The thermal performance of window glazing requires improvement for a sustainable built environment at an acceptable cost. This work has attempted to develop a smart composite coating that combines photosensitive metal oxide and phase change materials and investigate their thermal comfort performance as a glazed window. Current work demonstrates a multi-fold smart composite. consisting of an optimized In2O3:ZnO-polymethyl methacrylate-paraffin composite to reduce heat exchange through the combined self-cleaning and energy-saving envelope of the smart built environment. It is observed that the In2O3:ZnO (5 wt%) multi-fold composite film experienced better transmittance and thermal performance compared to its other wt% composite samples. Moreover, the multi-fold composite coated glass integrated into a prototype glazed window was further investigated for its thermal performance, where a steady average indoor temperature of ~30oC was achieved when the outside temperature reached ~55oC while maintaining good visibility. Interestingly, the transparency reached ~86% at 60oC and experienced a hydrophobic water contact angle (WCA) of ~138o. In contrast, a similar film exhibits ~64% transparency at 22oC, where the WCA becomes moderately hydrophilic (~68o). Temperature-dependent on transparency, and wettability properties were examined for up to 60 cycles, resulting in excellent indoor thermal comfort. In addition. a thermal simulation studywas executed for the smart multi-fold composite glazing. Moreover, tshis study offers dynamic glazing development options for energy saving in the smart built environment.

Concentrating photovoltaic technology harnesses solar energy by increasing the solar density upon solar cells using optical concentrators. Ongoing research on concentrating photovoltaic systems aim to improve the achievable energy harnessing and utilisation potential. Increasing the concentration ratio for high energy generation raises many advances and limitations in the concentrating photovoltaic design. However, the field of concentrating photovoltaic research is still in progress where new configurations, methods and materials are fabricated to reach a competitive cost by enhancing the efficiencies of the system to standard silicon photovoltaic systems.
The work presented in this thesis focuses on developing and demonstrating an ultrahigh concentrated photovoltaic system beyond 3000×. This system is based on a Silicon-on-Glass Fresnel lens resulting in a geometrical design of 5831×. The Fresnel lens as a primary optical interface was investigated theoretically, numerically, and experimentally to understand the operating limits in terms of power output, optical performance (optical efficiency and concentration ratio), and working temperature. The discrepancy between a Fresnel lens's theoretical and experimental optical characterisation results was studied. All the equations were elaborated for single- and multi-junction solar cells, emphasising the performance when the focal spot area is larger or lesser than the solar cell area. The prediction approach of optical characterisation has shown a strong agreement between the theoretical and experimental results of the multi-junction solar cells with a discrepancy of 2% at 7.7 W (77 suns) and 6% on the average cross a solar irradiance on the cell from 3.1 W – 7.7 W corresponding to 31 suns – 77 suns in concentration ratio. The numerical model using COMSOL Multiphysics software was established to study the Fresnel lens optically and thermally. The developed optical model was validated theoretically and experimentally to show a firm agreement with a discrepancy of ≤1%. Also, the developed thermal model was validated experimentally to show a difference of only 2.18%. Further, optical and electrical characterisations of the flawed glass have been conducted. The optical characterisation has shown a drop of 3.2% in optical efficiency. I-V and power curves of cracked and non-cracked Fresnel lenses were also compared to show a drop of 3.2% in short circuit current and power.
A theoretical analysis of the optical performance for a ¼ of the ultrahigh concentrated photovoltaic system design grouping three optical interfaces is performed to estimate the optical loss and its influence on the optical efficiency and concentration ratio. Also, a numerical model was established using COMSOL Multiphysics software to simultaneously evaluate the thermal and optical performance of a ¼ of the ultrahigh concentrated photovoltaic system. The system was analysed under direct normal irradiance ranging from 400. W/m^2. to 1000. W/m^2. in an interval of 100. W/m^2 , showing a simulative optical efficiency of ~93% and a simulative concentration ratio of 1361 suns at 1000. W/m^2. The thermal model was interlinked with the optical model to generate the results accordingly. The final stage receiver shows a maximum temperature ranging between 157.4 ℃ and 78.5 ℃.
Moving toward a ultrahigh concentrated photovoltaic design raises the importance of a cooling management system due to thermal excitation. Although the thermal performance and thermal management for the ultrahigh concentrated photovoltaic system are beyond this thesis's scope, the cooling mechanism arrangement based on either pre- or post-illumination techniques was explored. The post-cooling mechanism study was established using COMSOL Multiphysics software for numerical analysis. A flat-plate and micro fin heatsink studied the effect of concentration ratio up to 2000 suns to determine their limits as a passive cooling system and establish when an active cooling system is needed based on the recommended operating temperature of the solar cell of 80 °C. On the other hand, Graphene was experimentally exploited as a pre-illumination cooling technique for a solar cell with different graphene coating thicknesses. The concept of utilising graphene as a neutral density filter for focal spot concentrating photovoltaic (Fresnel lens primary optic) reduces the solar cell temperature significantly and maintains the cell temperature for a more extended period. The graphene coating orientation further influenced the temperature gradient behaviour of the focal spot and incident temperature.
The Fresnel lens working parameters (focal length and the focal spot) were defined to establish the mechanical structural design accordingly. The system was mechanically designed based on three optical interfaces, built in-house, and incorporated with a sun tracker. Different aspects were examined initially before the outdoor testing, the sun tracker alignment accuracy and payload capacity, windage load, and counterbalance weight and moments effects using SOLIDWORKS software. The ultrahigh concentrated photovoltaic system was tested outdoor with three types of secondary mirrors, resulting in an effective concentration ratio of 984 suns, 1220 suns, and 1291 suns and an average optical efficiency of 18.5%, 20.25%, and 22% for Aluminium reflective film, Pilkington Optimirror, and ReflecTech® Polymer secondary optic types, respectively. The fabricated ultrahigh concentrated photovoltaic system and tested experimentally outdoor is the highest in both geometrical and effective concentration ratios so far.
It would not be possible to design and perform the ultrahigh concentrated photovoltaic system without fully characterising its primary optic, which helps set the performance basis and associated losses. Although the experimented system showed the highest value in terms of both geometrical and effective concentration ratios, the subsequent optics to the Fresnel lens were standard optics. The attained outcomes are practical in progressing concentrating photovoltaic technologies to a higher concentration ratio.

