Concentrating Photovoltaic systems are good candidates for low cost and clean electricity generation from solar energy. CPV means replacing much of the expensive semiconductor photovoltaic cells with the cheaper optics. Although the idea is simple, CPV systems have several problems inherent to their system design, such as module thickness, expensive PV cells and overheating. Light guide systems are good alternatives to classical CPV systems that can clear off most of the problems of those systems. In this thesis we explore a new light-guide based solar concentrator by optical design and simulations. It is shown that this solar concentrator can reach 1000x geometric concentration, 96.5% optical efficiency with a &plusmn / 1 degree acceptance angle. As a result of simulations, effectiveness of the horizontally staggered light guide solar concentrators is proved. A practical module study is carried on to improve the knowledge related to light guide CPV systems. The concentrator geometry is fabricated as a medium concentrator system with a geometric concentration of 45x and +-2 degrees acceptance angle. With the prototype level injection molding 74% optical efficiency is achieved and can be improved with a better mold manufacturing. A cost analyses is also performed with real manufacturing parameters and it is shown that grid parity can be achieved with this kind of light guide solar concentrators.

Thermal radiation is a fundamental heat transfer process, with certain basic aspects still not fully understood. Furthermore, tailoring its properties has potential to affect a wide range of applications, particularly thermophotovoltaics (TPV) and radiative cooling. TPV converts heat into electricity using thermal radiation to illuminate a photovoltaic diode, with no moving parts. With its realistic efficiency limit up to 50% (heat source at 1200 ^oC), TPV has garnered substantial interest. However, state-of-the-art TPV demonstrations are still well below theoretical limits, because of losses from generating and efficiently converting or recycling thermal radiation. In this thesis, tailored integrated photonic crystal structures are numerically simulated to enhance the efficiency of solar TPV. Next, a high-temperature thin-film Si-based selective absorber and emitter is designed, fabricated and experimentally characterized. It exhibits great potential to open up new applications, as it lends itself to large-scale production with substantial mechanical flexibility and excellent spectral selectivity for extended time periods, even when operating under high operating temperatures (600 ^oC) for up to 6 hours, with partial degradation after 24 hours. To perform this high-temperature characterization, an emittance measurement setup has been built; its performance agrees well with numerical simulations. Second, a unique passive cooling mechanism known as radiative cooling is developed to reduce the operating temperature of the photovoltaic diode. The significant effect of radiative cooling as a complement for an all-passive-cooling TPV system is proposed and numerically analyzed under a range of conditions. Furthermore, an outdoor experiment has been performed to demonstrate the effect of radiative cooling on a concentrating photovoltaic system, which can potentially be applied to the thermal management of a TPV system. In summary, this work paves the way towards the development of reliable, quiet, lightweight, and sustainable TPV and radiatively cooled power sources for outdoor applications.

<p>  </p> <p>  </p> <p>Concentrator photovoltaics have demonstrated greater solar energy production efficiency than previous solar electric technologies.  However, recent research reveals that heat management is a significant difficulty in CPV systems, and if left unaddressed, it can have a severe influence on system efficiency and lifetime. Traditional CPV cooling relies on active methods such as forced air convection, or liquid cooling, which might lead to an extremely large parasitic power use. In addition, the moving parts of a cooling system result in a shorter lifespan and higher maintenance expenses. </p> <p><br></p> <p>CPV systems can boost their efficiency and lifespan by adopting passive cooling solutions. This work employed radiative cooling and natural convection to construct an efficient and cost-effective cooling system. The excess heat of a solar cell can be dispersed into space via electromagnetic waves via radiative cooling. Due to the fact that the radiative cooling power is related to the difference between the fourth powers of the solar cell and the ambient temperature, much greater cooling powers can be obtained at higher temperatures. Heat pipes were installed to act as a heat pump by transferring excessive heat from solar cells within a system to the exterior, where it can be dissipated via natural air cooling and thermal radiation. Experiments conducted in this study demonstrate that a temperature reduction of 21 ◦C was accomplished through radiative cooling and natural convection, resulting in an increase of 64 mV, or 17% in the open-circuit voltage of a GaSb solar cell.</p>