Start-up Pythagoras Solar has designed a window that doubles as a solar panel and layer of insulation.
The company on Tuesday detailed its photovoltaic glass unit, a replacement for the glass structures used on the facades or roofs of commercial buildings. Pythagoras Solar's first product, due in the third quarter this year, will be a skylight but the company also plans to make curtain walls for new buildings.
Typical commercial insulated glass units have two panes of glass, placed about one inch apart and held in a metal frame, which are coated with a film to block out heat from the sun. Pythagoras Solar's glass unit also uses two panes but the glass unit is made of several tiles, each of which has a solar cell to generate electricity. The rectangle-shaped tiles allow daylight in and have internal mirrors reflect light onto the solar cells.
The key to the design is a plastic prism, placed on the outside of the glass unit, and the adhesive materials used, said company Vice President Udi Paret. "We manipulate the light with optics so the direct light gets onto the cell and the materials make the heat dissipate," he explained.
The company, which was founded in 2007 and has raised $12 million in venture capital, has a partnership with cell provider China Sunergy for the monocrystalline silicon solar cells and contract manufacturer Flextronics to make the end product, said Paret. Production of the photovoltaic glass unit is scheduled for the third quarter this year and two projects are already in the works for this year, he added.
The mirrors within the tiles concentrate the light onto the solar cells, which helps the glass unit produce as much electricity as a comparably sized solar panel placed on a flat roof, Paret said.
He did not disclose pricing but the company says that building owners can get a return on investment of about five years.
Flexible, thin-film solar cells allow for several building-integrated photovoltaic (BIPV) products, such as power-generating windows, roofs, or awnings. But actual sales of BIPV material is still a tiny niche, about 100-megawatts worth of product last year, according to Paret.
In practice, Pythagoras Solar expects that its photovoltaic glass units will be used among other traditional insulated glass units. For example, one project under discussion could use the power-generating glass for about 20 percent of the façade, he said.