Steam from the Earth

"I was so surprised that I almost dropped my store teeth", says Walter Holmes, an official of the Interior Department. What amazed him was a new surge of interest in one of the nation's most exotic sources of energy. His office has been flooded by 2,456 applications for future rights to explore federal lands for geothermal energy -- the energy from the earth's heat.

There is no question that the source holds promise. Sprawling over The Geysers area in Northern California is the U.S.'s only full-scale (411,000 kw.) geothermal power plant. Trapped thousands of feet below it lies a huge reservoir of water surrounded by hot rock.

Intense subterranean heat turns the water to steam, which then escapes to the surface through natural fissures. The plant's owner, Pacific Gas & Electric Co., harnesses the steam to drive generator-turbines and sends the electricity 85 miles to San Francisco.

Cheap and Ample. Heat from the earth also powers the generators of plants in Italy, New Zealand, Mexico and Japan. Because the energy is cheap, almost inexhaustible and relatively clean, it is also being developed by some 25 other countries, from Chile to Taiwan, Ethiopia to Indonesia.

The U.S. is doing its share of pioneering. For the coming fiscal year, the Federal Government has requested $44.7 million for geothermal research and development, or ten times the amount budgeted two years ago. In January, the Interior Department began leasing exploration rights on public lands in Western states. Big oil firms and utilities have been especially eager bidders, attracted by forecasts that as much as 10% of the nation's energy might come from geothermal sources by 1985.

Making the prediction come true will require technological breakthroughs. Of the three different types of geothermal resources, only one can be easily tapped: the geologic formations producing steam as at The Geysers.

These are so rare that they count among nature's most valuable freaks. Indeed, prices for drilling rights around P. G. & E.'s plant have soared from 20-c- an acre a decade ago to the almost $1,360 an acre that Shell Oil recently committed itself to pay.

Subterranean reservoirs filled with superheated water or brine -- not steam -- are much more common, but rights to them are selling for as low as $1 an acre. Since exploration techniques are still rudimentary, the best way to get at the hot water is to drill and pray for success. Sinking a 5,000-ft. well costs about $125,000. If a driller hits, he still can be disappointed by the mixture of steam and briny water that hisses to the surface. Sometimes it is too cool to use efficiently; often it is laden with minerals and impurities that "crud up" turbine blades and even clog the bored hole itself. The steam can, in fact, be cleaned, but unfortunately the process is expensive. Its heat can be transferred to a non-corrosive gas and fed to the turbine, but that is inefficient.

Free Fuel. Even so, Union Oil in New Mexico, San Diego Gas & Electric and the city of Burbank, Calif., plan pilot plant projects, each costing more than $1 million. Explains Warren Hinchee, general manager of the Burbank Public Service Department: "We can't get natural gas and the price of low-sulfur oil keeps going up even if we can get it. We think a geothermal facility's cost will be competitive with oil -- less than half the price of coal-fired or nuclear generating equipment. And, of course, the fuel will be free."

Potentially the most promising geothermal sources lie in areas where molten rock, or "magma," is fairly close to the earth's surface. In theory, engineers can sink twin wells as deep as 20,000 feet to the hot underlying rock and then fracture it. Clean water, pumped down one hole, would be heated by the broken-up magma and would return up the other well as steam.

The Los Alamos Scientific Laboratory in New Mexico will soon give this process its first test. If it works, says Robert Rex, president of Republic Geothermal Inc., "the energy could provide all the additional power the nation will require until thermonuclear fusion and solar sources are developed." But until the "dry rock" technique is shown to be feasible, geothermal power seems bound to remain only a marginal, supplemental answer to U.S. energy problems.

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