Researchers from UCLA and Stanford University have developed a panel similar in appearance to a solar panel only in works in the opposite way.
Instead of using the heat of the sun to produce electricity, the panel uses the coolness of the night sky.
When the sun goes down and is no longer shining on the panel, the top side cools off quickly, while the underneath side stays warm much longer (from the radiant heat from the earth or a rooftop beneath it.)
The temperature difference pushes electrons through from one side of the electrically conductive material to the other, creating an electrical current.
Its called radiant cooling, or passive cooling, a concept that’s been around for millennia, but mostly forgotten and never used in this way.
It was employed 6000 years ago in the Middle East in the form of enormous beehive-shaped structures called yakhchal that allowed people to create and store ice in the desert.
The “darkness” panel created far less electricity than a solar panel at only .5 watts per square meter (compared to 200 watts per square meter for solar panels), but the researchers say it could be useful for low-wattage nighttime applications, when solar isn’t available.
They expect the technology could be improved to produce 4 watts per square meter and note that the material used to make the panels would be far cheaper than the photovoltaic cells used in solar panels.
The scientists published the results of their experiment in the scientific journal Joule last month.