The impending climate and fuel crises will adversely affect the quality of life and security of society. In order to prevent this problem from occurring, renewable energy solutions must become a larger percentage of the existing energy supply. However, at the current time the amount of solar energy generated electricity from conventional photovoltaic systems varies a great deal during the day due to atmospheric fluctuations such as obscurations from clouds. The proposed work provides a path to solving this problem by reducing the effect of solar intermittency on the output of photovoltaic systems. This will be accomplished through a design methodology that integrates the characteristics of photovoltaic and thermal energy converters, local and regional solar illumination conditions, and optics to optimize the solar conversion system temporal uniformity and overall output power. The systems will use several types of photovoltaic cells to increase solar conversion efficiency, thermal converters that respond more slowly to cloud obscuration to dampen variability, and optical techniques to increase utilization of the available sunlight for both types of converters and to optimize the overall system electricity output. This design process will lead to the production of higher quality renewable energy that will be more useful to utility companies for electrical grid applications. In addition to the technical benefits, the proposed work provides opportunities for new engineering students to learn the essentials of solar energy component and system design. Students are eager to become involved solving climate and energy problems and this project offers excellent opportunities to educate and train them for research and the work place. In addition, reliable, low cost solar energy systems will allow use on Native American reservations and in third world countries where electrical power is not readily available.
The goal of the proposed research is to develop a novel holographic light management methodology that integrates different types of solar converters to provide more useful electrical power from the solar resource. In particular, holographic light management techniques will be used to optimize the output of hybrid photovoltaic/solar thermal converters to mitigate the effects of daytime solar intermittency on photovoltaic (PV) system performance. This will be achieved by developing light management designs that provide: full spectrum utilization, high efficiency PV spectrum splitting, and solar thermal conversion for short term energy storage. In addition, holographic configurations will be examined to allow operation of high efficiency spectrum splitting PV systems during diffuse illumination conditions to further extend the energy yield capability of PV systems. Solving these two problems will significantly increase the energy capacity factor of PV systems. The potential contributions of this work include: 1) development of a holographic light management methodology that integrates imaging and non-imaging optical design, holographic and conventional optics, PV cell and solar thermal converter parameters, and local and regional solar illumination data to design systems for full solar spectrum utilization that mitigate daytime atmospheric intermittency effects on electricity output; 2) design, fabrication, and evaluation of holographic optics that control concentration ratio, spectral bandwidth, and geometrical form factor for optimum solar energy conversion under direct sunlight illumination conditions; and 3) development of high efficiency spectrum-splitting holographic systems for operation with diffuse illumination conditions. These contributions will lead to renewable energy systems that can be used more reliably by utility companies and greater insertion into the electrical grid. This in turn will diminish the negative effects of fossil fuels on the climate and provide a better quality of life for the Nation and World's population.
