LIVERMORE, Calif. – Researchers from a Sacramento energy firm and Lawrence Livermore National Laboratory believe a rocket technology may have a down-to-earth application — producing electricity.
Composed largely of retired rocket scientists, Clean Energy Systems Inc. officials have developed a technology they think can generate low-cost, pollution-free electricity from fossil fuels. But, since utility companies normally require five or six years of operation for a new technology before purchasing it, Clean Energy officials approached LLNL about building a research facility here.
"Utilities are known for wanting to buy the second or third plant, never the first," said Ray Smith, LLNL’s Applied Energy Technology Program leader. "We think the government should reduce the scientific and economic risk by building the first plant." Lab officials plan to submit a proposal this year to the Department of Energy to build a 10 megawatt, $70 million facility at the Laboratory based on Clean Energy’s technology.
"Clean Energy’s technology represents a whole new approach to producing steam and electricity cleanly. It replaces six-story high steam boilers with a generator that is seven to eight feet long and one-foot in diameter," Smith said.
The new technology also could help reduce U.S. dependence on imported energy, a boost to the nation’s economic and military security, Smith said, adding it could make use of extensive domestic energy resources, including coal.
A variety of fossil fuels — natural gas, synthetic gas from coal, petroleum and biomass — are among the possible sources that could power the Clean Energy system.
The firm’s gas generator burns the fuel, along with oxygen and water at high temperatures, about 2,600 degrees Fahrenheit, and produces a gas mixture of steam and carbon dioxide. Like a rocket engine, the generator burns pure oxygen to produce steam and avoids producing nitrogen oxides. The steam, in turn, powers the turbines that drive an electric generator and produces electricity without pollutants. A condenser cools the steam into water and separates it from the carbon dioxide. Much of the water returns to the generator and, with pure oxygen and the fuel source, provides more steam to drive the electric generator.
Since carbon dioxide is a greenhouse gas that contributes to global warming, new efforts are necessary to economically reduce its emissions into the atmosphere. The gas could, however, be sold as a commodity to soda pop and dry ice manufacturers, as well as to the petroleum industry to enhance oil and gas recovery.
As envisioned by Lab researchers, carbon dioxide from the proposed Zero Emission Steam Technology (ZEST) research facility, would be sent by a small pipeline to an oil field immediately east of the Laboratory, where it would be used to boost oil production. (A barrel of liquid carbon dioxide injected into an oil field typically yields about two barrels of oil.)
"A key part of the research we want to do is for the sequestration of carbon dioxide – how much of the gas stays in the oil field and whether it can also be sequestered in deep saline aquifers," Smith said.
It is believed carbon dioxide from the ZEST system could be deposited into the underground at less than $20 per ton of carbon, much less than the $100-plus per ton required for removing the gas from exhausts of today’s electricity plants, Smith said. Among the issues the Laboratory and Clean Energy would explore in a research plant would be the gas generator’s reliability, what maintenance is needed and the demonstration of high-speed controls, Smith said.
Other areas in which Livermore technologies would be applied include: improved oxygen separation techniques, thermal coatings for high-temperature steam turbines, geophysical imaging and analysis, and geologic carbon-dioxide sequestration, Smith noted. Also, a Livermore combustion simulation code, ALE3D, would be used to study the gas generator’s internal operations to make sure it would run at peak power and yet remain stable when at minimum power, Smith said.
Tests run from October to mid-January by Clean Energy at UC Davis on a subscale model generator, some 100 times smaller than the proposed 10 megawatt facility, turned out well, according to company President Steve Doyle."We met all of our expectations. We learned more about the gas kinetics and gas composition than we expected."
"We were trying to prove that we could cool down the gas, from 2,600 degrees Fahrenheit to 1,000 degrees, and keep the flow almost completely steam and carbon dioxide without forming any pollutants, and we did so," Doyle said. Beyond producing pollution-free electricity, another bonus of the ZEST technology, according to Doyle and Smith, is its flexibility.
The technology is extremely scalable and by simply changing the size of the gas generator and turbine, the facility’s power can be increased from 10 megawatts to 100 megawatts. As a result, factories or industrial complexes could set up their own on-site power plants.
One of the hurdles that needs to be overcome for ZEST is the development of steam turbines that can operate at much higher temperatures than commercially-available turbines. Higher temperatures increase the efficiency of the system, producing more electricity per pound of fuel. While currently-available commercial turbines can operate at 1,100 degrees Fahrenheit, the ZEST system will require turbines that function at about 2,600 degrees to achieve 60 percent efficiency, Smith said.
Otherwise, with the lower temperature turbines available today, the system’s efficiency is about 35 percent. Such advanced turbines could be developed under a recently-started program — the Next Generation Turbine— operated by the National Energy Technology Laboratory to upgrade steam turbine technology.