U.S. Water News Online
MIDDLETOWN, Calif. -- Geothermal plants in The Geysers area
north of the Napa Valley have tapped steam fields to produce
electricity since the 1960s. The 350-degree steam rushes more than
1,500 feet up from the earth, spinning turbines that create a
constant flow of electricity.
But mismanagement of the steam fields beneath the hilly
northwestern California region that straddles the Sonoma and Lake
county lines has led to a large decline of pressure -- and a drop of
more than 50 percent in the amount of power the plants produce.
The geothermal decline comes as California already faces short
supplies of hydroelectricity from the drought-ridden Pacific
Northwest and growing c ompetition for megawatts from other
State power grid managers estimate they're losing about 900
megawatts of geothermal electricity due to the gradual depletion of
the steam fields. That's enough power for roughly 675,000 homes.
``They just overproduced. It is a renewable source of power, but
it's renewable over geologic time,'' said Katherine Potter, a
spokeswoman for Calpine Energy, which owns 19 of the 21 geothermal
power plants in The Geysers region, which incidentally has no
The first electricity produced by tapping into pockets of steam
trapped in the earth debuted in 1904 in Larderello, Italy. That
plant, rebuilt due to World War II damage, is still operating. The
first U.S. geothermal plant was a small operation at The Geysers
built in 1962.
Steam fields are created when water flows through fissures in the
rock deep in the earth and is heated by hot magma. Geothermal plants
tap into that pressure and use it to spin turbines. The plants'
cooling towers release plumes of white steam, which can be seen for
miles on a clear day.
While The Geysers is a rare geologic formation called a dry steam
field, there is the potential for thousands of megawatts of
geothermal power from other regions that could use the more common
``wet steam'' process, said Karl Gawell, executive director of the
Geothermal Energy Association in Washington, D.C.
Wet steam plants tap into superheated water in the earth, separate
the steam and use it to power generators. The water and the condensed
steam is pumped back into the earth.
CalEnergy Corp. owns 10 power plants in Imperial County that
produce about 330 megawatts of power, enough for about 247,500 homes.
Those plants and others like them haven't seen a decline in pressure
like Calpine's plants.
Geothermal energy is second only to hydroelectricity as a
continuous, cheap source of power, said Jan Stewart, Calpine's public
The plants in The Geysers reached their peak power production in
the 1980s, producing about 2,000 megawatts of electricity -- enough
to power about 1.5 million homes.
At that time, about 30 companies were involved in various
geothermal ventures in the area and didn't work together, Stewart
``The resource wasn't being managed properly. As a result, it was
a very fractured environment,'' she said. ``If one plant shut down,
the steam would be vented to the atmosphere, instead of being
rerouted to another plant where it could be used.''
In the 1960s and '70s when The Geysers got started, there was ``a
real wildcatter's mentality'' among power generators, said Rich
Ferguson, energy chairman for Sierra Club California.
``Basically, they took out the water in the form of steam faster
than Mother Nature was putting it back in,'' he said.
The available steam declined, and the area now puts out about 850
megawatts, sufficient power for roughly 637,500 homes.
Since then, geothermal engineers have learned more about managing
the resource, Ferguson said.
The superheated, self-contained system at The Geysers has no water
running through it.
``The Geysers is unique worldwide. There really aren't other dry
steam fields,'' Gawell said. ``In effect, there was never a
sustainable level of production, you always would have depleted it
eventually. It's like a giant pressure cooker. As soon as you put the
first straw in, you began to deplete the resource.''
Calpine is experimenting with replenishing the steam fields by
pumping treated waste water back into the earth. It began three years
ago, when Lake County stopped pumping its treated waste water into
Now, more than 8 million gallons of treated waste water is
returned daily to the earth. The experiment appears to be working --
power output is up 68 megawatts.
``People like the stewardship that Calpine provides now,''
Ferguson said. ``Calpine has taken on as a long-term goal to make
Calpine is building a 50-mile pipeline to Santa Rosa and plans to
pump another 11 million gallons of treated waste water daily from
that city. The company expects that will boost production another 85
Even with the new project, power grid managers say they're
planning for diminishing geothermal electricity.
``We've lost a considerable portion of their output due to the
decline in the output of the steam,'' said Jim McIntosh, director of
grid operations for the Independent System Operator. ``All supplies
are very important to us at this point.''
The plants are relatively low-maintenance once they're running --
only one engineer staffs each of the 19 Calpine plants in The
Geysers. But geothermal plants are more expensive to build than
natural gas-fired power plants, Gawell said.
``It's like choosing between two identical cars -- one is $10,000
and the other is $30,000, but the $30,000 car comes with a lifetime
supply of fuel,'' he said. ``People are shortsighted on investments
and it takes more money upfront to build geothermal.''
Most geothermal resources are on public land, lengthening the
building process because more permits are needed, Gawell said.
Two new plants are in the application process in California.
Researchers estimate there are 2,500 megawatts of untapped
geothermal resources in Nevada, Gawell said. Idaho, New Mexico, and
Oregon also have sites that could be tapped, he said.
``Many of these sites were looked at in the '80s, but then nothing
happened because in the '90s natural gas was too cheap to meter,'' he
Ferguson said the state spent $540 million over the last four
years on incentives for renewable energy projects, including
geothermal, solar, wind and biomass, and he expects the plan will be
renewed when it expires in December.
``We think there will be an equivalent amount of money,'' he said.
``All the technologies have to compete against each other, but
geothermal should do pretty well.''
Return to the
U.S. Water News Archives page
Return to the U.S. Water
Use a comma to separate e-mail addresses:
Hi, I thought you might like to read this article.