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 (Voc,Isc,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.

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%.

Nowadays, the most recent optical configuration based on Cassegrain and Fresnel lens designs of concentrator photovoltaic(CPV) has shown a race to achieve the ultrahigh concentration ratio. Still, none of those has experimentally shown an optical concentration ratio (GC) beyond 2000 suns. This is because their energy concentration ratios are challenged by the excessive temperature raised throughout the optical stages, which diminishes the efficiency of the solar cell. In this context, this research work aims to numerically investigate a microscale pin-fins heat sink configuration to enhance the thermal performance and the cost-competitivity of ultrahigh CPV thermal receiver. The impacts of the solar cell area, cell efficiency, and heat sink's material have been analyzed and discussed. The results showed that a circular pin-fins heat sink could accomplish a drop of 23.28% in the maximum operating cell temperature at 10 000 suns for cell area of 1 × 1 mm2 relatively compared to the conventional flat-plate heat sink. Furthermore, for a circular pin-fins heat sink with a cell area of 2 × 2 mm2, the cell temperature started exceeding the safe operating range of temperature (80°C) at 8000 suns with an average temperature of 96.1°C and reaching a maximum of 113.91°C at 10 000 suns. A gradient temperature on the planar direction of the aluminum circular pin-fins heat sink was about 1.187°C at 10 000 suns whereas 0.703°C was recorded in the case of a copper circular pin-fins heat sink. The circular pin-fins heat sink showed the highest thermal performance resulting in maintaining the solar cell temperature within its safe operating range even beyond 10 000 suns. From an economic point of view, aluminum circular pin-fins heat sink has been found to be less costly than the copper one. Finally, it was found that at 8000 suns, the flat-plate heat sink cost is more expensive than the traditional pin-fins heat sink by 14.7%, where the flat-plate heat sink becomes the worst economic configuration at 10 000 suns. At that concentration ratio, the cost has increased by 43.38%, 5.75%, and 10.61% compared to the traditional pin-fins heat sink, cylindrical pin-fins heat sink, and circular pin-fins heat sink, respectively.

This article presents a novel Multi-Effect Distillation (MED) system which utilizes indirect brine heating such that a medium fluid is circulated through the concentrating solar collectors and store the energy in a charging tank. Each “effect” of a MED unit is a chamber in which cool feedwater brine is sprayed onto heat exchangers, partially evaporating the brine. The vapors and heated brine serve to pass thermal energy to subsequent effects. One of the uniqueness of the design is that the heat exchanger in the first effect of the system receives a flow of hot medium fluid, such that sensible heat is passed to the incoming feedwater. The thermal storage system consists of two identical, insulated tanks, each with sufficient volume to supply the medium fluid for a full day. A dynamic mathematical model is developed and simulated with four MED stages (“effects”). The number of concentrated solar arrays are optimized to generate a peak of 2200 metric ton per day of distilled water, with indispensable total array area of 92,000 square meter. The average daily performance ratio is 2, and the average specific thermal energy consumption is 1140 kJ per kg.