Researchers just created the first solar panels that work at night

So far companies have installed over 1 trillion watts of renewables around the world, and solar power is now the cheapest form of energy in over 58 countries. All that said though, despite advances in solar cell technology many people still think that solar panels are low efficiency and can only generate electricity when the sun’s shining. But, frankly, that all went out the window a while ago. Today, not only do we have a pathway to improve solar efficiency from the current record of 27 percent to 32 percent using 3D printed perskovite solar panels, 50 percent if we use genetically engineered bacteria, and even 80 percent if we recapture the lost heat using carbon nanotubes, but we also have solar panels that work in cloudy conditions, rain, and even when covered in snow.

So you’d be forgiven for thinking we’ve got every angle covered – but what about solar panels that can generate electricity during the night time?  Well, thanks to Jeremy Munday, a professor at the University of California Davis, and his team in the US we now have a solar, or should it be called a lunar, panel that can generate up to 50 watts of power per square meter, or about 10.75 square feet, under ideal conditions at night time which is about a quarter of what a conventional solar panel can generate in daytime, according to a concept paper in ACS Photonics.

Munday and his team have been developing prototypes of these night time solar cells for a while  now, and in time he and his team hope to improve the power output and efficiency of the devices.

Munday says that the process is similar to the way a normal solar cell works, but in reverse. An object that is hot compared to its surroundings will radiate heat as infrared light. A conventional solar cell is cool compared to the sun, so it absorbs light.

Space is really, really cold, so if you have a warm object and point it at the sky, it will radiate heat toward it. People have been using this phenomenon for night time cooling, which is also known as radiative cooling, for hundreds of years. And it’s so effective that elsewhere other teams in the US recently used this phenomenon to create another type of electricity panel that’s capable of generating infinite amounts of energy from the “coldness of space,” and another set of panels that can cool buildings without having to use any electricity.

It’s this phenomenon that Munday and his team have tapped into, and in the last five years, Munday says, there has been a lot of interest in devices that can do this during the daytime, by filtering out sunlight or pointing away from the sun. There’s also another kind of device called a thermoradiative cell that generates power by radiating heat to its surroundings, and researchers have explored using them to capture waste heat from engines.

“We were thinking, what if we took one of these devices and put it in a warm area and pointed it at the sky,” Munday says. This thermoradiative cell pointed at the night sky would emit infrared light because it is warmer than outer space.

“A regular solar cell generates power by absorbing sunlight, which causes a voltage to appear across the device and for current to flow. In these new devices, light is instead emitted and the current and voltage go in the opposite direction, but you still generate power,” Munday says. “You have to use different materials, but the physics is the same.”

However, while all this in itself is amazing Munday says the new panels will also work during the day as well, if you took steps to either block direct sunlight or pointed it away from the sun, and because this new type of solar cell could potentially operate around the clock it’s a very novel development that might further help us move the world off of fossil fuels.

Source: UC Davis