New solar panels suck water from air to cool themselves down

Like humans, solar panels also don’t operate at full capacity when overheated. Therefore, researchers have now found a new way to make them cool and increase their power output.

It’s a simple way to retrofit existing solar cell panels for an instant efficiency boost.

Today, more than 600 gigawatts of solar power capacity exists worldwide, providing 3% of global electricity demand. That capacity is expected to increase over the next decade. Most use silicon to convert sunlight into electricity. However, typical silicon cells convert only 20% of the Sun’s energy and much of the rest turns into heat, which results in heating the panels by as much as 40°C. In addition, with every degree of temperature above 25°C, the efficiency of the panel drops.

In recent years, researchers have devised materials that can suck water vapor from the air and condense it into liquid water for drinking. The best is a gel that strongly absorbs water vapor at night, when the air is cool and humidity is high. When heat rises during the day, the gel releases water vapor. If covered by a clear plastic, the released vapor is trapped, condenses back into liquid water, and flows into a storage container.

Peng Wang, an environmental engineer at Hong Kong Polytechnic University, and his colleagues thought of another use for the condensed water: coolant for solar panels. Their idea was that during the day, the gel would pull heat from the solar panel to evaporate water it had pulled out of the air the previous night, releasing the vapor through the bottom of the gel.  Then, the evaporating water would cool the solar panel as sweat evaporating from the skin cools us down.

The researchers found that the amount of gel depended primarily on the environment’s humidity. For example, in a desert environment with 35% humidity, a 1-square-meter solar panel required 1 kilogram of gel to cool it, whereas in a muggy area with 80% humidity, the gel required is only 0.3 kilograms of gel per square meter of panel.

This will result in a temperature of the water-cooled solar panel dropped by as much as 10°C. Not only this, the electricity output of the cooled panels increased by an average of 15% and up to 19% in one outdoor test, where the wind likely enhanced the cooling effect, Wang and his colleagues report today in Nature Sustainability.

“The efficiency increase is significant,” Zhou says. But according to him,  the rain could dissolve the calcium chloride salt in the gel, sapping its water-attracting performance. Wang agrees, but notes the hydrogel sits beneath the solar panel, which should shield it from rain.

Another design option, Wang says, is a setup that could trap and recondense water after it evaporates from the gel. That water could be used to clean any dust that accumulates on the solar panels, solving a second power-sapping problem at the same time. Alternatively, that same water could be stored for drinking, addressing another desperate need in arid regions.