February 15, 2005

Fuel cells reach MW class

Andrew Skok and Steven P. Eschbach, FuelCell Energy Inc.

A few years ago, skyrocketing energy costs and tighter emissions limits prompted officials at the Wastewater Treatment Division of King County's Department of Natural Resources and Parks in Washington State to explore innovative ways to provide electricity for its facilities. The end result? Locals are breathing easier and the county is spending less on energy since the world's largest high-temperature fuel cell power plant went on-line at the South Wastewater Treatment Plant in Renton, a Seattle suburb.

 

All fuel cells generate electricity without combustion, and as a result they generate virtually no air pollution. But high-temperature fuel cells (see box)—such as the 1-MW Direct FuelCell (DFC) unit from FuelCell Energy Inc. (Danbury, Conn.) now operating at King County's treatment plant (Figures 1 and 2)—also deliver a useful heat byproduct that can be used to power a district heating system or air-conditioning system's absorption chiller, or to provide hot water or process steam. In Renton the heat is used by the wastewater treatment plant to anaerobically convert sludge into a gas, which is then used to fuel a DFC1500-based power plant in a virtuous cycle. The synergistic relationship between the power plant and the wastewater treatment process, which squeezes the last Btu from the system, is truly a process engineer's delight.

 
Courtesy: FuelCell Energy Inc.

1. Sludge power. This wastewater treatment plant in King County, Wash., is home to one of FuelCell Energy's 1-MW Direct FuelCells, which produces heat as well as electricity.

 

Courtesy: FuelCell Energy Inc.

2. Checking it out. Technicians at FuelCell Energy's factory in Connecticut inspect a fuel cell module before it is shipped off to King County. Several modules are piggybacked to form a fuel cell stack—in this case, one with a generating capacity of 1 MW.

 

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