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Windows have one basic limitation: They let light in, but if you want to keep light out you have to use blinds or a curtain. Researchers at Japan’s National Institute of Advanced Industrial Science and Technology and Sumitomo Chemical have developed a new type of “power-saving” window skin that take blinds out of the equation. The passive sheet can be attached to any window, moderating the amount of sunlight that passes through in the summer, which should help people to save money on air conditioning.
In the winter, you want to let as much light (and warmth) in as possible. But in the summer, in order to stay cool, you want to do the opposite, limiting the amount of hot sunlight enters your windows. The amazing new window sheets are able to filter out powerful summer sun without using any energy.
Here’s how they work: The sheets are made from two transparent sheets that are fitted together. The position of the sun is different in the summer than it is in the winter, and the window skins take advantage of the different angles at which summer and winter light hit the window. The summer sun is high in the sky during daylight hours, meaning it hits the window at a wider angle, and is automatically reflected away by the window sheets. But winter sunlight, which hits the window at a less than 30-degree angle can pass directly through the sheet without any interference.
The sheets are still in development, but here’s hoping the folks at Sumitomo Chemical are able to bring them to market within the next few years.