Solar Power at Night: A New Twist on Energy

Scientists in Sydney are working on a cool idea: making energy from the sun even when it's dark. They're not using regular solar panels. Instead, they're creating devices that make electricity by giving off light, not absorbing it. Think of it like a solar panel in reverse. These scientists are part of a team at the University of New South Wales. They're exploring new ways to make solar energy work after sunset. During the day, the Earth soaks up the sun's heat. At night, this heat is released as infrared radiation, a type of light we can't see but can feel as warmth. The team is working on a special semiconductor called a thermoradiative diode. This tiny gadget can turn that infrared radiation into electricity. The idea of a thermoradiative diode isn't new. But the UNSW team was the first to show it working and producing electricity in 2022. Right now, the device can only make a tiny bit of power. It's enough to run a simple digital watch. The amount of power it can make depends on the difference between the heat source and the surrounding temperature. On Earth, the device isn't very powerful. That's because gases like water vapor and carbon dioxide in the air absorb heat from the sun. This reduces the temperature difference between the Earth's surface and the night sky. But in space, things are different. There's no atmosphere, so the environment is much colder. This makes the diode much more effective. The scientists see big potential for this technology in space. Satellites usually use solar panels for power. But these panels only work when the sun is shining. In lower orbits, satellites have 45 minutes of sunlight followed by 45 minutes of darkness. The diode could provide extra power during those dark periods. It would generate electricity from the heat absorbed by the satellite while it's in the sun's view. Then, it would radiate out into the incredibly cold space during darkness.Satellites currently use batteries during dark periods. These batteries are charged when the satellite is in sunlight. The diodes offer a chance to get a bit more power from the satellite's surface. This is especially useful for smaller satellites. These satellites fly in lower orbits but need to do the same jobs as larger ones. The diodes are lightweight and can generate power from surfaces not used for other purposes. The team plans to test the technology in space this year with a balloon flight. Meanwhile, scientists at NASA are also looking into this technology. They think it could be useful for satellites in deep space missions. These missions are currently powered by special generators. These generators convert heat from radioactive isotopes into electricity. The generators are heavy, expensive, and use a rare resource: plutonium. The diodes could be a better use of this resource. Many diodes would be connected to create a panel similar to solar cell arrays. The panel itself would give off waste heat as light. This would make the system more efficient and use less plutonium. However, more research is needed. The diodes need to work at high temperatures for long periods. Current thermoelectric systems operate at temperatures around 540° to 1, 000° Celsius. Nobody knows how the diodes will perform at these temperatures over time. The UNSW team has received funding to improve the diode for low-Earth satellites. They're also looking at using different materials. These materials are similar to those used in conventional solar cells. This could speed up production when the diode becomes commercially available. The team hopes this could happen within the next five years.