Electrical engineer Sid Assawaworrarit, who leads a research team from Stanford University (USA), developed a device. It enables the generation of photovoltaic electricity at night. This is an ordinary solar panel equipped with a thermoelectric generator.Generating a small amount of electricity from the small temperature difference between the ambient air and the surface of a solar panel pointing into space.
The new technology takes advantage of a surprising fact about solar panels. During the day there is light from the Sun hitting the solar cell, but at night it is the opposite. This is because solar panels emit infrared radiation like anything hotter than absolute zero.
“There’s actually light from the solar panel, and we use it to generate electricity at night. The photons that go up into the night sky actually cool the solar cell,” says the head of the team of scientists.
As these photons leave the surface of the solar panel towards the sky, they drag the heat with them. This is on a clear night, when there are no clouds to reflect infrared light back to Earth, the surface of a solar panel will be several degrees cooler than the surrounding air..
Assawaworrarit and colleagues take advantage of this temperature difference. 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 Assavorrarit device tested on Stanford’s roof produces about fifty milliwatts per square meter of solar panel (50 mW/m2).
The engineer claims that with a few improvements and in a good location, such a device can generate twice as much electricity.
“The theoretical limit is probably one or two watts per square metre.. It’s not a huge number, but there are many applications where that kind of power at night would be very useful,” he says.
Since the type of thermoelectric generators used in these solar panels is solid state, their lifetime is almost endless.
One use of this technology is to power the vast network of environmental sensors that researchers use to monitor everything from weather conditions to invasive species in far corners of the planet. Again, Solar panels that produce a small amount of electricity at night can reduce the need for batteriesand associated maintenance and replacement costs.
If you can achieve one watt per square metre, that would be very cost-effective.
An easily overlooked power supply
The Earth constantly receives an enormous amount of energy on the order of 173,000 TW from the Sun. Reflective surfaces such as clouds, particles in the atmosphere, and snowy mountains instantly reflect 30% of this energy back into space. The rest ends with warming the land, oceans, clouds, atmosphere and everything else on the planet.
But that energy does not stay here. Earth sends out as much energy as it receives, except for the additional heat captured by greenhouse gases since humans began burning copious amounts of fossil fuels since the Industrial Revolution. Like this the planet emits a truly mind-blowing amount of energy in the form of infrared radiation..
“It’s a kind of light. Infrared radiation emanating from the hot Earth (or anything else) has wavelengths longer than our eyes can see, but carries energy. In fact, more than half of the total amount of solar energy reaching it. Earth has to go through this process to get back into space.” passes,” says the engineer.
What Assawaworrarit and colleagues are doing is a new way of capturing this energy as it leaves the planet.. They’re not the first to use a thermoelectric generator to capture this type of energy. By integrating this new technology with solar panels that generate electricity during the day, the researchers have taken an important step towards enabling ordinary people to capture this energy for themselves.
Reference article: https://ecoinventos.com/stanford-panel-solar-genera-electricidad-por-la-noche/