Solar power, without those panels

 The main way for homes to harness solar power has been through bulky panels added to the rooftop or mounted on the ground.

But companies are now offering alternatives to these installations, in the less conspicuous form of shingles, tiles and other building materials that have photovoltaic cells sealed within them.

“The new materials are part of the building itself, not an addition, and they are taking photovoltaics to the next level — an aesthetic one,” said Alfonso Velosa III, a research director at Gartner Inc. and co-author of a coming report on the market for the new field, called building-integrated photovoltaics.

Companies are creating solar tiles and shingles in colors and shapes that fit in, for example, with the terra cotta tile roofing popular in the Southwest, or with the gray shingles of coastal saltbox cottages.

SRS Energy of Philadelphia is making curved solar roofing tiles designed to blend in with Southern California’s traditional clay tiles, said Martin R. Low, the chief executive of SRS. A solar tile system that met half the power needs of a typical California home would cost roughly $20,000 to install after rebates, he estimated, or about 10 to 20 percent more than solar panels providing comparable power.

U.S. Tile of Corona, California, a maker of clay tiles, will be selling SRS’s Sole Power Tiles, initially in California, and then in Arizona, New Mexico, Texas and other states, said Steve Gast, the company’s president. It will be taking orders perhaps as early as November for shipment in January, he said. SRS Energy buys the photovoltaic cells that cover its roofing from United Solar Ovonic, a maker of flexible solar modules that is based in Rochester Hills, Michigan. SRS bonds the silicon cells to the curved Sole tiles, which are made of the same basic material as car bumpers, said J.D. Albert, director of engineering at SRS.

The cells have been installed at several demonstration sites, including a home in Bermuda Dunes, California. Rather than creating an entire new roof with the solar tiles, the homeowner, Bill Thomas, a roofing contractor, chose to insert them in his existing roof, replacing about 300 square feet of terra cotta tiles; the job took about four hours, he said.

The solar insert in the roof will generate about 2,400 kilowatt hours of electricity a year, enough to cover a quarter to a third of a typical electric bill, Albert of SRS said.

A different solar material for the roofs and sides of buildings is being produced by Global Solar Energy of Tucson, Arizona. Atomized layers of a photovoltaic coating called CIGS are deposited in layers on a thin sheet.

Crystalline photovoltaic cells, the same type as in fixed panel installations, are used within the ceramic tiles available from, among others, the Italian company System Photonics. The cells are held in place and sealed from moisture by a clear plastic protective layer made by DuPont, said Stephen L. Cluff, DuPont’s global business director for photovoltaic encapsulants. The tiles come in 13 colors.

Velosa said the bulk of the installations were still experimental. But that will change, he said, because “we are seeing that the construction industry has realized that energy-efficient buildings are an opportunity for growth.”

Akhil Sivanandan, a research analyst in Madras, India, for the consulting firm Frost & Sullivan, said that government subsidies would speed adoption of building-integrated photovoltaics in the United States, as they already have in Europe.

“You need government incentives,” he said. “Even with drops in pricing and advances in technology, it is still too costly.”

In France, Germany and other countries, building-integrated solar markets are growing quickly because of subsidies and programs that pay homeowners for the electricity they generate and feed back to the power grid, he said.  The incentives help homeowners in repaying the systems’ costs in five to seven years.

But one other quality will be crucial to the popularity of building-integrated solar cells, Velosa said.

“Aesthetics is key,” he observed. “They have to look good.”