[caption id="attachment_38844" align="alignright" width="360" caption="This GDT Tek Phoenix system is being installed at the American Canyon landfill power station to turn heat produced during combustion of methane from decomposing garbage into additional electricity."][/caption]
AMERICAN CANYON -- In addition to a large solar electricity plant planned to cover much of the closed 80-acre American Canyon landfill and an existing power plant there that uses captured methane from decomposing garbage, a new project will harness heat normally lost during combustion of landfill gas to generate up to an additional 1.5 megawatts of electricity.
RTR Global Investments, a subsidiary of Florida-based GDT Tek, plans to install the first 150-kilowatt waste-heat-to-electricity unit -- one of several planned -- at the south Napa County landfill in the next couple of months. It's part of a $23 million project that will increase electricity produced at six greater Bay Area landfills by up to 9 megawatts, or enough to power nearly 12,000 average homes for a year.
"This is part of a pilot system, which has been running for five years, and we refurbished it for this site," said Bo Linton, president of the publicly traded parent company.
In 2008, PG&E signed a small-scale power purchase agreement, called a feed-in tariff, with RTR Global to supply up to 1.5 megawatt-hours per location to the grid. The other landfills are Guadalupe Mines, Milpitas and Menlo Park in Santa Clara; Visalia in Tulare County; and Santa Cruz. Fortistar Methane Group operates the landfill gas cogeneration plants, including the 1.6-megawatt plant in American Canyon.
Conversion of methane from decomposing matter in dairy manure, leftovers from winegrape fermentation and wastewater into electricity has come to the North Bay over the past several years. Key examples are Straus Family Creamery's and Clos Du Bois' biogas plants and Sonoma County Water Agency's planned Farms to Fuel project north of Santa Rosa.
GDT Tek's patented technology works like an air-conditioner in reverse, he explained. A nonpolluting mixture of refrigerants in a heat exchanger surrounding the 800- to 1,200-degree Fahrenheit exhaust of the methane generators captures heat that would otherwise just raise the temperature of the air.
"Rather than use power to take heat out, we use heat to turn a turbine," Mr. Linton said.
Because of the design of the system and refrigerants used, the device can use heat energy to make steam at lower temperatures than a conventional water boiler, potentially opening up more efficient electricity production from heat sources such as concentrated solar thermal arrays, geothermal and industrial exhaust stacks, according to an advice letter combustion researcher Robert Dibble of University of California, Berkeley, sent GDT Tek's Los Gatos-based chief technology officer, Ralf Horn.
The system going into the Bay Area landfills will be able to capture heat from the methane flares, which burn off the gas during times when the generators are being maintained or there is more gas being produced on hot days than the generators can handle, according to Mr. Linton.
Potential for a more-efficient form of solar electricity has captured the attention of San Jose-based construction company Barry Swenson Builder late last year for an optional renewable energy component on commercial buildings. No projects with such technology are currently in the works, Mr. Linton said.