Our directory of things of interest

University Directory

These scientists have invented a solar panel that works at night

  • Written by  Katie Burton
  • Published in Energy
These scientists have invented a solar panel that works at night
15 Jul
2019
A type of panel has been invented that can generate electricity when pointed at the night sky, but can it ever be scaled up to serve alongside solar power?

Everyone knows that it’s possible to harvest electricity from the sun, but in many locations the sun’s rays are a notoriously temperamental source of energy. So, what if it was possible to create energy from something much more predictable? Say, the night sky.

Keep an eye on the world
signup buttonGet Geographical’s latest news delivered straight to your inbox every Friday, plus a collection of free eBooks on the subjects that matter to you!

A group of international scientists have created an experimental device, which uses the same optoelectronic physics used to harness solar energy, that does just this. The first of its kind, the infrared semiconductor device creates a measurable amount of electricity when pointed at the night sky. It works through a process called the negative illumination effect. Unlike a solar cell which works due to an oversupply of photons beyond what the background environment supplies, this effect generates electricity through an undersupply of photons below that provided by the environment. One crucial part of this process is the temperature difference between Earth and space. When the device is pointed at the night sky the coldness of the universe compared to Earth means that heat outflows from the device. The negative illumination effect allows electrical energy to be harvested as this heat outflow happens. 

Blue dark night sky with many stars above field of trees. Yellowstone parkThe night sky above Yellowstone Park;  the new device works through a process called the negative illumination effect

At the moment, the device is a proof of concept and the negative illumination diode can only generate a very small amount of electricity – about 64 nanowatts per square metre – but the team say that the theoretical output is much higher than this. Shanhui Fan, one of the device’s creators and professor at Stanford University, explains that improvements to the device, which he believes are possible to implement, would increase this output. ‘In this paper we provided a calculation of how much one can expect, given the atmosphere, with this kind of technique. If we have an ideal device this comes to about four watts per square metre. I think we can improve the device quite a bit with optical techniques and that’s something we’re interested in developing.’ 

How dark energy works: Credit: Masashi OnoDiagram of the panel [Image: Masashi Ono]

This theoretical output is roughly one million times what the group’s initial device generated and could be enough to help power machinery that runs at night. That said, it is still much lower than the electricity generated by a solar cell. ‘To put this in context, a solar cell generates a couple of hundred watts per square metre. So, it is small compared to a solar cell,’ says Fan. ‘However, in the absence of the sun, this actually is a pretty large power density compared with other techniques.’ He adds that because an ideal device of this nature would be very similar to a solar panel, the technique could be used to compliment the generation of solar electricity.

This new device is just one strand of the work done by Fan and his team, which largely focuses on the potential to harvest energy from radiative cooling – the process by which bodies on Earth, and the planet itself, radiate heat out into the universe. If this heat loss could be harnessed to produce energy then waste heat, such as that from machines, could be utilised much more effectively than it is today.

geo line break v3

Free eBooks - Geographical Newsletter

Get the best of Geographical delivered straight to your inbox by signing up to our weekly newsletter and get a free collection of eBooks!

geo line break v3

Related items

NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in NATURE...

Climate

A report details how tropical storms are fuelling the rise…

Wildlife

After years of trials, talks, tweaks and test runs, EarthRanger…

Climate

Nationalism might gain political points in certain parts of the…

Geophoto

With guaranteed sunshine, bright blue skies and not a hint…

Oceans

A review of coral-saving methods is helping communities decide which…

Polar

A seven-year study of Patagonia’s ice sheets has revealed the…

Climate

The environmental impact of Bitcoin is higher than its virtual…

Geophoto

With a camera in everyone’s pocket, the once rarified world…

Climate

The idea of the Earth as a self-regulating, living organism…

Oceans

A temporary fishing ban has been imposed by the European…

Wildlife

A look at the contribution of hippos to the savannah…

Wildlife

The new app encourages young children to connect with the…

Energy

A type of panel has been invented that can generate…

Tectonics

In the 4th century BC, Aristotle proposed that earthquakes were…

Climate

The Chartered Institution of Water and Environmental Management pledges to achieve net…

Tectonics

Earthquakes from time immemorial have attracted the attention of the…

Tectonics

A planned kayaking expedition in Nepal took on a whole…

Tectonics

Scientists from Bristol University are working in conjunction with EDF…