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Summary:

Is combining solar cells and windows a case of chocolate and peanut butter (perfect combo) or one of those unions which equals less than the sum of its parts? Startup Pythagoras Solar has designed — and is selling — a double-pane window embedded with solar cells.

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Is combining solar cells and windows a case of chocolate and peanut butter (perfect combo) or one of those unions which equals less than the sum of its parts? While the market has yet to decide this, feel free to be your own judge. Here’s the case: Startup Pythagoras Solar has designed and is selling a double-pane window embedded with solar cells, and this week got recognition (and $100,000) from GE for its innovation.

The idea is that the window lets in less light, while still being transparent, so buildings get needed shade during hot sunny hours, reducing their air conditioning use and making the building more energy-efficient. At the same time, the panels produce solar power, which the building can use for electricity. The company is currently targeting architects and commercial building owners.

Four-year-old Pythagoras Solar will announce its first commercial installation in the coming weeks, CEO Gonen Fink told me in an interview, and the company has been working for several years on smaller pilot projects, like one on the south-facing side of the Willis Tower in Chicago. The company, which has its R&D and investors in Israel, is in the process of moving from the project stage into mass production. The company raised a $10 million series A round from Israel Cleantech Ventures, Pitango Venture Capital and Evergreen Venture Partners.

So when Pythagoras is churning out these solar windows on a grand scale will they fly off the shelves? Part of the success will depend on the math. The solar windows cost more than a standard window, bur will be priced on par with some of the new dynamic tinting windows that are coming to the market from firms like Soladigm and Sage, said Fink.

The windows are also more expensive per square foot than straight solar PV, but factoring in the energy efficiency savings and clean power savings of the solar windows, Fink says their return on investment is 3 to 5 years. Solar panels, on the other hand, take longer, like 7 to 12 years to deliver a return.

The power production of the solar windows isn’t all that high — 13 watts per square foot — so a big chunk of the return seems to be coming from the energy-efficient aspect of the window. So part of the market Pythagoras is competing with is lower-cost but energy-efficient windows like those made by Serious Energy, and super-cheap stuff like blinds.

The cool factor of the windows will be what drives the market for these solar windows initially: eco-minded architects and real estate developers that want an extra green touch. Pythagoras needs some high-profile buildings to showcase its solar windows to get the word out. The GE smart grid challenge was also good for that.

  1. I would love to have some of these in my home! We just replaced our aluminum single and dbl pane windows with lowE more efficient windows… I wish these were on the market then!

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