Seems unrealistic, right? After all, it is one of the biggest drawbacks of solar energy. But thanks to science & engineering, it is well within your reach. At night the lack of sunlight cannot generate electricity – a disadvantage for solar energy. However, what if they worked at night? That’s no joke, according to researcher Sid Assawaworrarit and his colleagues.
In a major breakthrough, researchers have designed a unique night solar panel (NSP) that can produce electricity under ideal conditions at night. In short, a clear night means infrared light from the surface of solar panels can freely radiate out into space which further generates electricity.
The device Assaworrarit and his colleagues created is basically a work of flow of energy. Basically, it is an ordinary solar panel outfitted with a thermoelectric generator. It helps to generate a small amount of electricity from the slight difference in temperature between the ambient air and the surface of a solar panel pointed deep into space.
At night, solar panels turn the table and emit photons
The new technology takes advantage of a surprising fact about solar panels. 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.
“There’s actually light going out [from the solar panel], and we use that to generate electricity at night. The photons going out into the night sky actually cool down the solar cell,” Assawaworrarit says.
Solar-cell-illustration by Tristan Deppe & Jeremy Munday
As those photons leave the skyward surface of the solar panel, they carry heat with them. That means that on a clear night — when there are no clouds to reflect infrared light back toward the Earth — the surface of a solar panel will be a few degrees cooler than the air around it. That temperature differential is what Assawaworrarit and his colleagues are taking advantage of. A device called a thermoelectric generator can capture some of the heat flowing from the warmer air to the cooler solar panel and convert it into electricity.
On a clear night, the device Assawaworrarit tested on the Stanford rooftop generates roughly fifty milliwatts for every square meter of solar panel (50 mW/m2).
“I think that’s probably a record number,” he says. But Assawaworrarit and his team aren’t stopping there. He says that with a couple of improvements (and in a good location) such a device could generate twice that amount of electricity.
Another good use for the technology is powering the immense network of environmental sensors researchers use to keep tabs on everything from weather conditions to invasive species in far-flung corners of the globe. Again, solar panels that generate a small amount of electricity at night could reduce the need for batteries — and the maintenance and replacement costs they incur.
Modern scientists are hardly the first people to notice that a surface pointed toward the cloudless night sky can become colder than the air around it. The phenomenon is called radiative cooling, and you’ve probably seen it yourself first thing in the morning.
What does this mean to you?
Well, firstly you will consume more electricity in the future. As you buy more appliances, your energy consumption will increase. What’s worse is that you will need to pay more as scarcity of resources means electricity will only get costlier.
On the other hand, developing such technology poses several engineering challenges. Understanding the physics behind these nighttime solar panels is only part of the battle. Engineers have been working for years to make them efficient enough to be worthwhile for use in the real world.
Solar energy is a good option for sustainability. Solar power is a non-exhaustible resource and helps reduce the carbon footprint of individuals. And it is here to stay for a very long time. Hence choosing solar panels is your best choice against hefty electricity bills. Book a call with Staten to answer your solar-related question. Dial +1 (408) 780-2889 or fill a short form here.