Performance analysis of a broadband selective absorber/emitter for hybrid utilization of solar thermal and radiative cooling

Harvesting energy from the hot sun and the cold universe is being investigated and has attracted much attention due to its clean utilization. Herein, a broadband selective absorber/emitter (BS-A/E) is designed and fabricated for the hybrid utilization of diurnal solar thermal and nocturnal radiative cooling. The BS-A/E exhibits high photon absorption in the solar band (i.e., 0.3–3 μm) with a weighted solar absorption of ∼0.83, a strong thermal emission mainly within the atmospheric window (i.e., 8–13 μm), and a low thermal emissivity in other infrared wavelength bands. The outdoor experiment demonstrates that the stagnation temperature of the BS-A/E is 11.6 °C greater than black paint under sunshine and 0.6 °C lower than that of black paint under darkness, showing considerable solar thermal and radiative cooling performance. In addition, thermal prediction also reveals that the BS-A/E can not only achieve solar heating during the day but also obtain sub-ambient cooling phenomenon during the night, indicating that the BS-A/E is capable of providing continuous heating and cooling for humans in various potential applications, such as all-day thermoelectric power generation and thermal storage-based space heating/cooling.