[ Page 3 of 5 ]

By Peter Fairley

PV is making a mark on infrastructure projects, too. A 1-megawatt installation for a car-park canopy at Naval Base Coronado in San Diego employs 3,000 blue crystalline PV panels, bathing the vehicles below in a mix of shade and light. The structure was installed by Berkeley, California–based PowerLight. Tom Dinwoodie, the engineer-turned-architect who founded PowerLight, says the company aimed to match the airy feel of European train stations, hoping that visitors will step out of their cars and enjoy the view. As with Colorado Court’s solar walls and awnings, natural light filters around the PV cells, providing enough illumination underneath to read by while protecting commuters and cars from blazing sunlight. “It’s a fabulous effect,” says Dinwoodie.

San Francisco–based 450 Architects brought this shadow-and-light effect indoors when they designed the Argonne Child Development Center in San Francisco. The firm used 17 semitransparent solar panels to build three south-facing skylights in the school’s north-facing roof. Last year, the school was honored as one of AIA’s Top Ten Green projects [RECORD, May 2003, page 54].

PV technology: The rigid and the flexible Photovoltaic cells are composed of semiconducting material, usually silicon, which makes them capable of producing electricity from sunlight. Two technologies for making cells offer different looks and applications as they vie for space on rooftops, facades, and shading structures. Wafer (or cell) technology Crystalline cells, the most widely used technology on the market, are grown in long cylinders and sliced into wafers. Polycrystalline cells are either drawn in sheets or made into ingots and then cut into squares. They’re cheaper but produce less power than crystalline cells. Photography: Courtesy National Renewable Energy Laboratory Thin-film technology Thin-film cells are made by depositing layers of semiconductive material onto a glass, metal, or plastic surface. They’re less rigid than crystalline cells and even cheaper than polycrystalline, but less efficient than either.

Even for installations on commercial roofs, where aesthetics are a secondary concern, PV is considered a huge improvement on what came beforehand. Solar panels backed by insulation are sprouting up atop big-box retail stores, manufacturing plants, and office buildings in California. A visual makeover is the inevitable by-product of this trend, Dinwoodie says. “We tile roofs with these blue sparkling [PV] tiles. What was there before? Usually a gravel or a bituminous roof with puddles of mud.” Though many rooftop systems are invisible to all but air travelers, some are distinctly high-profile. In San Francisco, a 675-kW system atop the Moscone Convention Center is a magnificent blue field visible from downtown high-rises. Then there’s the shimmering solar rooftop of Napa Valley winery Domaine Carneros, which visitors can admire from the surrounding vine-covered hills. “It’s like the sea on this rooftop, and then you have the green from the hills. The rows of solar arrays bleed into the rows of the vineyard,” says Dinwoodie.

ADVERTISEMENT