3M Film Turns Windows Into Transparent Solar Panels

3M has developed a see-through film that turns ordinary windows into solar panels. It will go sale next year.

The solar film, on display at the Ceatec electronics conference in Japan, is arrayed in narrow, translucent green strips with clear gaps between and then glued to windows in large patches. A square meter of the film can generate roughly enough electricity to charge an iPhone under peak sunlight, but still allows for high visibility.

The product currently generates only about 20 percent of the electricity that a traditional silicon solar panel does, and will cost about half as much, though the final price has not been decided.

But it is also far easier to install and takes up no additional space. 3M has strong expertise in adhesives, where its less technical products include Scotch tape and Post-it sticky notes.

"An average person could go to the store, buy some of this, and then bring it home and install it themselves," said Yasuhiro Aoyagi, a senior manager in the company's construction markets division.

He said it is made from an organic photovoltaic material that is printed on in sheets, and will come down in price as production increases. The film blocks or absorbs about 80 percent of visible light and over 90 percent of infrared light, so it also acts as a sunshade.

In the demonstration at Ceatec, thermometers on either side of a sheet of film attached to the outside of a window lit up by strong lights showed a difference of 10 degrees Celsius between the two sides, about 8 centimeters from the surface. Aoyagi said a square meter of the material can generate about 5 volts at 7 watts under peak conditions, and can operate under far less sunlight than it takes to power a conventional panel, so it will be active for more of the day.

3M hopes to target corporate and government buildings initially, then ramp up production for general use.

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