Australia is known for its bright sunshine and beautiful beaches. In Sydney, some scientists are taking a fresh approach to harnessing solar energy. Jamie Hanson, a postgraduate student at the University of New South Wales (UNSW), explains, “We’re developing devices that create electricity by emitting light instead of absorbing it. It’s like a reverse solar panel.”
Hanson works with a team at UNSW’s School of Photovoltaic and Renewable Energy Engineering. They’re exploring how to generate power from solar energy even after dusk. When the sun goes down, the Earth releases heat as infrared radiation, a kind of light we can’t see but can feel. The researchers are focusing on a device called a thermoradiative diode, which can turn that invisible heat into electricity.
Professor Ned Ekins-Daukes, who leads the team, notes that if you looked at Earth at night with an infrared camera, it would appear to glow, radiating heat into the cold universe. Although UNSW isn’t the first to develop this kind of diode, it was the first to successfully show that one could generate electricity in 2022. However, the current output is quite small—about 100,000 times less than a typical solar panel. Ekins-Daukes humorously says it produces enough energy to power a digital watch using body heat.
The diode’s efficiency depends on the temperature difference between the heat source and the environment. Unfortunately, factors like water vapor and carbon dioxide in the atmosphere can reduce this temperature gap, lowering the device’s potential on Earth. But Ekins-Daukes believes that the real magic of this technology could be in space, where temperatures are cooler, making the diode more effective.
Currently, satellites rely on solar panels, which only work when in sunlight. “In low Earth orbit, satellites experience 45 minutes of light and then 45 minutes of darkness,” Ekins-Daukes explains. This makes it challenging for them to stay powered through the night. His team aims to use the heat absorbed by satellites during daylight to generate electricity at night as they radiate heat into cold space.
Dr. Geoffrey Landis at NASA points out that cost is a critical factor. “Batteries are cheap,” he says, suggesting that using a thermoradiative diode for short periods might not be economically viable. Instead, his research focuses on deep-space missions, where conventional power sources like thermoelectric generators—which are heavy and costly—are used.
Unlike these heavy generators, thermoradiative diodes could be lighter and simpler, making them ideal for small satellites. The team at UNSW plans to test the technology in a balloon flight this year. Meanwhile, they’re also investigating new materials to improve the diode’s performance, targeting future applications in deep-space missions or areas like permanently shadowed regions of the moon.
With advancements in materials and efficiency, Ekins-Daukes hopes to roll out a commercially viable diode within five years. The potential for this technology is immense, making space exploration safer and more efficient.
