoured to establish BSO-carbon-based DSSC device. Investigation on the adequate performance of natural source derived carbon-based counter electrode for BSO-based DSSCs, explored as a significant alternative to costly Pt and TiO2, respectively, which could elucidate better photo-stability and more extended device performance compared to TiO2-Pt-based DSSCs.

The spectral mismatch between the incoming solar spectrum and photovoltaic cells is a fundamental factor which curtails their efficiencies. Through luminescent processes, known as spectral conversion, the wavelengths of the incident sunlight may be changed to better match the optimal values for charge carrier generation by the solar cell. There are three means by which this can occur: upconversion, downconversion and luminescent downshifting, whereby two low energy photons can combine into one of a higher energy, one high energy photon can split its energy into two lower energy ones and a single high energy photon can reduce its energy, respectively. Collectively, these processes have attracted interest as an area of research for their application to solar cells as a method to enhance PV device performance, an important technological challenge to aid in the transition to a decarbonised economy.
in this thesis, particles with spectral conversion properties are incorporated into two kinds of novel solar PV devices of relevance to the emerging and building integrated photovoltaic technology sectors, 3D static SEH concentrator photovoltaic modules with potential for building integration and high stability dye sensitized solar cells. Following an introduction to the topic, concisely discussing the underlying mechanisms of each spectral conversion process, and conducting a literature review which catalogues the evolution of state-of-the-art results from the field, experiments are designed to test two candidate spectral conversion materials (Sr4Al14O25: Eu2+, Dy3+ and NaYF4: Er3+, Yb3+) on silicon PV and dye sensitized solar cells, both with and without SEH concentrators. Under an A+A+A+ solar simulator at 1000 W/m2, the power conversion efficiency of silicon PV devices improved up to 11.1% relative to controls through the addition of these materials. At lower irradiances and compared to cells without concentrators, the relative efficiency gains were more pronounced and external quantum efficiency (EQE) measurements suggested spectral conversion was potentially responsible for these enhancements. For a large scale BICPV system, a simple analysis showed cost per watt could fall by up to 8.1% and power output increase from 19.3 to 21.4 W/m2 through this approach. For the dye sensitized solar cells a 53.4% efficiency enhancement (relative to un-doped controls) was achieved with a potential cost reduction of 39.6%. Finally, simple optical models (including one developed in-house) and a statistical analysis are used to justify the findings and develop understanding of the physical processes behind the results, while conclusions are drawn with regards to the future outlook of this approach and its impact on the drive towards lower cost sources of clean electricity.

Among all passive methods for photovoltaics (PV) cooling, phase change material (PCM) can be highly effective due to high latent heat capacity. However, very low thermal-conductivity of PCM restricts its potential. The proposed work focuses on the enhancement of rate of heat transfer from PV to PCM by using conductivity-enhancing-containers. The proposed approach was experimented outdoor and compared with the reference panel for different seasons at Chennai, India. PV temperature, open circuit voltage, short circuit current, Current-Voltage (I–V) and Power-Voltage (P–V) curves, fill-factors, power outputs, efficiency and daily electricity generation are reported. The results show that the proposed heat sink was able to decrease the maximum PV temperature from 64.4 °C to 46.4 °C for January and 77.1 °C to 53.8 °C for June. It increased the open circuit voltage of PV from 24.3 V to 26.4 V for January and 23.6 V to 26.0 V for June. The fill-factor increased from 0.678 to 0.705 for January. Consequently, the electrical efficiency increased from 9.5% to 10.5% during noon. Daily electricity generation increased from 769 Wh/day to 817 Wh/day during January and 948 Wh/day to 1026 Wh/day during June. Thus, daily electricity generation increased by 6.2% for January and 8.3% for June using proposed approach.

Perovskite solar cell (PSC) technology is the flag bearer for the future of photovoltaics allowing unlimited possibilities for its application.

The accumulation of soiling on photovoltaic (PV) modules affects PV systems worldwide. Soiling consists of mineral dust, soot particles, aerosols, pollen, fungi and/or other contaminants that deposit on the surface of PV modules. Soiling absorbs, scatters, and reflects a fraction of the incoming sunlight, reducing the intensity that reaches the active part of the solar cell. Here, we report on the comparison of naturally accumulated soiling on coupons of PV glass soiled at seven locations worldwide. The spectral hemispherical transmittance was measured. It was found that natural soiling disproportionately impacts the blue and ultraviolet (UV) portions of the spectrum compared to the visible and infrared (IR). Also, the general shape of the transmittance spectra was similar at all the studied sites and could adequately be described by a modified form of the Ångström turbidity equation. In addition, the distribution of particles sizes was found to follow the IEST-STD-CC 1246E cleanliness standard. The fractional coverage of the glass surface by particles could be determined directly or indirectly and, as expected, has a linear correlation with the transmittance. It thus becomes feasible to estimate the optical consequences of the soiling of PV modules from the particle size distribution and the cleanliness value.

In this work, a three-dimensional steady state thermal model is developed for a compound parabolic concentrator of 2× concentration considering the effects of surface radiation and wall conduction. The performance of the compound parabolic concentrator is modeled to obtain the convective and radiative heat loss under the influence of different parameters such as absorber temperature, absorber emissivity, ambient temperature, external heat loss coefficient, aspect ratio and concentrator tilt. The turbulent natural convection in the concentrator is modeled using standard two equation k-ε turbulent model with enhanced wall treatment. For the surface radiation inside the concentrator, discrete ordinate radiation model is used. The thermo physical properties of air inside the cavity are assumed to be constant except the density which is modeled as incompressible ideal gas. The conduction at the walls is accounted by setting suitable wall thickness for reflectors, glass cover and end walls in the solver. This work clearly demonstrates the need for a three dimensional numerical simulation and coupled natural convection and radiation to exactly reproduce the velocity fields as would be obtained in experiments. The convective Nusselt number, radiative Nusselt Number and thermal stratification are obtained from the parametric study. This study on estimation of heat losses in compound parabolic concentrator is applicable to both solar thermal and solar photo-voltaic collectors with a view of modifying the concentrator design to optimize its thermal performance.

Façade buildings are generally highly glazed and energy-intensive especially in countries with hot weather. Power consumption in these buildings is even more significant when air conditioning (AC) is added to the figures. Building with semi-transparent photovoltaic (STPV) materials is bringing advantageous energy-saving features to these façade structures. Energy is saved by more heat being reflected resulting in less AC power consumption with the STPV thermal properties. In addition, the optical and electrical properties provide indoor sunlight with power generation. This paper investigates the net potential energy saving via applying cadmium telluride (CdTe) in Façade buildings. The analysis has been carried out using indoor and outdoor experiments considering different orientations and transparencies. Compared to a single glazing case as a reference, the application CdTe achieved a net energy saving to be as high as 20%. Furthermore, a trade-off between saving energy and environment comfort has been discussed as less transparency windows lead to more artificial light consumption. The findings indicate that STPV is a promising solution for sustainable buildings.

Fins enabled Phase Change Material (FPCM) has potential to take away the thermal energy from photovoltaic (PV) and increase the efficiency. This study analyses the PV-FPCM arrangement and presents a mathematical model. The arrangement is studied under various azimuths of wind, its flow rates, temperature of surroundings, phase change temperature and dimensions of FPCM confinement. The duration of power improvement of PV using FPCM, power production, efficiency improvement and Power-Voltage (P–V) curves are reported. The outcomes convey that as azimuth of wind changes from 75° to 0°, the duration of power improvement elevates from 6.1 h to 7.3 h for 5 cm deep FPCM confinement. It increases from 4.9 h to 5.8 h for 4 cm deep FPCM confinement. Moreover, decrement in wind flow rate from 6 m/s to 1 m/s, contracts the duration of power improvement from 7.8 h to 6.1 h.

Phase change material (PCM) based passive cooling of photovoltaics (PV) can be highly productive due to high latent heat capacity. However, the low rate of heat transfer limits its usefulness. Thus, the presented work aims at the improvement in PV cooling by using finned PCM (FPCM) heat sinks. In the present study, PCM heat sink and FPCM heat sinks were investigated numerically for PV cooling and the extracted heat is used for space heating. 4 kWp PV, PV-PCM and PV-FPCM systems were studied under the weather conditions of Southeast of England. It was observed that the PCM heat sinks can drop the peak PV temperature by 13 K, whereas FPCM heat sinks can enhance the PV cooling by 19 K. The PCM heat sinks can increase the PV electrical efficiency from 13% to 14%. Moreover, the daily electricity generation can be boosted by 7% using PCM and 8% by using FPCM heat sinks. In addition, 7 kWh of thermal output was achieved using the FPCM heat sink, and the overall efficiency of system increased from 13% to 19%.

Cost effective energy storage solutions are increasingly in demand for electrical grid and renewable energy applications. The zinc-nickel redox flow battery (RFB) is a promising technology due to its potential cost competitiveness. However, a number of obstacles must be overcome before the zinc-nickel RFB can be commercialised. Many of these relate to the zinc electrode in alkaline electrolytes. Therefore, this work is focused on development of the alkaline zinc electrode, aiming to improve performance in the zinc-nickel RFB by addressing the issues of zinc morphology and hydrogen evolution.
Sixteen electrolyte additives are screened, tetraethylammonium hydroxide (TEAH) at 15 mM L-1 concentration being identified as promising. Zinc-nickel flow cell cycling tests provide coulombic and energy efficiencies of 97.8 % and 86.0 % respectively, with compact zinc morphologies obtained after 80 cycles.
Increasing KOH and ZnO concentrations are shown to be beneficial to both the zinc and nickel electrodes. An electrolyte of 6 M L-1 KOH and 0.5 M ZnO is identified as optimal at 293 K. The effect of zinc electrode substrate material on coulombic efficiency is shown to relate to hydrogen evolution reaction (HER) overpotentials. A graphite composite with 5 % polyvinylidenefluoride (PVDF) (BMA5, Eisenhuth) demonstrates the highest coulombic efficiency (96.7 %) and most negative HER onset potential (-1.595 V vs. Hg/HgO).
The effect of electrolyte velocity on zinc morphology is related to Reynolds numbers. At 20 mA cm-2 in an electrolyte containing 0.5 M ZnO compact zinc depositions result from Reynolds numbers over 2000. The ratio of applied current density to limiting current density is used as an indicator of zinc morphology, with values of 0.4 and below providing compact zinc depositions.
Zinc-nickel flow cell cycling employing the selected electrolyte composition, zinc electrode substrate material and operational parameters yields average coulombic and energy efficiencies of 98.3 % and 86.6 % respectively over 200 stable cycles. This is comparable to the highest efficiencies previously reported but is achieved at an increased current density of 20 mA cm-2, resulting in improved power density. The electrolyte flow rate is also reduced by 64 %, representing a significant reduction in required pumping energy.

COVID-19 transmission in London city was discussed in this work from an urban context. The association between COVID-19 cases and climate indicators in London, UK were analysed statistically employing published data from national health services, UK and Time and Date AS based weather data. The climatic indicators included in the study were the daily averages of maximum and minimum temperatures, humidity, and wind speed. Pearson, Kendall, and Spearman rank correlation tests were selected for data analysis. The data was considered up to two different dates to study the climatic effect (10th May in the first study and then updated up to 16th of July in the next study when the rest of the data was available). The results were contradictory in the two studies and it can be concluded that climatic parameters cannot solely determine the changes in the number of cases in the pandemic. Distance from London to four other cities (Birmingham, Leeds, Manchester, and Sheffield) showed that as the distance from the epicentre of the UK (London) increases, the number of COVID-19 cases decrease. What should be the necessary measure to be taken to control the transmission in cities have been discussed.

We propose two energy-mapping methods to produce a uniformly illuminated area for a nontilted (straight) and a tilted light source toward a target plane. These energy-mapping methods define the positions of the desired points (the destination points of the refracted rays of a light source) on an illuminated area. The surface of the lenses can then be formed through the position of the desired points. Based on these design methods, two freeform lenses, (i) a symmetric lens and (ii) an asymmetric lens, were designed to provide uniformity within a rectangular illumination footprint for a nontilted and a tilted light source, respectively. This method can produce uniformity for a tilted light source within 0 deg to 45 deg toward the normal vector on the target plane. Two freeform lenses for 0 deg and 20 deg tilted toward a target plane were designed. The illumination footprint of the symmetric and asymmetric freeform lenses was evaluated through ray-tracing simulations and experiments. Both models produce over 90% uniformity within an illuminated area.

Concentrator photovoltaics have several advantages over flat plate systems. However, the increase in solar concentration usually leads to an increase in the solar cell temperature, which decreases the performance of the system. Therefore, in this paper, we investigate the performance and temperature limits of a high concentration photovoltaic Thermal system (HCPVT) based on a 1 cm2 multi-junction solar cell subjected to a concentration ratio from 500× to 2000× by using three different types of cooling fluids (water, ethylene glycol and water mixture (60:40), and syltherm oil 800). The results show that, for this configuration, the maximum volumetric temperature of the solar cell did not exceed the manufacturer’s recommended limit for the tested fluids. At 2000× the lowest solar cell temperature obtained by using water was 93.5 °C, while it reached as high as 109 °C by using syltherm oil 800, which is almost equal to the maximum operating limit provided by the manufacturer (110 °C). Overall, the best performance in terms of temperature distribution, thermal, and electrical efficiency was achieved by using water, while the highest outlet temperature was obtained by using syltherm oil 800.

Semi-transparent photovoltaic (PV) technology is attractive for building-integrated photovoltaics (BIPV) due to its ability to lower the admitted solar heat gain, to control the penetrating daylight and to generate onsite benevolent direct current power. In this work, semi-transparent cadmium telluride (CdTe) based BIPV as window was experimentally characterized using outdoor test cell in temperate UK climate. Spectral measurement confirmed its 25% visible transmission and 12% solar transmission. Thermal transmission and solar heat gain coefficient were calculated from measured thermal data. Overall heat transfer coefficient (U-value) of 2.7 W/m. K was found for outdoor and indoor characterization of CdTe BIPV window. A comparison with single glazed window has been produced emphasis its feasibility for Facade buildings. 2

A new coupled optical, thermal and electrical model is presented in this study and applied to a concentrating photovoltaic thermal (PV/T) system for predicting the system performance under various operational conditions. Firstly, a three-point-based electrical model and a method for extracting its five model parameters are developed by using the currents and voltages at the short-, open-circuit and maximum power points provided in usual PV module/panel datasheets. Then, the model and method are validated with the existing six flat-plate PV modules and subsequently are used to predict the hourly electrical performance of the CPV/T roof-top system designed by us under outdoor conditions on four clear days by integrating with a scaling law developed by us. Additionally, transient effect and water temperature on the storage tank are examined. It turned out that the CPV system could operate for 6 h a day with a peak instant electrical power of 50W/m. and could generate 0.22kWh/m. electricity a day in May–July. The error in hourly electrical energy gained between the predictions and observations is in a range of (3.64–8.95)% with the mean of 5.53% in four days, and the estimated water temperature in the storage tank agrees with the monitored one in range of 0.2–1 °C. The proposed methods as well as the electrical models could potentially be applied widely across the solar energy field for the management and operation of the electrical energy production from any CPV/T roof-top system. 2 2

A low concentrator photovoltaic is presented and the optical losses within a double glazed window assembly are described. The use of plastic instead of glass is analyzed for its reduced weight and hence greater power to weight ratios. Although the transmittance of glass is higher, the power to weight ratio of the plastic devices was almost double that of the glass counterparts and even higher than the original non concentrating silicon cell. The plastic Topas material was found to be the best performing material overall. Crystal Clear, a plastic resin, had a higher average transmittance but had a lower optical efficiency due to the cold cast manufacturing process in comparison to injection moulding of the other materials. This proves the importance of considering both the materials and their associated manufacturing quality. External quantum efficiencies, optical properties, silicon cell temperatures and performance is analyzed for concentrating photovoltaic devices made of varying optical materials. The measurement methods for optical analysis are given in an attempt to separate the optical losses experimentally. The Silicon cells were found to gain higher temperatures due to the insulating plastic optics in comparison to glass but these effects are eliminated during vertical window orientation where instead the encapsulate dominates the insulation of the cell. The results presented here prove plastic optics to be a worthwhile alternative to glass for use in low concentration photovoltaic systems and have the significant effect of reversing the weight disadvantage concentrator photovoltaic technology has compared to standard flat plate solar panels.

The main purpose of the present study is to investigate the melting characteristics of a PCM cylindrical thermal storage system using experimental and numerical approaches. Three inclination positions are considered from vertical to horizontal. Paraffin wax has been used as the phase change material with a melting temperature ranged between 35 and 37 ºC. The melting behaviour of the PCM inside the storage is characterised using different parameters of temperature distribution, imaging of PCM melting profiles, rate of stored heat, and liquid PCM flow within the storage. The results show that the PCM storage inclination angle has a significant effect on the PCM temperature distribution, PCM melting time and profile. It is noted that PCM in the storage in the 45° inclination angle from the horizontal location has the fastest melting rate is the fastest in melting compared to the 0° and 90° inclination angles. The simulation models enable understanding the internal flow of liquid PCM where it has been found that the direction of buoyant force resulting from the melted liquid PCM has a major role in both melting rate and melting direction within the PCM storage. In addition, it has been observed that the charging rate has no effect on the PCM melting profile.

Low heat loss vacuum glazing offers high heat insulation for indoor space, which reduces the building's heating energy demand. However, the transparent nature of this glazing allows similar daylight to double glazing that creates discomfort glare. Double pane semi-transparent type photovoltaic (PV) glazing introduces control of solar heat gain, daylight and generates clean electricity. The transparent portion between regularly distributed PV cells allows light penetration. Addition of these two technologies can offer low heat loss PV-vacuum glazing that will control heat loss, heat gain, and daylight and generate renewable power. In this work, two different areas of multicrystalline PV cells were employed to form 35% and 42% transparent PV-vacuum glazing. Spectral characterisation, glazing factor and entering light quality through the transparent part of this PV-vacuum glazing were evaluated. Colour rendering and correlated colour temperature of this glazing were compared with an electrically actuated switchable suspended particle device glazing.

This paper presents the results of an investigation on the spectral losses of photovoltaic (PV) soiling. The transmittance of a glass coupon exposed to natural soiling outdoors in Jaén, southern Spain, has been measured weekly and used to estimate the soiling losses that various types of photovoltaic materials would experience if installed in the same location. The results suggest that measuring the hemispherical transmittance of the soiling accumulated on a PV glass coupon can give enough information to quantify the impact of soiling on energy production. Each PV technology is found to have a preferred spectral region, or a specific single wavelength, for which the transmittance through a PV glass coupon could be used for the best estimation of soiling losses. Overall, considering the average spectral transmittance between the extreme wavelengths of the material-specific absorption band, or the transmittance of soiling at a single wavelength between 500 and 600 nm yields the best estimations for different PV technologies. The results of this work can lead to innovative approaches to detect soiling in the field and to estimate the impact of spectral changes induced by soiling on PV energy production.

Solar energy is a large, exploitable, renewable resource where it can supply the earth with enough energy in one hour, equivalent to the mankind’s total energy consumption in a year. Nanomaterials, for semiconductor material, used as a photocatalyst to convert sunlight into chemical fuel (hydrogen) via photoelectrochemical water splitting process, has been considered as the Holy Grail to a carbon free hydrogen economy. Conversion of sunlight into hydrogen is a promising, clean and sustainable way of generating hydrogen.

