A double duty solar window

What do you get when you cross a solar panel, a window and venetian blinds? Pythagoras Solar's idea for windows that generate power and cut air-conditioning needs.
Written by Melissa Mahony, Contributor

What do you get when you cross a solar panel, a window and a set of venetian blinds? Pythagoras Solar's idea for a window that simultaneously generates power and cuts air-conditioning needs.

Last week the company won a $100,000-award from GE's ecoimagination Challenge. In its four years, the company has raised another $11 million from investors for their BIPVs (building-integrated photovoltaic units). These are basically a high tech solar installation that resembles a low-tech window treatment: blinds. 

Skyscrapers consume massive amounts of energy. But they also have a lot of surface area for sunshine to strike through the course of the day. Windows typically comprise much of the vertical surfaces. So it's little wonder companies, scientists, and architects are seeing windows as opportunities to green up buildings.

Self-tinting windows, for instance, could welcome the sun's heat in or block it out, potentially enhancing a building's energy efficiency. Thin film solar windows are another approach that might boost a building's self-sufficiency by generating power.

But Pythagoras Solar, which operates out of California, Israel and China, wants to do both. Its photovoltaic cells have the dual responsibility of shading rooms from incoming light and then putting that blocked light to work producing electricity. Sandwiched horizontally between two panes of glass, the silicon PV cells' power generation comes in at 13 watts per square foot.

Gonen Fink, Pythagoras' CEO, tells theSan Francisco Chronicle:

Instead of heating the room, the light generates clean solar power. It's relatively simple and straightforward optics. The challenge is making everything work together.

Since last November, one pilot project has been underway in a high profile position. Chicago's Willis Tower is testing out the window units on the south-facing side of its 56th floor (the former Sears Tower has 110 stories). According to the company, commercial installations are in the works, too. So does the price reach the sky as well? Possibly, but just how much the units cost per watt was not given.

Fink did estimate, however, that the energy savings could recoup costs within three to five years.

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Image: Pythagoras Solar

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