Published by the American Geological Institute
of the Earth Sciences
in the West
On Aug. 9, the Department of Energy (DOE) teamed up with private industry to rally for geothermal energy. Their joint efforts “move us one step closer to our goal of providing 10 percent of the electricity needs of the western states with geothermal resources by 2020,” says Secretary of Energy Bill Richardson, who, along with Sen. Harry Reid (D-Nev.), made the announcement.
Crops surround this plant in Imperial Valley, Calif. High mineral contents of some southern
California geothermal reservoirs provide salable by-products like silica and zinc.
Photo courtesy of the Geothermal Education Office.
Twenty-one companies plan to expand geothermal activities in California, New Mexico, Nevada and Utah. The DOE will fund $3.5 million for one year to increase research and development in small-scale geothermal electric power plants, enhanced geothermal systems technology and geothermal resource exploration.
In January, the DOE launched an initiative, GeoPowering the West, to expand the production of geothermal activities in 19 western states. Other goals of the initiative include supplying geothermal electricity to at least 7 million homes by 2010 and doubling to eight the number of states with geothermal electric power facilities. “Clean, reliable and renewable energy sources such as geothermal energy can become a significant contributor to the energy mix in the West,” Richardson says. Especially, he adds, at a time when parts of the region are experiencing power shortages.
The country currently houses 69 working geothermal electric power plants at 18 different sites, providing more than 2,700 megawatts (MW) of power — the equivalent of three large coal-fired or nuclear power plants and enough to provide electricity to 3.5 million homes. John Lund, Director of the Geoheat Center at the Oregon Institute of Technology, calculated the effects of using electricity and direct heat from geothermal resources rather than conventional coal-fired plants. “Each year the United States saves 22 million tons of carbon dioxide, 6 million tons of carbon, 41.5 million barrels of oil and 200 thousand tons of sulfur dioxide.” he says. Geothermal resources come in five forms: hydrothermal fluids, hot dry rock, geopressured brines, magma and ambient ground heat. Of these five, only hydrothermal fluids have been developed commercially for power generation. The state and temperature of water in a reservoir determines what type of power plant can be built.
Flash-steam power plants built in the 1980s tapped into reservoirs of water with temperatures greater than 182 degrees Celsius. The hot water flows up through wells in the ground under its own pressure. As it flows upward, the pressure decreases and some of the hot water “flashes” into steam. The Geysers in northern California, which uses steam piped directly from wells, produces the world’s largest single source of geothermal power.
A third type, known as a binary cycle power plant, operates on water at lower temperatures of about 107 degrees Celsius to 182 degrees Celsius. These plants use the heat from the hot water to boil a fluid, usually an organic compound with a low boiling point.
Generating electricity from geothermal power has some challenges. “It is hard to compete with the cheap price of natural gas,” says engineer Manuel Nathenson of the USGS in Menlo Park, Calif. Unlike oil, which is expensive, and coal, with its environmental issues, natural gas is a plentiful resource that only needs a slight scrubbing to be considered a clean fuel. “Natural gas as a way to heat your house is very convenient,” Nathenson says.
But its value may become questionable in the future, he adds. “With the run up in oil prices the whole energy economics begins to change.” If the high oil and gas prices stick, competing energy sources may follow. “If the price of natural gas comes up then the price of geothermal may become more competitive.”
AGI/AIPG Geoscience Policy Intern