One of the most efficient ways to produce power at future coal-gasification power plants is with solid-oxide fuel cells, which use the hydrogen from the gas stream to generate electricity through chemical reactions. This is more efficient than simply combusting the gas stream from coal gasification. And unlike other types of fuel cells, the solid-oxide variety can operate at very high temperatures and efficiencies, and be scaled up to provide cities with power.
But among the various challenges to developing the technology, manufacturing cost has been a potential deal breaker. Now, researchers at GE have demonstrated a manufacturing method that assembles layers of ceramic and electrolyte materials cheaply so that the final product can be built for about $800 a kilowatt, which starts to approach the $500-to-$550-per-kilowatt cost of building a conventional gas-fired power plant.
GE’s six-kilowatt prototype achieves 49 percent efficiency in converting fuel into electricity, which compares favorably with the 35 percent efficiency of conventional coal-burning power plants. “I do believe GE has established a new state of the art,” says Wayne Surdoval, technology manager for fuel cells at the National Energy Technology Laboratory, part of the U.S. Department of Energy, which is funding this project and others aimed at producing better solid-oxide fuel cells. “The bottom line,” he adds, is that the GE prototype “is a particularly inexpensive fuel cell to make. Basically, you are using simple manufacturing techniques using fairly inexpensive materials in the cell.”
Surdoval likens the process to making pizza dough. Three sets of materials–representing the two electrodes and one electrolyte that make up each layer of a fuel cell–are mixed and put through two rollers that squeeze them. “You have three different doughs, you flatten each one, then layer them, then flatten them,” he explains. “Then basically, you bake it.”
The process paves the way for mass manufacture, according to Kelley Fletcher, the advanced-technology leader for sustainable-energy programs at GE Global Research, in Niskayuna, NY. “People have made fuel cells that make more power, and people have also made ones that have done this efficiency level,” he says. “But to do so in one package, and at the cost estimate that we have done, is the real achievement here.” Previous prototypes have cost thousands of dollars per kilowatt to manufacture, he says.