Solar radiation durability of materials components and systems for Low Concentration Photovoltaic Systems

Low Concentration Photovoltaic Systems (LCPV), where solar irradiance is concentrated by a factor of 1-10, present real opportunities for cost competitiveness. In these systems electrical output per unit area of active materials increases nearly linearly with concentration factor, thereby reducing the cost of active materials per watt by up to a factor of 10. All PV systems are exposed to multifactor and cyclic environmental stressors including solar irradiance, temperature and humidity which can each cause degradation over time. This issue is compounded in LCPV because concentration of solar irradiance can amplify these stressors. While primary optical elements of LCPV systems are typically only exposed to normal sun irradiance, secondary optical elements are exposed to multiple sun intensities which can degrade them faster. Concentrating sunlight intensifies the problem of thermal management and since most LCPV systems use crystalline silicon cells, increased temperature decreases overall efficiency. From this point of view, it is very important to have foresight about materials in PV system before they have been used. This paper will discuss solar and environmental durability of acrylic and mirror components of PV systems from a standpoint of durability and reliability of LCPV. Photodarkening and photobleaching were observed in a typical silicone at 3.8 kW/m² irradiance and measurements we used to calculate the Induced Absorbance to Dose (IAD) values of 0.3 and -1.25 ΔAbs/cm per GJ dose. At 48 kW/m² irradiance, only photodarkening appears with 0.2ΔAbs/cm per GJ dose. In addition, photodarkening and photobleaching were also observed in PMMA sample with IAD values of 0.2 and -0.4 ΔAbs/cm per GJ dose, respectively.