Enhanced near-field thermophotovoltaics based on hyperbolic metasurface

The advancement of high-efficiency technologies to convert low-temperature thermal energy (< 600 K) is vital for optimizing energy utilization and supporting carbon mitigation. Near-field thermophotovoltaics (NF-TPV) convert medium- to high-temperature heat (> 600 K) from solar collectors into electrical energy through evanescent wave coupling, offering a promising approach to enhance the efficiency of solar thermal systems. However, the utilization of low temperature heat energy by NF-TPV system deserves further investigation. Herein, we propose an enhanced NF-TPV system based on hyperbolic metasurface for the efficient recovery of low-temperature thermal energy. Results show that NF-TPV systems utilizing calcite (CaCO3) metasurface as thermal emitters can achieve performance exceeding those of systems using CaCO3 films by up to six times. The metasurface system achieves 61.6 W/cm(2) power density and an upper bound efficiency of up to 63.2 % of the Carnot limit when the emitter temperature is only 600 K. The improved performance is attributed to the strong collective near-field coupling in the metasurface. The findings contribute to understanding the strong collective near-field coupling in the hyperbolic metasurface system and provide a novel way to utilize low temperature thermal energy.