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Squeezing Energy from A Rock

New geothermal approaches bring massive resources within reach.

Fortnightly Magazine - December 2008

geothermal energy from the Geysers field.

Such small projects add up, but vastly greater volumes of geothermal resources simmer at temperatures below 200 degrees. With potential capacity in many states of the Union, low-temperature geothermal technology might change the industry drastically. “As production capability goes down to 150-F or lower, it becomes a whole new ball game,” says Gawell.

A low-temperature DOE-sponsored geothermal pilot project was installed in 2006 at Chena Hot Springs, near Fairbanks, Alaska, where a 280-kW PureCycle binary generator from UTC Power, of New Windsor, Conn., operates with water that’s less than 165-F. Unlike many other U.S. low-temperature fields, the surface water in Alaska is very cold, providing a wide delta for heat exchange. “If you don’t pay for the (hot) water, who cares what the efficiency is?” asks Bernie Karl, geothermal project developer and owner of the Chena Hot Springs Resort.

Other developers are spreading out to tap into low-temperature geothermal resources. Nevada Geothermal Power in September hired Ormat Technologies to supply a 49.5-MW geothermal power plant at Blue Mountain, with generation expected to start by December 2009. The power generated by the unit will be sold to Nevada Power Co. under a 20-year contract.

Similarly, Raser Technologies completed in November construction of a $33 million, 10-MW low-temperature geothermal project in Beaver County, Utah, and expects to deliver electricity under contract to the city of Anaheim, Calif., for $78 a MWh. Raser is using 50 modular 280-kW binary-cycle generators from UTC Power, a strategic partner in the project. Raser also has begun building a low-temperature geothermal project at Lightning Dock, near Animas, N.M., and has amassed land rights in several states.

Geo Gusher

Most new geothermal projects being developed today involve new drilling to delineate fields. But by using a hybrid production method involving associated water in existing oil wells, significant power could be generated relatively quickly with much less drilling—and at places never previously considered geothermal hot spots.

“Geothermal resources could yield several thousands of megawatts in untapped places like the Dakotas, Oklahoma and along the Gulf coast,” says Karl Gawell, GEA executive director. For example, Ormat and DOE are developing an oil-well geothermal project at the Rocky Mountain Oil Test Center in Wyoming. The $1 million project involves hot water from an oil field at 190 degrees or more, and utilizes Ormat’s Organic Rankine Cycle generator, with an expected output of 200 kW.

Some 8,000 oil wells with similar potential have been identified in Texas by Professor Richard Erdlac of the University of Texas and by DOE’s Geothermal Research Project Office. Ormat is assessing the feasibility of some of these wells to support on-site power generation.

“There are 250,000 producing oil and gas wells in Texas alone, and these wells produce about 95 percent water and five percent oil,” Karl says. “That could represent 10,000 MW.” Karl’s resort was the site of a DOE low-temperature geothermal demonstration project, and he’s also developing an oil-well geothermal project with Quantum Oil & Gas in Jay, Fla. Beginning in early 2009, the project will start generating power from a