On a global level, solar energy has grown exponentially over the last few decades as costs have plummeted and demand has risen accordingly. It is estimated that the world added a third more solar power in 2025 than it did in 2024, marking a remarkable quantity of added capacity. But while renewables are proving too cheap to fail, there are some notable drawbacks to the rapid addition of these resources – most notably the insufficient co-addition of supportive grid and transmission infrastructure and the variability of solar and wind energy, both of which pose significant threat to energy security around the world. 

Unlike fossil fuels, the level of production of which can be manipulated at will to meet demand, solar and wind energy are dependent upon natural variables outside of human control. The production rate of solar panels depends on the length of day and the quality of the sunlight, and the most productive hours are often at odds with demand peaks. 

But a team of scientists in Australia is working on a way to fix that problem by developing a novel type of solar panel that could work at night. It’s a sort of solar panel in reverse, which works by emitting light rather than absorbing it. Instead of using photovoltaics to capture sunlight, this device uses a semiconductor called a thermoradiative diode capable of converting heat into energy. The heat that these devices are using is solar energy, but captured through the heat absorbed by the Earth during sunlight hours, which is then released as infrared energy even well after the sun has set. 

“If you were to look at the Earth at night, what you’d see with an infrared camera is the Earth glowing,” says Professor Ned Ekins-Daukes, who leads the research team developing these thermoradiative ‘solar panels’ at Sydney’s University of New South Wales (UNSW). “What’s happening is the Earth is radiating heat out into the cold universe,” he adds. His team aims to capture that heat and convert it into a useable and reliable energy source.

In more scientific terms, “Solar cells generate an electric current by absorbing photons from a hotter object (i.e. the Sun), whereas thermoradiative diodes generate a current by emitting photons of infrared light into colder surroundings,” explains a companion article by Nature Portfolio. “As long as thermoradiative diodes are warmer than their surroundings, they will emit infrared radiation and generate electricity.”

The research team at UNSW is building on prior research and modeling of thermoradiative diodes developed at Harvard and Stanford universities in the United States. The UNSW team has taken this foundation and run with it, and was the first to successfully use one of the devices to “directly demonstrate electrical power” back in 2022. 

The research has continued to advance since then, but is still a long way from being competitive with conventional solar. “So far, the device can generate only a very small amount of electricity — around 100,000 times less than that of a conventional solar panel,” reports CNN. 

In the not-so-distant future, these diodes could power small devices overnight, functionally replacing batteries or serving to recharge them. “Many people leave their WiFi on overnight and charge their phones,” says Ekins-Dauke. “There’s a light electrical load at night, which thermoradiative diodes could help supply in the future.” 

But someday, these thermoradiative diode semiconductors could have a much grander application, powering satellites orbiting the earth. These satellites vacillate between light and darkness in relatively quick cycles – about every 45 minutes – and attaching thermoradiative diodes could help to power these devices when they’re out of the reach of sunlight and in the extremely cold temperatures of space. 

By Haley Zaremba for Oilprice.com

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