An effective design of thermophotovoltaic metamaterial emitter for medium-temperature solar energy storage utilization

Solar energy is one of the most important new energy sources with huge reserves. However, it has the disadvantage of discontinuous and instability, which can be compensated with a molten salt energy storage system. In this study, a novel molten salt energy storage-solar thermophotovoltaic integrated system was proposed for the application in small-scale distributed energy utilization. To adjust the radiation spectrum in the operating temperature of 800-1000 K to better match with InAs cell, a Ta-based stacked-cross pyramid broadband emitter was designed and geometrically optimized. Its effective impedance and magnetic field distribution at different wavelength were analyzed to reveal its radiation mechanism. By introducing the emitter, the spectral efficiency of the system increased from 51% to 88%, and the TPV efficiency increased from 11.4% to 24.24% at 1000 K compared with blackbody radiation and maintains above 20% at the range of 800-1000 K. Compared with narmwband emitters, the broadband emitter has better comprehensive performance when integrated with the molten salt energy storage system, with the TPV efficiency slightly reduced but the output power significantly increased from 4.96 kW.m(-2) to 2.26 kW.m(-2) at 1000 K.