Modelling and performance evaluation of a novel passive thermoelectric system based on radiative cooling and solar heating for 24-hour power-generation

Harvesting energy from the sun and ultracold outer space for electricity generation is green access to green energy and helps reduce carbon dioxide emissions. However, current work on passive electricity generation is restrained to daytime or nighttime. In this paper, we propose a passive thermoelectric system that produces continuous electric power during a full 24-hour day - even in winter. The thermoelectric output is maintained and amplified by integrating radiative cooling and solar heating. The utterly passive system consists of a thermoelectric generator (TEG), a radiative cooling film, and a greenhouse cavity. Radiative cooling is used to cool the sky-facing end of the TEG below ambient temperature without the need for fuel. Meanwhile, the solar-heating-based greenhouse is used to heat the hot end of the TEG to enhance the temperature difference between the cold and hot ends and, thus, the output. An energy balance model that considers the varying solar radiation is developed to determine the temperature difference between the TEG ends and system output. The accuracy of the evaluation model is first confirmed by the good agreement between the modelled performance of the system and the experimentally measured data. Afterwards, the effects of radiative cooler, solar absorption rate, and cloud cover on the system performance are studied. Finally, the seasonal and locational performance of the system in China is evaluated. Results indicate that the proposed passive TEG system that integrates radiative cooling and solar heating can produce 24-hour continuous and impregnable output. Therefore, the proposed system in this work may help the development of passive electricity generation.