Research at the University of New South Wales in Australia shows that radiant infrared heat from the Earth can be used to generate electricity, even after the Sun has set.
Researchers at the School of Photovoltaic and Renewable Energy Engineering at the University of New South Wales in Australia have generated electricity from heat radiated as infrared light.
During the day the Earth’s surface heats up when it receives sunlight, but at night it returns that heat in the form of infrared radiation, which is emitted by any body whose temperature is minimally significant.
The new technology takes advantage of that thermal energy radiated upwards from the Earth, towards a colder zone, and converts that flow of energy into electrical potential, through the temperature differential.
To achieve this, it uses a semiconductor device called thermo-radiative diodecomposed of materials found in night vision goggles: generates electrical energy from the emission of infrared light, even at night.
The device uses the same type of semiconductor technology to produce energy from the emission of infrared light. It is the first time that it applies for this purpose. The results of the research are published in ACS Photonics.
Although the amount of energy generated in this development is very small, about 100,000 times less than that supplied by a solar panel, the researchers believe that the result can be improved in the future.
“We have made an unequivocal demonstration of obtaining electrical energy through a thermo-radiative diode”, highlights the team leader, associate professor Ned Ekins-Daukes.
“Using thermal imaging cameras we can see how much radiation there is at night. What we have done is make a device that can generate electrical energy from that emission of infrared thermal radiation,” he adds.
“Whenever there is a flow of energy, we can convert it between different forms,” he explains. Phoebe Pearlone of the co-authors of the article.
This development is confirmation of a previously theoretical process and the first step in making specialized and much more efficient devices that could one day capture energy on a much larger scale.
Ekins-Daukes compares the new research to the work of engineers at Bell Labs, who demonstrated the first practical silicon solar cell in 1954.
That first silicon solar cell was only about 2% efficient, but now modern cells can convert about 23% of sunlight into electricity.
The research team believe the new technology could have a variety of uses in the future, helping to produce electricity in ways not currently possible.
One such use could be to power bionic devices, such as artificial hearts, which currently run on batteries that must be replaced periodically.
Ekins-Daukes says: “In principle, it’s possible that we generate energy in the way we’ve shown just from body heat, which you can see glowing if you look through a thermal camera.”
And he adds: “in the future, this technology could potentially harvest that body energy and eliminate the need for batteries in certain devices, or help recharge them. That’s not something where conventional solar is necessarily a viable option.”
Thermoradiative Power Conversion from HgCdTe Photodiodes and Their Current–Voltage Characteristics. Michael P. Nielsen et al. ACS Photonics 2022, 9, 5, 1535–1540; May 9, 2022. DOI:https://doi.org/10.1021/acsphotonics.2c00223