King-sized project
The 1-MW-class DFC1500 has been adapted from FuelCell Energy's standard, natural gas–fueled DFC module by adding the equipment and controls necessary to pretreat and handle unscrubbed digester gas. King County's South Wastewater Treatment Plant generates enough sludge to fuel 4 MW of DFC power plants.
Few permits were required for the project. For example, because its emissions are so low, the project was exempted from air permit requirements of the Puget Sound Clean Air Agency. However, although all of its power output is used by King County, the DFC1500 is connected to the local grid and thus is dispatched by Puget Sound Energy.
Don't waste that waste
The King County project is one of a limited number of waste gas–powered fuel cell power plants in the world. Two of FuelCell Energy's plants are in Japan. One, fueled by industrial waste gas, is at Kirin Brewery; the second, in the city of Fukuoka, is fueled by a municipal wastewater treatment facility. Another plant is likewise at a municipal wastewater facility, in Palmdale, Calif. Several smaller plants based on the company's 250-kW DFC300A unit also are up and running. They include one operated by the Los Angeles Department of Water and Power on Terminal Island (it is currently being fueled by natural gas before it is switched to anaerobic digester gas); two at a municipal wastewater facility in Santa Barbara, Calif.; and four at an industrial wastewater facility near Sierra Nevada Brewing Co. in Chico, Calif.
The ability to use waste gas as fuel could be a boon for fuel cell manufacturers. King County recently identified more than 400 wastewater facilities in the U.S. that generate enough digester gas to fuel a 1-MW power plant. And a few years earlier, FuelCell Energy sponsored a study that concluded that more than 550 municipal wastewater treatment facilities in the U.S. generate enough gas to keep a 250-kW fuel cell power plant running. In Japan the potential is estimated as approximately 2,000 MW.
One niche at a time
Based on early positive results at the first megawatt-scale DFC power plant (Figure 3), as well as the cumulative operating experience at nearly three dozen sub-megawatt units, fuel cells seem to have broken the code on how to integrate themselves with industrial applications. But other market segments are also getting traction. As an example, FuelCell Energy and its distribution partner, Caterpillar Inc., recently dedicated the first DFC power plant designed for "utility grid support" in the city of Westerville, Ohio.
Courtesy: FuelCell Energy Inc.
3. A little to the right. Construction workers at the King County treatment plant maneuver a fuel cell fuel tank into place. All of the components were manufactured in Connecticut and then transported to Washington, where they were assembled.
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