By Barbara Wolcott

One of Werner von Braun's staff who helped develop the V-2 rocket, Rudi Beichel, had an idea for an oxygen-assisted gas generator before he came to the United States. At the end of World War II, Beichel came to this country along with other German scientists and engineers by way of Operation Paper Clip. Von Braun surrendered himself and his staff of about 120 to the Allies, to keep from falling into the hands of the Russians. The scientists and engineers were housed first at White Sands, N.M., and then moved to the Army's Redstone Arsenal in Huntsville, Ala.

Beichel designed the test stands for the Jupiter rocket that put the first successful American satellite in orbit. He joined Aerojet Corp. in Sacramento and worked there from the mid-1950s until 1979. When he retired, Aerojet kept him employed as a consultant.

All his life Beichel had a dream: to use hydrogen and oxygen, the stuff of rocket propulsion, to make steam to drive power plants without pollution. The product of combustion would be the process steam. He realized that high volumes of hydrogen would be very difficult to come by and moved to an alternate fuel for the idea.

In 1993, Beichel decided it could work with methane found in natural gas, combined with oxygen. With it, he could make a drive gas comprising steam and carbon dioxide. As a non-condensable gas, the CO₂ could stay in steam used to rotate turbines for the generation of electricity. He reasoned that the steam could be cooled and turned back into water, with the only change being the addition and deletion of a relatively pure carbon dioxide.

In 1996, a group of retired Aerojet Corp. engineers formed Clean Energy Systems to design and produce a gas generator with zero atmospheric emissions. The CES president, Stephen Doyle, said the company has been talking with people in the power industry and finds that even though the basic technology has been proven for 30 years in powering military and NASA rockets, it's necessary to complete a hot-fire field test before the idea will be taken seriously as a source of electricity. With the help of a grant from the state of California, CES has built a scale model and tested it at the University of California, Davis, from last October until January this year.

Harry Brandt, a professor emeritus in the department of mechanical and aeronautical engineering at UC, Davis, heads the mechanical engineering side of CES, which is based in Sacramento. Brandt said the grant, from the California Energy Commission, was for $75,000. He added that the total cost for the design and testing of the gas generator was approximately $300,000.

"We had a very successful scale model test program," Doyle said, adding that the objectives of the test program were met, and demonstration goals achieved, with the generator routinely igniting on command. The test model worked in stable fashion over a range of temperatures and pressures for extended periods of time, and measured gas compositions showed good correlation with predictions of a computer model, he said.

With proprietary mixing techniques, the generator can precisely mix and control the oxygen and methane ratio. Burning each molecule of methane with two molecules of oxygen will produce one molecule of pure CO₂ and two molecules of water in the form of steam.

By itself, the combustion of oxygen and methane would result in temperatures far hotter than any available steam turbine can handle, said Ray Smith, deputy associate director for applied energy technologies at Lawrence Livermore National Laboratory, who wants to investigate the technology further.

A scale-model generator, aided by a grant from the state, was tested at the University of California, Davis, from last October until January this year.

Adding water to the combustor can bring down the temperature, with a consequent sacrifice of efficiency. According to Smith, 80 to 90 percent of the water produced by the process as exhaust would be recycled to the combustor.

Estimates are for an early phase plant producing 10 megawatts of electricity to require the thermal input of 30 MW. A plant of that size would produce 280 gallons an hour of excess water. The rest would flow back to the combustor to reduce the temperature to a level compatible with current steam turbines.

According to Smith, the system is "a rocket engine with a lot of water thrown in."

Doyle said the U.S. Department of Energy awarded CES a $1.8 million contract to build and test a 10-megawatt oxygen-assisted gas generator.

The basic necessities for the new generator are a gas line and air. In a schematic of the proposed plant, incoming oxygen comes from a plant that cryogenically separates air into its components.

The high-temperature steam and CO₂ mixture is used to drive turbines to produce electricity, and then it is cooled in a condenser to produce water and carbon dioxide. There is a commercial market for this type of CO₂ in many different applications, Doyle said. If there is no market in the vicinity, the gas can be sequestered underground.

He said disposition of the water and CO₂ depends on the location of the plant.

The best power generating systems being built today produce electricity in combined-cycle plants at a cost of about 3.2 to 3.5 cents per kilowatt-hour.

CES claims that it can operate power plants, using its technology and available steam turbines, at a cost of approximately 5 cents per kilowatt-hour.

According to Brandt, "For a new 400-MW CES plant using future high-temperature steam turbines, the cost of electrical power generation with carbon dioxide sequestration is estimated to be 3.4 cents per kilowatt-hour. This cost includes the power to separate the oxygen from the air."

CES's first marketing goal is southern California, where 60,000 oil wells have substantial reserves remaining, but the cost of bringing the oil to the surface exceeds its value. CES hopes to use its oxygen-assisted gas generator to pump exhaust steam and CO₂ down into the wells, raising the oil temperature and reducing its viscosity. That would make the cost of recovering the oil far less than it is with present methods.

