Generating Light from Darkness

A large fraction of the world's population still lacks access to electricity, particularly at night when photovoltaic systems no longer operate. The ability to generate electricity at night could be a fundamentally enabling capability for a wide range of applications, including lighting and low-power sensors. Here, we demonstrate a low-cost strategy to harness the cold of space through radiative cooling to generate electricity with an off-the-shelf thermoelectric generator- Unlike traditional thermoelectric generators, our device couples the cold side of the thermoelectric module to a sky-facing surface that radiates heat to the cold of space and has its warm side heated by the surrounding air, enabling electricity generation at night. We experimentally demonstrate 25 mW/m(2) of power generation and validate a model that accurately captures the device's performance. Further, we show that the device can directly power a light emitting diode, thereby generating light from the darkness of space itself.