In this research project we have designed, synthesised, characterised and tested new materials for which can generate hydrogen from water using solar energy. Due to the lack of suitable p-type semiconductor materials, this work has focused on synthesising and developing new, stable, visible light active photocathodes for solar hydrogen generation.

In pursuit of this stable photocathode, we have synthesised stable visible light active LaFeO₃ which has shown some promise as a future candidate p-type photocathode. This was produced by cheap, novel and scalable spray pyrolysis technique which has resulted in current densities of 0.16 mA cm⁻² at 0.26 V vs RHE and shown stability over 21 hours. Subsequently, this led to hydrogen generation of 0.18 μmol cm⁻². Furthermore, LaFeO₃-Ag and LaFeO₃-Ni were fabricated by spin coating silver and nickel nanoparticles on to the spray pyrolysed LaFeO₃, to enhance photocurrent density for enhance hydrogen generation via solar water splitting. This led to over double the amount of hydrogen being produced. Similarly, TaFeO₄ was fabricated by sol-gel method which yielded 0.091 μmol g⁻¹ of hydrogen. Future work is required on TaFeO₄ to fabricate electrode form of the material so its band structure many be determined. This may be done by microwave assisted annealing.

Temperature management in photovoltaic (PV) is critical for the power output. Phase Change Material (PCM) usage enables one to remove heat from the system and achieve enhanced electrical output. This study aims at finding the period of PV electrical enhancement, the increase in power and increase in electrical efficiency achieved using PCM under different working circumstances. Results suggest that as the angle of approach of wind changes from 75° to 0° the electrical enhancement period elevates from 7.0 h to 8.6 h for 5 cm deep PCM box. But, the increase in power drops from 17.6 W/m. to 13.6 W/m. As wind speed changes from 6 m/s to 0.2 m/s, the electrical enhancement period drops from 9.1 h to 6.4 h. But, the increase in power rises from 11.8 W/m. to 22.8 W/m. The rise in ambient temperature 289 K to 299 K leads to decrement of electrical enhancement period from 12.6 h to 7.1 h. But the increase in power rises from 15.9 W/m. to 21.4 W/m. Elevation in temperature for liquification from 291 K to 301 K leads to increment of electrical enhancement period from 6.5 h to 12.3 h. 2 2 2 2 2 2

A major challenge facing silicon solar cells used in building-integrated concentrator photovoltaics (BICPV)is their reduced electrical response when exposed to light of short or long wavelengths. In an attempt to tackle this problem, single cell static CPV modules were fabricated with some of the devices containing rare earth doped compounds which were dispersed into the system in varying concentrations and geometries. Under a solar simulator at 1000 W/m , the power conversion efficiency (PCE)of devices improved up to 11.1% relative through the addition of these materials. At lower irradiances and compared to cells without concentrators, the relative efficiency gains were more pronounced and external quantum efficiency (EQE)measurements suggested spectral conversion was responsible for these enhancements. For a large scale BICPV system, a simple analysis showed cost per watt could fall by up to 8.1% and power output increased from 25.7 to 28.4 W/m. through this approach. 2 2

The building sector is responsible for more than one-third of global energy consumption. With increasing global population, the demand for energy efficiency buildings and on-site electricity production is rising. Building integrated photovoltaics (BIPV) is one of the most promising contributors to net-zero energy buildings, while also increasing the aesthetic value of the built environment. Among all the transparent solar cells, dye-sensitised solar cells (DSSCs) have low production cost, semi-transparency nature and a range of colours for building design.
This thesis presents an overview of the current energy scenario and future prospects, state-of-the-art of photovoltaic technologies and the challenges in commercialising new generation solar cells. The first approach here is to find an efficient and low-cost alternative photoanode, sensitiser and counter electrode for DSSC. The tested materials are high surface area mesoporous TiO2, new ruthenium complex (m-HRD-1) sensitiser and Jet nebulizer spray coated CZTS. All the obtained results are compared with the commercial materials. Secondly, semi-transparent DSSCs are fabricated with different transparencies and their colour properties such as correlated colour temperature and colour rendering index are evaluated. Moreover, glazing properties and daylight glare analysis are studied to assess the possibility of adopting semi-transparent DSSCs into building architectures. Finally, a low solar concentrator is placed on the transparent-DSSCs to enhance their photovoltaic performance. The internal charge transfer mechanism of the DSSCs is also studied to understand the impact of the concentrated light. Furthermore, the performance of the concentrator coupled devices under different light intensities is studied.
the results presented here provide a fertile base for further investigation, which will focus on improving the performance of all the new generation low cost solar cells using optical elements with new designs. The target is to improve the performance and stability of the transparent solar cell devices and use them as BIPV materials to overcome the challenges of the increasing energy demand.

Concentrating Photovoltaic technology is considered now as a promising option for solar electricity generation along with the conventional flat plate PV technology especially in high direct normal irradiance areas. However, the concentrating photovoltaic industry sector still struggles to gain market share and to achieve adequate economic returns due to challenges such as the high temperature of the solar cell which causes a reduction its efficiency.
The work presented in this thesis is targeted to influence the overall performance of a high concentrated photovoltaic system by integrating both the multi-layered microchannel heat sink technique and a phase change material storage system. The proposed integrated system is composed of a multi-layered microchannel heat sink attached to a single solar cell high concentrated photovoltaic module for thermal regulation purposes. This is expected to reduce the solar cell temperature hence increasing the electrical output power. The high concentrated photovoltaic and multi-layered microchannel heat sink system is then connected to a phase change material thermal storage system to store efficiently the thermal energy discharged by the high concentrated photovoltaic and multi-layered microchannel heat sink system.
The first part of the thesis discusses the influence of the multi-layered microchannel heat sink on the high concentrated photovoltaic module using both the numerical and experimental approaches. The multi-layered microchannel heat sink has been integrated for the first time with the single cell receiver and tested successfully. A numerical analysis of the high concentrated photovoltaic and multi-layered microchannel heat sink system shows the potential of the heat sink to reduce the solar cell maximum temperature and its uniformity.
The thermal behaviour of the multi-layered microchannel heat sink under non-uniform heat source was experimentally investigated. The results show that in extreme heating load of 30W/cm² and in heat transfer fluid flow rate of 30ml/min, increasing the number of layers from 1-layer to 4-layers reduced the heat source temperature from 88.55°C to 73.57°C, respectively. In addition, the single layer multi-layered microchannel heat sink suffers of the most heat source temperature non-uniform compared to the heat sinks with higher number of layers. Also, the results show that increasing the number of layers from 1-layer to 4-layers reduced the pressure drop from 16.6mm H2O to 3.34 mm H2O.
The indoor characterization of the high concentrated photovoltaic and multi-layered microchannel heat sink system investigated the effect of the number of layers, the homogeniser materials, and the heat transfer fluid flow rate and inlet temperature on the electrical and thermal performance of the system. The results show that the maximum power of the high concentrated photovoltaic module with glass homogeniser is 3.46W compared to 2.49W when using the crystal resin homogeniser for the 2-layers multi-layered microchannel heat sink and 30ml/min under 1000W/m² irradiance intensity. Increasing the number of layers from 1-layer to 3-layers on the high concentrated photovoltaic and multi-layered microchannel heat sink system increased the maximum electrical power by 10% and decreased the solar cell temperature 3.15°C for the heat transfer fluid flow rate of 30ml/min. This gives an increase in the maximum electrical power of 98.4mW/°C.
The outdoor characterisation of the high concentrated photovoltaic and multi-layered microchannel heat sink system performance was evaluated at the University of Exeter, Penryn Campus, UK. The achieved maximum output electrical power of the system was 4.59W, filling factor of 75.1%, short circuit current of 1.96A and extracted heat of 12.84W which represents of 74.9% of the maximum solar irradiance of 881W/m². In addition, the maximum solar cell temperature reached to 60.25°C.
Secondly, the experimental studies were carried out in order to investigate the performance of the phase change material storage system using paraffin wax as the PCM materials. The thermal storage system performance was evaluated in various conditions. The results show that inclination of the phase change material storage influences the melting behaviour of the phase change material where the phase change material storage of 45º inclination position melts faster than the phase change material storages in the 0º and 90º inclination positions. The phase change material melting time is reduced in the PCM storage of 45º inclination position by 13% compared to the 0º inclination position.
The last part of the thesis discusses the integration of the phase change material storage with the high concentrated photovoltaic and multi-layered microchannel heat sink system. A 3D numerical model was developed to predict the behaviour of the integrated high concentrated photovoltaic and multi-layered microchannel heat sink system with the phase change material storage system using variable source conditions. The results show a higher heat absorption rate on phase change material storage that uses a lower melting temperature phase change material compared to the higher phase change material melting temperature. The multi-stages storage with different phase change materials melting temperature showed a lower heat absorption compared to the phase change material arrangement with the lower melting temperature. Also, the rate of the absorbed heat fluctuation is less affected by the phase change material arrangement with higher melting temperature.

In concentrating photovoltaic (CPV), increasing the incoming sunlight to the solar cell influences the performance of the solar cells. The optical efficiency of the CPV components is a key factor to improve the electrical efficiency. Two types of homogeniser materials (K9 glass and crystal resin) were investigated in the CPV application. The results show a higher power generation of the CPV module when using K9 glass homogeniser compared to the crystal resin homogeniser by 27% due to the high transmittance value of the K9 glass material. In addition, the K9 glass material shows an excellent resistance to the heat produced by the concentrated sunlight compared to the crystal resin material.

Solar and luminous light transmission control using Cadmium Telluride (CdTe) based PV glazing systems (15 cm × 15 cm × 0.6 cm) were evaluated in this work. Indoor spectral characterisation showed that average solar transmission for investigated three different CdTe glazing systems were 5.77% (CdTe1), 9.54% (CdTe2) and 12.34% (CdTe3). Spectral behaviour of reflections in the range of solar and visible wavelengths was similar for these three different transparent CdTe glazing. Near infrared (NIR) reflection was higher compared to luminous reflection after 1500 nm for all three glazing systems. Solar factor (SF) for CdTe1, CdTe2 and CdTe3 glazing were 0.23, 0.28, 0.26. CdTe3 is the best candidate for glazing application as it has 113% higher luminous transmission while SF only increases by 21% compared to CdTe1.

The spectral mismatch between solar cells and incident radiation is a fundamental factor limiting their efficiencies. There exist materials and luminescent processes which can modify the incident sunlight's properties to better suit the cell's optimal absorption regions. This makes for an interesting area of research and promising technique for enhancing the efficiency of solar cells which is important for environmental reasons. It is intended for this review to provide the reader with historical and up-to-date developments of the application of spectral modification to solar cells and contribute to growing its impact on real-world PV devices. We concisely outline the underlying principles of three spectral modification processes: upconversion (UC), downconversion (DC) and luminescent downshifting (LDS). For each section we present up to date experimental results for applications to a range of solar PV technologies and discuss their drawbacks. With particular focus on UC, we then review how nanostructures or integrated optics might overcome these problems. Finally, we discuss practical challenges associated with advancing this approach for commercialisation and opportunities spectral modification presents; namely where future research should focus and via a cost analysis with a simple formula that can be used to determine financial viability for the deployment of this technology.

In this work, a hybrid microgrid framework was created with the assistance of a photovoltaic (PV) and wind turbine (WT) generator. Additionally, bidirectional control mechanisms were implemented where an AC system was integrated with permanent magnet synchronous generator (PMSG)-based WT and a DC system was integrated with a sliding mode algorithm controlled maximum power point tracker (MPPT)-integrated PV system. The wind and PV interconnected microgrid system was mathematically modeled for steady-state conditions. This hybrid microgrid model was simulated using the MATLAB/SIMULINK platform. Optimal load management strategy was performed on a chosen hybrid microgrid system. Various case studies pertaining to connection and disconnection of sources and loads were performed on the test system. The outcomes establish that the system can be kept up in a steady-state condition under the recommended control plans when the network is changed, starting with one working condition then onto the next.

The use of nanomaterials in solar energy conversion and photocatalytic degradation of environmental pollutants represents an opportunity to improve the performance, density, and ease of transportation in renewable resources. Among renewables resources, solar energy is considered as the largest exploitable resource, supplying the earth with energy in 1 hour equivalent to mankind’s total energy consumption in an entire year. Collecting and storing sunlight in chemical bonds (solar fuel) using photoelectrochemical water splitting (PEC) is a promising, a clean and sustainable way for hydrogen generation. Moreover, the photocatalytic process has great potential and high efficiency for removal of organic pollutants from water under direct natural sunlight irradiation. The aim of this project is to design, fabricate, characterize and performance enhancement of novel semiconductor materials that could efficiently harvest and store solar energy by splitting water to produce hydrogen and to perform dye degradation as well. The lack of suitable p-type photocathode has been considered and the focus of this work was to design and develop the new stable visible light absorbing photocathode materials.
. In pursuit of the stable photocathode, in this work YFeO3, which is a cheap and abundant material, with promising properties, and so was chosen as the photocathode in the development of the PEC cell. YFeO3 thin films were produced by spray pyrolysis technique onto fluorine-doped tin oxide film on glass. Results showed that YFeO3 photoelectrode has achieved a photocurrent of 0.6 mA cm-2 at 0.5 V vs. RHE and maximum of 0.41 μmol/cm2 of hydrogen has obtained as well.
. Similarly, to look for suitable and cheap materials for environmental remediation, Bi2WO6 thin films were produced by spray pyrolysis and aerosol-assisted chemical vapour deposition techniques. Results showed that the nanostructure and texture of the films can be controlled by controlling the deposition parameters. Moreover, photocatalytic degradation of rhodamine B (RhB) and methylene blue (MB) dyes have been successfully achieved.
. Finally, α-Fe2O3 films were fabricated as counter electrodes for dye-sensitized solar cells in order to compete for platinum counter electrode. These films were fabricated using aerosol-assisted chemical vapour deposition and spray pyrolysis techniques. The results showed that the performance of the samples prepared by aerosol-assisted chemical vapour deposition as a counter electrodes is higher than of the samples prepared by spray pyrolysis.

Building integrated photovoltaic (BIPV)-vacuum system is promising for advanced window application due to its ability to reduce heat transfer, control over admitted solar heat and generates environmentally benign electricity. In this work, numerically thermal comfort for an unfurnished room comprising of BIPV-vacuum glazing was evaluated for the United Kingdom (UK) climate. Required parameters to determine thermal comfort, one-dimensional heat transfer model was developed and validated for BIPV-vacuum glazing and results were compared with BIPV-double-pane glazing system. PV cell temperature difference between these two different types of glazing was 24 °C. For the UK climate, BIPV-vacuum glazing offered 26% higher room temperature at clear sunny day compared to BIPV-double system. BIPV–vacuum glazing system provided soothing or comfortable thermal comfort during mid-day period for a clear sunny day at temperate climate. In a combined BIPV-vacuum glazing, it was also predicted that vacuum glass facing external ambient is suitable for the UK climate whilst vacuum glass facing internal room ambient is applicable for Indian climate.

SPS-ALPHA as the most innovative and practical concept of Solar Power Satellite (SPS), has been widely concerned in the world. It adopts axisymmetric sigmoid curve-based/cocktail shape as the entire structure composed by several thousands of hexagonal “Reflectors and Deployment Modules” (RDM) that enables extremely high modularity and low cost of machining/space transport. SPS-ALPHA system, on the whole, can be treated as a dense array concentrated photovoltaic (DA-CPV) system. The blocking shadow effect and cosine effect of ray path exist that make the optical efficiency fluctuate with different tracking angles, resulting the trade-off exists between optical efficiency and irradiance uniformity. The current study aims to find the optimal design parameters of RDM when high optical efficiencies and stable irradiance distribution are both achieved for effective PV layout design. To meet this target, Ant Colony Optimization (ACO) algorithm combined with dynamic source-target mapping was adopted to find suitable aiming vectors of modular reflectors. The optical transmission characteristics under different incident degrees were investigated using a two-step Monte-Carlo ray tracing (MCRT) method. Afterwards the optimized results and sensitivity analysis for RDM would be undertook. The article can provide basic data and reference for engineering constructions of SPS-ALPHA in next step.

The present work aims at the optimization of fins fitted phase change material equipped photovoltaic system under different working circumstances for proper power enhancement. Setup has been modelled and the best deepness of fins fitted phase change material enclosure has been computed for a range of daily collective solar flux at photovoltaic panel surface, wind pace, wind azimuth, surroundings temperature, melting point, successive fins distance, fins deepness and fins width in order to analyse the influence of working circumstances. It is shown that the change in wind pace from 0.2 m/s to 6 m/s results in reduction of best deepness of phase change material enclosure from 5.2 cm to 3.7 cm, 5.6 cm to 4.0 cm, 5.8 cm to 4.2 cm, 5.9 cm to 4.3 cm and 5.9 cm to 4.3 cm for successive fins distance of 1 m, 1/2 m, 1/3 m, 1/4 m and 1/5 m respectively for daily collective solar flux at photovoltaic panel as 5000Wh/m. The change in wind azimuth from 0° to 75° results in increment in the best deepness of enclosure from 3.9 cm to 4.8 cm, 4.3 cm to 5.2 cm, 4.5 cm to 5.4 cm, 4.6 cm to 5.5 cm and 4.6 cm to 5.5 cm for respective fins distances. The power production is increased from 125 W/m. to 137 W/m , 140 W/m , 142 W/m , 143 W/m. and 143 W/m. with fins width of 0 mm, 0.5 mm, 1 mm, 2 mm and 4 mm respectively. 2 2 2 2 2 2 2

In recent years, building integrated photovoltaic (BIPV) applications have gained a considerable interest. Different semi-transparent photovoltaic (STPV) glazing can be used in such applications. This thesis aims to investigate the thermal performance, energy performance and daylight performance of a CdTe thin-film based semi-transparent PV glazing of different transparencies.
Outdoor and indoor experimental setups were installed, in Penryn, UK, to investigate the performance of 35%, 25%, 19% and 0.5% CdTe thin-film based semi-transparent photovoltaic glazing in comparison to conventional clear glazing under realistic conditions. Data from the experimental setups were collected in different day conditions and different orientations that are South and South West. Overall heat transfer coefficient (U-value) and solar heat gain coefficient (SHGC) were calculated for thermal performance evaluation. Net energy performance was evaluated for energy performance assessment. Daylight glare index (DGI) and daylight factor (DF) were calculated for daylight performance evaluation.
Results showed that, CdTe STPV glazing are better thermal insulators than conventional single glazing, and CdTe STPV glazing with lower transparencies have better thermal insulation property than higher transparency ones. In addition, compared to conventional single glazing, the application CdTe STPV glazing can achieved a net energy saving up to 20%. Moreover, Using CdTe STPV as a glazing façade can control the daylight glare inside the enclosures to acceptable levels, it also permits for usable daylight to be transmitted into enclosures.