"We could build power plants at the oil fields," Doyle said, "where the owner could use the power to run oilfield equipment and use all the CO₂ to assist in the recovery of additional oil. That's where we hope to break into the market."

Doyle predicted that, if the CO₂ were sold at $15 a ton, a conservative figure below the current market value, it would make the cost of a kilowatt-hour competitive with the newest plants in the present power market. All these are figures that were worked up before the current energy crisis.

"The added value we bring is zero emissions," said Doyle. "No oxides of nitrogen, no sulfur oxides, no particulate matter; in fact, our power plants when they are built will have no smoke stacks. Nothing will go out of the plant except CO₂ and water." The CO₂ would be sequestered or used for enhanced oil recovery.

Smaller Power Plants

Power plants with this technology producing the same electrical output could be about 10 to 15 percent smaller than conventional plants, Doyle predicted. "What we do is produce cheap, clean electricity with no atmospheric emissions," said Doyle. "The industry has never seen anything like this done, so we have to demonstrate our technology. We know it can be done because we have done it with rockets."

CES power production is done with the same technology that was developed over the last 30 years for aerospace defense applications. On September 1 last year, CES was awarded the contract by the Department of Energy to build an advanced stoichiometric gas generator of a nominal 10-MW class.

The company expects to do preliminary testing at the place of manufacture during the summer months, and to deliver the generator to Aerojet Corp. in Sacramento for full-scale hot-fire testing in the fall and winter.

Doyle foresees other possible markets for the generator technology. For example, a university could install a system to run all its facilities with a modest power plant. When school is not in session, the excess power could be sold back to the grid.

The first large installation of the generators may be done at the Lawrence Livermore National Laboratory in California, at a proposed Zero Emission Steam Technology research plant. Estimated to cost in the neighborhood of $70 million, the project would operate the facility and iron out any bugs to ready the technology for commercial use. Only about half the cost will go into the actual installation, with the rest going toward startup and testing.

The Need to Log Hours

Ray Smith, the applied energy technologies researcher, said that Livermore and CES are working up a proposal to the Department of Energy to build a small research facility that also supplies electricity.

"Large power companies are conservative and want to see testing in the range of 30,000 to 50,000 hours of operation before embracing the technology," he said. "When you get to this class of machine, it's necessary to sell some of the power to reduce operating cost. Here at the lab, we would be using the electricity and that would defray part of the cost for us." Smith added that power companies are famous for saying they will buy system No. 2 or 3, but never No. 1.

When CES approached the lab to build a research power plant, the initial reaction was: Go find yourself a greenfield site and build it; you don't need a national lab. However, the more it was discussed, the more Smith realized that research had to be done before the new technology was likely to make it to the marketplace.

"The one drawback to the project is the lack of availability of high-temperature steam turbines," Smith said. "The ones available now only go to 1,100 to 1,150°F."

The CES oxygen-assisted gas generator has the capability to go to 3,000°F, but an operator can control the temperature and pressure independently, so it can be used with a variety of steam turbines, Doyle said.

Temperature increments improve the thermodynamic cycle and, therefore, the efficiency of the plant. Smith said, "With commercial turbines today, we project about 35 percent efficiency overall, and if we go all the way to, say, between 2,600 and 3,000°F, it will be in the 60 percent range of efficiency."

Smith pointed out that today's combustion turbines run up to 2,600°F in relatively new plants. The hotter turbines have appeared during the past six to eight years.

However, while those high temperatures improved efficiency, they are close to the limit for firing with air, without the NO_x output going too high. In addition, advancement is limited by materials in the turbines.

Smith said he thinks that, through hard work and years of development, steam turbine temperatures can be pushed up to the same range that combustion turbines have reached. Water at such high temperatures is extremely corrosive to most materials. New alloys, ceramics, or coatings must be developed for very high-temperature steam turbines.

Smith said the Livermore lab sits across the street from an oilfield. After generating the electricity with the CES generator, a very pure stream of CO₂ could be pumped into the field for oil recovery. "A rough rule of thumb is that you get two barrels of oil for each barrel of CO₂ that you inject into a well, which makes the proposition attractive for both sides," he said.

$700 a kilowatt

Preliminary analysis shows that the capital cost per kilowatt for these plants will be in the $700 to $800 range, which compares with larger combined-cycle plants being installed at about $450 per kilowatt.

CES's marketing argument is that its plants permit inexpensive control of all the CO₂ and emit absolutely no NO_x. The technology is suitable to be quickly sited in impacted air basins, for instance, Doyle said.

In promoting the advanced gas generator research, the Lawrence Livermore proposal is meeting a mandate to provide the country with options for producing electricity with minimum environmental impact. This time, it will team with the new National Energy Technology Lab in Morgantown, W.Va., the former Federal Energy Technology Center.

In the event that the Department of Energy and Congress agree to promote and fund the proposal, the lab will likely partner with Oak Ridge National Laboratory for high-temperature materials testing. Lawrence Livermore said it is interested in the CES oxygen-assisted generator because a research power plant can be built with off-the-shelf hardware, and the plant may reach 55 to 60 percent efficiency.


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