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Renewable Energy

Device Harnesses Heat Energy From Solar Panels At Night

Biel Morro

Outside of food and water (which are forms of energy), energy may be the most valuable resource on the planet. It impacts every facet of our lives, from train and car transportation to the temperatures of our homes and nighttime street lights. 

For it to be so important, energy production is a fickle thing. Every single source and technique, whether it be fossil fuels, nuclear, or even renewables, comes with an Achilles heel. Fossil fuels are the quickest and easiest energy generation method but come with a defined timeline for usage before harming the environment. Nuclear power plants are less damaging in theory but present an inherent risk of causing significantly more harm in the event of a meltdown. Renewables can be inconsistent — after all, you can’t draw power from the sun if it’s midnight where you live.

Photo Courtesy Karsten Wurth

But is the solar dilemma an immutable law of nature? A team of Stanford University researchers has made it their mission to question that idea, developing a prototypical device that can draw a certain degree of solar power in the dead of night. Though the process is more effective during cloudless nights, the fact that a piece of equipment can harness any energy in the first place is a significant step toward the future viability of solar as a stable power source. 

It all has to do with trace amounts of heat around panels relative to the cooler nighttime temperatures. “During the day, there’s a light coming in from the Sun and hitting the solar cell, but during the night, something of a reverse happens,” says Sid Assawaworrarit, lead researcher, electrical engineer, and Ph.D. candidate at the university. Assawaworrarit describes how trace amounts of energy photons are emitted from solar panels at night, taking a lot of heat with them. As a result, the panels end up slightly cooler than the air around them.

Photo Courtesy Evgeni Tcherkasski

The cooler panels create a vacuum effect as the warmer night air moves toward the cooler surface. The researchers then created a thermoelectric generator, which draws in that heat energy. The generator is attached to the solar panel and transfers that heat to be transmitted as usable power.

Although the amount of energy generated is minimal compared to a panel operating at peak hours, the potential uses for this technology are substantial. Roughly one billion people live in places without a stable power grid, relying on solar panels for the majority of their energy. Assawaworrarit argues that, for these people, the ability to power a light or charge a phone could be the difference between life and death, especially in areas plagued by civil wars and government unrest. “There are a lot of applications,” he says.