The Department of Energy’s Pacific Northwest National Laboratory (PNNL), in collaboration with San Jose based Vitex Systems and Battelle Memorial Institute (which operates PNNL), is working on creating a thin-film encapsulation process that would enable the use of flexible solar panels made from copper indium gallium selenide, or CIGS, from the same material and process used to protect flat screen televisions from moisture.
CIGS solar panels, which are more efficient than other solar panels, need a moisture barrier to make them durable when exposed to the elements.
The thin film technology was first developed by PNNL in the 1990s. At the time, solar panels were seen as one possible application. The technology was licensed to Vitex in 2000, and they focused their efforts on using the technology for flat screen television protection. The goal is to now integrate the flexible film with PVs to make a mass produced and easy to install solar panel.
Mark Gross, a PNNL senior scientist working on the project, says there are two main challenges; cost and durability. “Solar power made from panels with this thin-film encapsulation technology needs to cost less than $1 per watt of power,” says Gross. “The same technology is already a proven moisture barrier for OLED flat-panel displays, but the film barrier costs about $50 per meter squared for that application. Our film barrier will have to cost less than $5 per meter squared to meet the less than $1 per watt of power price point.”
In January of 2008, Vitex achieved a lifetime record for durability of flexible CIGS solar cells exposure to moisture and oxygen. Currently, commercially available flexible CIGS solar cells have a guaranteed lifetime of only two to three years. PNNL and Vitex are hoping to reach a durability of much longer.
“Solar panels that are encapsulated with our barrier film will have to withstand 25 years of being exposed to the elements, including wind, hail, rain, dust and, of course, the sun,” according to Gross. “Our barrier film has proven itself indoors on flat-panel displays and other sensitive electronic devices. Now, we’re focusing on choosing a substrate for the film and designing a barrier structure that enables flexible solar panels.”
According to Gross, the most promising substrate right now is a flouropolymer (a Teflon-like film) or a less expensive alternative which will be laminated to both sides of the solar panel.
The building-integrated photovoltaics (BIPVs) could be installed on roof tops like shingles, replacing current solar photovoltaics made from silicon and requiring mounting on metal frames, which have had limited success due to cost and installation issues. Gross believes that because BIPVs would be cheaper and easier to install, they could be easily integrated into the architecture of commercial and residential buildings converting wasted rooftop space into power generators.
The costs of the research are being split between $350,000 from the DOE's Energy Efficiency and Renewable Energy Technology Commercialization Fund and Vitex which is providing $350,000 in labor, equipment and materials.
Gross says that there are several different types of flexible solar panels in development right now. PNNL is focusing on CIGS panels, and they believe that those could be available in the next two to four years.
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