Researchers from University of Gothenburg have developed a way to transform ordinary windows into solar-powered heaters that use the sun's energy to increase the window temperature by up to 15 °F in cold weather. The researchers expect that the new solar thermal surfaces will lead to significant energy savings through reduced heating costs.
See-through solar materials that can be applied to windows represent a massive source of untapped energy and could harvest as much power as bigger and bulkier rooftop solar units.
When sunlight shines on the surface, light is absorbed more efficiently from the front side than the back side. This directionality in light absorption makes the surfaces attractive for window applications, as sunlight can be absorbed most efficiently from the outside of the window. In addition, the surfaces are highly transparent, appear colorless, and almost completely preserve the color spectrum of sunlight.
Although transparent solar technologies will never be more efficient at converting solar energy to electricity than their opaque counterparts, they can get close and offer the potential to be applied to a lot more additional surface area
In the future, the researchers plan to work on achieving even larger temperature increases by enabling the surfaces to absorb ultraviolet and near-infrared radiation, which constitute a significant portion of solar radiation.
Source: https://phys.org/news/2017-10-passive-solar-windows-cold-weather.html