Having solar panels on your roof is nowadays almost as common as having a roof in the first place. More and more innovations are thought up to provide power in a green manner, through things like wind and solar power. Soon enough, your curtains, made from solar and wind charged fabric, will be able to charge your phone, but what if your windows could provide power for your laptop? The start-up Physee from Delft, the Netherlands, introduces fully transparent windows, called the PowerWindow, to make this possible.

The idea of glass that can charge solar power is not new. After all, we have so much glass around us; in every house, office building, and greenhouse, it is used. If all those surfaces could provide us with energy, we would hardly need powerplants anymore. With that in mind, researchers have tried to come up with fully transparent solar charged windows.

In August 2014, scientists at the Michigan State University succeeded in this by inventing a transparent luminescent solar concentrator (TLSC). The TLSC consists of organic salts that absorb specific non-visible wavelengths of ultraviolet and infrared light, which they then luminesce as another wavelength of infrared light. This emitted infrared light is guided to the edge of plastic, where thin strips of conventional photovoltaic solar cell convert it into electricity.

While effective, the TLSC-glass is not enough to keep your phone or laptop running, only extend the length of the battery charge. This is where the new windows come in. One square meter of this glass charges 20 Watt all year round, which is enough to keep your laptop running.

The PowerWindow is treated with a coating that, instead of reflecting 30% of the light like conventional windows do, collects it and transports it through the glass, so that it can be converted into electricity in the solar cells on the inside of the window frame. The coating is a couple of hundred nanometers thick, and is made of an industry-standard host-crystal with a 3% concentration of the luminescent solar concentrators (LSCs). The PowerWindows are less costly than solar panels, about one tenth of the price, but the energy generation is only about one seventh of what a solar panel can do.

In June this year, a pilot project was done with the PowerWindows in a bank building in Eindhoven, the Netherlands, where thirty square meters of the new glass was placed. On 14 September, the invention won first prize in the Dutch Postcode Lottery Green Challenge.