Plasmonic Ni nanoparticles were incorporated into LaFeO. photocathode (LFO-Ni) to excite the surface plasmon resonances (SPR) for enhanced light harvesting for enhancing the photoelectrochemical (PEC) hydrogen evolution reaction. The nanostructured LFO photocathode was prepared by spray pyrolysis method and Ni nanoparticles were incorporated on to the photocathode by spin coating technique. The LFO-Ni photocathode demonstrated strong optical absorption and higher current density where the untreated LFO film exhibited a maximum photocurrent of 0.036 mA/cm. at 0.6 V vs RHE, and when incorporating 2.84 mmol Ni nanoparticles the photocurrent density reached a maximum of 0.066 mA/cm. at 0.6 V vs RHE due to the SPR effect. This subsequently led to enhanced hydrogen production, where more than double (2.64 times) the amount of hydrogen was generated compared to the untreated LFO photocathode. Ni nanoparticles were modelled using Finite Difference Time Domain (FDTD) analysis and the results showed optimal particle size in the range of 70–100 nm for Surface Plasmon Resonance (SPR) enhancement. 3 2 2

In the present work, 10 to 14 nm titania nanoparticles with high-packing density are synthesized by the soft-template method using a range of cationic surfactants including cetyl trimethylammonium bromide (CTAB), Sodium dodecyl sulfate (SDS), and dodecyl trimethylammonium bromide (DTAB). The synthesized nanoparticles are used as a photoanode material in dye solar cells. Density functional theory (DFT) simulations reproduce our experimental results of charge transfer and strong interaction between the TiO. and N719. N719-TiO. complex establishes strong electrostatic bonding through H of the dye with the O of TiO. surface. Solar cell efficiency of 6.08% with 12.63 mA/cm , 793 mV, and 48.5% for short circuit current density, open circuit voltage, and fill factor, respectively, are obtained under 1 sun illumination for the dye-sensitized solar cell (DSSC) using a film of mesoporous TiO. synthesized from the SDS surfactant. On the other hand, the 21 nm commercial TiO. powder (P25) device results in 4.60% efficiency under similar conditions. Electrochemical impedance spectroscopic studies show that the SDS device has lesser charge transport resistance than the other devices because of its higher surface area, packing density, and dye loading capacity. Our results show that employing high packing density-based TiO. nanoparticles represents a commercially viable approach for highly beneficial photoanode development for future DSSC applications. 2 2 2 2 2 2 2

Integrated renewable energy system (IRES) is integration of different energy sources to provide uninterrupted and viable solution for electrification especially for areas not connected to main grid due to difficult terrain and economic reasons. IRES has many advantages like non-depleting, non-polluting nature, better load matching and better renewable energy utilization. In the present study, mathematical modelling, size optimization and techno-economic analysis of standalone IRES have been carried out. Hybrid system is modelled to have maximum contribution from wind and solar energy with minimum net present cost (NPC) of system to meet electric load demand of CRC building, IIT Madras, India (13.01°N and 80.24°E). The results show that most feasible system configuration consists of 12 kW Photovoltaics, 3 kW wind turbine and 15 kW biogas generator with NPC and cost of energy equal to $ 117,098 and $ 0.09/kWh respectively. The IRES generates 71,826 kWh of energy to meet AC load of 64,396 kWh per year. The capacity factor and percentage contribution of PV, wind turbine and biogas generator are 17.8%, 6.57%, 39.1% and 26%, 2.4%, 71.6% respectively. The paper also presents sensitivity analysis of hybrid system with variation in capital cost of different components.

A high concentrator photovoltaic design is proposed of 5800x geometrical concentration ratio based on multiple primary Fresnel lenses focusing to one central solar cell. The final stage optic is of a novel design, made of a high refractive index (n = ∼1.76), to accept light from four different directions but very easily manufactured. The high geometrical concentration of 5800x was chosen in anticipation of the losses accompanied due to alignment difficulties. Two scenarios are however simulated, one with state of the art optics (achromatic Fresnel lenses and 98% reflective mirrors) and one of standard, relatively cheap optics. An optical efficiency of ∼75% is achieved in simulations if high quality optics are utilised, which gives an optical concentration ratio of just over 4300x. Simulating standard optical constraints with less accurate optics results in an optical efficiency of ∼55% which translates to an optical concentration ratio of ∼3000x. In this way the quality of the optics can be chosen depending on the trade of between cost and efficiency with room for future advanced optics to be incorporated at a later date. The optical efficiency of each component is simulated as well as experimentally measured to ensure the accuracy of the simulations. A theoretical acceptance angle of 0.4° was achieved in ray trace simulations for this design which is considered good for such a high concentration level. The need for achromatic Fresnel lenses is apparent from this study to reach optimum performance and concentration but even 55% optical efficiency results in a >3000x concentration not yet experimentally tested. The solar cells irradiance distribution of the design is also presented along with performance and rough cost comparisons to other systems in the literature. The cost of the optics compared to more complex shaped optics is also given.

Membrane distillation (MD) is a promising thermally driven membrane separation technique. In MD, water vapor is being separated from the hot feed water solution using a microporous hydrophobic membrane, due to the difference in temperature, and hence vapor pressure, across the membrane. Air gap membrane distillation (AGMD) process is one of the common configurations of applying the MD process for water desalination and other applications. In AGMD, a stagnant air gap is introduced between the membrane and a condensation surface within the membrane module to reduce the conduction heat loss through the membrane. In this review article, design characteristics and operating conditions of AGMD and its modified designs to enhance the productivity and reduce the energy consumption are surveyed and discussed. Previous work on pilot AGMD systems and multi-stage or multi-effect systems with energy saving modules is highlighted. Membrane materials and developments used with the AGMD modules are presented with discussion of membrane fouling and scaling problems. In addition, modeling techniques based on the heat and mass transfer equations and simulation approaches of the AGMD process are presented. The merits of operating the AGMD systems with solar and other renewable energies are discussed along with the economic aspects. The future research directions of AGMD are highlighted in this review. This will help researchers to direct their research without repetition of previous known studies.

A contribution of counter electrode (CE) emphasis a great impact towards enhancement of a dye-sensitized solar cell's (DSSC) performance and Pt based CE sets a significant benchmark in this field. Owing to cost effective noble metal, less abundance and industrial large scale application purpose, an effective replacement for Pt is highly demanded. There are several approaches to improve the performance of a CE for enhancing the power conversion efficiency with a less costly and facile device. To address this issue, reasonable efforts execute to find out suitable replacement of Pt is becoming a challenge by keeping the same electrochemical properties of Pt in a cheaper and eco-friendlier manner. With this, cheaper element based quaternary chalcogenide, Cu ZnSnS. (CZTS) becomes a prominent alternative to Pt and used as a successful CE in DSSC also. This review presents brief discussion about the basic properties of CZTS including its synthesis strategy, physicochemical properties and morphology execution and ultimate application as an alternative Pt free CE for a low cost based enhanced DSSC device. It is therefore, imperative for engineering of CZTS material and optimization of the fabrication method for the improvement of DSSC performance. 2 4

In dye-sensitized solar cells (DSSCs), the incoming sunlight can influence many of the key electron transfer processes occurring at the TiO /dye/electrolyte interface. So, the intensity of incident light is crucial in determining the overall efficiency of the devices. Here, transparent DSSC exhibiting an average light transmittance of 53% and high energy conversion efficiency (5.93%) is fabricated. A low solar concentrator with 3X optical concentration is coupled with the device to improve the photovoltaic performance without affecting its transparency. The internal resistances of the fabricated transparent DSSCs with and without the low solar concentrator are analysed using impedance spectroscopy. The results indicate that the charge transfer resistance at the TiO /dye/electrolyte interface of concentrator coupled devices are lower than the bare devices. Moreover, the device active area is scaled up and charge transport properties are compared with a low concentrator coupled device. The overall results show that the concentrator coupled device performs better than the scaled-up device. 2 2

In photovoltaic (PV) cells, a large portion of the solar-irradiance becomes heat which shoots the cell temperature up and decreases its electrical efficiency. The heat can be removed using phase-change-material (PCM) at the rear of the PV. In literature, the researchers have reported the performance of PV-PCM for their respective locations. However, selection criteria for climates suitable for PCM integration are not reported yet. Thus, it has been carried out in the current work. The model has been validated against the experimental measurements. It has been concluded that (i) the climates having less variations in the ambient temperature are more suitable for PCM integration. The electricity enhancement achieved by PV cooling is 9.7%. It reduces to 6.6% for the climate having large variations, (ii) Heat extraction by PCM-systems is more effective in warm climates in comparison to cold climates, (iii) PCM integration performs better in climates with low wind-speed, (iv) PCM is more effective for the climates where wind-flow is across the PV and (v) Climates having high solar-radiation is better for heat removal by PCM.

Concentrating sunlight and focussing it on smaller sized solar cells increases the device's power output per unit active area. However, this process tends to increase the solar cell temperature considerably and has the potential to compromise system reliability. Adding a heat exchanger system to regulate this temperature rise, can improve the electrical performance whilst simultaneously providing an additional source of low temperature heat. In this study the performance of a low concentrator photovoltaic system with thermal (LCPV/T) extraction was conceptualised and evaluated in depth. An experimental analysis was performed using a first-generation prototype consisting of 5 units of Cross Compound Parabolic Concentrators (CCPC) connected to a heat extraction unit. A bespoke rotating table was used as experimental apparatus to effectively evaluate the optical performance of the system, as a function of its angular positions to replicate the motion of actual sun. Key design performance parameters for the LCPV/T collector are presented and discussed. This work also provides a useful technique to effectively calculate system performance, as a function of the orientation-dependant electrical characterisation parameters data. Finally, a Computational Fluid Dynamics (CFD) model was also applied to investigate the efficacy of the heat exchanger and hence estimate the overall co-generation benefit of using such optimisation techniques on realistic CPV systems. It was highlighted through these simulations that the water flow rate had the potential to be a critical power-generation optimisation criterion for LCPV-T systems. The maximum power output at normal incidence with concentrators and no water flow was found to be 78.4 mW. The system was found to perform with an average electrical efficiency ranging between 10 and 16% when evaluated at five different geographic locations. Experimental analysis of the data obtained showed an increase in power of 141% (power ratio 2.41) compared to the analogous non-concentrating counterpart. For example, in the case of London which receives an annual solar radiation of 1300 kWh/m. the system is expected to generate 210 kWh/m. This may reduce further to include losses due to temperature, reflectance/glazing losses, and electrical losses in cabling and inverter by up to 36% leading to an annual power output of 134 kWh/m. of module. 2 2 2

The daylighting performance of a polymer dispersed liquid crystal (PDLC) switchable glazing has been evaluated using an unfurnished outdoor south-facing test cell with a glazing-to-wall ratio of 1:9. Useful daylight illuminance levels (UDI) were determined for clear sunny, intermittent cloudy and overcast cloudy days. Daylight glare indexes (DGI ) was calculated for the PDLC glazing in its transparent and translucent states. An electrically-actuated adaptive PDLC switchable glazing with transparency that varied between 27% and 71% was able to control daylight glare. N

Present study aims at minimising the risk of bending in receiver of Parabolic Trough Collector (PTC) using double layered absorber held at pillars and mathematical equations are formulated. Tube is modelled for practical scenarios supported by pillars made up of movable structure that can slide to help absorber expand when heated. Ball joints at contact points enable tube to rotate. Equations are validated against the experimental measurements. Effects of placement of conductive material, focal length, PTC width, geometrical imperfections and HTF flow rate on bending and energy losses due to bending are studied. It is found that (i) single layered absorber leads to bending and energy loss of −15.1 mm and 2.3%. Double layered absorber with high conductivity material as inside layer reduces bending/energy loss to −10.0mm/1.0%. However, use of high conductivity as outside layer further reduces bending/energy loss to −6.1mm/0.4%, (ii) change in HTF flow rate from 0.4 kg/s to 1.4 kg/s reduces bending/energy loss from −15.1mm/2.3% to −10.2mm/1.0% for single layered absorber and −6.1mm/0.4% to −4.5mm/0.2% for double layered and (iii) focal length near to 0.7 m reduces bending/energy loss to 0mm/0%.

In this paper, we compare the optical and electrical performance of different Fresnel-based HCPV systems equipped with different refractive secondary optical elements (SOEs) through both optical modelling and experiments. The SOEs (designed with a thorough optical modelling): i) Dielectric-cross compound-parabolic-concentrator (DCCPC), ii) (SIngle-Lens-Optical element) SILO-Pyramid, iii) Refractive truncated pyramid (RTP) and, iv) Trumpet; are fabricated (made of PMMA) and mounted on commercially available concentrator solar cell assemblies. An indoor characterisation of all these HCPV units, under controlled conditions, using a CPV Solar Simulator “Helios 3198” is performed. The angular behaviour of the HCPV units is predicted properly, in general, although the measured optical efficiencies result in lower values than in the optical simulations. The reasons for those differences are explored through some fabrication and mounting imperfections detected, among others. The impact of changed irradiance and spectrum is analysed separately. No high dependence in the efficiency or in the acceptance angle, in terms of the maximum power point, was found due to changes in the irradiance. For changed spectral conditions, the decrease in the fill factor results in up to around 4% lower than the maximum values. Moreover, the impact of the spectrum on the acceptance angle was analysed. The results showed an increment of the power-based acceptance angle for blue-rich spectra for the HCPV units with SOEs working as light pipes. From the results of efficiency and acceptance angle, none of the SOEs produces a notably performance than the others.

Photovoltaic (PV) cells absorb the incident solar radiation while operation of which, majority part causes heating leading to the hampered electrical efficiency. PVs can be integrated with phase change material (PCM) to maintain cell temperature within desired limits and the effect can be improved by deploying fins. The current work aims at analysing the effect of climate on the electrical performance of finned PCM integrated PV. Modelling of system has been done which has been validated using experimental results. For the study, fins with various spacings, thicknesses and lengths are used. The main conclusions of the study are, (a) for less alterative climate, the improvement in the PV electrical output (using finned PCM) is 9.7%, 10.8%, 11.3%, 11.6% and 11.6% respectively for a spacing of 1 m, 1/2 m, 1/3 m, 1/4 m and 1/5 m. For highly alterative climate, the respective values reduce to 6.6%, 7.6%, 8.1%, 8.4% and 8.4%, (b) for warmer climate, the output increases by 10.1%, 11.3%, 11.8%, 12.1% and 12.1% while for colder climate, it increases only by 5.4%, 6.1%, 6.5%, 6.7% and 6.7%, (c) for windy climate, the power increments are significantly lesser as compared to the other case, (d) climate having higher wind azimuth results in better performance of finned PCM, and (e) for clear sky climate, performance of finned PCM is better.

Recently, oxynitrides materials such as β-TaON has been using as a photoanode material in the field of photocatalysis and is found to be promising due to its suitable band gap and charge carrier mobility. Computational study of the crystalline β-TaON in the form of primitive unit cell, supercell and its N, Ta, and O terminated surfaces are carried out with the help of periodic density functional theory (DFT). Optical and electronic properties of all these different species are simulated, which predict TaON as the best candidate for photocatalytic water splitting contrast to their Ta O. and Ta N. counterparts. The calculated bandgap, valence band, and conduction band edge positions predict that β-TaON should be an efficient photoanodic material. The valence band is made up of N 2p orbitals with a minor contribution from O 2p, while the conduction band is made up of Ta 5d. Turning to thin films, the valence band maximum; VBM (−6.4 eV vs. vacuum) and the conduction band minimum; CBM (−3.3 eV vs. vacuum) of (010)-O terminated surface are respectively well below and above the redox potentials of water as required for photocatalysis. Charge carriers have smaller effective masses than in the (001)-N terminated film (VBM −5.8 and CBM −3.7 eV vs. vacuum). However, due to wide band gap (3.0 eV) of (010)-O terminated surface, it cannot absorb visible wavelengths. On the other hand, the (001)-N terminated TaON thin film has a smaller band gap in the visible region (2.1 eV) but the bands are not aligned to the redox potential of water. Possibly a mixed phase material would produce an efficient photoanode for solar water splitting, where one phase performs the oxidation and the other reduction. 2 5 3 5

In this study, intermediate transmissions, colour-rendering index (CRI) and correlated colour temperature (CCT) of an electrically actuated, switchable polymer dispersed liquid crystal (PDLC) glazing have been investigated. This 0.03 m. PDLC glazing changes its state from translucent to transparent in the presence of a 20 V AC power supply. Modulation of visible and NIR transmissions were observed for different applied voltages and no modulation was found in the UV range. For this particular type PDLC glazing, the CCT and CRI varied between 5430 K and 6100 K and 93 to 98, while luminous transmittance varied from 0.27 to 0.71 respectively. Low contrast ratio between the translucent and transparent states of this PDLC glazing offered a strong linear correlation between CCT and CRI. 2

Polymer dispersed liquid crystal (PDLC) glazing is a potential electrically actuated switchable adaptive glazing for low energy building application as it become transparent in the presence of alternating current (AC) power supply and become translucent/opaque without power supply. Optical properties and protection factor for a particular type of PDLC glazing was investigated in this work. Using UV–vis–NIR (1050) spectrophotometer spectral transmittance of this glazing was measured for its both states. PDLC on state needs 20 V AC power supply to offer 41% transmission while without any supply this glazing becomes 23% transparent. In the switch off state LC particles offer forward scattering which makes this glazing translucent with high 82.6% haze. Solar factor for PDLC transparent and translucent state was found to be 0.53 and 0.39 respectively. Glazing protection factors were calculated using spectral transmittance data. Switchable transparency and switchable solar factor makes this glazing suitable to match adaptability of building occupants.

Currently, the photovoltaic (PV) panels widely manufactured on market are composed of stiff front and back layers and the solar cells embedded in a soft polymeric interlayer. The wind and snow pressure are the usual loads to which working PV panels need to face, and it needs the panels keep undamaged under those pressure when they generate electricity. Therefore, an accurate and systematic research on bending behavior of PV panels is important and necessary. In this paper, classical lamination theory (CLT) considering soft interlayer is applied to build governing equations of the solar panel. A Rayleigh–Rita method is modified to solve the governing equations and calculate the static deformation of the PV panel. Different from many previous researches only analyzing simply supported boundary condition for four edges, a special boundary condition which consists of two opposite edges simply supported and the others two free is studied in this paper. A closed form solution is derived out and used to do the numerical calculation. The corresponding bending experiments of PV panels are completed. Comparing the numerical results with experiment results, the accuracy of the analytical solutions are verified.

