PETALUMA, Calif. — Solar panels have sprouted on countless rooftops, carports and fields in Northern California. Now, several startup companies see potential for solar panels that float on water.
Already, 144 solar panels sit atop pontoons moored on a 3-acre irrigation pond surrounded by vineyards in Petaluma in Sonoma County. Some 35 miles north, in the heart of the Napa Valley, an array of 994 solar panels covers the surface of a pond at the Far Niente Winery.
"Vineyard land in this part of the Napa Valley runs somewhere between $200,000 and $300,000 an acre," said Larry Maguire, Far Niente's chief executive. "We wanted to go solar, but we didn't want to pull out vines."
The company that installed the two arrays, SPG Solar of Novato, Calif., as well as Sunengy of Australia and Solaris Synergy of Israel, are among the companies trying to develop a market for solar panels on agricultural and mining ponds, hydroelectric reservoirs and canals. While it's a niche market, it's potentially a large one, globally. The solar panel aqua farms have drawn interest from municipal water agencies, farmers and mining companies enticed by the prospect of finding a new use for — and new revenue from — their liquid assets, solar executives said.
Sunengy, for example, is courting markets in developing countries that are plagued by electricity shortages but have abundant water resources and intense sunshine, said Philip Connor, the company's co-founder and chief technology officer.
SPG Solar's main business is installing conventional solar systems for homes and commercial operations. It built Far Niente's 400-kilowatt floating array on a 1.3-acre pond in 2007 as a special project and has spent the last four years developing a commercial version called Floatovoltaics that executives say is competitive in cost with a conventional ground-mounted system.
The Floatovoltaics model now being brought to market by SPG Solar is the array that bobs on the surface of the Petaluma irrigation pond.
"We have been able to utilize a seemingly very simple system, minimizing the amount of steel," said Phil Alwitt, project development manager for SPG Solar, standing on a walkway built into the 38-kilowatt array.
"With steel being so expensive, that's our main cost," he said.
Long rows of standard photovoltaic panels sit tilted at an 8-degree angle on a metal lattice fitted to pontoons and anchored by tie lines to buoys to withstand wind and waves.
The array, which is not yet operational, will be hooked up to a transmission line through a cable laid under the pond bed. Alwitt said that when the array is completed, 2,016 panels would cover most of the pond's surface and generate 1 megawatt of electricity at peak output.
He noted that the cooling effect of the water increased electricity production at the Far Niente winery by 1 percent over a typical ground-mounted system.
SPG Solar executives said an environmental engineering firm that evaluated its technology concluded that water evaporation under the floating arrays decreased by 70 percent. The companies also say that their systems inhibit destructive algae growth by blocking the sunlight the algae need to grow.
Sunengy's plan would deploy rafts of solar units that use a plastic lens to track the sun and concentrate sunlight on small photovoltaic cells that use less expensive silicon than conventional cells.
"If you have a drought on a hydroelectric dam, your asset is dead," said Connor, the company's co-founder. "If you have solar power on that dam, you can continue to generate electricity."