Solar Thermoradiative-Photovoltaic Energy Conversion

A continuous supply of renewable energy requires intermittent sources to be paired with storage. Thermal storage is an excellent match for solar energy, but concentrating solar power plants must use high optical concentrations and large plants to be cost competitive. Here, we propose an alternative, solid-state heat engine for solar-thermal conversion consisting of a solar absorber, a thermoradiative cell, and a photovoltaic cell. Heat from the solar absorber or thermal storage drives radiative recombination current in the thermoradiative cell, and its emitted light is used by the photovoltaic cell. Based on the principle of detailed balance, we calculate a limiting solar conversion efficiency of 85% for fully concentrated sunlight and 45% for one sun with an absorber and single-junction cells of equal areas. Solar thermoradiative-photovoltaic systems outperform similar solar thermophotovoltaic converters for low band gaps and practical absorber temperatures, and for a realistic device, this improvement can be up to 7.9% (absolute). Tervo et al. propose a solid-state heat engine for solar-thermal conversion: a solar thermoradiative-photovoltaic system. The thermoradiative cell is heated and generates electricity as it emits light to the photovoltaic cell. Combining these two devices enables efficient operation at low temperatures, with low band-gap materials, and at low optical concentrations.