A breakthrough discovery from Australian scientists points at the possibility of harnessing energy that flows out of the Earth at night, a process called ‘nighttime’ solar power.
ICYMI: UNSW researchers have shown that Earth’s radiant infrared heat can be used to generate solar electricity at night. ☀️
— UNSW (@UNSW) May 19, 2022
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1. Thermoradiative diode
Previously conceived only theoretically, researchers from the University of New South Wales (UNSW) claim that the discovery could mean being able to achieve the ultimate dream of renewable energy: power generation uninterrupted by the setting of the sun.
How exactly is the heat trapped under this system? The Earth absorbs heat from the sun on a daily basis. At night, this heat escapes the Earth in the form of infrared light and is sucked out into the icy vacuum of space.
UNSW scientists use the term ‘thermoradiative diode’, a type of semiconductor also used in night vision goggles, to capture the infrared radiation as it escapes Earth. Once captured, it is converted into electricity.
We have made an unambiguous demonstration of electrical power from a thermoradiative diode. Using thermal imaging cameras you can see how much radiation there is at night, but just in the infrared rather than the visible wavelengths. What we have done is make a device that can generate electrical power from the emission of infrared thermal radiation.
Ned Ekins-Daukes, Professor at the UNSW
Ekins-Daukes explained that the process is still a harnessing of solar power — solar energy that hit the Earth during the day, warming the planet. But instead of that energy radiating back out into space in the form of infrared light, it can now be harvested.
2. Far away from commercialization
Despite the promising results and the potential that it may bring, ‘nighttime solar’ power is still in the early stages of development. Nevertheless, fellow co-author Michael Nielsen noted that despite how far away commercialisation of this technology is, the evolving idea is extremely exciting.
By leveraging our knowledge of how to design and optimise solar cells and borrowing materials from the existing mid-infrared photodetector community, we hope for rapid progress towards delivering the dream of solar power at night.
Michael Nielsen, co-author of the discovery
3. Global research on ‘nighttime solar’ power
Solar energy is an intermittent renewable given its reliance on meteorological conditions. However, technology to combat this much-discussed flaw is already being developed at a fast pace, focusing both on different ways to harnessing the energy and also on designed photovoltaic panels capable of generating power once the sun has gone down.
The concept of ‘nighttime solar’ power in particular has been developed by other teams around the world, including Stanford scientists who are using the differences in day and night temperatures to generate electricity. Research coming from the University of California Davis is using specific methods to harvest electricity from the night sky.