The use of non-imaging collectors has a wide scope in process heat applications based on its performance and economics. An experimental investigation of trapezoidal/concave cavity surface receiver (TSR) for non-imaging solar concentrating collector is carried out in this paper. The implementation of surface/coil receiver instead of tubular receiver for non-imaging collector is presented in this paper. A TSR with helical coil is developed for non – imaging concentrating collector, Elliptical Hyperbolic Collector (EHC). Experiments are carried to estimate the thermal performance of the system under various operating conditions such as two operating modes: series and parallel modes of operation of the collector, two circulation modes: passive and active modes. The stagnation temperature of the trapezoidal/concave cavity surface receiver is measured to be 118 °C on a clear sunny day in October and 102 °C on a cloudy day in February. The daily performance tests are performed under different operating conditions. Based on the experimental study, for the flow rate of 0.03 kg/min and 0.5 kg/min, the fluid outlet temperature is estimated to be 87 °C at 768 W/m. and 49 °C at 908 W/m. respectively. The corresponding instantaneous efficiency was calculated to be 9% and 40% respectively. The numerical model is developed to predict the temperature of the fluid along the receiver. The pressure drop across a receiver is estimated to be 9.3 kPa for a flow rate of 0.5 kg/min. Exergy analysis of the system is carried out and it ranges between 10 and 20%. The costs involved in fabricating the EHC system are compared to that of a non-imaging concentrating collector (CPC) of same aperture area. An economic analysis of the system is also carried out to study the feasibility of the system based on the life cycle savings method by estimating the annual solar savings from the EHC system. The present system can be a suitable option for low and medium temperature process heat applications. 2 2

Electrically activated switchable polymer dispersed liquid crystal (PDLC) is suitable for adaptive windows. A particular type requires 20 V to become 71% transparent while in the absence of power it is 27% transparent. Glazing transmission changes with light incident angle. As the clearness of a sky changes the fraction changes alter of direct insolation (that has an azimuthally changing incident) and diffuse insolation (that has a largely constant incident). Thus, the effective overall incident angle determining the glazing transmittance also changes. In this work for the first time, the variation of PDLC glazing transmission with clearness index has been investigated. For diffuse sky condition, single glazing transmittance value can be used below a particular clearness index for building energy calculation. This threshold clearness index changes with different azimuthal direction. In Dublin for south facing vertical plane PDLC glazing, yearly usable single transmittance (38% for transparent and 25% for translucent state), transmitted solar energy (TSE) (70 W/m. for transparent state and 20 W/m. for translucent state) and solar heat gain coefficient (SHGC) (0.17 for transparent state and 0.005 for translucent state) for transparent and translucent states were investigated. 2 2

When integrating photovoltaics into building windows, the photovoltaic glazing modules inhibit the function that glass performs, with the additional function of energy production. Semi-transparent Photovoltaic (STPV) glazing will absorb part of the solar radiation incident on the window surface to generate electrical power. In turn, this affects the overall solar energy and natural daylight penetrating into the indoor space. Various factors determine the building energy performance and indoor comfort level as a result of adopting STPV glazing. The factors regarding window design alone (window size, PV glazing coverage ratio and PV glazing placing position) require rigorous study. In this paper, an innovate model (combined optical, electrical and energy model) was developed to comprehensively evaluate the performance of an office equipped with STPV window and firstly analyse the effect of window design on overall energy efficiency. A double-glazing unit integrated with thin film CdTe solar cells with 10% transparency was electrically characterised by Sandia Array Performance Model (SAPM). The annual energy performance of a typical office served by window integrated STPV glazing was investigated through EnergyPlus simulation for various window designs under five typical climatic conditions in China (using weather files of Harbin, Beijing, Shanghai, Guangzhou and Kunming for representation). The optical performance (defined by a Bidirectional Scattering Distribution Function) of this STPV glazing was also obtained using a ray-tracing technique. Then, the annual daylight performance of the porotype office was assessed using RADIANCE. We found that when compared to a conventional double-glazed system, the application of PV window can result in considerable energy saving if the office has a relatively large window-to-wall ratio (i.e. ≥ 45%), while the position of placing STPV glazing has significant influence on the lighting energy consumption. In the specific climates under test, the optimal design scenario of applying window integrated PV can result in a reduction in energy consumption of up to 73%. The simulation results also show that this PV window offers better daylight performance than conventional double glazing and effectively reduces the possibility of glare.

Hybrid PV/Thermal (PV/T) systems can generate both electrical and thermal energy simultaneously. These systems are already finding interesting applications in the fields of desalination, sensible heating/cooling and other allied industrial processes. An effective way to further improve the overall system efficiency is by using V-Trough's to concentrate incoming sunlight and enhance the power output from these systems. In this work, we study the performance of a V-Trough PV/T system connected to a reverse osmosis plant in India. A coupled optical, electrical, and thermal model is presented and validated by experiments. The optical analysis was carried out while including the variations in suns altitude and zenith angle over the day. The impact of the variable inlet water temperature with time is included in the model. The performance of a V-Trough PV/T system is compared with a standard PV system. An average increase of 35% was observed in the electrical power output from the V-Trough PV/T system as compared to the conventional one, with the maximum being 63%. Using the water circulation, an average of 778 BTU/m. of thermal energy was extracted from the V-Trough PV/T system. A maximum temperature difference of 5.2 °C was observed in the feed water at the system outlet, this accounted for a maximum 1/3rd of the total energy recovery when using the V-Trough PV/T system. Feeding heated water to the RO unit in the PV-RO system helped in significantly increasing the quantity and quality of the permeate obtained from the system. A parametric study of the effect of varying mass flow rate on the performance of the system is also discussed. 2

A small-scale phase change material (PCM)-based heat sink can regulate the temperature of electronics due to high latent-heat capacity. Three different heat sinks are examined to study the effects of PCM combination, arrangement of PCMs in multiple-PCM heat sink, PCM thickness, melting temperature and intensity of heat source on the thermal behavior of heat sink. Results are obtained for the temperature distribution across the heat sink and the PCM melting profile. It is concluded that (i) PCM combination RT50-RT55 increases the thermal regulation period and also reduces the heat sink temperature at the end of the operation, (ii) the RT58-RT47 arrangement slightly reduces the maximum temperature as compared to RT47-RT58, (iii) As PCM thickness increases from 30 mm to 60 mm, the thermal-regulation-period increases by 50 min, (iv) As the PCM melting temperature increases, the thermal-regulation-period and the heat sink temperature increase and (v) the thermal-regulation-period decreases as the power rating increases from 1 to 2 W.

Heat generation during the operation of the photovoltaic (PV) cell raises its temperature and results in reduced electrical output. The heat produced in the process can be removed by attaching phase change material (PCM) at the back of the PV panel which can contain the PV temperature substantially and increase its efficiency. Fins can be used inside the PCM container to enhance the heat transfer. In literature, it is observed that as soon as PCM is melted completely, the heat extraction rate of PCM reduces which again leads to increase in PV temperature. However, the study carrying out the optimization of Finned-PV-PCM system to keep PV temperature low during operation for different solar irradiance levels is not available in literature. Thus, in the current study, the most suitable depth of PCM container is calculated for different solar irradiance levels. In addition, how it is affected with spacing between successive fins, fin length and fin thickness has been studied. The best fin dimensions are also calculated. The results show that the most suitable depth of PCM container is 2.8 cm for ∑I. = 3 kWh/m /day and 4.6 cm for ∑I. = 5 kWh/m /day for the chosen parameters. The best spacing between successive fins (to keep PV temperature low) is 25 cm, best fin thickness is 2 mm and best fin length is the one when it touches the bottom of the container. PV, PV-PCM and Finned-PV-PCM systems are also compared. For PV-PCM system (without fins), the most suitable depth of PCM container is 2.3 cm for ∑I. = 3 kWh/m /day and 3.9 cm for ∑I. = 5 kWh/m /day. T T T T 2 2 2 2

The rise in the temperature of photovoltaic (PV) leads to decrease in the solar to electricity conversion efficiency. This paper presents a simulated study to investigate the thermal management of the PV panel using phase change material (PCM). It is found that once the PCM is fully melted, the rate of heat extraction by PCM decreases and, thus, the PV temperature starts increasing rapidly. In literature, the studies related to the performance analysis of the PV-PCM system are available. However, the optimization of the PCM quantity to cool the PV in various operating conditions and solar radiation levels is not available. Thus, it has been carried out in the presented work. The effects of the operating conditions (wind azimuth angle i.e. wind direction, wind velocity, melting temperature of PCM and ambient temperature) on the optimum depth of the PCM container have been analysed. The results show that as wind azimuth angle increases from 0° to 90°, the optimum depth of the PCM container (to maintain the PV at lower temperature) increases from 3.9 cm to 5.3 cm for ∑I. = 5 kWh/m /day and from 2.4 cm to 3.2 cm for ∑I. = 3 kWh/m /day for the chosen parameters. T T 2 2

This paper proposes a new design method to create a novel optical element to generate uniform illumination within a rectangular area. Based on this model, an illuminated area is irradiated by two sets of rays; the first one irradiates the target plane after refraction from the top section of the lens, and the second one irradiates from the reflection at the side profile of the lens and then from refraction at the top part of the lens. The results show that a uniformity of over 90% can be achieved.

Thermal energy storage is important to counter balance demand and supply of energy and maintain balance in the system and boost the use of intermittent renewable energy source. Phase change material-based thermal energy storage has massive potential to substitute large-scale energy demand and assist both economic and environmental benefits. This paper reviews functional principle, thermophysical properties and other material characteristics of different phase change materials for thermal energy storage system. Long-term stability of phase change material and its interaction with storage container have been discussed. Various heat transfer and thermal conductivity enhancement technique to enhance latent thermal energy storage system have been discussed. The paper also examines the schematics of some of the proposed & tested systems and describes the results of prototype setup for thermal load management and application in water heating system and buildings. The paper also summarizes energy and exergy analysis of some thermal energy storage systems.

The colour rendering index (CRI) and correlated colour temperature (CCT) of transmitted daylight through a DSSC glazing is an essential parameter for building interior space comfort. Six small-scale dye-sensitized solar cells (DSSCs) were fabricated by varying TiO. electrode thickness, which offered luminous transmittance between 0.19 and 0.53. Below 0.5 transmittance, the CRI for this TiO. electrode based DSSC glazing was less than 80. A strong linear correlation was found between CCT and CRI. The CRI of 53% transparent DSSC glazing had only 2.7% lower CRI than 77% transparent double glazing and 72% transparent vacuum glazing. 2 2

The absorber-tube of the parabolic trough collector (PTC) witnesses compression and tension while operation due to the thermal gradient developed over the cross-section of the tube. While the researchers have proposed a number of receiver models to improve the energy collection by heat transfer fluid inside the absorber-tube, the stress developed that forms the essential frameworks for the tube's and glass-envelope's safety has not been modelled for real life scenarios where the absorber is held at a number of pillars. The current study models the stress due to compression and tension in a double-layered absorber (held at pillars) having a high conducting material's layer to mitigate the risk of stress significantly. The pillars are movable that ensure the smooth elongation of the absorber-tube under stress. The pillars are equipped with ball-joints that help the tube to rotate in longitudinal plane. The verification of the proposed model has been carried out against the reported results. The impact of placing the high conductive material as inside or outside layer of the double-layered absorber, width and focal-length of PTC, HTF's rate of flow, and the geometrical imperfections on the normal-stress are found out. The performance of the modelled double-layered absorber is observed in contrast with the single-layered one. It is concluded that (i) the single-layered absorber witnesses stress of −127 MPa/+101 MPa due to compression/tension. The one with double-layer undergoes lesser respective stress of −78 MPa/+59 MPa when the high conductivity material is placed on the inner side. Besides, the use of high conductivity material as outside layer reduces the stress further to −38 MPa/+35 MPa. Thus, for minimum stress, the outside layer should always be made up of high conducting material, (ii) increasing the HTF's rate of flow from 0.4 kg/s to 1.4 kg/s results in the reduction of stress from −127 MPa/+101 MPa to −86 MPa/+66 MPa for single-layered absorber. For double-layered absorber, stress comes down from −38 MPa/+35 MPa to −29 MPa/+26 MPa and (iii) an appropriate focal-length of around 0.7 m results in the reduction of stress to almost negligible value of 3 MPa for 3rd generation Luz PTC.

A crossed compound parabolic concentrator (CCPC) is applied into a photovoltaic/thermal (PV/T) hybrid solar collector, i.e. concentrating PV/T (CPV/T) collector, to develop new hybrid roof-top CPV/T systems. However, to optimise the system configuration and operational parameters as well as to predict their performances, a coupled optical, thermal and electrical model is essential. We establish this model by integrating a number of submodels sourced from literature as well as from our recent work on incidence-dependent optical efficiency, six-parameter electrical model and scaling law for outdoor conditions. With the model, electrical performance and cell temperature are predicted on specific days for the roof-top systems installed in Glasgow, Penryn and Jaen. Results obtained by the proposed model reasonably agree with monitored data and it is also clarified that the systems operate under off-optimal operating condition. Long-term electric performance of the CPV/T systems is estimated as well. In addition, effects of transient terms in heat transfer and diffuse solar irradiance on electric energy are identified and discussed.

Scaling laws serve as a tool to convert the five parameters in a lumped one-diode electrical model of a photovoltaic (PV) cell/module/panel under indoor standard test conditions (STC) into the parameters under any outdoor conditions. By using the transformed parameters, a current-voltage curve can be established under any outdoor conditions to predict the PV cell/module/panel performance. A scaling law is developed for PV modules with and without crossed compound parabolic concentrator (CCPC) based on the experimental current-voltage curves of six flat monocrystalline PV modules collected from literature at variable irradiances and cell temperatures by using nonlinear least squares method. Experiments are performed to validate the model and method on a monocrystalline PV cell at various irradiances and cell temperatures. The proposed scaling law is compared with the existing one, and the former exhibits a much better accuracy when the cell temperature is higher than 40 °C. The scaling law of a triple junction flat PV cell is also compared with that of the monocrystalline cell and the CCPC effects on the scaling law are investigated with the monocrystalline PV cell. It is identified that the CCPCs impose a more significant influence on the scaling law for the monocrystalline PV cell in comparison with the triple junction PV cell. The proposed scaling law is applied to predict the electrical performance of PV/thermal modules with CCPC.

The environmental profile of a dielectric-based 3D Building-Integrated Concentrating Photovoltaic (BICPV) device is investigated. Several scenarios and life-cycle impact assessment methods are adopted, including the newly-developed method ReCiPe. Multiple environmental indicators are evaluated for different cities: Barcelona, Seville, Paris, Marseille, London and Aberdeen. The results from the material manufacturing phase demonstrate that the PV cells and the concentrator are the components with the highest contribution to the total impact of the BICPV, based on ReCiPe, Eco-indicator 99, USEtox, CED (cumulative energy demand), GWP (global warming potential) according to different time horizons (20a, 100a, 500a) and Ecological footprint. Among the studied cities, Barcelona, Marseille and Seville present the lowest GWP and CED: less than 142 g CO /kWh and less than 2.9 MJ /kWh, based on all the studied scenarios. Moreover, by considering 30-years lifespan, Barcelona, Marseille and Seville show 0.0107–0.0111 ReCiPe Pts/kWh while London, Paris and Aberdeen present 0.0161-0.0173 ReCiPe Pts/kWh. Results about greenhouse-gas-, energy-, ReCiPe-payback times and energy-return-on-investment are also presented and critically discussed. In addition, comparisons with the literature and issues for the improvement of the environmental profile of the proposed system are included. 2.eq prim

Density functional theory study has been carried out to design a new All-Solid-State dye-sensitized solar cell (SDSC), by applying a donor-acceptor conjugated polymer instead of liquid electrolyte. The typical redox mediator (I /I ) is replaced with a narrow band gap, hole transporting material (HTM). The electronic and optical properties predict that donor and acceptor moieties in the polymeric body have increased the visible light absorption and charge transporting ability, compared to their parent polymers. A unique “upstairs” like band energy diagram is created by packing N3 between HTM and TiO. Upon light irradiation on the proposed configuration, electrons will move from the dye to TiO and from HTM to dye (to regenerate dye), simultaneously. Our theoretical simulations prove that the proposed configuration will be highly efficient as the HOMO level of HTM is 1.19 eV above the HOMO of sanitizer (dye); providing an efficient pathway for charge transfer. High short-circuit current density and power conversion efficiency is promised from the strong overlapping of molecular orbitals of HTM and sensitizer. A low reorganization energy of 0.21 eV and exciton binding energy of 0.55 eV, confirm the high efficiency of HTM. Finally, a theoretical open-circuit voltage of 1.49 eV would results high quantum yield while, the chemical stability of HTM towards oxidation can be estimated from its high ionization potential value (4.57 eV). 1− 3− 2 2

Hydrogen-rich syngas was generated from Jatropha curcas (J. curcas) shell biomass char in a Fresnel lens solar concentrator assembly using solar thermal energy. The assembly had two lenses arranged in such a manner that the focal point of both coincided at a glass reactor, having a specially designed water inlet mechanism. A dual axis automatic solar tracking system working in a closed loop was utilized for continuously maintaining the focal point on the reactor so that the desired high temperature could be obtained for the reaction. The maximum temperature of 1087°C with a geometrical concentration of 215x was reached at the focal plane. The theoretical efficiency of the system was found to be 67.44%. The simulated results of the predicted temperature were first verified experimentally without any reaction mixture, and they differed with an average error of 7.85%. J. curcas shell char was then steam gasified at the focus. A maximum char bed temperature of 736°C could be achieved during the reaction, and 42.77% hydrogen gas was obtained in the combustible gas mixture. In this work, a cost-effective and modular assembly for high-temperature solar steam gasification is designed and fabricated to make the process attractive and environmentally benign.

Transient and steady-state multiphysics numerical simulations are performed to investigate the thermal and electrical performances of a thermoelectric generator (TEG) module placed between hot and cold blocks. Effects of heat radiation, leg length and Seebeck coefficient on the TEG thermal and electrical performances are identified. A new correlation for the Seebeck coefficient with temperature is proposed. Radiation effects on the thermal and electric performances are found to be negligible under both transient and steady-state conditions. The leg length of the TEG module shows a considerable influence on the electrical performance but little on the thermal performance under transient conditions. A nearly linear temperature profile on a leg of the TEG module is identified. The temperature profile of the substrate surfaces is non-uniform, especially in the contacted areas between the straps (tabs) and the substrates.

The natural convective heat transfer phenomenon in an isolated, walled CCPC with PV cell is studied experimentally at 1000 W/m. irradiance and 28.5 °C ambient temperature as well as 0°, 10°, 20°, 30° and 40° incidences in indoor laboratory by using solar simulator. Then a series of numerical simulations are launched to estimate the CCPC natural heat transfer behaviour and optical performance based on steady heat transfer and laminar flow models with grey optical option. It is identified that the heat transfer and optical performances of CCPC are dependent on the incidence. Especially, the PV cell is subject to the highest temperature at an incidence less than 20°, and otherwise the top glass cover is with the highest temperature. The predicted temperatures, Nusselt numbers and heat loss ratios are consistent with the experimental observations basically, especially at the incidence less than 20° with (-10.1∼+3) % error in temperature, (-35.6∼+12.6) % in Nusselt number, and (-1.2∼+20.5) % in CCPC wall heat loss ratio. The optical parameters predicted agree very well with the measurements. The heat loss from the CCPC walls accounts for nearly 60% of the total incoming solar irradiance and should be paid significant attention in the design of CCPC. 2

High Concentrator Photovoltaic (HCPV) units are typically based on the use of Fresnel lenses, refractive secondary optical elements (SOE), and triple-junction (TJ) solar cells. In this work, a detailed optical modeling is applied to analyze the performance of four Fresnel-based HCPV units equipped with different refractive SOEs while considering the subcells current density generation. Wavelength-dependent material properties are utilized while simulating the optical performance. The spectral response of a typical TJ solar cell is also included. This modeling allows to establish the subcell current limitation and the spectral matching ratio, SMR, values in each case. The following SOEs have been used for simulating the HCPV units: (i) Dielectric-cross compound-parabolic-concentrator (DCCPC), (ii) (SIngle-Lens-Optical element) SILO-Pyramid, (iii) Refractive truncated pyramid (RTP) and, (iv) Trumpet. Results show that the HCPV units with SOEs RTP and Trumpet, exhibit bottom subcell current limitation and lowest optical polychromatic efficiency, this is partly due to the irradiance absorption in the bottom cell spectral region and longer optical path length of the concentrated rays within the SOE material. In the case of the HCPV unit with the DCCPC SOE, top and bottom subcells limit the current generation alternatively depending on the misalignment angle of the HCPV unit respect to the simulated sunrays. None of the SMR parameters are equal to 1 under normal alignment of the HCPV units. The short-circuit current density distributions for each subcell in each case are studied under normal alignment and under 1° of misalignment angle.

