Radiative sky cooling occurs wherever there are ground and a sky. A surface facing the sky will eventually eject some of its heat, and that rejection takes the form of thermal radiation. A UCLA team has figured out a way to take the temperatures differences from this process and turn it into electricity.
Using parts purchased at a hardware store, the team built a proof-of-concept device for under $30. In their testing, the team was able to generate 25 milliwatts per square meter, which could power a single LED light bulb. The researchers think that with better equipment they could generate 0.5 watts per square meter, this would be enough to charge a smartphone or a whole room filled with LED lights.
Although these devices output modest levels of electricity, it’s an intriguing renewable energy resource that works at night.