Good Thinking

Polymer gel pulls in water vapor to cool solar panels

Polymer gel pulls in water vap...
Although the use of air conditioning and refrigeration systems has been explored for the cooling of solar panels, such systems often use more electricity than the panel generates
Although the use of air conditioning and refrigeration systems has been explored for the cooling of solar panels, such systems often use more electricity than the panel generates
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A diagram illustrating how the gel works
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A diagram illustrating how the gel works
Although the use of air conditioning and refrigeration systems has been explored for the cooling of solar panels, such systems often use more electricity than the panel generates
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Although the use of air conditioning and refrigeration systems has been explored for the cooling of solar panels, such systems often use more electricity than the panel generates

Given that solar panels lie in direct sunlight, it goes without saying that they can get pretty hot. Unfortunately, though, they also get less efficient as they heat up. That said, a new gel could help cool them … without using any electricity.

Developed at Saudi Arabia's King Abdullah University of Science and Technology (KAUST), the polymer gel contains both calcium chloride and carbon nanotubes. The material is very adhesive, so it can easily be applied to the back of existing photovoltaic panels.

At night, the calcium chloride – which is a powerful desiccant – draws water vapor out of the humid air and into the gel, where it's stored as a liquid. That gel expands as it takes on water, potentially doubling its dry weight.

In the daytime, the carbon nanotubes absorb solar heat from the panel. Once enough of that heat has been passed into the gel, the stored water gets hot enough that it turns back into vapor. It then evaporates out of the gel, carrying the heat away with it.

A diagram illustrating how the gel works
A diagram illustrating how the gel works

When the fully water-loaded material was tested on solar panels under artificial sunlight in a lab, it was found to reduce their temperature by a total of 10 ºC. An even greater temperature-drop was achieved when the gel was later tested outdoors under natural sunlight, improving a panel's efficiency at converting solar energy into electricity by up to 19 percent.

"We believe this cooling technology can fulfill the requirements of many applications because water vapor is everywhere and this cooling technology is easy to adapt to different scales," says postdoctoral researcher Renyuan Li. "The technology could be made as small as several millimeters for electronic devices, hundreds of square meters for a building, or even larger for passive cooling of power plants."

A paper on the study, which is being led by Prof. Peng Wang, was recently published in the journal Nature Sustainability.

Source: KAUST via EurekAlert

3 comments
Gary Tulie
Could make a big difference to air conditioning load if used for evaporative cooling of the intake air of external split units in air conditioning when used for cooling in hot climates with a significant diurnal temperature change.
Expanded Viewpoint
Why not just use a storage tank, a shaded radiator and glycol coolant to pull the heat out of the solar panels? Convection currents will move the warmed up coolant from the solar panel, through a radiator hidden from the sun's rays, and then dumped into a tank, then pulled back out of the tank to go through the solar panel again. Or just put enough fins inside and outside the tank so it acts as a radiator itself.
ljaques
I'd sure love to see the heat dissipation curves of that stuff over a full summer day. If it works large-scale, it could save billions a year, and/or reduce the size of the solar array needed.