This paper compares the features and performance of two secondary optics when combined with an LED. The aim and application of the secondary optic are explained in the introduction section. Sections 2 and 3 introduce two optics: a freeform lens and a novel circular dielectric totally internally reflecting optic (CDTIRO), which can provide uniform illumination. The design process, ray tracing simulations and experimental performance of the freeform lens are described in detail in Section 2. The ray tracing simulation and experimental performance of the CDTIRO are presented in Section 3. Section 4 presents a comparison of the features of both lenses and their performance. Both optics can produce over 95% uniformity within an illuminated area. However, the uniformity produced by the freeform lens reduces abruptly compared with the CDTIRO when some parameters such as size and the position of the light source are changed.

To address the intermittency in solar energy system due to unforeseen weather conditions and to improve dispachability, the requirement of Thermal Energy Storage (TES) system is becoming increasingly inevitable. A single tank packed bed thermocline TES system has potential to provide an effective solution. A comprehensive one-dimensional non-thermal equilibrium model is considered and is solved using method of characteristics to investigate energy storage in a single tank packed bed thermocline storage system. Thermal characteristics including temperature profiles and discharge effectiveness with different commercially available Heat Transfer Fluids (HTFs) are explored and analyzed. A tank size of 12.5 m in height and 8 m in diameter is considered with a capacity of 40 MW h for the present study. The effect of porosity on discharge effectiveness of the storage tank with different HTFs is investigated with porosity, ε varied from 0.1 to 0.7. It is found that the discharge effectiveness consistently drops when ε value increases from 0.1 to 0.7 for all the HTFs. Two-dimensional numerical simulation is also carried out to explore the transient temperature distribution inside the tank for different HTFs with a porosity of 0.2. It is observed that as the operation time of the tank increases, filler material eventually loses heat to adjacent fluid and attains equilibrium. The thermocline moves at a faster rate in Solar Salt than the HITEC due to its higher viscosity. t

This paper discusses the prospect of integrating a novel type of low concentration photovoltaic (LCPV) design known as the rotationally asymmetrical compound parabolic concentrator (RACPC) in a building in the United Kingdom. This is done by proposing a number of building integration designs to create a zero carbon building. A cost reduction analysis of installing the LCPV systems in the country is also presented. It was found that an RACPC design could reduce the LCPV module's manufacturing cost by 31.75% and the LCPV module's cost per unit power output by 33.87% when compared with the conventional PV module.

The conjugate refractive reflective homogeniser (CRRH) is experimentally tested within a cassegrain concentrator of geometrical concentration ratio 500× and its power output compared to the theoretical predictions of a 7.76% increase. I–V traces are taken at various angles of incidence and experimental results showed a maximum of 4.5% increase in power output using the CRRH instead of its purely refractive counterpart. The CRRH utilises both total internal reflection (TIR) within its core refractive medium (sylguard) and an outer reflective film (with an air gap between) to direct more rays towards the receiver. The reflective film captures scattered refracted light which is caused by non-ideal surface finishes of the refractive medium. The CRRH prototype utilises a 3D printed support which is thermally tested, withstanding temperatures of up to 60 °C but deforming at >100 °C. A maximum temperature of 226.3 °C was reached within the closed system at the focal spot of the concentrated light. The material properties are presented, in particular the transmittance of sylguard 184 is shown to be dependent on thickness but not significantly on temperature. Utilising both TIR and standard reflection can be applied to other geometries other than the homogeniser presented here. This could be a simple but effective method to increase the power of many concentrator photovoltaics.

Technologies influencing alternative means of transportation have been expanding in recent years due to increasing urbanization and motorization. In this paper, a solar powered electric auto-rickshaw (SPEA) is designed and developed for Indian conditions. The vehicle developed is comprehensively analyzed techno-economically for its viability in the Indian market. The performance analysis of SPEA results in an optimal charging rate of 2 kWh per day with an average solar irradiance of 325 W/m. on a typical sunny day. The discharging characteristics are studied based on different loading conditions. The vehicle achieved a maximum speed of 21.69 km/h with battery discharge rate of 296 W at 90 kg load and also reached a maximum discharge rate of 540 W at 390 kg loading with a maximum speed of 12.11 km/h. Environmental analysis of SPEA indicated that the yearly CO. emissions of 1777 kg, 1987 kg and 1938 kg from using Compressed Natural Gas, Liquefied Petroleum Gas and gasoline engines respectively can be mitigated using SPEA. The financial analysis of SPEA concluded that the investor's payback duration is 24.44% less compared to a gasoline-run vehicle. Socio-Economic analysis of SPEA discussed its significant advantages and showed 15.74% and 0.85% increase in yearly income over gasoline driven and battery driven vehicles. 2 2

The Crossed Compound Parabolic Concentrator (CCPC) is one of the most efficient non-imaging solar concentrators used as a stationary solar concentrator or as a second stage solar concentrator. In this study, the CCPC is modified to demonstrate for the first time a new generation of solar concentrators working simultaneously as an electricity generator and thermal collector. The CCPC is designed to have two complementary surfaces, one reflective and one absorptive, and is named as an absorptive/reflective CCPC (AR-CCPC). Usually, the height of the CCPC is truncated with a minor sacrifice of the geometric concentration. These truncated surfaces rather than being eliminated are instead replaced with absorbent surfaces to collect heat from solar radiation. The optical efficiency including absorptive/reflective part of the AR-CCPC was simulated and compared for different geometric concentration ratios varying from 3.6x to 4x. It was found that the combined optical efficiency of the AR-CCPC 3.6x/4x remained constant and high all day long and that it had the highest total optical efficiency compared to other concentrators. In addition, the temperature distributions of AR-CCPC surfaces and the assembled solar cell were simulated based on those heat flux boundary conditions. It was shown that the addition of a thermal absorbent surface can increase the wall temperature. The maximum value reached 321.5 K at the front wall under 50° incidence. The experimental verification was also adopted to show the benefits of using absorbent surfaces. The initial results are very promising and significant for the enhancement of solar concentrator systems with lower concentrations.

The presentwork analyses, for the first time, the heat transfer frompin micro-fins. The scope of the present paper is comparing thermal performance of plate micro-fin and pin micro-fin arrays under natural convection conditionsin air.Two fin geometries are considered: plate and pin fin arrayswith the same thermal exchanging surfaceare tested. The investigation shows that the pin micro-fins can improve the thermal performance compared toplate micro-fin arrays. Indeed, pin micro-fins are found to have higher heat transfer coefficients and lower thermalresistances, as well as a better material usage. This makes pin micro-fins able to achieve both thermal enhancementand weight reduction than plate micro-fins. The radiative heat transfer is also calculated: a new model to determine the radiative view factors of pin fins is proposed and is used in the analysis. The effect of the orientation is considered as well.

A surfactant-free solution methodology, simply using water as a solvent, has been developed for the straightforward synthesis of single-phase orthorhombic SnSe nanoplates in gram quantities. Individual nanoplates are composed of {100} surfaces with {011} edge facets. Hot-pressed nanostructured compacts (Eg ≈0.85�
eV) exhibit excellent electrical conductivity and thermoelectric power factors (S(2) σ) at 550�
K. S(2) σ values are 8-fold higher than equivalent materials prepared using citric acid as a structure-directing agent, and electrical properties are comparable to the best-performing, extrinsically doped p-type polycrystalline tin selenides. The method offers an energy-efficient, rapid route to p-type SnSe nanostructures.

Unequal impedances of interconnecting cables between paralleled inverters in island mode of microgrids cause inaccurate reactive power sharing when traditional droop control is used. Many in the literature adopt low speed communications between the inverters and a central control unit to overcome this problem. However, the loss of this communication link can be very detrimental to the performance of the controller. This paper proposes an improved reactive power-sharing control method. It employs infrequent measurements of the voltage at the point of common coupling (PCC) to estimate the output impedance between the inverters and the PCC and readjust the voltage droop controller gains accordingly. The controller then reverts to being a traditional droop controller using the newly calculated gains. This increases the immunity of the controller against any loss in the communication links between the central control unit and the inverters. The capability of the proposed control method has been demonstrated in simulation and experiment using a laboratory scale microgrid.

The optical analysis of a concentrating photovoltaic system plays an important role in determining its overall performance. Typically, ray tracing with a standard AM1.5 source spectrum is utilized to carry out this process. However, this does not represent the actual operating conditions experienced by the device. The solar spectrum changes depending on the time and geographic location. In this work, we propose and demonstrate a procedure to include the changing solar spectrum whilst predicting the annual performance of a building integrated concentrating photovoltaic system. Using a statistical approach a frequency of occurrence of the different solar spectrum is estimated for different locations and utilized for carrying out the annual performance prediction of the system. It is found that using the standard spectrum underestimates the actual system performance. The highest optical efficiency of 79.8% was observed for Kemi when considering the actual spectrum values. This value was found to be 1.6% higher than that obtained using AM1.5D spectrum. An average difference of 1.25% was found in the annual performance of the system when evaluated for six different geographic locations.

Integration of renewable energy systems with the appropriate technology plays a pivotal role in resolving the problem of sustainable energy supply. This paper is aimed to describe the concept of integration of biomass and solar concentrated photovoltaic (CPV) energy system. The present study focused particularly on the investigation of performance and emission from a 1.4 kVA Spark Ignition, constant speed generator using raw biogas integrated in hybrid energy system. The experiments are conducted at different fuel flow rates under varying electric loading conditions. Comparing with LPG as fuel, the power deterioration is observed to be 32% on raw biogas, due to its low calorific value. The maximum power output and brake thermal efficiency using biogas is witnessed to be 812W and 19.50% respectively. The exhaust emission analysis of generator using biogas displays considerably reduced carbon monoxide and hydrocarbons whereas there is no significant difference in nitrogen oxides concentration levels while comparing with LPG, ascertaining it to be an eco-friendly fuel. The biogas fuelled electric generator integration with CPV system can attain sustainable rural energy supply.

The race towards achieving a sustainable zero carbon building has spurred the introduction of many new technologies, including the BIPV (building integrated photovoltaic) system. To tackle the high capital cost of BIPV systems, LCPV (low-concentration photovoltaic) technology was developed. Besides the reduction of cost, the LCPV technology also produces clean energy for the building and promotes innovative architectural design. This paper presents a novel type of concentrator for BIPV systems. This concentrator, known as the RADTIRC (rotationally asymmetrical dielectric totally internally reflecting concentrator), was incorporated in a small double glazing window. The RADTIRC has a geometrical concentration ratio of 4.9069x. A series of experiments were carried out to evaluate the performance of the solar PV window both indoors and outdoors. It was found that the RADTIRC-PV window increases the short circuit current by 4.13x when compared with a non-concentrating solar PV window. In terms of maximum power generation, the RADTIRC-PV window generates 0.749 W at normal incidence, 4.8x higher than the non-concentrating counterpart.

Building-Integrated Concentrated Photovoltaic (BICPV) systems integrate easily into built environments, replacing building material, providing benefits of generating electricity at the point of use, allowing light efficacy within the building envelope and providing thermal management. This paper presents a novel experimental evaluation of phase change materials (PCM) to enhance performance of low concentration BICPV system via thermal regulation. Previous studies have primarily focussed on temporal and spatial studies of PCM temperature within the BIPV systems but the current work also discusses the effect of PCM on electrical parameters of the BICPV systems. Due to the inadequacy of the earlier reported model, a new analytical model is proposed and implemented with the in-house controlled experiments. Paraffin wax based RT42 was used within an in-house designed and fabricated PCM containment. An indoor experiment was performed using highly collimated continuous light source at 1000 Wm-2. Results show an increase in relative electrical efficiency by 7.7% with PCM incorporation. An average reduction in module centre temperature by 3.8°C was recorded in the BICPV–PCM integrated system as compared to the naturally ventilated system without PCM. Studies showed that PCM effectiveness varies with irradiance; an increase in relative electrical efficiency by 1.15% at 500 Wm-2, 4.20% at 750 Wm-2 and 6.80% at 1200 Wm-2 was observed.

It is known that compound parabolic concentrators (CPCs) can improve electrical performance of a photovoltaic (PV) flat-plate system. However, a lumped electrical model of a PV cell/module with CPC for assessing performance under different operating conditions is unavailable. In this paper, a six-parameter based model is developed and applied to a PV cell, two PV models with CPC, and a PV module with 2D asymmetric CPC (trough). For validation, CPC with a single PV cell and two CPC modules with 2 × 2 and 9 × 9 PV cells are fabricated and measured in an indoor laboratory under standard test conditions. Results show that the optimised algorithm precisely predicts the six model parameters. A sensitivity analysis is performed to identify the importance of each parameter in the model. Ideality factor, circuit current and reverse saturation current are found to be the most dominant factor, while shunt resistance is the least important with CPC gain coefficient and series resistance are in between. Transient performance of a PV cell with CPC under variable outdoor climate conditions is also examined by coupling optical, thermal and electrical effects.

The Concentrating Photovoltaic (CPV) market is gaining attention worldwide but. a lack of information on the module’s manufacturing is registered. The present work describes the challenges faced to fabricate a densely packed cell assembly for 500× CPV applications. The reasons behind the choice of components, material and processes are highlighted and all the solutions applied to overtake the problems appeared after the prototype’s production are reported. The article explains all the stages required to achieve a successful fabrication, proved by the results of quality tests and experimental investigations conducted on the prototype. A cost breakdown is reported and commented.

In this study we present the Conjugate Refractive Reflective Homogeniser (CRRH) to be used in a 500X Cassegrain photovoltaic concentrator. The CRRH is a dielectric crossed v-trough lined with a reflective film whilst maintaining an air gap between them. This air gap between the two surfaces helps in trapping the scattered light from the refractive geometry and ensures both total internal reflection (TIR) and standard reflection of the escaped rays. A 10-42% drop in optical efficiency has been shown to occur due to varying the surface roughness of the homogeniser in these ray trace simulations for the Cassegrain set up. The CRRH increased the overall optical efficiency by a maximum of 7.75% in comparison to that of a standard refractive homogeniser simulated within the same concentrator system. The acceptance angle and flux distribution of these homogenisers was also investigated. The simple shape of the CRRH ensures easy manufacturing and produces a relatively uniform irradiance distribution upon the receiver. The theoretical benefit of the CRRH is also validated via practical measurements. Further research is required but a 6.7% power increase was measured under a 1000 W/m2 solar simulator at normal incidence for the experimental test.

A compact high concentrating photovoltaic module based on cassegrain optics is presented; consisting of a primary parabolic reflector, secondary inverse parabolic reflector and a third stage homogeniser. The effect of parabolic curvatures, reflector separation distance and the homogeniser’s height and width on the acceptance angle has been investigated for optimization. Simulated optical efficiencies of 84.82 – 81.89 % over a range of ±1 degree tracking error and 55.49% at a tracking error of ±1.5 degrees were obtained. The final singular module measures 169mm in height and 230mm in width (not including structural components such as cover glass).The primary reflector dish has a focal length of 200mm and is afocal with the secondary inverse reflector which has a focal length of 70mm. The transparent homogenising optic has a height of 70mm, an entry aperture of 30 x 30mm and an output aperture of 10 x 10mm to match the solar cell. This study includes an analysis of the optical efficiency, acceptance angle, irradiance distribution and component errors for this type of concentrator. In particular material stability and the surface error of the homogeniser proved to be detrimental in theoretical and experimental testing – reducing the optical efficiency to ~40%. This study proves the importance of material choice and simulating optical surface quality, not simply assuming ideal conditions. In the experimental testing, the acceptance angle followed simulation results as did the optical efficiency of the primary and secondary reflectors. The optical efficiency of the system against increasing solar misalignment angles is given for the theoretical and experimental work carried out.

The thermal performance of a heat exchanger is important for the potential application in an integrated solar cell/module and thermoelectric generator (TEG) system. Usually, the thermal performance of a heat exchanger for TEGs is analysed by using 1D heat conduction theory which ignores the detailed phenomena associated with thermo-hydraulics. In this paper, thermal and momentum transports in two different heat exchangers are simulated by means of a steady-state, 3D turbulent flow k-ϵ model with a heat conduction module under various flow rates. In order to simulate the actual working conditions of the heat exchangers, a hot block with an electric heater is included in the model. The TEG module is simplified by using a 1D heat conduction theory, so its thermal performance is equivalent to a real TEG. Natural convection effects on the outside surfaces of the computational domains are considered. Computational models and methods used are validated under transient thermal and electrical experimental conditions of a TEG. The two heat exchangers designed in this paper have better thermal performance than an existing heat exchanger for TEGs. More importantly, the fin heat exchanger is more compact and efficient than the tube heat exchanger.

Due to the fact that solar and wind power is intermittent and unpredictable in nature, higher penetration of their types in existing power system could cause and create high technical challenges especially to weak grids or stand-alone systems without proper and enough storage capacity. By integrating the two renewable resources into an optimum combination, the impact of the variable nature of solar and wind resources can be partially resolved and the overall system becomes more reliable and economical to run. This paper provides a review of challenges and opportunities / solutions of hybrid solar PV and wind energy integration systems. Voltage and frequency fluctuation, and harmonics are major power quality issues for both grid-connected and stand-alone systems with bigger impact in case of weak grid. This can be resolved to a large extent by having proper design, advanced fast response control facilities, and good optimization of the hybrid systems. The paper gives a review of the main research work reported in the literature with regard to optimal sizing design, power electronics topologies and control. The paper presents a review of the state of the art of both grid-connected and stand-alone hybrid solar and wind systems.

The goal of this paper is to introduce a model to predict the maximum power of a high concentrator photovoltaic module. The model is based on simple mathematical expressions and atmospheric parameters. The maximum power of a HCPV module is estimated as a function of direct normal irradiance, cell temperature, and two spectral corrections based on air mass and aerosol optical depth. In order to check the quality of the model, a HCPV module was measured during one year at a wide range of operating conditions. The new proposed model shows an adequate match between actual and estimated data with a root mean square error (RMSE) of 2.67%, a mean absolute error (MAE) of 4.23 W, a mean bias error (MBE) of around 0%, and a determination coefficient (R 2) of 0.99.

In concentrating photovoltaic (CPV) applications, the sunlight is focused onto solar cells up to thousands of times and, without an adequate cooling system, the cell’s temperature can dangerously raise over the operating temperature range in few seconds. In this study, an investigation on micro-finned heat sink for high concentrating photovoltaics has been conducted. The geometry of the system and the choice of the components play an important role in the thermal management of CPV. The size of cell, as well as the optics, can strongly affect the thermal behaviour of the CPV: the effects of the CPV geometry on the thermal performance of the heat sink are experimentally investigated and discussed in order to design an optimised system for passive cooling. A micro-fin array is developed to handle the heat generated by the cell and the system is studied in different conditions to prove the applicability of this passive solution to the harsh CPV conditions. It has been found that micro-fins are a suitable solution for passive cooling at concentrations up to 500×. Moreover, this kind of solutions shows the potential to achieve high mass-specific power values, proving its competitiveness in mobile or tracked systems, such as CPV.

