Generate electricity at night with solar cells
In order for solar cells to generate electricity, they usually need sunlight, which is naturally only available during the day. This reduces the productivity of the modules to zero at night. However, researchers at Stanford University have now succeeded in solving this problem and using solar panels to generate electricity at night. As the website Interesting Engineering reports, scientists led by electrical engineer Sid Assaworrarit tested a solar panel equipped with a thermoelectric generator on the roof of Stanford University last October to study its night-time performance. Conditions were good as there was not a single cloud in the California sky for several nights. Under these conditions, the experiment was successful. According to Interesting Engineering, the tested device generated about 50 milliwatts per square meter at night. “I think that’s probably a record number,” Assaworrarit told the website. According to Assaworrarit, however, with a few improvements and an optimized location, power generation could be significantly increased. “The theoretical limit is probably around one to two watts per square meter,” the researcher announces. “That’s not a huge number, but there are many applications where this type of night energy would be useful.”
New solar cells could make batteries superfluous
The new technology could be useful wherever batteries previously had to be used for night-time power requirements. Since solar modules usually only work during the day, the electricity generated must be stored in batteries for later use in order to provide energy at night. This circumstance has two disadvantages. Firstly, the necessary batteries are quite expensive and secondly, they lose considerably in capacity with the increase in charging cycles. Thanks to the nocturnal power generation with thermoelectric generators, many batteries can be dispensed with. Since the devices are also solid-state generators, Assaworrarit says their lifespan is pretty much infinite.
According to Interesting Engineering, about a billion people do not have access to a power grid. These people depend, among other things, on solar energy for their electricity supply. During the day you can rely on the solar panels in these areas, but this is not the case at night. The newly developed solar modules could help here. Many scientists and research projects around the world are also dependent on nocturnal energy. The nocturnal solar panels could generate the required electricity and significantly reduce the need for batteries for the continuous investigation of, for example, weather conditions or animal species in the most remote corners of the globe.
Infrared radiation makes it possible to generate electricity at night
The researchers at Stanford University manage to generate electricity at night using infrared radiation. “During the day, light comes in from the sun and hits the solar cell, but during the night something of the opposite happens,” Assawaworrarit told Interesting Engineering. The earth constantly receives an enormous amount of energy amounting to 173,000 terawatts from the sun. Clouds, atmospheric particles, and snow-covered surfaces would reflect around 30 percent of that energy directly back into space. The rest warm the planet. However, this heat does not remain on earth, except for a certain amount caused by the greenhouse effect. Practically every object that is warmer than absolute zero gives off the energy it has absorbed via infrared radiation. This is a type of light that cannot be perceived by the human eye due to its long wavelength. “The lights are actually off [vom Solarpanel], and we use that to generate electricity at night. The photons that go out into the night sky actually cool the solar cell,” explains Assawaworrarit. The photons that go out skyward take the heat with them and leave the earth for space. When there are no clouds in the sky at night, the infrared rays return to the planet throw back, the air around the solar module heats up while the surface of the device cools down at the same time.Assawaworrarit and his colleagues use this temperature difference between the solar panel, which is a few degrees cooler, and the ambient air to generate electricity via a thermoelectric generator.
Nicolas Flohr / Editor finanzen.net
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