The Design of Beam Splitter for Two-Stage Reflective Spectral Beam Splitting Concentrating PV/Thermal System

The design method of the spectral beam filter, which is employed in the solar concentrating system to improve solar energy utilization and electronic conversion efficiency, is presented. The layer stack is designed by using the needle optimization technique to match the spectrum range of silicon photovoltaic (PV) solar cells, and the reflection film materials are Nb₂O₅ and SiO₂. The coating is performed by employing a sputtering apparatus and the spectral reflectivity of the beam splitter is measured by the spectrophotometer. The test results show good agreement with the designed spectral reflectivity. The spectral distribution of energy flux density of the two-stage reflective spectral beam splitting concentrating PV/Thermal system is also calculated. It shows that almost all the invalid radiation energy for PV conversion is filtered for thermal conversion.