PV you can't see

Saf-Glas introduces transparent solar glass
September 15, 2011
FABRICATION : TECHNOLOGY

EnergyGlass uses inorganic nanoparticles that are co-extruded with a polycarbonate interlayer, which is then laminated between two lites of 4-millimeter glass. The nanoparticles redirect components of the light spectrum to the edge of the glass, where it is collected with traditional monocrystalline solar cells.

Saf-Glas, www.saf-glas.com, is changing the way the building industry sees—or rather doesn't see—photovoltaics. The company introduced its transparent PV product, EnergyGlass, www.energyglass.com, during the solar seminar at GlassBuild America, Sept. 14.

"In the solar market, we've had mostly opaque products, or products that let some light through. What we've not had are photovoltaics that you can see through—modules that will give you electricity through a transparent piece of glass," says Steve Coonen, BIPV consultant and principal, PV Glassworks, Grass Valley, Calif. "Many attempts have been made in R&D labs; very large corporations have tried to do this. Finally, we have a successful product, and it comes from the glass industry, not the solar industry."

This photo, taken through an EnergyGlass window, demonstrates the PV product's transparency.

Saf-Glas is a fabricator of laminated safety glass products, and has been supplying forced entry, bullet-resistant, bomb blast, hurricane and tornado products for two decades. While solar might seem like a divergence from its traditional product line, Saf-Glas Owner Patrick Smith says EnergyGlass technology is based on the same proprietary interlayer found in its safety products. "We are still a laminating company," he says.

The company fell into the solar market a bit by chance. "Many years ago, we were asked to do a design solution to protect solar panels against hail, flying debris and vandalism," Smith says. "A simple fix would be to put a protective panel in front of the solar module, but that would hinder the performance and efficiency. Realizing conventional solar wafer panels are more efficient, but are limited to four-to-six sunlight hours and also affected by rainy and cloudy days, I focused on amorphous thin-film solar panels, which have less efficiency but can still produce some energy even when no direct sunlight is present. Upon further extensive research, I found that no company has a product that is truly clear and also creates energy. Since my work is mostly with façade glazing, I decided to direct all my R&D into this particular solution."

EnergyGlass uses inorganic nanoparticles that are co-extruded with a polycarbonate interlayer, which is then laminated between two lites of 4-millimeter glass, Coonen says. The nanoparticles redirect components of the light spectrum to the edge of the glass, while letting most of the spectrum through. "The light that reaches the edge of the glass is collected with traditional monocrystalline solar cells, which are the highest efficiency out there in the market," Coonen says.

Smith says EnergyGlass won't produce as much electricity as traditional PV—the glass only features thin strips of monocrystalline cells, located around the edge of the laminated glass glass panel. However, it allows users to generate some electricity while maintaining transparent views through the glass.

Additionally, the cells collect ambient light and artificial light, in addition to direct sunlight. "Our product creates electricity as long as there is light present," Smith says. "Most conventional solar panels are only efficient when facing towards the sun, such as on rooftops or solar farms, and are limited to one size."

"This product did not reinvent solar cells," Coonen says. "They took a product from the solar industry and married it with a relatively standard glazing industry product."

As a laminated product, EnergyGlass also provides impact resistance. Saf-Glas spent four years developing EnergyGlass.

The glass is available to quote now, and will be out in the market in the first quarter of 2012, Smith says. Additionally, it is applicable for all incentives that are available for traditional solar panels and the IRS 1603 Program, if certain criteria are met by the end of 2011. The IRS 1603 Program: Payments for Specific Energy Property in Lieu of Tax Credits provides "60 percent accelerated depreciation, of which 30 percent is a cash rebate back to them if [project architects, owners, developers or glaziers] take advantage of the 5 percent Safe Harbor," Smith says. "This is only available if certain criteria are met by the end of 2011. This end-of-year application will ensure their project and 30 percent cash rebate to the end of the project."