An international team of scientists looks to provide a potential path to generating electricity like solar cells but that can power electronics at night. Some have observed that for a device on Earth facing space, which has a frigid temperature, the chilling outflow of energy from the device can be harvested using the same kind of optoelectronic physics we have used to harness solar energy. The team expects to overcome the obvious drawback of solar panels in that they require sunlight to generate electricity.

The new research work has been published in Applied Physics Letters.

A schematic of the experimental infrared photodiode that has generated electricity directly from the coldness of space.  Image Credit: Masashi Ono. Click image for the largest view.

The team of scientists has demonstrated for the first time that it is possible to generate a measurable amount of electricity in a diode directly from the coldness of the universe. The infrared semiconductor device faces the sky and uses the temperature difference between Earth and space to produce the electricity.

Shanhui Fan, an author on the paper said, “The vastness of the universe is a thermodynamic resource. 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 negative illumination effect allows electrical energy to be harvested as heat leaves a surface. Today’s technology, though, does not capture energy over these negative temperature differences as efficiently.

By pointing their device toward space, whose temperature approaches mere degrees from absolute zero, the group was able to find a great enough temperature difference to generate power through an early design.

Masashi Ono, another author on the paper said, “The amount of power that we can generate with this experiment, at the moment, is far below what the theoretical limit is.”

The group found that their negative illumination diode generated about 64 nanowatts per square meter, a tiny amount of electricity, but an important proof of concept, that the authors can improve on by enhancing the quantum optoelectronic properties of the materials they use.

Calculations made after the diode created electricity showed that, when atmospheric effects are taken into consideration, the current device can theoretically generate almost 4 watts per square meter, roughly one million times what the group’s device generated and enough to help power machinery that is required to run at night.

By comparison, today’s solar panels generate 100 to 200 watts per square meter.

While the results show promise for ground-based devices directed to the sky, Fan said the same principle could be used to recover waste heat from machines. For now, he and his group are focusing on improving their device’s performance.

We are just now seeing the advent of a new technology. This one is really amazing, with imagination potential yet to be defined. The idea we will run out of power seems less and less likely all the time.


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