On the performance of concentrating fluid-based spectral-splitting hybrid PV-thermal (PV-T) solar collectors

Abstract

Concentrating fluid-based spectral-splitting hybrid PV-thermal (SSPVT) collectors are capable of high electrical and thermal efficiencies, as well as high-temperature thermal outputs. However, the optimal optical filter and the maximum potential of such collectors remain unclear. In this study, we develop a comprehensive two-dimensional model of a fluid-based SSPVT collector. The temperature distributions reveal that these designs are effective in thermally decoupling the PV module from the high-temperature filter flow-channel, improving the electrical performance of the module. For a Si solar cell-based SSPVT collector with optical filter #Si400-1100, the filter channel is able to produce high-temperature thermal energy (400 °C) with an efficiency of 19.5%, low-temperature thermal energy (70 °C) with an efficiency of 49.5%, and electricity with an efficiency 17.5%. Of note is that the relative fraction of high-temperature thermal energy, low-temperature thermal energy and electricity generated by such a SSPVT collector can be adjusted by shifting the upper- and lower-bound cut-off wavelengths of the optical filter, which are found to strongly affect the spectral and energy distributions through the collector. The optimal upper-bound cut-off always equals the bandgap wavelength of the solar cell material (e.g., 1100 nm for Si, and 850 nm for CdTe), while the optimal lower-bound cut-off follows more complex selection criteria. The SSPVT collector with the optimal filter has a significantly higher total effective efficiency than an equivalent conventional solar-thermal collector when the relative value of the high-temperature heat to that of electricity is lower than 0.5. Detailed guidance for selecting optimal filters and their role in controlling SSPVT collector performance under different conditions is provided.