Solar radiation durability of materials, components and systems for photovoltaics

In renewable energy technologies, a critical challenge is achieving expected service lifetimes of 20-25 years and beyond. Our approach to the physics of failure is to develop new metrology and metrics, coupled to degradation mechanisms and rates, as the basis for lifetime and degradation science (L&DS). Induced absorbance to dose (IAD), a new metric being developed for solar radiation durability studies of solar and environmentally exposed photovoltaic materials, is defined as the rate of photodarkening or photobleaching of a material as a function of total absorbed solar radiation dose. In a reliability engineering framework, these quantitative degradation rates can be determined at various solar irradiances making possible real time or accelerated testing. The potential to predict power losses in a photovoltaic system over time caused by the accumulation of this kind of degradation can be calculated for real time applications or extrapolated for accelerated exposure conditions. Comparisons of IADs at multiple irradiance levels leads to the acceleration prefactor (k_a) which may be useful for linking and quantifying the degradation mechanisms at play in a given system, and enable accelerated testing of materials, components and systems. Using matrix math and published data, comparisons have been made showing the reduction of solar irradiance incident on the PV absorber for two types of CPV systems; two silicones used in Fresnel lenses, and an acrylic PMMA used for mirror augmented PV systems.