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New fuel cell marries technologies to create energy efficiently, cleanly A one-two power punch Monday, January 08, 2001 By Byron Spice, Science Editor, Post-Gazette
The future of electrical generation may arrive in southern California this week when engineers from Siemens Westinghouse Power Corp. switch on a revolutionary new power plant.
It's not that this power plant is an immediate solution to the Golden State's power woes. No bigger than a trailer-truck, it generates 220 kilowatts of electricity. That's enough to power an office building, 100 homes or perhaps a small ship, but not to relieve power shortages in a state where demands reach 32,000 megawatts.
What is notable is the way it generates power. Rather than burning fuel to turn a generator, it electrochemically converts natural gas directly into electrical current. It then uses heat produced by this process to run a turbine, generating even more electricity. The result is a system of unprecedented efficiency that produces little in the way of pollution.
Siemens Westinghouse calls it a solid oxide fuel cell/gas turbine hybrid. Mark Williams of the National Energy Technology Laboratory calls it "remarkable."
"As far as I know, there's no device that can match it," said Williams, who heads fuel cell development at the lab's Strategic Center for Natural Gas. "It's got incredible efficiency," converting almost 60 percent of the energy in natural gas into electricity, compared with the 35 percent typical of conventional power plants. "It produces half the carbon dioxide [of a conventional plant] and has no regulated emissions."
The hybrid plant was trucked last month from the Siemens Westinghouse Science and Technology Center in Churchill to the National Fuel Cell Research Center in Irvine, Calif. An extended demonstration run for Southern California Edison and the U.S. Department of Energy is to begin there this week.
Siemens Westinghouse sees the Irvine demonstration, as well as a one-megawatt hybrid slated to begin operation next year at Fort Meade, Md., as a prelude to producing commercial versions by 2003 or 2004. The company now makes its prototypes in Churchill and will decide this year whether to locate a fuel cell factory in the Pittsburgh area.
But Williams hopes the demonstrations will be further evidence that the fuel cell may finally be ready to shed its perennial label as a power source of the future and become a power source of the here and now.
A gentleman's theory
Fuel cells were invented in 1839 by Sir William Grove, an English gentleman-scientist who reasoned that if electrical current could split water into hydrogen and oxygen, then combining hydrogen and oxygen could produce electricity and water.
He was right, but making it work wasn't easy. Simply combining hydrogen with oxygen results in an explosion. So the simplest fuel cells rely on a catalyst, called an electrolyte, to split hydrogen atoms apart into a positively charged proton and a negatively charged electron. The electron passes through a positive electrode, called an anode, and out of the cell as electrical current; the proton passes through a special membrane to the negative electrode, or cathode. The electrons from the external circuit re-enter the cell through the cathode, where they combine with the protons and with oxygen atoms to form water.
Fuel cells remained a curiosity until about 40 years ago, when NASA was looking for a reliable power source for Apollo spacecraft. The simplest fuel cells are fueled with hydrogen and oxygen, which just happens to be rocket fuel. The scheme worked well for the space agency, despite the explosion of a fuel cell oxygen tank that aborted the Apollo 13 mission.
The exotic materials required to build fuel cells can be expensive. High costs weren't an issue for NASA, but they have limited their terrestrial applications. Nevertheless, Williams says that a combination of reduced costs, new demands for reliable, clean, yet portable power and a renewed interest in efficiency is once again bringing fuel cells to the fore.
The automotive industry is prominent in fuel cell development. BMW has said it will soon replace the lead-acid batteries in its cars with fuel cells that convert gasoline directly into electricity. The fuel cells, more efficient than the engine's alternator, would provide all of the on-board electrical power, relieving the engine of the need to generate electricity. But eventually automakers, under pressure to reduce car emissions, expect fuel cells to provide the power to propel vehicles, as well.
"I believe fuel-cell vehicles will finally end the 100-year reign of the internal combustion engine as the dominant source of power for personal transportation," William Ford Jr., chairman of the Ford Motor Co., said last year.
And, as evidenced by the Siemens Westinghouse hybrid plant, there is renewed interest in distributed generation -- greater reliance on small power plants that might power a single building, rather than on large, centralized power stations.
If costs can be cut further, homeowners might someday replace their home furnaces with fuel cells that could provide not only heat, but electrical power, Williams said.
