Among various solar energy converting technologies, photovoltaic cells (PV) is the most widely used. However, the mismatch between the broad solar spectrum and the mono-energetic absorption of PV results in the non-absorption of photons with energy below the bandgap (Eg). Previous CPV-T systems were proposed to recycle the below Eg loss of PV. Another dominant loss, thermalization loss, could not be reduced in CPV-T systems. Moreover, CPV-T systems recycle all the energy loss as heat. In these systems, solar energy is converted to thermal energy firstly, which is further utilized to generate other products. Two converting processes increase the irreversible loss. In our opinion, the two different kinds of loss should not be treated equally without discrimination. So we proposed a solar cascade utilization system with concentrated photochemical-photovoltaic-thermochemical (CP-PV-T) processes to make the most use of the full spectrum of solar energy. The photons with energy far above Eg of PV are utilized in the photochemical process, and thus the thermalisation loss of PV cell is reduced. The below Eg loss of PV is recycled to provide heat for thermochemical process. Results show that the utilization rate of photon energy at the first 600 nm is increased to 80.68% from 44.01% with the addition of photochemical process in front of PV, and the total solar energy utilization efficiency of the proposed system is 64.24% on the design condition.
Keywords solar energy; full spectrum; photochemical process; PV; thermochemical process