Green Mountain Power operates the first U.S. solar microgrid installed on a capped landfill. Stafford Hill Solar Farm, in Rutland, Vt., a city of 16,000 inhabitants, is also among the first U.S. microgrids to be powered solely by solar energy and battery backup. Its 7,700 solar panels generate 2 megawatts of power, backed up by a 4-megawatt battery storage system. The solar modules are installed on racks anchored on concrete ballast blocks over crushed stone on 9.5 acres of the landfill cap. The storage portion includes four 500-kilowatt Dynapower multiport inverters, four 500-kilowatt/250-kilowatt-hour lithium-ion batteries, and four 500-kilowatt/600-kilowatt-hour advanced lead acid batteries.
Vermont suffered massive flooding and other damage in August 2011 during Hurricane Irene, one of the mid-Atlantic’s costliest storms. So, Stafford Hill Solar Farm can be islanded from the grid and can power an emergency shelter at Rutland High School.
The microgrid also helps Green Mountain Power address a projected 400-megawatt capacity shortfall by 2018, and contributes to the state’s goal to be 90 percent renewably powered by 2050. Because the system’s batteries provide nearly instantaneous voltage regulation, Stafford Hill Solar Farm also improves power quality on Green Mountain Power’s distribution system.
The solar installation cost about $5.77 million, the storage component about $4.2 million, and the utility makes lease payments of about $30,000 per year to the city for use of the landfill. The microgrid derives revenue from energy generated, capacity payments, avoided Regional Network Service charges, energy arbitrage, transmission, ancillary services, and renewable energy credits – totaling about 18.7 cents per kilowatt-hour. This exceeds the 17.1 cents per kilowatt-hour levelized cost that Green Mountain Power estimates the solar power will cost over 25 years.
In addition to compensating for the intermittency of solar, last year Green Mountain Power was able to reduce its overall energy demand by the judicious use of Stafford Hill Solar Farm’s solar power plus the energy stored in the batteries there during the hour New England hit its annual peak. Utilities are charged year-round according to the percentage they contribute to the overall New England peak demand. By significantly reducing Green Mountain Power’s peak demand during that single peak hour, the Stafford Hill Solar Farm project saved customers $200,000.
“This project provides resilient power during emergencies while benefiting the grid at other times. The technical innovations reduce cost and make the project commercially viable,” said Imre Gyuk, energy-storage program manager in the U.S. Department of Energy’s Office of Electricity Delivery and Energy Reliability. “This is the perfect project. It has social value, technical innovation, and furthers renewable integration for the grid.”
Rutland is on its way to becoming the solar capital of New England and a model that other communities might emulate. According to Rutland Mayor Chris Louras, “The microgrid creates energy and income for the city, using property that has no real development value. Equally important, projects like this put Rutland on the renewable energy map.”
How about us Midcoast Mainers? We, too, have our storm-prone grid, but also our rooftops and our capped landfills. We could have virtually unlimited solar panels and storage batteries. But do we have the conviction and the chutzpah to remove the barriers holding us back?
(Paul Kando is a co-founder of the Midcoast Green Collaborative, which works to promote environmental protection and economic development via energy conservation. For more information, go to midcoastgreencollaborative.org.)