Self-adaptive photothermal/radiative cooling-thermoelectric conversion system for 24 h electricity generation

The ability to generate electricity in a passive manner for 24 h could be a fundamental capability for wide applications, especially for population who lack access to electricity. However, traditional non-selective solar absorbers, characterized by high absorption in the whole waveband, cannot avoid daytime heat loss especially in the presence of strong sunlight. In this work, we demonstrate a self-adaptive system for thermoelectric (TE) conversion through photothermal (PT) and radiative cooling (RC) effects. The proposed self-adaptive system features an upper PT/RC subsystem and a lower TE subsystem. Simulation results suggest that, to realize daytime and nighttime electricity generation simultaneously, PT mode should be turned on at daytime with high solar absorptivity and low emissivity within 8–13 μm, at night, RC mode ensures that the TE subsystem radiates heat to the cold outer space with high emissivity. The ability of self-adaptive spectral adjustment benefits from the intelligent switch of vanadium dioxide (VO2) film. Detailed one-day performances reveal that a peak power density of 1552 mW/m2 for PT mode and 45.7 mW/m2 for RC mode can be achieved. The results of the self-adaptive PT/RC-TE system indicate the prospect of electricity generation for 24 h without storage in an intelligent way.