Thermochromic windows capable of converting sunlight into electricity at a high efficiency have been developed by scientists at the US Department of Energy’s National Renewable Energy Laboratory (NREL).   Relying on advanced materials as perovskites and single-walled carbon nanotubes, the new technology responds to heat by transforming from transparent to tinted. As the window darkens, it generates electricity. The color change is driven by molecules (methylamine) that are reversibly absorbed ...