Stanford Engineers Have Gotten Solar Panels to Generate Electricity at Night

(Photo: Caspar Rae/Unsplash) Solar panels are an excellent alternative to more traditional energy sources, but they come with a caveat: they can only be used during the day. That is, until now. Sid Assawaworrarit, an electrical engineer and PhD candidate at Stanford University, is leading the effort to make ordinary solar panels functional at night. 

Assaworrarit has been successful so far. He and his colleagues have created a device that helps regular solar panels generate electricity using the fluctuating temperature of ambient air. As it turns out, solar panels can kind of work in reverse; solar panels emit infrared radiation even in the absence of light. This takes the form of protons carrying heat away from the solar panel via wavelengths invisible to the human eye. On a clear day (when there aren’t any clouds in the sky to reflect infrared light back toward Earth) this heat transfer creates a temperature difference of a few degrees, which is the secret sauce to Assaworrarit’s device.

On a clear night, the team’s technology can capture 50 milliwatts per square meter of solar panel. (Photo: Lucas Gallone/Unsplash)

The device, called a thermoelectric generator, catches the heat that flows between the warm air and the solar panel and turns it into energy. Assaworrarit’s team is currently able to obtain about 50 milliwatts per square meter of solar panel. Though this is a small fraction of the amount of electricity a solar panel can generate during the day (most are capable of about 150 watts per square meter), Assaworrarit says the right location and a few tweaks to the technology may allow the device to pick up “about one or two watts per square meter,” which is far more than solar panels were previously able to generate at night. 

Assaworrarit’s team isn’t the first to use a thermoelectric generator to capture heat from the night, but their approach looks promising when it comes to using solar panels that already exist for daytime use. By using an aluminum plate to reduce the amount of heat that could escape from the edges of their solar panels, the team was able to multiply their technology’s generated energy nearly ten times. 

Night-effective solar panels carry a significant amount of potential. Scientists who use solar-powered equipment, like meteorologists and wildlife researchers, could benefit from more reliable power sources and lighter backup battery loads. Those who rely on solar power and other off-grid solutions for daily life—i.e. around one billion people globally—could also benefit from panels capable of providing a more consistent stream of electricity.  

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