Reliably renewable
Central Vermont Public Service is a small utility serving about 158,000 customers in Vermont principally through long-term contracts with Vermont Yankee and Hydro Quebec (54% nuclear and 38% hydro). Another 6.5% of its customers’ power needs are served by 20 small hydro stations owned by CVPS. Most of the remainder is delivered by independent power producer contracts, most involving renewable sources. A new addition to the CVPS renewable portfolio is power generated by biogas that’s derived from digested cow manure at several large dairy farms (Figure 1).
1. Tanks for the manure. Steve Dvorak (far left), who designed the digester at Blue Spruce Farm, Dave Dunn, Earl Audet (with Sierra at his feet), and Melissa Dvorak discuss the separation process, which divides liquids from solids after the manure spends 21 days in the digester. Courtesy: CVPS
The gaseous engine fuel comes from manure and other farm waste held in a sealed concrete tank at the same temperature as a cow’s stomach (approximately 101F) for about 21 days. Bacteria digest the volatile components, creating methane while killing pathogens and weed seeds. The methane is then piped to a modified, naturally aspirated engine-generator (Figure 2).
2. Low-Btu gas. David Dunn, CVPS Cow Power coordinator (left), and Ernie Audet discuss generator operation at the Blue Spruce Farm in Bridport, Vt. Audet and his brothers own the farm, the first to begin producing CVPS Cow Power. Four farms are now part of the program. Courtesy: CVPS
Several dozen farms across the United States are now generating electricity in this way, but CVPS Cow Power was the first program designed to support this effort by linking local customers and producers in an entirely new farm-to-market model and by providing cash grants to defray the costs of interconnection to the rural grid.
By enrolling in CVPS Cow Power, retail customers help support Vermont dairy farms develop biogas-fueled generators, renewable generation in the region, and incentives to farmers for getting into the business. These farms are significant customers for CVPS, so helping them improve their financial strength is good for the local economy as well as the utility.
The program has garnered strong public support: More than 4,570, or 2.8%, of the company’s customers participate. CVPS expects to have 5% of its customers enrolled by year-end 2010. “Our goal has been to make CVPS Cow Power one of the top 10 programs in the country by year-end 2010, and we are well on our way toward meeting that goal,” CVPS President Bob Young said. “Customers continue to enroll by the dozens each week, voting with their energy choice for Vermont farming, an improved environment, and renewable energy production.”
Green Mountain College, known for its emphasis on the environment and energy sustainability, has committed to purchase 50% of its main campus’s electricity as Cow Power and 100% on all its other accounts, which include the president’s house, the college farm, the college inn and alumni house, and an off-campus residence hall in Killington, Vt. The college’s total Cow Power purchases will eventually rise to approximately 1.2 million kilowatt-hours annually.
“This is a great step for us toward a sustainably powered campus,” said Provost Bill Throop. “We are very happy to be supporting not just renewable energy but also the regional economy and the family farms that are so important to the Vermont way of life. It is a good fit with our mission, and departments across campus are supporting the project from their own budgets because they feel it’s a priority.”
Email
Comments
Print
Reuse
