Six months after turning on what's arguably the largest rooftop solar electricity and hot-water cogeneration system in the U.S., Jackson Family Wines is finalizing plans to go even bigger in the next few months with installations in Sonoma and Monterey counties.

[caption id="attachment_63926" align="alignright" width="411"] Smaller versions of this 241-kilowatt solar electricity and hot-water array at Jackson Family Wines' north Santa Rosa facility are planned at two other company wineries. (photo credit: Jackson Family Wines)[/caption]

The Santa Rosa-based company plans to have combined-heat-and-power systems installed at the Vinwood Cellars production winery in Alexander Valley and at a winery in Monterey County around the beginning of 2013, according to Robert Boller, vice president of sustainability.

"If all goes well, we'll be the largest user of solar cogen in any industry in the U.S.," Mr. Boller said.

The company also has called together engineers and experts in heating and cooling systems to devise another cogen system that will generate electricity via natural gas-powered microturbines then recapture combustion heat to preheat cleaning water and recapture heat from the water to keep wine in barrel cellars warm enough to sustain fermentation on cold winter days.

That project is aimed for installation nine or more months after the new photovoltaic-thermal systems. Natural gas could eventually come from the Sonoma County Water Agency's Farm to Fuel biodigester-biogas power plant project planned for across the street from the Kittyhawk facility, Mr. Boller noted.

In April, Mountain View-based Cogenra Solar installed 96 of its photovoltaic-thermal panels on 9,000 square feet of a roof at Jackson's Kittyhawk blending and bottling facility near Charles M. Schulz--Sonoma County Airport north of Santa Rosa. The Kittyhawk array is rated at 241 kilowatts of electricity production and can preheat 1.4 million gallons of water annually, enough  to wash seven 15,000-gallon and one 100,000-gallon wine tank daily.

Each panel of the array has mirrors that focus sunlight onto photovoltaic cells that produce electricity. A tracking system keeps the panels pointed at the sun throughout the day. Photovoltaic cells typically are around 15 percent efficient in converting solar energy received to electricity, with much of the energy lost to heating the cells themselves.

To boost efficiency in energy conversion as high as 75 percent, the Cogenra panels channel water at 60 to 65 degrees through the assembly that holds the photovoltaic cells. The water cools the cells to boost their efficiency, and heat from the cells is transferred to the water, increasing its temperature to 160 to 165 degrees.

Instead of using energy to heat water by 120 degrees for washing, the preheated water only has to be heated about 20 degrees in a boiler.

The Vinwood system will be sized about 10 percent smaller than the Kittyhawk array, and the one in Monterey will be up to 25 percent smaller, even though the Central Coast facility is larger than Vinwood, Mr. Boller said. One of the challenges in designing photovoltaic-thermal systems for these two facilities is their use of hot water is much more cyclical -- peaking around harvest -- than that of the continually operating Kittyhawk facility, according to Mr. Boller.

Renewable-energy systems typically are sized based on the largest minimal demand for electricity for a facility, rather than peak demand, which can be much higher. Otherwise, a user would pay a lot more for a system with much more capacity than would be needed most of the time.

Jackson Family Wines' three-step approach to environmental sustainability -- conserve resources through more-efficient procedures, optimize or retrofit equipment to further shrink energy demand and generate renewable energy on or off site -- also helps to reduce the size of the energy-generation systems. Similarly, Sonoma County Energy Independence Program started using an efficiency-first requirement before funding property-assessed loans on homes and businesses for solar and  other renewable-energy systems.

Other North Bay solar electricity and hot-water systems installed by Cogenra are a 272-kilowatt system for Sonoma Wine Co. in Graton and a 50.6-kilowatt for Clover Stornetta Farms in Petaluma. Cogenra partnered with One Sun of Sebastopol on the latter project.

To reduce its carbon footprint companywide, Jackson Family Wines has been purchasing renewable energy credits through the U.S. Environmental Protection Agency's Green Power Partnership program. In the past three years, the company has purchased 96 million kilowatt-hours of credits of wind-energy production by Native Energy of Burlington, Vt.

Those purchases, including 36,000 one-megawatt-hour credits this year, cover 130 percent of the company's electricity consumption to include the home consumption of its more than 1,000 employees.

Those credits have cost 80 cents to nearly $1 per megawatt-hour. A typical three-person household in the North Bay consumes roughly 6 megawatt-hours a year.