Engineers develop solar panels that can produce electricity at night with no need for batteries 

Solar panels are an excellent alternative to traditional energy sources, but they come with a pitfall—they can only generate electricity during the day. Stanford engineers have developed a new solution to this problem.

Researchers came up with a breakthrough solar panel that can serve as a “continuous renewable power source for both day- and nighttime,” according to the study recently published in the Applied Physics Letters journal.

The device can charge a phone, or even run an LED light at night.

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Each solar panel includes a set solar cells made of layers of semiconducting material. Solar energy is created when the sun emits energy towards one.

Traditional solar panels can only produce power during daylight hours so many rural areas that rely solely on solar off-grid systems will need to install battery storage. This will allow them to capture energy during the daytime, and then store it for the night. These batteries can be quite expensive.

Fortunately, there may be an alternative that is better and more affordable.

solar panels on a roof
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When the sun is out, solar panels radiate heat to outer space with a temperature of around -270.15ºC while heat travels toward lower temperatures. Researchers believe that solar panels are cooler than night air and can therefore be used to produce solar energy.

The thermoelectric generator pulls electricity from the slight temperature difference between the cell and the atmosphere. This process depends on the system’s thermal design, which has a hot and cold side.

Nighttime power generation from radiative cooling of a PV cell. (a) Schematic showing the energy balance of the PV cell and (b) thermal circuit model of the PV-TEG device.
Applied Physics Letters

“You want the thermoelectric to have very good contact with both the cold side, which is the solar cell, and the hot side, which is the ambient environment,” explained author Sid Assawaworrarit. “If you don’t have that, you’re not going to get much power out of it.”

The setup is very affordable and can be incorporated into existing cells. The thermoelectric is actually the most expensive part of the system. It is also easy to make, so they are possible to be built in remote locations with limited resources.

“Our approach can provide nighttime standby lighting and power in off-grid and mini-grid applications, where [solar] cell installations are gaining popularity,” said the study.

Mini-grid applications are independent electricity networks that can also be used when there is not enough power or too far to extend the grid.

Design and prototype of a PV-TEG device. (a) Design drawing and (b) constructed prototype.
Applied Physics Letters

Only a few watts are required to use electricity at night for lighting. The current device produces 50 watts per square meter. This means that lighting would require approximately 20 square meters of solar area.

“None of these components were specifically engineered for this purpose,” said author Shanhui Fan. “So, I think there’s room for improvement, in the sense that, if one really engineered each of these components for our purpose, I think the performance could be better.”

Researchers aim to improve the device’s thermoelectric components and thermal insulation. They are researching engineering developments for the solar cell in order to improve its radiative cooling performance and solar energy harvesting ability.

solar cells
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The price of solar energy has fallen in recent years, making it more affordable for the general public. Some companies have used solar energy. California even incentivizes the switch to solar.

Alternative energy investments are necessary as Ukraine continues to be at war.

“In the face of global supply uncertainty, we must ramp up clean energy production and eliminate our reliance on hostile nations for our energy needs,” Abigail Ross Hopper, president and CEO of Solar Energy Industries Association, told CNBC.

These new solar cells could prove to be a game-changer, as there are an estimated 770 millions people in the world without electricity.

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