An engine that works thanks to the cold of the night and the heat of the earth

An obscure discovery, researchers from the University of California at Davis, in the United States, have just developed an engine that works thanks to the night sky. How does this work?

A heat engine, which transforms thermal energy into movement, always works on the same principle: an exchange of heat between two systems of different temperatures, one hot, the other colder. Mechanics know it well, you need both a system that heats the engine, in the car, it’s the fuel, and a cooling system.

But this time, physicists from the University of California, Davis, USA, have invented an engine that uses no fuel or coolant.

For the heat source, it is simply the earth. Specifically the ground, which in California at night is about 27 degrees. As for cooling, it is carried out by an antenna, which radiates excess heat directly towards space.

The principle of this engine was invented in 1816 by Dr. Robert Stirling, as an alternative to the steam engine. It is air which, by compressing in the cold then expanding in the heat, activates a wheel by means of a piston. It was a laboratory curiosity for a long time, because it was too inefficient compared to steam engines. Then, it was used a little in cryogenics, where the extreme cold made it possible to obtain good yields.

From now on, it is at ambient temperature that this engine can operate, and thanks only to the cold of the night, and the heat of the earth.

It’s effective, but not powerful. This motor generates around 400 milliwatts per square meter, so just enough to power a small fan or LED lighting. The great thing is that it does not consume any energy other than the waste heat of the earth. No battery, no fuel and it requires very little maintenance.

A promising invention, especially for powering electronic systems in very isolated areas, in a completely ecological way. Science therefore hopes that this little nocturnal engine, which lights us up thanks to the dark night, will turn the movement towards more sustainable energy sources.