Solar panels at sundown.
The biggest drawback of solar power is that panels generate very little power on cloudy days and zero at night. People with residential solar systems usually have a setup that generates more electricity than they use during the day, so they can live off the power company or a battery at night.
The monetary savings come from generating more power during the day than you take from the grid at night over the course of the year.
This arrangement is fine for people who live in developed areas. But for the 750 million people around the world who live in areas without an electrical grid, solar panels aren’t a reliable power source and battery storage is expensive.
A new development from Stanford University may be a big help to people living in underdeveloped areas that are completely off the grid. The university researchers created a solar panel that generates a significant amout of power during the day and a small amount at night.
According to the study published earlier this month in the journal Applied Physics Letters, the new panels can serve as a "continuous renewable power source for both day and nighttime.”
The new panels are pretty easy to make, too.
“What we managed to do here is build the whole thing from off-the-shelf components, have a very good thermal contact, and the most expensive thing in the whole setup was the thermoelectric itself,” Zunaid Omair, a metrology engineer from Stanford University and one of the study’s authors, said.
The solar panels function like a traditional panel during the day but run in reverse to continue generating electricity at night. After the sun goes down, the panels are able to generate electricity off the difference in temperature between the ambient air and the solar panel's surface.
(Or for you physicists out there, it works by tapping into the heat being radiated from the surface of the solar cells as infrared light into outer space.)
A big drawback is that the panels aren’t very effective on cloudy nights.
When pointed at the night sky, the solar panels generated a power output of 50 milliwatts per square meter or about 0.04% of the power output of a traditional solar cell during the daytime. This is enough power to run a low-wattage LED light or to charge a cell phone.
“The nice aspect about this approach is that you essentially have a direct power source at night that does not require any battery storage,” Shanhui Fan, a professor at Stanford’s School of Engineering, said according to New Scientist.
Battery storage for solar power can be unreliable and expensive, so these new panels can be a big benefit to people in areas that are without a traditional power grid. "Our approach can provide nighttime standby lighting and power in off-grid and mini-grid applications, where [solar] cell installations are gaining popularity," the study said.
The ability to run an LED light or a phone charger in the middle of the night may not seem like a game-changer to most people in the developed world, but it can make a huge difference in the quality of life for people living in remote areas of the planet. Further, this is just the beginning. Traditional solar panels have come a long way over the past few decades. Who knows what the future holds for this promising new technology?
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