The Westinghouse innovations
Westinghouse began work on solid oxide fuel cells four decades ago. "Solid oxide" refers to ceramic materials, principally zirconium oxide, which serve as the electrolyte. The solid oxide cells operate at high temperatures and are more complicated than some fuel cell designs. But they can also use a wider variety of fuels, such as natural gas, gasoline or diesel fuel, rather than relying on difficult-to-handle and more volatile hydrogen gas.
In the Westinghouse design, the cells are configured as long tubes, with the cathode lining the inside, the anode coating the outside and the solid oxide electrolyte in the middle.
Heated air is pumped through the center of the tubes, where oxygen atoms from the air pick up electrons from the cathode. These negatively charged oxygen ions migrate through the electrode layer to the anode, where they react with natural gas or other fuel that is flowing along the outside of the tube. The ions oxidize hydrocarbons in the fuel, producing water and carbon dioxide and releasing their electrons to the anode, where they flow out of the cell as electrical current before returning to the cathode.
A 100-kilowatt version of this cell recently completed a demonstration in the Netherlands, where it produced both power for the electric grid and hot water for heating 120 homes, said Allan Casanova, director of business development for the Siemens Westinghouse stationary fuel cell program.
The latest innovation, the hybrid, marries the fuel cell to a small turbine. A turbine runs a compressor that pressurizes the air being pumped through the fuel cell, which increases the cell's efficiency. Hot air exhaust from the fuel cell -- the cell operates at 1,800 degrees Fahrenheit -- is then used to run the turbine, which turns both the compressor and a conventional generator, which produces additional electric current.
The solid oxide fuel cell normally runs at 46 percent efficiency, but the hybrid design boosts that to 58 percent. Larger versions, such as the one-megawatt plant that will power the Environmental Protection Agency's Environmental Science Center at Fort Meade, are expected to reach efficiencies above 60 percent.
"The combination of a fuel cell and microturbine is one of the most exciting new advances coming out of our energy research program," Energy Secretary Bill Richardson said last fall when he announced the Fort Meade project.
That's such a huge leap that it amounts to a paradigm shift in the fuel cell community, said Scott Samuelson, director of the fuel cell research facility in Irvine. Mechanical engineers are accustomed to systems with 20 or 30 percent efficiencies, he noted, yet this new hybrid appears, on paper at least, to be capable of efficiencies of up to 80 percent.
"It's a big deal," he said. "This is the kind of efficiency that we in this field had hoped would evolve someday. We just hadn't expected it this soon."
The future
Samuelson is eager to see whether the first-of-its-kind hybrid will be able to sustain the performance it displayed during a 210-hour test run in Churchill last May. It initially will be operated for 3,000 hours at the Irvine facility while its power is fed into a bank of electrical resistors. Engineers will evaluate its behavior and identify changes that need to be incorporated into the next prototype, Samuelson said.
"This system has been put together in a rapid fashion," he explained, so it doesn't have the engineering elegance of a commercial system. "It's like building the first airplane."
If the first phase of the demonstration goes as expected, the system will be plugged into the electrical grid.
Much of the engineering efforts are now focused on reducing the cost of the hybrid, Casanova said. To be competitive with other power sources, the cost of purchasing a fuel cell plant will need to be between $1,000 and $2,000 per kilowatt. The first commercial units likely will cost substantially more -- perhaps $4,000 or $5,000 per kilowatt, he said.
Even so, some niche customers won't mind paying that premium, Samuelson predicted. For instance, companies and organizations that are building "green" buildings or otherwise want to project an environmentally conscious image will pay for fuel cells. Industries that can't afford to lose electricity, such ATM banking networks, also are potential early customers.
The extra cost of fuel cells may be acceptable in military ships, Samuelson said. Not only would the greater efficiency extend the range of diesel-powered ships, but the greater efficiency means less energy would be lost as heat up the ship stacks, making the ship easier to conceal from infrared sensors in enemy satellites, aircraft and missiles.
California may also have some motivated buyers. During an interview last month, when the state was on alert for possible rolling brownouts, Samuelson joked, "You could probably sell more than a dozen in just the next two hours."
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Siemens Westinghouse Power Corp. expects to find customers willing to spend $1,000 to $2,000 per kilowatt for fuel cells, but researchers will have to drive costs down much further to get widespread use of the cells.