Solar energy is the go to for renewable energy but what happens at night? Especially when you can’t store the energy gained during the day? Rather than what are currently expensive battery options, we may be able to harness the power of darkness.

Well, that’s just a bit of fun. It’s not really darkness. Researchers have developed a type of energy cell that works at night and it harnesses its power from the heat that radiates off the Earth at night, or in dark areas. So not exactly a reverse solar panel but still pretty neat.

The system is just a proof of concept but it was about $30 in materials and if scaled up with better conditions, may be able to draw more energy and perhaps one day help close the gap in renewable energy.