Alameda in pictures: The Geysers

Alameda in pictures: The Geysers

Michele Ellson

A few hours north of San Francisco, in the Mayacamas Mountains, sits the world’s largest geothermal field. The Geysers steam field covers more than 2,000 acres and provides electricity to thousands of Californians, and Alameda Municipal Power owns a significant share of its output.

The utility took more than 60 customers and staffers on a tour of one of The Geysers’ power plants Friday, leading a pair of tour buses through the Bay Area fog, the vines of wine country and a winding maze of steam and water pipes to the Northern California Power Agency plants.

The plants generate electricity by mining superheated steam from porous rock as far as two miles below the Earth’s surface and using it to power turbines that create electricity. Alameda Municipal Power gets 17 percent of the 100 megawatts of power the plant produces. A megawatt is typically considered enough electricity to power 1,000 homes.

Twenty-two percent of Alameda Municipal Power’s output in 2013 came from “green” power sources, its power content label says. It says the utility didn’t get any of its state-eligible renewable power from geothermal sources in 2013 and 4 percent of its power from those sources in 2012; spokeswoman Rebecca Irwin said that since the utility is generating more green power than the state requires, it is selling the power to the State Department of Water Resources for the next few years. The money will go back into the utility's effort to expand its green power projects.

PG&E drilled the first commercial wells at The Geysers in 1960, and a host of other companies soon followed. The agency – which includes 15 public agencies, including Alameda Municipal Power – entered purchase agreements with Shell in 1977 and 1980, buying out the company’s steam leases in 1985. Its plants are on property owned by the federal Bureau of Land Management.

The agency built its first plant in 1983 and a second one in 1986. The plants are encircled by a network of twisted 30-inch pipes – built with bends to mitigate spikes in pressure – and smaller pipes that carry water back into the ground, plus a cooling system that pumps 60,000 gallons of water per minute and storage for the mercury and hydrogen sulfite pulled from the steam (prior to the fields’ use for energy production, they were home to mercury mines).

But the year after the second plant was completed, the amount of steam power companies pumped out of the ground dropped by 18 percent – a catastrophic decline, according to one of the plant’s engineers. While the heat source producing the steam was still at full force, the steam itself turned out to be a finite resource that was being exhausted – largely due to the fact that most of it dissipates into the air as exhaust.

Power companies mining The Geysers cut production in an effort to slow the loss of steam pressure. That reduction, combined with an agreement with Lake County to pump millions of gallons of treated wastewater mixed with lake water into the field to create more steam, has slowed the losses to between 1.5 percent to 2 percent a year, plant staffers said.

But this past year, that solution faced its own challenge in the guise of California’s drought. For the first time since the wastewater agreement was put in place, in 1997, the lake the power plant is drawing some of its water from fell below the level county officials sought to maintain. That slowed the flow of water to a quarter of what it had been before the drought.

Nevertheless, the plants’ engineers projected that they will be viable until 2040 – and probably beyond that date.

“We’ll provide power as long as people want it,” he said.


Submitted by Ian Crawford (not verified) on Tue, Oct 14, 2014

Congratulations on your trip up to The Geysers!

The Geysers Geothermal Field in Northern California is the largest single geothermal field in the world (over 900 MW), consisting of a complex of 22 geothermal power plants.

More information at: and

Submitted by Tom (not verified) on Tue, Oct 14, 2014

Looks like this power will end up non renewable.

Essentially the steam power plants exhaust the underground water supply. Non renewable in real time.

Would be interesting to see the financials on the absolute costs over the lifetime of this dying operation.

Submitted by Picturesque (not verified) on Tue, Oct 14, 2014

Where are the pictures? :)

Alameda in pictures: The Geysers

Submitted by Michele Ellson on Tue, Oct 14, 2014

Click "Read More."

Submitted by Bill Morrison (not verified) on Wed, Oct 15, 2014

Tom's dismissal of geothermal power production at the Geysers as nonrenewable and dying ignores the undiminished heat source, which is the heart of the power production. The water that is injected into the field (groundwater and recovered condensate), and the resulting high-energy, superheated steam that is recovered, is just the medium that translates geothermal heat into electrical energy. The reduced decline in steam pressure, currently at 1%-2%, is continuing to slow and trends indicate that the steam pressure will eventually stabilize. And other technologies, such as organic Rankine cycles, that are better suited to low-energy geothermal resources, may be introduced to the Geysers if marginal portions of the reservoir suffer worst-case degradation.

The Geysers will be generating electrical power for the foreseeable future. After fifty years, the reservoir is still generating several hundred megawatts. Based on the current trends and operating conditions, the Geysers will continue to produce hundreds of megawatts of power through this century. Which makes it a sustainable resource over a duration that would reasonably be considered real time.

As for the financials, the NCPA plants are over thirty years old and the capital investment was paid off in the first fifteen years. And these are the newest plants in the Geysers; the older plants of other geothermal operators have been operating debt-free even longer. Currently, projects that will improve efficiency are entertained if the benefits will recoup the capital investment within a few years or less.

Submitted by Picturesque (not verified) on Wed, Oct 15, 2014

Sorry ... not seeing any "Read More" in this link

Submitted by frank on Thu, Oct 23, 2014

What is missing from this Article is the fact that this Energy is currently being produced by 'the dreaded F-word' fracking. Since this process has been initiated there has been an increase in the frequency of Earthquakes in the area. Also as has been seen in OTHER areas of CA pollution of the Aquifers. We tend to view this all as 'warm and fuzzy' Energy but like anything there is a downside.