The sun itself could soon become a low-cost air conditioner. An Israeli company is working on a light-filtering paint that can help actively cool buildings using zero electricity. The technology is based on the counterintuitive principle of laser cooling, whereby hitting specially designed materials with a laser can cool them up to 150°C.

In hot weather, electricity consumption soars as people turn on the air conditioning, pushing the electric grid to its limits and also raising energy bills. According to SolCold’s co-founder Yaron Shenhav, “It’s like putting a layer of ice on your rooftop which is thicker when there is more sun. As long as the sun is shining on it, it would be continuously cooled.”

To date, the paint has been successfully tested in the lab, where researchers discovered that the cooling effects are more pronounced on metal roofs than on concrete. Simulations show that a room on the top floor of a house that has had the paint applied to the roof can feel up to 10°C cooler than a house without the coating. 

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