Stanford engineers make solar panels work at night

The tired knock on renewables is that they don't work when the sun isn't shining or the wind isn't blowing. That's why we need battery storage, but new research shows a novel way to continue harvesting energy from solar panels long after the sun goes down.

The Stanford team used a device known as a thermoelectric generator. As the name hints, the device generates electricity from difference in temperature between the ambient air and solar cells. The device basically harvests energy that passes between solar panels back into space at night, a process known as radiative cooling. (That process isn't limited to solar panels, either.)

It has a particularly strong effect on clear nights, which is when the researchers found they were able to generate the most power. The new system can offer a "continuous renewable power source" throughout both the day and nighttime and could cost less to maintain over the long run compared to battery storage, according to the new paper published in Applied Physics Letters.

"The demonstrated power density is already of interest for nighttime lighting applications," the report states. "Our design can also power sensors in remote locations, reducing the size or eliminating the requirement for battery storage."

The device was also able to harness energy from solar panels heating up during the day as the sun beat down on them, though it was only a marginal amount of power compared to the solar power generated by the panels. Still, every bit of carbon-free efficiency helps. That's particularly true for off-the-grid homes and communities that rely on mini grids for power, which are where the thermoelectric generator could likely pay the biggest dividends. In both cases, every little bit of power generation can help keep the lights on and reduce the need for either battery storage or backup gas-powered generators. It could also be a huge boost in parts of the developing world where electrification is in short supply.

This is a small-scale experiment, so it's not like this is coming to the masses any time soon. But it's part of an interesting wave of innovation around solar panels. Scientists have found ways to create double-sided solar panels that can capture even more energy. California has also recently moved ahead with a plan to cover canals in solar panels, generating power and saving massive amounts of water, something the state dearly needs to do.

Solar panel costs have plummeted rapidly over the past decade, something the recent United Nations climate change report was quick to point out. That's good, since we need to rapidly draw down carbon emissions, and building out as much solar power as possible is a key way to do that starting now. Adding another way to wring even more power out of panels — or, in this case, the air around them — seems like a no-brainer.