© 2015 the Author(s) Semiconducting Ba6−3xNd8+2xTi18O54 ceramics (with x = 0.00 to 0.85) were synthesized by the mixed oxide route followed by annealing in a reducing atmosphere; their high-temperature thermoelectric properties have been investigated. In conjunction with the experimental observations, atomistic simulations have been performed to investigate the anisotropic behavior of the lattice thermal conductivity. The ceramics show promising n-type thermoelectric properties with relatively high Seebeck coefficient, moderate electrical conductivity, and temperature-stable, low thermal conductivity; for example, the composition with x = 0.27 (i.e. Ba5.19Nd8.54Ti18O54) exhibited a Seebeck coefficient of S1000K = 210 µV/K, electrical conductivity of σ1000K = 60 S/cm, and thermal conductivity of k1000K = 1.45 W/(m K), leading to a ZT value of 0.16 at 1000 K.

News article published on Butterfly-inspired technique could make solar energy cheaper, our discovery initially published in our University of Exeter website, followed by more than 110 press article world wide

A series of four new porphyrin-furan dyads were designed and synthesized by having anchoring group either at meso-phenyl or pyrrole-β position of a zinc porphyrin based on donor-π-acceptor (D-π-A) approach. The porphyrin macrocycle acts as donor, furan hertero cycle acts as π-spacer and either cyanoacetic acid or malonic acid group acts as acceptor. These dyads were fully characterized by UV-Visible, 1H NMR, MALDI-MS and fluorescence spectroscopies and cyclic voltammetry. Both of the observed and TD-DFT simulated UV-vis spectra has strong correllation which validate and confirm the synthesiszed dyads and theoretical method for this type of compounds. Both soret and Q-bands are red shifted in the case of pyrrole-β substituted dyads. The redox potentials of all four dyads are not altered in comparison with their individual constituents. The dyads were tested in dye sensitized solar cells and found pyrrole-β substituted zinc porphyrins are showing better performance in comparison with the corresponding meso-phenyl dyads. Optical band gap, Natural bonding, and Molecular bonding orbital (HOMO-LUMO) analysis are in favour of pyrrole-β substituted zinc porphyrins contrast to meso-phenyl dyads.

A prototype concentrating photovoltaic (CPV) module was designed and constructed with a low concentrating dielectric compound parabolic concentrator (DiACPC) for outdoor characterisation. The designed concentrator has acceptance half angles of 0° & 55° with a concentration ratio of 2.8. This concentrator design is suitable for building facade integration in higher latitude (>55°) locations. A small prototype CPV module of 300mm×300mm was constructed with 2 strings of 14 solar cells in series. The prototype CPV module was characterised in Edinburgh for different weather conditions and the performance is compared with a similar non-concentrating counterpart (i.e. a flat-plate module with the same PV cell area and technology) in real time. The electrical output results for a cloudy day, rainy day and a day with sunny intervals have been reported to evaluate the performance of the concentrating system with direct and diffuse irradiance. The maximum power output of the CPV module on the day with sunny intervals was found to be 5.88W for a solar radiation input of 943W/m , which is 2.27times higher than that for the flat-plate module. The average short circuit current of the CPV module was found to be 2.22times higher than that of the flat-plate module. The average open circuit voltage and fill factor of the CPV module were also found to be 2.5% and 1.6% higher than that for the flat-plate module. The CPV module is found to be very effective on the rainy day with an average power output of 0.13W, which is 2.17times higher than the average output power for the flat-plate module. 2

The increasing environmental concerns on photovoltaic (PV) materials have attracted much attention to environment-friendly materials for solar energy conversion. In this paper, the environment-friendly materials based on dye-sensitized solar cells (DSSC), CuZnSnSSe2 (CZTS), and CH3NH3SnI3 based on perovskite solar cells have been studied for their spectral dependence at selected different locations with varying parameters such as air mass, aerosol optical depth, and precipitable water. The spectral dependences of the materials have been obtained by the use of the spectral factor, and ground-based long-Term climatologies in conjunction with the Simple Model of the Atmospheric Radiative Transfer of Sunshine have been used. Results show that the perovskite and DSSC solar cells show an important spectral dependence with annual spectral gains up to 3% and spectral losses up to-15%. On the other hand, CZTS solar cells show a low spectral dependence with annual spectral gains up to 2% and spectral losses up to-4%.

The high conversion efficiency of perovskite solar cells has opened a potential market for solar cells based on low cost manufacturing techniques which could change the photovoltaic (PV) production road map. Although the 9% efficient 10 cm x 10 cm perovskite mini module has been reported, in depth analysis of the longevity of perovskite modules is required before being introduced to the market. Apart from the impressive demonstrated conversion efficiencies, these cells need to be tested under real climatic conditions in order to understand the integrity of their performance. This article briefly outlines significant spectral dependence at selected locations with varying parameters such as air mass, aerosol optical depth and precipitable water. Perovskite solar cells have shown significant dependence on the incident spectrum due to their strong absorption in the visible region. The influences of spectral variations on the performance of perovskite solar cells were studied under different atmospheric conditions. The demonstrated spectral losses by the perovskite solar cells in different climatic conditions are vital for the perovskite solar cell community to further improve their stability.

The interest in micro-technologies has increased in the last decades, because of the low volumes and high performance granted by their application. Micro-fins can find application in several fields, such as power electronics, concentrating photovoltaics and LED. Although micro-technologies have been widely applied in cooling, there is still a lack of knowledge on the thermal behavior of micro-finned heat sinks under natural convective conditions. In the present study, the correspondences between fin geometries and heat transfer coefficients, as well as the effects of the orientation, are experimentally investigated using silicon micro-finned heat sinks with different geometries. The heat sinks are made of 5cm × 5cm squared silicon wafer and the fin height ranges between 0.6mm and 0.8mm, the spacing between 0.2mm and 0.8mm and the thickness between 0.2 and 0.8mm. Power loads higher than those considered in previous works are studied. The experimental setup is validated using a software simulation and the Nusselt number correlation available in literature. The influence of the fin thickness on this parameter is analyzed and a modified correlation is proposed. Also, the effect of the radiative heat exchange on the overall heat transfer is considered and commented. An analysis of the uncertainty is conducted and reported too.

The electrical modelling of HCPV (high concentrator photovoltaic) modules is a key issue for systems design and energy prediction. However, the electrical modelling of HCPV modules shows a significantly level of complexity than conventional photovoltaic technology because of the use of multi-junction solar cells and optical devices. In this paper, a method for the simulation of the I-V curves of a HCPV module at any operating condition is introduced. The method is based on three different ANN (artificial neural networks)-based models: one to spectrally correct the direct normal irradiance, one to predict the cell temperature and one to generate the I-V curve of the HCPV module. The method has the advantage that is fully based on atmospheric parameter and outdoor measurements. The analysis of results shows that the method accurately predicts the I-V curve of a HCPV module for a wide range of atmospheric operating conditions with a RMSE (root mean square error) ranging from 0.19% to 1.66% and a MBE (mean bias error) ranging from-0.38% to 0.40%.

The concept of a high-concentration optical system is introduced detailing the various design types and focusing only on those aimed at photovoltaic (PV) applications. This will include point focus, line focus, imaging, nonimaging, and the classical cassegrain set-up. The theory of high-concentration optics is explained in terms of idealised concepts and maximum limits for each concentrator type and combination. The optical system is broken down into the different stages and materials possible in a high-concentration configuration. The physics of reflective and refractive optics are described, and their associated errors, advantages and a brief overview of past milestones, and recent research trends in the area of high-concentration PVs are presented. Current primary and secondary optics are geometrically explained covering Fresnel, parabolic, heliostat, compound parabolic, hyperboloid, v-trough, and dome-shaped optics. This chapter also covers examples of new secondary optics, such as the three-dimensional crossed-compound parabolic concentrator and the square elliptical hyperboloid concentrator. The aim of this chapter is to provide the basic optical behaviour of high-concentration designs aimed at PV applications considering their geometry, materials, and reliability.

The optical analysis of a concentrating photovoltaic system plays an important role in determining its overall performance. Typically, ray tracing with a standard AM 1.5 source spectrum is utilized to carry out this process. However, this does not represent the actual operating conditions experienced by the device. The solar spectrum changes depending on the time and geographic location. In this work, we propose and demonstrate a procedure to include the changing solar spectrum whilst predicting the annual performance of a building integrated concentrating photovoltaic system. Using a statistical approach a frequency of occurrence of the different solar spectrum is estimated for different locations and utilized for carrying out the annual performance prediction of the system. It is found that using the standard spectrum underestimates the actual system performance. The highest optical efficiency of 79.8% was observed for Kemi when considering the actual spectrum values. This value was found to be 1.6% higher than that obtained using AM 1.5D spectrum. An average difference of 1.25% was found in the annual performance of the system when evaluated for six different geographic locations.

Life-cycle analysis of a Concentrating Photovoltaic (CPV) for building-integrated applications is conducted. Two configurations (with and without reflective film) are examined: based on embodied energy/embodied carbon, multiple scenarios and databases. Several environmental indicators are calculated for Exeter, Barcelona, Madrid, Dublin and Paris. Among the studied cities, considering both configurations, Greenhouse-gas Payback Time (GPBT) has the highest values for Paris (27.2-33.1 years) and the lowest values for Dublin (3.3-4 years). Regarding Energy Payback Time (EPBT) (average based on two databases; CPV with reflective film), Barcelona and Madrid show the minimum values (about 2.4 years) while Paris, Exeter and Dublin show EPBTs 3.2-3.5 years. Reflective film results in 0.2% increase in system initial footprint (embodied energy and embodied carbon; material manufacturing of the modules) while on a long-term basis, this additional impact is compensated (since the CPV with reflective film has higher electrical output). By using the reflective film there is a reduction of about 11-12% in EPBT and GPBT, depending on the scenario. The energy return on the investment is also evaluated, showing the highest values for Madrid and Barcelona among the studied cities. Moreover, EPBT is calculated with an alternative way by considering replacement of the materials of a wall.

Solar energy is one of the renewable energy sources that has shown promising potential in addressing the world's energy needs, particularly via the solar PV (photovoltaic) technology. However, the high cost of installation is still being considered as the main obstacle to the widespread adoption of solar PV system. The use of solar concentrators is one of the solutions that could help to produce lower cost solar PV systems. One of the existing concentrator designs is known as the RADTIRC (rotationally asymmetrical dielectric totally internally reflecting concentrator) which was developed in GCU (Glasgow Caledonian University) since 2010. This paper aims at optimising the existing RADTIRC prototype by increasing its electrical output whilst keeping the cost of the system at minimum. This is achieved by adopting a better material and a different technique to fabricate the concentrator. The optimised RADTIRC prototype was fabricated from PMMA (polymethyl-methacrylate) using injection moulding. It was found that the optimised RADTIRC-PV prototype generated an opto-electronic gain of 4.48 when compared with the bare cell under STC (standard test conditions). A comparison with the old prototype showed that the optimised RADTIRC-PV prototype increased the short circuit current by 13.57% under STC.

Due to its special features, one of the problems of high concentrator photovoltaic (HCPV) technology is the estimation of the electrical output of an HCPV module. Although there are several methods for doing this, only some of them can be applied using easily obtainable atmospheric parameters. In this paper, four models to estimate the maximum power of an HCPV module are studied and compared. The models that have been taken into account are the standard ASTM E2527, the linear coefficient model, the Sandia National Laboratories model, and an artificial neural network-based model. Results demonstrate that the four methods show adequate behavior in the estimation of the maximum power of several HCPV modules from different manufacturers.

The low-concentration photovoltaic (LCPV) system has been identified as one of the potential solutions in lowering the overall installation cost of a building integrated photovoltaic (BIPV) system. This paper evaluates the performance of a novel type of LCPV concentrator known as the rotationally asymmetrical compound parabolic concentrator (RACPC). A specific RACPC design with a geometrical concentration ratio of 3.6675× was fabricated and integrated with a 1. cm by 1. cm monocrystalline laser grooved buried contact silicon solar cell. This design was tested indoors to evaluate its current-voltage (. I-. V), angular response and thermal characteristics. Under standard test conditions, it was found that the RACPC increases the short circuit current by 3.01× and the maximum power by 3.33× when compared with a bare solar cell. The opto-electronic gain from the experiment showed good agreement when compared with the simulation results, with a deviation of 11%.

Building Integrated Concentrating Photovoltaics (BICPV) is a promising solution leading toward self-sustaining buildings. In this work, we have evaluated the performance of one such system carrying out detailed modeling and indoor experiments. The system has a geometric concentration of 6× and typically consists of a dielectric based Symmetric Elliptical Hyperboloid (SEH) concentrating element attached to a silicon solar cell. The incoming light incident on the top surface is concentrated and reaches the solar cell in a non-uniform fashion. Part of this concentrated light is converted to electricity and rest is dissipated in the form of heat. In order to analyze the performance of such a system, a coupled optical, electrical and thermal analysis is required. Using the non-uniform flux distribution obtained by the optical analysis, the electrical modeling of the solar cell is carried out at different incident angles. Modeling showed a maximum power ratio of 3.7 which is in line with the experimental values under a constant solar cell temperature. Several loss mechanisms occur in the system under actual operating conditions. Losses occurring due to the absorption of light over a range of spectrum were quantified by performing an External Quantum efficiency analysis. The losses occurring due to the solar cell temperature were evaluated while carrying out a coupled electrical and thermal analysis of the system. A maximum temperature of 319 K was observed on the solar cell surface under normal incidence. An average drop of 11.7% was found making the effective power ratio of the system 3.4.

Dye sensitized solar cells (DSSC) have become a topic of significant research in the last two decades because of their fundamental and scientific importance in the area of energy conversion. Ease of fabrication with widely available materials coupled with reasonable efficiency has made DSSC a promising candidate in low cost solar cells and its research. The use of synthetic dyes as sensitizer in DSSC provide better efficiency and high durability, but they suffer from several limitations such as higher cost, tendency to undergo degradation, and usage of toxic materials. These limitations have opened up for alternate sensitizers that are bio compatible natural sensitizers. Natural sensitizers contain plant pigments such as anthocyanin, carotenoid, flavonoid, and chlorophyll that are responsible for chemical reactions such as absorption of light as well as injection of charges to the conduction band of TiO2 by the sensitizer. Therefore, dyes containing these pigments can easily be extracted from natural products like fruits, flowers, leaves, seeds, barks etc and can be employed as sensitizer for DSSC.
The main objective of this review is to discuss the operation of natural dye based DSSC along with the various components that are present in it. It also details and tabulates the various plant pigments present in the natural products which are employed as sensitizer in DSSC. Furthermore, a detailed summary of the work carried out by different research groups on natural dye based DSSC is also reviewed. Issues on stability and future development of natural dye based DSSCs have been addressed.

In recent times, the micro-technologies have gained prominence in various engineering applications. The micro-technologies are already in use for cooling purposes in several systems, but the information on the thermal performance of micro-fins under natural convective heat transfer conditions is yet limited. The correlations between heat transfer coefficients and fin geometry have already been investigated, but are not sufficient to optimize the design of the micro-finned arrays. For this reason, the present investigation gives an overview of micro-fins behavior taking into account, for the first time, different heat sink metrics: the fin effectiveness and the mass specific heat transfer coefficient. The results of an original experimental investigation are merged with the data available in literature. Natural convective micro-fins are able to achieve overall fin effectivenesses higher than 1.1. Even if not always beneficial in terms of heat transfer, micro-fins are found always positive in terms of the material usage. In this light, micro-fins can be considered advantageous in those applications that require a minimized weight of the heat sinks. Moreover, a limited effect due to the orientation is observed.

The encapsulant is an important element used for mechanical bonding and optical coupling between the concentrator and the solar cell in a typical concentrating photovoltaic system. In this work we explain the concept of trapping the light escaping through the optical concentrator - encapsulant interface. Understanding how the losses incur is important for the development of concentrating photovoltaic systems. A case study is performed on a 3D Cross Compound Parabolic Concentrator (3DCCPC) based low concentrating photovoltaic system. Detailed optical analysis is presented quantifying the losses based on the thickness of the encapsulant spillage. Simulation results show that the optical efficiency drops from 84.5% to 55.6% whilst increase in the encapsulant spillage thickness from 0.1 mm to 3 mm. Use of reflective film is made along the bottom edges of the concentrator in order to make the interface region optically inactive to carry out refraction and trap the escaping light. Modelling shows that the optical losses can be completely managed by the use of the reflective film. Experiments are carried out by building a prototype in order to demonstrate the concept and validate the results. The short circuit current is found to increase by a maximum of 8.5%. A maximum power ratio of 2.73 is observed at an incidence angle of 10° for the system using the reflective film compared to 2.56 without the reflective film.

Low concentration photovoltaic (LCPV) modules for building integration are considered to have great potential because it offers several advantages over conventional photovoltaic technology. However, one of the problems of this technology is that as yet there are no models in the literature to directly calculate the maximum power of these kinds of systems. The development of models is an important task to promote the application of this technology because it allows the prediction of the energy yield. In this paper a model based on artificial neural networks has been developed to address this important issue. The model takes into account all the main important parameters that influence the electrical output of these kinds of systems: direct irradiance, diffuse irradiance, module temperature and the transverse and longitudinal incidence angles. The results show that the proposed model can be used for estimating the maximum power of a LCPV module for building integration with an adequate margin of error. © 2013 Elsevier Ltd.

Smart grid is a technology for reliable integration and intelligent control of multiple generation units where the loads spread across a non-uniform or a uniform distribution network. The basic frame work of a smart grid is made to ease the complexity of integration of Distributed Renewable Energy Sources (DRES) with greater grid penetration, reduction of transmission losses, optimized energy capacity expansion with better demand side management and hierarchical control for grid security. Smart grids consists of four unique features which can be given as Integration, Control, Communication and Metering (ICCM). Integration refers to connection of heterogeneous type of energy sources with AC or DC grid using appropriate converters. Power output of the DRES is dependent on climatic conditions like wind speed and solar irradiance. Controls in smart grids are made intelligent to extract the maximum power from the sources, operational scheduling of energy sources and overloads, control of transients, real and reactive power. For effective operation of the diverse smart grid, communication between various control nodes is necessary. Communication standards for smart grids usually are set by protocols, and most of them involve the interconnection of Secure Communication Line (SCL) to the main control unit by LAN (Local Area Network), HAN (Home Area Network), and WAN (Wide Area Network). The interconnection should be accompanied with a firewall at various levels for the cyber security of the smart grid. Smart metering employed in smart grids provides additional information of the electrical energy consumed compared to conventional energy meters. Smart metering can measure the energy parameters of the load remotely and transfer the data through the communication network. This paper presents different methods of ICCM in smart grid. © 2014 Elsevier Ltd.

