In the cold winter months you'll do everything you can to maximize your exposure to the sun. In the scorching summer, though, it's just the opposite. So what if there were a way to harness/banish the sun's rays without a constant battle with curtains or venetian blinds?
Researchers at Japan's National Institute of Advanced Industrial Science and Technology, working alongside a company called Sumitomo Chemical, have developed a clever way to moderate the amount of sunlight entering a window from season to season: a passive sheet that automatically lets in less light during the summer to keep things cool, and more light in the winter for added warmth.
But how does the miracle sheet do this without using a drop of electricity? By taking advantage of the very thing that makes it hot in the summer and cold in the winter: the position of the sun. The sheet acts like a very thin prism, taking advantage of the fact that sunlight hits a window at different angles throughout the year. So in the winter it passes right through the sheet to heat a room, but in the summer a lot of the light ends up getting bounced away.
The sheets, which don't result in any visual distortion, should help reduce heating and cooling bills from season to season. And once its creators have refined the manufacturing process and find an easy way to adhere it to existing windows, they're optimistic it could go into product in just a couple of years.