Harvesting solar energy without excess environmental heating

In this study, an entirely radiative heat sink for solar energy harvesting is demonstrated, using a solar thermoelectric generator as a specific example of a solar energy harvester. With a radiative cooling surface within a vacuum shield as the heat sink, the unutilized solar thermal energy is removed irreversibly from the terrestrial environment entirely via radiation toward the sky. The purely radiative heat sink also addresses the main drawback of solar energy harvesting devices—their unavailability at night—by harvesting energy from the coldness of the night sky. Implemented in a scalable form where solar energy harvesting and radiative heat sinking are achieved within the same area, the presented energy harvester generates electricity continuously throughout the day without interruptions or reversing the polarity. These findings open doors to the sustainable implementation of synergistic energy harvesting from the sky.