This paper presents the design and experimental analysis of a static 3-D solar elliptical hyperboloid concentrator (EHC) for process heat applications. The 3-D static elliptical hyperboloid concentrator is designed to accept a wide range of incidence angles (±30°) and has a concentration ratio of 20× for medium temperature applications (100-150°C). Ray tracing analysis has been used to obtain, the solar flux distribution on the receiver aperture plane for the EHC configuration. The optical efficiency has been obtained theoretically using Optis , a ray tracing program and optimisation has been carried out, before the design of the EHC was finalised and experimentally tested. The experiments were carried out for different conditions to study the performance of EHC. The experimental study has also been carried out to obtain the inlet and outlet temperature of a fluids supplied to a coil heat exchanger solar receiver. © 2014. TM

The desalination of water is a process wherein the brackish water is purified by removing the salts. With increasing demand for fresh water, there is a vast scope for development of sea water desalination process. A number of methods exist for the desalination process, but solar desalination method promises to save energy in today's energy crunch scenario. A novel solar desalination setup is proposed here. It uses an elliptic hyperboloid concentrator and a helical receiver along with a multi-tray desalination unit to purify water in the most effective manner. The helical receiver proposed in the present work aims at the Dean Flow effect in order to enhance heat transfer in laminar flow. The effectiveness of this property with respect to various physical parameters has been observed and an optimum design has been suggested based on this. The elliptic hyperboloid concentrator is a special design for concentrating solar radiation because of it offers to operate at high efficiency without the requirement of tracking. A detailed ray-tracing code was developed to simulate the radiation incident on the concentrator and an accurate estimation of the optical efficiency was made based on this. The two systems were integrated in order to arrive at a maximum output level for the solar desalination system as a whole. © 2014 Elsevier Ltd.

A novel densely packed receiver for concentrating photovoltaics has been designed to fit a 125× primary and a 4× secondary reflective optics. It can allocate 16 1cm2-sized high concentrating solar cells and is expected to work at about 300 Wp, with a short-circuit current of 6.6 a and an open circuit voltage of 50.72 V. In the light of a preliminary thermal simulation, an aluminum-based insulated metal substrate has been use as baseplate. The original outline of the conductive copper layer has been developed to minimize the Joule losses, by reducing the number of interconnections between the cells in series. Slightly oversized Schottky diodes have been applied for bypassing purposes and the whole design fits the IPC-2221 requirements. A fullscale thermal simulation has been implemented to prove the reliability of an insulated metal substrate in CPV application, even if compared to the widely-used direct bonded copper board. The Joule heating phenomenon has been analytically calculated first, to understand the effect on the electrical power output, and then simulate, to predict the consequences on the thermal management of the board. The outcomes of the present research will be used to optimize the design of a novel actively cooled 144-cell receiver for high concentrating photovoltaic applications. © 2014 the Authors.

A numerical heat transfer model was developed to investigate the temperature of a triple junction solar cell and the thermal characteristics of the airflow in a channel behind the solar cell assembly using nonuniform incident illumination. The effects of nonuniformity parameters, emissivity of the two channel walls, and Reynolds number were studied. The maximum solar cell temperature sharply increased in the presence of nonuniform light profiles, causing a drastic reduction in overall efficiency. This resulted in two possible solutions for solar cells to operate in optimum efficiency level: (i) adding new receiver plate with higher surface area or (ii) using forced cooling techniques to reduce the solar cell temperature. Thus, surface radiation exchanges inside the duct and Re significantly reduced the maximum solar cell temperature, but a conventional plain channel cooling system was inefficient for cooling the solar cell at medium concentrations when the system was subjected to a nonuniform light distribution. Nonuniformity of the incident light and surface radiation in the duct had negligible effects on the collected thermal energy. © 2014 Fahad Al-Amri and Tapas Kumar Mallick.

In the present study, we model and analyse the performance of a dielectric based linear concentrating photovoltaic system using ray tracing and finite element methods. The results obtained are compared with the experiments. The system under study is a linear asymmetric CPC (Compound Parabolic Concentrator) designed to operate under extreme incident angles of 0° and 55° and have a geometrical concentration ratio of 2.8×. Initial experiments showed a maximum PR (power ratio) of 2.2 compared to a non concentrating counterpart. An improvement to this has been proposed and verified by adding a reflective film along the edges of the concentrator to capture the escaping rays and minimise optical losses. The addition of the reflective film changes the incoming distribution on the solar cell. Results show an increase of 16% in the average power output while using this reflective film. On including the thermal effects it was found that the overall benefit changes to about 6% while using a reflective film. Additionally, the effects of the non-uniformity of the incoming radiation are also analysed and reported for both the cases. It is found that adding the reflective film drops the maximum power at the output by only 0.5% due to the effect of non-uniformity. © 2014 Elsevier Ltd.

Results are presented for a concentrated solar photovoltaic and thermal powered membrane distillation (MD) system for seawater desalination. Solar intensity data was input into a mathematical model for the solar energy system and outlet temperature from the energy system was calculated. The MD module was tested for a fluctuating inlet temperature, as would be produced from a solar energy source. A maximum distillate flux of 3.4 l/m2h was recorded, though this did not correspond to the highest inlet temperature. An observed delay in the modules response to the fluctuations in temperature was due to the thermal mass of the MD unit. The conductivity of the distillate was measured to assess the effects of transient operation on the quality of the distillate produced. It was determined that although the quantity and quality of the distillate varied with the fluctuations in power supplied to the module, the effects were not significant enough to rule out the integration of the MD module with solar energy. © 2014 the Authors.

Japan started implementing a national Feed-In Tariff (FiT) mechanism on the 1st July 2012, which included specific payment tariffs for solar photovoltaic (PV) installations. This marks a new era in the renewable energy landscape in Japan. This paper aims at analysing the solar PV prospect in Japan, particularly in both residential and non-residential sectors. The paper presents, first, an overview of energy trends in Japan prior to the Fukushima event. This is followed by a short review of solar PV progress in the country, highlighting the major policies and programmes that have been implemented as well as the installations that have been carried out over the past two decades. Next, the financial impact of the new FiT scheme on consumers is evaluated. The financial analysis investigates the total profit, the average annual return on investment and the payback period. For a comparison purposes, a similar financial analysis is also conducted with selected countries around the world - namely Germany, Italy and the United Kingdom. The results from this analysis indicate that the new Japanese FiT rate generates a good profit, a moderate annual return on investment and an acceptable payback period, suggesting an increasing trend of solar PV uptake over the next years. © 2014 Elsevier Ltd.

This short communication paper focuses on the renewable heat incentive (RHI) scheme in the United Kingdom (UK); and in particular, on its implication on domestic installations of solar thermal systems (STSs). First, a short review on the STS in the UK is provided. Then, a detailed description of the RHI is discussed. A financial analysis is presented afterwards, analysing the impact of the RHI scheme on the applicants, in terms of the net present value and the internal rate of return. From the financial analysis it has been found that the RHI scheme for domestic installations is only attractive if a longer period of RHI payment, i.e. 17 years, or a higher RHI rate i.e. £0.32 per kW. h is implemented. The current proposal from the UK government is not financially viable, and as a result, it may hinder the penetration of domestic solar thermal systems in the residential sector in the UK. © 2013 Elsevier Ltd.

The electrical modelling of HCPV (high concentrator photovoltaic) modules is a key issue for systems design and energy prediction. However, the electrical modelling of HCPV modules shows a significantly level of complexity than conventional photovoltaic technology because of the use of multi-junction solar cells and optical devices. In this paper, a method for the simulation of the I-V curves of a HCPV module at any operating condition is introduced. The method is based on three different ANN (artificial neural networks)-based models: one to spectrally correct the direct normal irradiance, one to predict the cell temperature and one to generate the I-V curve of the HCPV module. The method has the advantage that is fully based on atmospheric parameter and outdoor measurements. The analysis of results shows that the method accurately predicts the I-V curve of a HCPV module for a wide range of atmospheric operating conditions with a RMSE (root mean square error) ranging from 0.19% to 1.66% and a MBE (mean bias error) ranging from-0.38% to 0.40%.

This paper describes a novel type of solar concentrator - a mirror symmetrical dielectric totally internally reflecting concentrator (MSDTIRC). This new concentrator type has been designed to satisfy the following objectives: (i) to provide optimum gain in two different planes, therefore increasing the electrical output of a solar photovoltaic (PV) system, and (ii) to reduce the amount of the PV cell material needed, hence minimising the cost of the system. The concentrator is capable of having two different acceptance angles on different planes. The procedure of designing an MSDTIRC is explained and the geometrical properties are analysed in detail. In addition, the optical concentration gain is presented for various angles of incidence. Through simulation results, it is demonstrated that the MSDTIRC provides significant optical concentration gain within its acceptance angle, as high as 13.54× when compared with non-concentrating solar cell. It can be concluded that the MSDTIRC can be a way to produce a low cost solar PV system and can be chosen as an alternative design for the BIPV systems. © 2013 Elsevier Ltd.

Concentrating photovoltaic (CPV) technology is one of the fastest growing solar energy technologies achieving higher electrical conversion efficiencies. The increase in temperature of solar CPV cell significantly reduces the performance; the efficiency of a CPV system can be improved by introducing effective thermal management or cooling system. This paper presents the design and numerical analysis of a heat sink based on micro-channels for efficient cooling of a commercial high concentration photovoltaic (HCPV) cell. A combinatory model of an array of micro-channels enclosed in a wide parallel flow channel design is developed. The optimized geometry of the micro-channel heat sink was found by using commercial CFD software ANSYS 13. Based on numerical simulations, it is found that the optimum configuration of micro-channel with 0.5mm width and aspect ratio of 8. The micro-channels provided high heat transfer over heat generations spots and parallel flow channels resulted in lower pressure drop. The temperature rise across the micro-channel is estimated as10K in CPV module of 120 × 120 mm2 and with a pressure drop of 8.5 kPa along a single channel with six such channels in each modules at a flow rate of 0.105 liter/s. © 2014 the Authors.

The use of concentrating photovoltaic systems (CPV) in building integration has spurred towards the development of newer products, which have the potential to offer the convenience of pleasing architecture and day lighting along with simultaneous production of clean energy. This paper addresses the energy transformations and the expected energy output of a low concentrating photovoltaic system designed to have a geometric concentration of 3.6×. The optical element used is a three dimensional Cross Compound Concentrator (3DCCPC) made from clear polyurethane material. Small sized silicon solar cells based on the Laser Grooved Buried Contact (LGBC) technology having an absorber area of 1cm. are utilised in the system. Both experimental and numerical analyses are performed confirming the optical, electrical and thermal performance of the system. While performing the optical analysis the concentrator was found to have a maximum optical efficiency of 73.4%. A maximum power ratio of 2.67 was observed when comparing the electrical output of the concentrator unit with a non-concentrating counterpart. The effects of non-uniformity caused by the use of the concentrator are analysed. The non-uniformity of flux distribution showed an average drop of 2.2% in the I. values which is again reflected in the overall power output. Manufacturing defects like the cell and concentrator misalignments are addressed and their impact on the overall performance are verified by numerical simulations. The operating temperature of the solar cells was found to have a parasitic effect on the overall performance of the system. A maximum temperature of 332K was observed in the solar cell at 0° incidence and a incoming radiation of 1000W/m. which brings down the overall power production by 14.6%. Finally, the expected system output over a given time period is presented showing the strengths and weakness while employing such a system. © 2014 Elsevier Ltd. 2 2 sc

This paper describes a novel type of solar concentrator - a rotationally asymmetrical compound parabolic concentrator (RACPC). The RACPC aims at addressing the following objectives: (i) to increase the electrical output of a concentrating photovoltaic (CPV) system by providing sufficient concentration gain; (ii) to minimise the usage of the PV material with the corresponding reduction of CPV system cost, and (iii) to eliminate the requirement of mechanical tracking by providing a wide field-of-view. This paper first provides a short review on variations of compound parabolic concentrator designs available to date. Next, the process of designing the RACPC is presented and the geometrical concentration gain of the concentrator is discussed. In addition, the optical concentration gain is also presented for various angles of incidence. Through simulations, it is demonstrated that the RACPC can provide significant optical concentration gains within its designed acceptance angle. An RACPC based system is an attractive alternative to conventional solar photovoltaic systems.

In the present paper, a heat transfer model for a multi-junction concentrating solar cell system has been developed. The model presented in this work includes the GaInP/GaAs/Ge triple-junction solar cell with a ventilation system in which air is forced to flow within a duct behind the solar cell assembly and its holders and accessories (anti-reflective glass cover, adhesive material, and aluminum back plate). A mathematical model for the entire system is presented and the finite difference technique has been used to solve the governing equations. Results showed that the interaction of surface radiation and air convection could adequately cool the solar cell at medium concentration ratios. For high concentration ratios, the channel width would need to be narrowed to micro-meter values to maintain the required efficiency of cooling. The conjugation effect has been shown to be significant and has a noticeable effect on the maximum solar cell temperature. Furthermore, the air inlet velocity and channel width were also found to have major effects on the cell temperature. © 2013 Elsevier Ltd. All rights reserved.

Concentrating technology is long established in the field of solar thermal applications. However, there is still scope for improvement due to innovation in design, materials and manufacturing methods. The optical efficiency of a solar concentrator depends largely on the geometry of the concentrator profile. This paper evaluates the optical performance of a static 3-D Elliptical Hyperboloid Concentrator (EHC) using ray tracing software. Ray tracing has been used extensively to calculate the optical efficiency of the static 3-D EHC. Performance parameters such as effective concentration ratio, optical efficiency and geometric concentration ratio are also evaluated for different aspect ratios of the elliptical profile. Optimization of the concentrator profile and geometry is also carried out to improve the overall performance; this parametric study includes the concentrator height, solar incidence angle and aspect ratio of the ellipse. The overall performance of the concentrator was assessed based on the acceptance angle, effective concentration ratio and optical efficiency. Finally, the flux distribution on the receiver area for different concentrator heights is also presented. © 2012.

Optical fibres can add interesting possibilities in solar concentrator systems, such as transport of light for remote illumination as well as solar energy conversion. In order to effectively couple light from the sun into optical fibres, the key parameters that control the coupling efficiency should be identified. In this paper, the results of ray-tracing simulations of a novel two-stage solar concentrator and optical fibre are compared to experimental measurements. In particular, the coupling efficiency is optimised by analysing focal ratio and acceptance angle of the primary and secondary concentrators respectively, while solar concentration is exceptionally obtained as a function of wavelength to examine the spectral dependence of the system. The trend towards narrower acceptance angles resulted in improvement of the coupling efficiency and a maximum concentration ratio of 2000 suns (1 sun=1KW/m ) at the end of a single fibre, spectrally adjusted by controlling the chromatic aberration of the primary concentrator. Any mismatch between the primary and secondary concentrators significantly reduces the coupling efficiency, especially the angle of the secondary concentrator, which should be kept below the 50% of the numerical aperture of the fibre for maximum performance. By optimising these parameters and achieving efficient coupling, utilisation of solar energy applications via optical fibres, can be brought one step closer to useful commercial applications. © 2013 Elsevier Ltd. 2

This paper focuses on the renewable heat incentive (RHI) scheme in the United Kingdom (UK); and in particular, on its implications in relation to solar thermal systems (STSs). First, a short review on the UK's energy demand is provided. Then, an overview of the past and present activities related to STS installations is discussed, covering regulation, policies and programmes, research and development expenditures and implementations. A financial analysis is presented afterwards, analysing the RHI scheme, in terms of total profit, payback period and average annual return on investment. This is based on installations of different sizes and at various levels of solar insolation. The analysis also presents the reduction of carbon dioxide emissions that could be achieved by installing an STS. From the financial analysis it is found that the RHI scheme could generate a good total profit, a high average annual return on the investment and an 'acceptable' payback period, depending on locations. As a result, it could increase the penetration of solar thermal systems in the UK. Significant reductions of carbon dioxide emission can also be achieved by installing an STS on a building. © 2013 Elsevier Ltd.

Concentrator solar cells need to be designed optimally depending on the concentrating photovoltaic (CPV) system, application and operating conditions to ensure the best system performance. The important factors while designing include concentration ratio, cell material properties, expected operating temperature, cell shape, bus bar configuration, number of fingers their size and spacing. The irradiation incident on the solar cell while being concentrated experiences several losses caused by the different physical phenomena's occurring in the system. A particular issue for CPV technology is the non-uniformity of the incident flux on the solar cell which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Understanding of this effect and designing the cell while considering these issues, would help in improving the overall performance of the system. This study focuses on modelling a low concentrating photovoltaic system used for building integration, optimising the cell metallisation and analysing the effects of temperature on the overall output of the system. The optical analysis of the concentrator is carried out using ray tracing and finite element methods to determine electrical and thermal performance under operating conditions. Furthermore, an analysis is made to understand the effects of non-uniformity on the output of the device. About 0.5% absolute drop in solar cell efficiency was observed due to non-uniformity at 5. incident angle. A relative drop of 1.85% was observed in the fill factor due to non-uniformity of the flux distribution. A maximum cell temperature of 349.5 K was observed across the cell in both uniform and non-uniform conditions under an incident solar radiation of 1000 W/m. which further reduced the performance of the solar cell. The solar cell design was also analysed by varying the number of fingers and the optimum grid design reported. A small prototype concentrator based on the design proposed was made using polyurethane and tested experimentally with the optimized solar cell design. On comparing the results obtained using the experimental data a good agreement in the system output could be seen. The difference in the overall system output was seen to be of the order of 11% which could be due to several losses occurring in the prototype which were not accounted in the model. © 2013 Published by Elsevier B.V. All rights reserved. o 2

Concentrating photovoltaic technology is one of the fastest growing solar energy technologies achieving electrical conversion efficiency in excess of 43%. The operating temperature of a solar cell strongly influences the performance of a photovoltaic system reducing its efficiency with a negative temperature coefficient. Thus, cooling systems represent a very important aspect in concentrating photovoltaic applications. This work presents an overview of micro- and nano-technologies applicable to passive CPV cooling and associated manufacturing technologies (such as monolithic applications). Among the different technologies, carbon nano-tubes and high-conductive coating are the most promising technologies to offer the best CPV cooling performance. A critical assessment of the technological review has also been made. © 2012 Elsevier Ltd.

In this work, three different geometrical properties have been considered to develop a new solar concentrator design for Window Integrated Concentrating Photovoltaic (WICPV). They are (i) elliptical entry aperture; (ii) hyperbolic profile section and (iii) square exit aperture. Due to the increasing demands for stationary solar concentrators for building integrated photovoltaic (BIPV), this new design focuses on the use as a stationary solar concentrator. The complete optical analysis of the concentrator is carried out via 3-D ray trace technique. The analysis is based on all necessary design parameters, i.e. elliptical entry axis, concentrator height and the exit aperture geometry, in order to obtain the optimal overall optical performance of the new 3-D solar concentrator. Four different geometrical low concentration ratios were investigated: 4×, 6×, 8× and 10×. Results of the computer simulation show that the designed concentrator of 4× concentration ratio gives the higher optical efficiency of 68% compared to the other low concentration ratios. The 6×, however, gives a higher optical concentration ratio, despite having a lower optical efficiency (55%) than the 4×. A prototype of the designed concentrator was manufactured and tested under indoors conditions. The experimental results have shown an agreement by a difference of 5% with the simulation results. These results highlight how different factors need to be taken into consideration when carrying out optimisation studies. Overall, the proposed concentrator looks promising with sound results to confirm its performance and validate it as a stationary solar concentrator and thereby promote its use in WICPV. © 2013 Elsevier Ltd.

