A heat sink is a substance or environment that can both store heat and transfer it rapidly to another object. In the case of the reservoirs and the business park, the water maintains heat from the ambient atmosphere. The reservoirs are big enough and Sonoma County's climate sufficiently moderate so that the water stays within a narrow temperature range. To heat or cool the business park, water is drawn from the reservoirs to the complex's buildings. Each has a heat exchanger to obtain heat from or transfer heat to the water. A compressor then uses this energy to warm or cool air. Because the water hovers close to the temperatures required for human comfort, around 60°F, much less energy is required to bring the buildings up or down to the desired temperature range. And once its heat energy is harvested, the water can be used to irrigate landscaping and nearby vineyards, or flush toilets.

Mound zero: Sonoma County Water Agency engineer Cordel Stillman (left) is working on a geothermal heating and cooling system. Randy Poole (right) is the agency's general manager and a major force behind the initiative. Michael Sugrue

Similar "geothermal" heat pump systems already are in use in individual homes in the Midwest and at a military housing tract at Ft. Polk in Louisiana. But those systems rely on capturing temperature differentials in subterranean pipes. Sonoma's plan, which will incorporate two business parks and a large winery complex as pilot projects, is the first to address large commercial complexes, and the first to rely on wastewater as a heat sink. "Until now, this was something of an alternative technology that an ambitious handyman in the Midwest might use to reduce the heating and cooling costs in his home," Stillman says. "But by scaling up the process and turning to water as a heat sink, we're showing you can use these systems for large commercial, industrial and residential developments. And as you scale up, your savings in energy and reductions in carbon emissions become dramatic."

Sonoma's goals will seem hyper-ambitious to many energy pundits. What chance, after all, does a small county best known for exceedingly complex pinot noirs and bucolic lifestyles have of affecting national and international policies? Conventional wisdom dictates: none. A group of UC professors thinks otherwise. The county, they say, could be the fulcrum for a global tipping point. These days, says Dan Kammen, the director of UC's Renewable and Appropriate Energy Laboratory, the only significant response to global warming is coming from the grassroots. The feds have whiffed. And while some states—most notably, California—have set lofty and laudable goals for greenhouse gas reduction, little has been implemented. It's in the nation's small to mid-sized communities that things are happening. Sonoma is at the vanguard with projects that are already breaking ground, but cities such as Santa Fe and Boulder also are proposing broad-based, technologically sophisticated responses to carbon emissions. These programs are so promising, Kammen says, they ultimately could serve as a template for a national initiative.

"The Sonoma plan is looking very, very attractive to me," says Kammen, who looks preternaturally youthful for someone who took his Ph.D. 20 years ago. "Geothermal heat pumps are not a new technology, but the proposal to utilize them on this scale is new. It points to a ramping up of the technology that ultimately could make a huge difference."

The Sonoma plan incorporates many of the elements promoted by Kammen's lab, including the extensive use of plug-in hybrid cars, methane captured from landfills, liquid biofuels derived from waste products, and widespread employment of photovoltaic panels. Other academics, including Michael Hanemann, the director of Berkeley's California Climate Change Center, and Margaret Taylor, an assistant professor at the Richard and Rhoda Goldman School of Public Policy, are also advising the county on its initiative.

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