Radical device can generate electricity just by pointing at space

7 May 2019

A star-strewn night-time sky over the Chilean landscape. Image: ESO/P Horálek

Just by pointing a highly experimental device into space, researchers have uncovered a new potential source of renewable energy.

One of solar energy’s biggest drawbacks is the fact that once the sun goes down, its usefulness as a source of electricity comes almost entirely to a halt. While storing the day’s haul in huge batteries is an option, some other radical ideas have been put forward, such as 24/7 solar stations placed in orbit.

Now, an international team of scientists has developed a radical new device that can generate electricity just by pointing into space.

In a paper published to Applied Physics Letters, the team detailed how the device harvests energy from the temperature difference between Earth and the near absolute zero outside of our protective atmosphere. The device essentially uses the same kind of optoelectronic physics used by existing solar energy harvesters.

“The vastness of the universe is a thermodynamic resource,” said Shanhui Fan, an author on the paper. “In terms of optoelectronic physics, there is really this very beautiful symmetry between harvesting incoming radiation and harvesting outgoing radiation.”

In contrast to leveraging incoming energy as a normal solar cell would, the so-called negative illumination effect allows electrical energy to be harvested as heat leaves a surface. By pointing the device at space, the team of researchers was able to find a great enough temperature difference to generate power through an early design.

The group found that its negative illumination diode generated about 64 nanowatts per square metre. While a tiny amount of electricity – and nowhere near what could be considered usable – the team believes it is an important proof of concept. Theorising how it could be improved, it said it could be done by enhancing the quantum optoelectronic properties of the materials used.

When taking into account atmospheric effects, the current device can theoretically generate almost 4W per square metre, giving it enough electricity to power some machinery through the night. The team also believes that aside from trying to increase the amount of electricity the device generates, it could also be used in the future to recover waste heat from machines.

Colm Gorey was a senior journalist with Silicon Republic