Peterborough, N.H. is building a 947-KW solar array—the state's largest photovoltaic system and first solar-on-landfill project. The array is sited on former sewer lagoons at the town's wastewater treatment facility.
The project has no up-front costs, thanks to a $1.2-million grant approved on Jan. 15 by the state Public Utilities Commission Renewable Energy grant program and financing through a power purchase agreement with Water Street Solar 1.
The subsidiary of Borrego Solar, Oakland, Calif., will build, own and operate the plant. The town will pay Borrego 8¢ per KW-hour for electricity. Currently, it pays 13.9¢ per KW-hour.
The fixed-tilt solar system, consisting of 3,157 Yingli 300-watt panels with an efficiency rating of about 15%, will generate 1.2 million KW-hours of electricity annually.
The wastewater treatment plant will draw nearly 60% of the electricity, says Rodney Bartlett, Peterborough Public Works Dept. director. The rest will be credited to other town buildings through a new net-metering system.
The town estimates it will save, on average, between $24,000 and $57,000 per year in energy costs. Poert-purchase agreement negotiations should end by early April, Bartlett says.
In preconstruction, Bartlett says he expects challenges when filling the wastewater lagoon because of the influence of groundwater.
"One of the options is to vacuum up the sludge on the bottom before filling the lagoon with 90,000 cubic yards of clean common fill," he says.
Joe Harrison, Borrego senior project developer, says crews will place concrete ballast blocks before installing the solar array, similar to installation work at another five Borrego landfill projects in Massachusetts.
"Our preference is to drive piles and mount our solar racks on steel piles driven 6 ft to 12 ft into the ground, but with the high water table, it is not cost-effective to compact the site for driving piles," he says.