Static solar concentrators present a solution to the challenge of reducing the cost of Building Integrated Photovoltaic (BIPV) by reducing the area of solar cells. In this study a 3-D ray trace code has been developed using MATLAB in order to determine the theoretical optical efficiency and the optical flux distribution at the photovoltaic cell of a 3-D Crossed Compound Parabolic Concentrator (CCPC) for different incidence angles of light rays. It was found that the CCPC with a concentration ratio of 3.6× represents an improved geometry compared to a 3-D Compound Parabolic Concentrator (CPC) for the use as a static solar concentrator. The CCPC has a maximum optical efficiency of 95%, in line with the optical efficiency of the 3-D CPC, with the added advantage of having a square entry and exit aperture. A series of preliminary experimental measurements were taken on a setup of nine solar cells. The experimental results provide validation of the MATLAB code developed, showing a deviation of 12 ± 2% from the simulation results, thus confirming that the code can be used to investigate different concentration ratios of the CCPC. © 2012 Elsevier Ltd.

A reflective 3D crossed compound parabolic-based photovoltaic module (3D CCPC PV) was designed and its electrical and optical performance was analyzed for building integrated photovoltaic applications. A maximum power concentration of 3.0× was achieved compared to similar type of non-concentrating module. The reduction of the concentration factor from the geometrical concentration of 3.61× for the designed 3D CCPC were due to manufacturing errors, mismatch losses, series resistance losses, and thermal loses. The experimental output was validated by developing a MATLAB simulation code for its electrical performance. Good agreements were observed between experimental and electrical simulation with maximum electrical conversion efficiency of the concentrating system of 14%. The experimental characterization of the optical efficiency was found to show a deviation of 19.4% from the 3D ray tracing simulation efficiency of 94.6% for direct incidence. This deviation is mainly due to the fact that 3D ray tracing simulation does not take the non-uniform illumination distribution into account. Copyright © 2012 John Wiley & Sons, Ltd. In this paper, a reflective 3D crossed compound parabolic concentrator based photovoltaic module was designed, fabricated and characterised for BIPV application. The measurements shows that the power increased by a factor of 3 compared to the similar solar cell area. Copyright © 2012 John Wiley & Sons, Ltd.

An extensive indoor experimental characterisation program to investigate the heat loss from a point focus Fresnel lens PV Concentrator (FPVC) with a concentration ratio of 100× was performed for a range of simulated solar radiation intensities between 200 and 1000W/m. different ambient air temperatures, and natural and forced convection. From the experimental program it was found that the solar cell temperature increased proportionally with the increase in simulated solar radiation for all experimental tests, indicating that conductive and convective heat transfer were significantly larger than the long wave radiative heat transfer within and from the FPVC system. For the simulated worst case scenario, in which the FPVC system was tested under a simulated solar radiation intensity of 1000W/m. and ambient air temperature of 50°C with no forced convection, the predicted silicon solar cell efficiency in the FPVC system was reduced to approximately half that at standard test conditions. © 2011 Elsevier Ltd. 2 2

In this paper, a numerical study of combined natural convection and surface radiation heat transfer in a solar trapezoidal cavity absorber for Compact Linear Fresnel Reflector (CLFR) is presented. The CFD package, FLUENT 6.3 is used to develop the 2-D, non-Boussinesq, steady state, laminar, combined natural convection and surface radiation heat transfer model for a trapezoidal cavity absorber. The validation of the present non-Boussinesq numerical procedure is compared with other closed cavity model. Based on the validated non-Boussinesq model, the combined heat loss coefficients are predicted for various parameters such as Grashof number, absorber angles, surface emissivity, aspect ratio, temperature ratio and radiation-conduction number. The numerical simulation results are presented in terms of Nusselt number correlation to show the effect of these parameters on combined natural convection and surface radiation heat loss. © 2011 Elsevier Ltd.

After a gap of more than two decades, Concentrator Photovoltaics (CPV) technology is once again under spotlight for making use of the best available solar cell technologies and improving the overall performance. CPV finds its use in a number of applications ranging from building integration to huge power generation units. Although the principles of solar concentration are well understood, many practical design, operation, control issues require further understanding and research. A particular issue for CPV technology is the non-uniformity of the incident flux which tends to cause hot spots, current mismatch and reduce the overall efficiency of the system. Understanding of this effect requires further research, and shall help to employ the most successful means of using solar concentrators. This study reviews the causes and effects of the non-uniformity in the CPV systems. It highlights the importance of this issue in solar cell design and reviews the methods for the solar cell characterization under non-uniform flux conditions. Finally, it puts forward a few methods of improving the CPV performance by reducing the non-uniformity effect on the concentrator solar cells. © 2012 Elsevier Ltd.

The low concentrating photovoltaic (PV) system such as a 2× V-trough system can be a promising choice for enhancing the power output from conventional PV panels with the inclusion of thermal management. This system is more attractive when the reflectors are retrofitted to the stationary PV panels installed in a high aspect ratio in the north-south direction and are tracked 12 times a year manually according to preset angles, thus eliminating the need of diurnal expensive tracking. In the present analysis, a V-trough system facing exactly the south direction is considered, where the tilt angle of the PV panels' row is kept constant at 18.34°. The system is installed on the terrace of CSIR-Central Salt and Marine Chemicals Research Institute in Bhavnagar, Gujarat, India (21.47 N, 71.15 E). The dimension of the entire PV system is 9.64 m×0.55 m. The V-troughs made of anodized aluminum reflectors (70% specular reflectivity) had the same dimensions. An in-house developed; experimentally validated Monte Carlo ray-trace model was used to study the effect of the angular variation of the reflectors throughout a year for the present assembly. Results of the ray trace for the optimized angles showed the maximum simulated optical efficiency to be 85.9%. The spatial distribution of solar intensity over the 0.55 m dimension of the PV panel due to the V-trough reflectors was also studied for the optimized days in periods that included solstices and equinoxes. The measured solar intensity profiles with and without the V-trough system were used to calculate the actual optical efficiencies for several sunny days in the year, and results were validated with the simulated efficiencies within an average error limit of 10%.

The focus of this research is to develop a solar concentrator which is compact, static and, at the same time, able to collect maximum solar energy. A novel geometry of a 3-D static concentrator has been designed and coined the Square Elliptical Hyperboloid (SEH) to be integrated in glazing windows or facades for photovoltaic application. The 4× SEH is optically optimised for different incident angles of the incoming light rays. The optimised SEH is obtained by investigating its different non-dimensional parameters such as major axis over minor axis of the elliptical entry and the height over side of the exit aperture. Evaluating the best combination of the optical efficiency and the acceptance angle, results confirm that the 4× SEH built from dielectric material, working with total internal reflection, is found to have a constant optical efficiency of 40% for an acceptance angle equal to 120° (-60°, +60°). This enables capture of the sun rays all day long from both direct beam light and diffuse light making it highly suitable for use in northern European countries. A higher optical efficiency of 70% is obtained for different dimensions of the SEH; however, the acceptance angle is only 50°. The optimised SEH concentrator has been manufactured and tested; the experimental results show an agreement with the simulation results thus validating the optical model. © 2012 Elsevier Ltd. All rights reserved.

In this paper, a novel multi-stage evacuated solar desalination system is developed by utilizing latent heat recovery. A transient model is proposed for the solar desalination system. The effect of various design and operating parameters on the system performance is studied to optimize the configuration. The distillate yield increases initially due to enhanced evaporation caused by the presence of a thin layer of water in the stages. The distillate yield decreases with increase in salinity of water due to an increase in ion activity and the reduction of thermodynamically spontaneous change from liquid to vapor. The optimum number of stages, gap between the stages and the supplied mass flow rate for the system were found to be 4, 100mm and 55kg/m. /day respectively throughout the year. The overall thermal efficiency of the system is found to be 53.9% and 29.6% for the months March and December respectively in India. The maximum yield of 53.2kg/m. /day is found in March at an operating pressure of 0.03bar. The multi-stage evacuated solar desalination system is a viable option to meet the needs of rural and urban communities. © 2011 Elsevier B.V. 2 2

The integration of concentrating solar thermal collectors into the structural envelope of buildings can significantly increase the cost effectiveness of solar thermal utilisation in the UK. The key, however, to their wide scale application is performance. Typically, most solar thermal collectors are mounted on inclined roof structures, thus presenting an optimal surface area for solar gain. Vertical building facades offer an alternative mounting surface and whilst they may have an overall lower level of incident solar radiation, the collector receives a more uniform annual distribution of solar radiation, reducing potential summer over heating problems. Furthermore, facade integration is beneficial to the building performance as the collector unit results in a higher U-value realising higher building heat retention. In concentrating solar thermal collector systems, the absorbing surface area is reduced relative to that of the aperture, leading to a reduction in the overall heat loss from the system, hence improving thermal efficiency. To maximise collection in a vertically mounted concentrating solar thermal collector however, the concentrator profile should be optimised to benefit solar collection relative to the mounting inclination. This paper presents the optical and experimental investigation of a low concentration line axis solar thermal collector employing symmetric and asymmetric CPC geometries. The potential for collected solar radiation when façade integrated has been investigated with the use of three-dimensional ray trace. Several prototype units were fabricated and experimentally evaluated. A series of fluid flow configurations (serpentine and parallel) using different flow velocities have been investigated and a range of slope angles (β) considered. Results from this study have shown that this type of concentrating solar thermal collector has particular application for domestic hot water production and that the design can effectively operate in the vertical orientation and is suitable for building façade integration in Northern European locations. © Springer-Verlag Berlin Heidelberg 2011.

Three different greenhouse prototype designs: gable, flat and semi-circle roof shapes were investigated at the Faculty of Agriculture, Suez-Canal University, Egypt. Investigations were carried out to find out the effect of using the adobe (trombe) wall as solar heat storage used for greenhouse passives heating. The study was conducted under controllable weather conditions and outdoor under the prevailing weather conditions of the site of experiments. A range of cheap and readily available materials were said to form the adobe or adobe wall, i.e. clay (13.3%), clay painted with matt black paint (which has absorbability of 0.95%), sand (96.7% sandy attached by 2.5% gypsum, on the weight basis) and the sandy wall was painted black. These walls were compared with the controlled greenhouse without the wall. Investigations were carried out on greenhouse sandy soil (96.7%) with five different moisture contents of air dry, 25, 50, 75, and 100% from the field capacity. Greenhouse air temperature, soil-depth and solar wall temperatures gradient were investigated for the different walls of the different greenhouses deign under different investigation conditions. The study revealed that, the flat shape greenhouse surfaces gives higher air temperatures when the direction of the greenhouse was north-south, while the span surfaces shape for the east-west direction at the same investigation conditions. © 2010 Elsevier B.V. All rights reserved.

Recent research in Building Integrated Photovoltaics (BIPV) is reviewed with the emphases on a range of key systems whose improvement would be likely to lead to improved solar energy conversion efficiency and/or economic viability. These include invertors, concentrators and thermal management systems. Advances in techniques for specific aspects of systems design, installation and operation are also discussed. © 2009 Elsevier Ltd.

We present a detailed design concept and optical performance evaluation of stationary dielectric asymmetric compound parabolic concentrators (DiACPCs) using ray-tracing methods. Three DiACPC designs, DiACPC-55, DiACPC-66, and DiACPC-77, of acceptance half-angles (0° and 55°), (0° and 66°), and (0° and 77°), respectively, are designed in order to optimize the concentrator for building façade photovoltaic applications in northern latitudes (>55 °N). The dielectric concentrator profiles have been realized via truncation of the complete compound parabolic concentrator profiles to achieve a geometric concentration ratio of 2.82. Ray-tracing simulation results show that all rays entering the designed concentrators within the acceptance half-angle range can be collected without escaping from the parabolic sides and aperture. The maximum optical efficiency of the designed concentrators is found to be 83%, which tends to decrease with the increase in incidence angle. The intensity is found to be distributed at the receiver (solar cell) area in an inhomogeneous pattern for a wide range of incident angles of direct solar irradiance with high-intensity peaks at certain points of the receiver. However, peaks become more intense for the irradiation incident close to the extreme acceptance angles, shifting the peaks to the edge of the receiver. Energy flux distribution at the receiver for diffuse radiation is found to be homogeneous within ±12% with an average intensity of 520 W/m².

The numerical study of solar cell temperature for concentrating PV with concentration ratio of 10× is presented in this paper. A two dimensional thermal model has been developed to predict the temperature for PV concentrator system (solar cell and lens) with and without passive cooling arrangements. Based on a thermal model, the result shows that maximum of four numbers of uniform fins of 5 mm height and 1 mm thickness can be effectively used to reduce the solar cell temperature. In addition to that, the effects of ambient temperature and solar radiation intensity on the solar cell temperature have also been investigated for the system with and without cooling fins. Based on the influencing parameters of ambient temperature and solar radiation, two separate solar cell temperature correlations has been proposed for systems with and without cooling fins to predict the cell temperature for the range of given parameters. In our previous studies, the present 2-D model was extensively validated with a comprehensive unified model [8-10]. Crown Copyright © 2011 Published by Elsevier Masson SAS. All rights reserved.

Second generation prototype photovoltaic facades of reduced costs incorporating devices with optically concentrating elements (PRIDE) incorporate 6 mm wide 'Saturn' solar cells at the absorber of the dielectric concentrator. The concentrators were made using injection moulding technique with potential to manufacture in large-scale applications. Four different concentrator panels have been experimentally verified at outdoors to identify the non-identical current-voltage (I-V) curves. The I-V curve, fill factor and solar to electrical conversion efficiency of four PRIDE concentrator modules have been evaluated from the 24 manufactured in the 'IDEOCONTE' project. The maximum solar to electrical conversion efficiency and the fill factor of the PRIDE concentrator were 91 and 70%, respectively. The mismatch loss of the 'unit concentrators ' has been identified that occurred due to the lack of bonding between the concentrator unit and the solar cell and the rear glass. The average power concentration ratio of PRIDE concentrators manufactured by the improved method was 210 compared to a similar non-concentrating panel and the optical efficiency of the PRIDE system was 83%. Copyright ©2008 John Wiley & Sons, Ltd.

Prototype first generation Photovoltaic Facades of Reduced Costs Incorporating Devices with Optically Concentrating Elements (PRIDE) technology incorporating 3 and 9 mm wide single crystal silicon solar cells showed excellent power output compared to a similar non-concentrating system when it was characterized both indoors using a flash and continuous solar simulator. However, durability and instability of the dielectric material occurred in long-term characterisation when the concentrator was made by using casting technology. For large scale manufacturing process, durability, and to reduce the weight of the concentrator, second generation PRIDE design incorporated 6 mm wide "Saturn" solar cells at the absorber of dielectric concentrators. Injection moulding was used to manufacture 3 kWp of such PV concentrator module for building façade integration in Europe. Special design techniques and cost implications are implemented in this paper. A randomly selected PV concentrator was characterised at outdoors from twenty-four (≈3 kWp) 2nd-G PRIDE manufactured concentrators. The initial PV concentrators achieved a power ratio of 2.01 when compared to a similar non-concentrating system. The solar to electrical conversion efficiency achieved for the PV panel was 10.2% when characterised outdoors. In large scale manufacturing process, cost reduction of 40% is achievable using this concentrator manufacturing technology. © 2007 Elsevier B.V. All rights reserved.

An asymmetric compound parabolic photovoltaic concentrator (ACPPVC) of geometrical concentration ratio 2 was designed, developed and evaluated for building façade integration. Despite the two times theoretical concentration, the maximum output power achieved was only 1.62 times that of a similar non-concentrating system for a wide range of solar radiation intensities due to a combination of optical and electrical resistance losses. In this paper, the power loss of the ACPPVC system is explained by a comparative power loss analysis of the non-concentrating photovoltaic system for long- and short-tabbed solar cell strings that showed an average of 3.4% electrical power loss due to resistance in the interconnections between each individual solar cell. The optical losses of the ACPPVC were 15% caused by the combined effect of the number of reflections at the reflectors and the misalignment of the imperfection in the reflector geometry solar cells in addition to the power loss due to increased temperature of 0.6%. Good agreement was found between the measured and calculated optical efficiency of the system. © 2007 Elsevier B.V. All rights reserved.

Air filled asymmetric compound parabolic photovoltaic concentrators (ACPPVC) have been studied using a comprehensive validated unified model for optics and heat transfer in line-axis solar energy systems. The heat transfer that occurs within the cavity of a single concentrator, multiple concentrators, the space between adjacent concentrators and in an air duct behind the photovoltaics was simulated and is presented. For a range of insolation intensities incident at the aperture cover the maximum PV cell operating temperatures are determined. From the simulations undertaken the effects on solar cell surface temperatures resulting from air flow in the air filled space at the front of the system and in the air duct to the rear of the solar cells are clearly evident. © 2006 Elsevier Ltd. All rights reserved.

Concentration of solar energy increases the illuminated flux on the photovoltaic (PV) surface thus less PV material is required. A novel asymmetric compound parabolic photovoltaic concentrator has been characterised experimentally with a similar non-concentrating system. Different numbers of PV strings connected within the system have been analysed and a power ratio of 1.62 measured compared to a similar non-concentrating PV panel with the same cell area. The solar to electrical conversion efficiency of 8.6% and 6.8% was achieved for the non-concentrating panel the concentrating system, respectively. The measured average solar cell temperature of the PV in the concentrator system was only 12 °C higher than that of the similar non-concentrating system with same cell area. © 2005 Elsevier Ltd. All rights reserved.

SYNOPSIS: a novel non-imaging asymmetric compound parabolic photovoltaic concentrator (ACPPVC) has been designed, constructed and experimentally characterised at the University of Ulster, Northern Ireland (54°36′N, 5°37′W). Different numbers of PV strings connected in series were experimentally characterised under outdoor conditions both with and without concentrators. Transient I-V curves for each set of parameter data points were determined and the maximum power generation, fill factor and efficiency of the system calculated for each individual I-V curve. The experiments showed that the use of an ACPPVC increased the maximum power point by 62% (i.e. the power by a factor of 1.62) when compared with a similar non-concentrating PV panel of identical cell area. © 2004 Taylor & Francis Group, LLC.

A novel non-imaging asymmetric compound parabolic photovoltaic concentrator (ACPPVC) has been designed, constructed and experimentally characterised at the University of Ulster, Northern Ireland (54°36 N, 5°37 W). Different numbers of PV strings connected in series were experimentally characterised under outdoor conditions both with and without concentrators. Transient I-V curves for each set of parameter data points were determined and the maximum power generation, fill factor and efficiency of the system calculated for each individual I-V curve. Experiments showed that the use of an ACPPVC increased the maximum power point by 62% (i.e. the power by a factor of 1.62) when compared to a similar non-concentrating PV panel. © 2004 Elsevier Ltd. All rights reserved. ′ ′

Fuel poverty in Scotland is rising and is currently experienced in a quarter of households. Large-scale renewable generation does not reduce fuel poverty because citizens still have to pay for their imported energy. However, building-integrated solar systems do reduce the amount of energy imported into homes and have demonstrably already taken some families out of fuel poverty in Scotland. This study is of the solar potential of Dundee, a city with higher than average levels of fuel poverty. A review of the Scottish Index of Multiple Deprivation presents the deprivation status of the population in the centre of the city. The total roof area practically available for solar integration was estimated using RoofRay software. Energy efficiency measures, combined with building integrated solar systems were shown to potentially eliminate fuel poverty in central Dundee. Energetic and economic analyses of the solar systems using TRNSYS software resulted in optimal PV/inverter system sizing ratios of 1.02 and 1.06, respectively. The solar water system optimally performed with a 230 L tank of 1 m height and an inlet fluid flow rate of 40 kg/h. The study indicates that city level solar installation programmes can help eliminate fuel poverty in Scotland at an acceptable cost.