Photovoltaic/thermal system performance utilizing thin film and nanoparticle dispersion based optical filters

Hybrid photovoltaic/thermal (PV/T) collectors would benefit from the use of fluid based optical filters as a means to separate the useful irradiance for the PV cell from those wavelengths which are more suited to heat generation. Nanoparticle based dispersions within a working fluid can be designed/tuned to serve as optical filters for this purpose. The advantage of this concept is that the thermal part of the system is separated, allowing the photovoltaic and thermal components to operate at significantly different temperatures. Additionally, by using a fluid filter, it is relatively easy to remove heat from the thermal side. This paper theoretically investigates the performance of nanoparticle-based and conventional thin film-based optical fluid filters within a concentrating hybrid PV/T system. General results are presented to demonstrate the impact to overall efficiency when a realistic (i.e., non-ideal) filter is used at a wide-range of operating conditions. The results demonstrate that nanoparticle based filters have a slightly lower overall efficiency compared to the conventional thin film filters due to their lower performance within the window of high transmittance to the PV cell. However, nanoparticle based filters achieve up to 4% higher thermal efficiencies as a result of their significantly reduced filter thickness demonstrating their potential as a favorable compact and lower cost design.