A sorption-based atmospheric water harvester developed in Saudi Arabia could make photovoltaic devices more efficient in hot climates.
The cooling system developed at KAUST is said to have improved the efficiency of a prototype solar panel up to 20 per cent and requires no external energy source to operate.
Commercial silicon photovoltaic panels transform a small portion of absorbed sunlight into electricity, while the remainder of the radiation becomes heat. Efforts to cool solar panels with techniques including refrigeration or air conditioning tend to consume more energy than can be gained back through efficiency boosts.
Now, a team led by Peng Wang from KAUST’s Water Desalination and Reuse Center has developed a proof-of-concept device that aims to reverse this situation via the natural properties of the Earth’s climate. The team’s results are published in Nature Sustainability.
The KAUST researchers have already developed a polymer containing calcium chloride, which is a powerful desiccant. When exposed to humid air, this material gradually expands as the calcium salts pull water into the gel, eventually doubling its initial weight. By incorporating heat-absorbing carbon nanotubes into the polymer framework, the team found they could reverse this cycle and trigger the release of water with solar energy.
Renyuan Li, a postdoctoral researcher in Wang’s group, noted that one of the interesting properties of the gel was its ability to self-adhere to numerous surfaces, including the underside of solar panels. The team built a prototype for outdoor tests after experiments with artificial sunlight revealed that a fully filled gel could free enough water to reduce panel temperatures by 10oC,
During summer and winter, the researchers observed the gel absorbing water from overnight air and then releasing the liquid as the daytime temperatures ramped up. According to KAUST, the solar panels showed an increase in efficiency (13–19 per cent) even greater than that of the indoor experiments, a jump the researchers theorise may be due to improved heat and mass transfer outdoors.
“This work shows the benefits of using atmospheric water generation to help fight climate change,” said Li. “We believe this cooling technology can fulfil the requirements of many applications because water vapour is everywhere, and this cooling technology is easy to adapt to different scales. The technology could be made as small as several millimetres for electronic devices, hundreds of square meters for a building, or even larger for passive cooling of power plants.”