Solar panels that sweat…

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Engineers across the world are searching for way to improve the efficiency of solar panels. As new materials and designs are tested, any efficiency improvement – even a few percent – is announced as a breakthrough.

Most solar panels convert only around 20% of solar energy into power, and that’s measuring them in laboratory conditions. The vast majority of solar energy turns into heat, and solar panels function less efficiently when they are overheated. So while desert regions might otherwise seem obvious locations for the construction of solar power stations, desert temperatures can be a problem, with the panels heating to more than 40°C, when their energy generation is already affected at just 25°C.

Scientists from the Hong Kong Polytechnic University have now introduced an ingenious idea that can help the solar cells get rid of the heat – they have taught solar panels how to sweat.

The main element of the invention is a gel made of carbon nanotubes mixed with polymers that are linked with calcium chloride. The gel absorbs water vapour at night, when temperatures are low and the air humidity relatively high. During the day, when temperatures rise and air humidity falls, the water then evaporates from the gel again.

The scientists added a layer of the gel to solar panels to test if the evaporation of water could cool them. The effect was surprising. The sweating gel cooled the solar panels by up to 10°C, while energy generation increased by 15%. When the scientists tested the set-up outdoors, the gain proved to be even higher at 19%, because the cooling was still more efficient in the presence of wind.

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