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New Technology

Someday we'll see photos of giant upright metal panels on rooftops and beside buildings and we'll be amused at our early clunky efforts to capture sunlight and convert it into electricity. We have entered the age of the polymer. It's in everything from our airplanes to our sweatshirts, and now it's in some PV cells. Rather than adding-on solar panels, the trend is toward incorporating thin-film solar technology directly into the fabrication of building materials including roofs, shingles, windows, and siding. Thin-film photovoltaic modules are produced by applying extremely thin layers of light-sensitive semiconductor material to a low-cost backing.

Just about everybody from labs to universities is working on the thin-film technology. The race is on amongst the largest manufacturers of PVs to create the most efficient, thin, and flexible solar films. German-owned Siemens, the world's largest manufacturer of solar cells and modules based in Camarillo, California, has teamed up with the Department of Energy's National Renewable Energy Lab in Golden, Colorado to research the film. The National Renewable Energy Lab also signed a contract in August with Solarex of Frederick, Maryland to conduct further research on thin film photovoltaics. Solarex, a business unit of Amoco/Enron Solar, is the largest U.S.-owned manufacturer of photovoltaic modules. The technology uses half-mile long substrates in a roll-to-roll process for producing solar cells in a manner similar to the production of newsprint or photographic film.

The thin-film joint venture that claims the highest rate of efficiency has a patent on a thin polymer film called lumeloid. Scientists at Advanced Research Development in Atol, Massachusetts, in cooperation with Argonne National Laboratory in Chicago, are working on a $1.8 million project to develop the lumeloid "solar cell on a roll." Lumeloid polarizes light, and its inventor Alvin Marks claims it changes about 70 percent of it into electricity, while other films claim an efficiency rate of less than 20 percent. But in order to be practically applicable, lumeloid has to be paired with another material being developed by Argonne, which will bring that efficiency level down an uncertain percentage. Marks also holds the patent on what he calls "through the looking glass" technology, a see-through solar window material he hopes to sell for $30 per square meter.

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The trend is toward incorporating thin-film solar technology directly into fabrication of building materials, from windows to shingles.

Speaking of joint ventures, United Solar, a subsidiary of Energy Conversion Devices of Troy, Michigan, in a joint venture with Canon, is using the thin film in various roof products including a large metal roof panel that can replace a regular roof on a building, and a thin-film solar shingle that can be put on a roof the same way as regular asphalt shingles. United Solar has been making small quantities of the flexible solar shingle product for demonstration purposes for about a year, and has been producing it in larger quantities since May. Most of these, as is the case with many solar products, have gone to distributors outside of the U.S. The flexible shingles are lightweight, seven feet long, and made to emulate asphalt shingles: they can be installed by nailing them down to the roof deck. Electrical wires from the shingles go through hooks in the roof deck and an electrician can wire them from below. In the U.S., the installed cost of the solar shingle is $7 to $8 per watt. The total installed price is $14,000 to $16,000, cheaper than a power line in some places, but much higher than local electricity.

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