Note that 900mw is less than just one modern fuel-fired or nuclear plant.
I have several labels beginning with "energy." But I don't have one for geo. It still takes special geological structures to produce geothermal power, so I'm not going to make an energyGeo label since these plants are rare. (The oil and gas industry is researching for ways that drilling and fracking technologies can produce more geothermal fields.)
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| geysers |
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| Corey Johnson posted One of about twenty power plants in The Geysers geothermal power complex in California. The system produces about 900 MW in total. Gary Wetzler: 835 MW total for the 18 plants. [Some comments discuss steam generators for nuclear plants built in the 1970s that used a new alloy for the tubes. The new alloy caused premature failure of the tubes.] Bob Koch: 900 MW is impressive with this set up. Corey Johnson: Lesley Otwell Nice! Yes there are a lot of eyes on it in that region because it's renewable power that doesn't depend on weather. Even oil and gas industry is getting into it to apply their sub-surface expertise. Jimmy Mac McMullen: Not many places to build them at all . Corey Johnson: Jimmy Mac McMullen That's a reason why there is R&D going on to try to stimulate production in other areas - fracking is one idea, and being able to drill the required depths both vertical and horizontal. There are even some ideas of using a completely artificial system and running supercritical CO2 as the heat transfer and working fluid. |
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| bartellj, Dec 2021 |
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| geysers_map |
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| geysers_geothermal |
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| geysers_history11 "A million years ago, a plume of molten magma intruded close to the Earth's surface. The heat from this 1400˚F intrusion recrystallized the overlying rocks, making them hard and brittle, then caused fracturing to create permeability. Subsequent magmatic activity over the next half-million years maintained high temperatures as water seeped down through fractures to form a hot water geothermal reservoir. At about a quarter million years ago, the caprock overlying the ancestral Geysers reservoir fractured, allowing steam eruptions as the high temperature water boiled down to form the current steam reservoir." |
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| USGS, Sources/Usage: Public Domain. "Numerous geothermal wells are located In the Mayacamas Mountains, north of San Francisco. The Geysers cover 45 square miles between Lake, Mendocino, and, Sonoma counties; and provide power to Sonoma, Mendocino, Lake, Marin, and Napa counties. Commercial geothermal power has been continuously generated at The Geysers since 1960, and it is the largest complex of geothermal power plants in the world. There are 18 geothermal plants which use heat from the earth's interior to produce electricity around the clock. The plants produce about 835 megawatts of electricity." [This article provides a technical description of the underlying geology.] |
"Although the nearby Clear Lake volcanic field was still erupting as recently as a few thousand years ago, there were never any geysers at this geothermal field. The Geysers is a misnomer that came from 19th century settlers to the area who misunderstood the hot springs and fumaroles bubbling and steaming away in the canyon of Big Sulphur Creek. From the mid-19th to the mid-20th century, a popular resort hotel operated in the area, while indigenous people of the region have visited the springs since prehistoric times." [nasa]
During the 1800s, the geysers were used for health spas and mineral water. [geysers_history11, click 1890]
Given the above screenshot, these must be injection wells.
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| geysers_history11, click 1923 "Grant and his family organize The Geysers Development Company and build a 35 kilowatt power plant, generating the first geothermal electricity in the Americas." |
"Grant’s experiment with geothermal power fails due to competition from cheap oil, but it is only a temporary setback. In modern times, The Geysers Development Company goes on to become the most productive leaseholder in The Geysers." [geysers_history11, click 1934]
The health SPA business continues.
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| geysers_history11, click 1960 "PG&E completes Unit 1, the first commercial geothermal electric unit in the Western Hemisphere, generating 11 megawatts of electricity." |
1980: The health SPA business ends.
1987: "Production peaks at The Geysers. Twenty-one power plants are in operation, with a total installed capacity of 2,043 megawatts. Over the next eight years, power generation rapidly declines as a result of pressure loss in the steam reservoir."
1989: "Geysers operators begin cooperative studies on the use of augmented water injection to create steam, sustain reservoir pressure and maintain power generation."
1995: "Calpine, NCPA and Lake County Sanitation agree to construct the Southeast Geysers Effluent Pipeline (SEGEP), a 29-mile pipeline to deliver treated wastewater to The Geysers."
"Delivery of wastewater to The Geysers commenced in October 1997. The original 29-mile pipeline, now lengthened to 40 miles to include effluent from additional communities in the Clear Lake area, delivers approximately 9 million gallons per day of secondary treated wastewater for injection into The Geysers Reservoir." [geysers_water]
2000: "Calpine acquires 19 Geysers power plants and associated steamfields. Consolidated ownership eliminates contractual barriers, allowing a fieldwide approach to sustainably managing The Geysers geothermal resource.
"Calpine constructs pipeline inter-ties (crossovers) linking steamfields and power plants, minimizing the need to vent wells during plant outages. During power plant shutdowns, the steam is diverted to other plants, reducing the loss of electrical generation."
2003: "Calpine and the City of Santa Rosa complete a 40-mile pipeline, bringing an average of 11 million gallons per day of treated wastewater to The Geysers and further helping to restore the steam reservoir."
I have not been able to determine if the sources of the water replenisment pipelines are from a watershed that would otherwise feed the aquaduct to southern California. Or if this water would otherwise end up in the Pacific Ocean.
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| geysers_water |
"A direct relationship between water injection and low-magnitude seismicity has been firmly established. However, the relationships of fieldwide steam production and water injection to larger but less frequent seismic events are more complicated. Importantly, the frequency of seismic events greater than magnitude 3.0 has been trending downward since about 1990." [geysers_seismicity]
Since the first commercial plant in 1970, more than 400 production wells and 28 plants have been built. The capacity peaked at 2,034mw in 1987. [geysers, click video, @ 0:21]
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| Screenshot |
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| Screenshot |
Given the above screenshot, these must be injection wells.
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| Satellite |
The statistics for the geothermal field obviously depends on which year they were measured. Here is a June 2015 status: "At present, 424 wells produce a combined total of 125 billion pounds (62.5 million tons) of steam per year, with 21 turbine-driven generating units converting it into about 8.4 million megawatt-hours per year; or an instantaneous output of 955 megawatts, enough to supply power to approximately 1.2 million Californians. The Geysers is a vapor-dominated geothermal resource, meaning gaseous steam exists in the
reservoir. The reservoir is found at a depth of a mile or more, and at a temperature of 500-600
degrees F....At present, there are 424 production wells at the Geysers producing 125 billion pounds (62.5
million tons) of steam per year and 88 wells used for injection of water. Those injection wells
handle 96 billion pounds of water (48 million tons) per year, equating to 22,400 gallons per
minute, or 248 gallons per minute per well. Therefore, 77% of the mass withdrawn from the
reservoir is replaced on an annual basis. Water injection at The Geysers occurs into the geothermal reservoir, a mile or more deep, and
not into near-surface aquifers. The geothermal reservoir is completed isolated from near-surface
water supplies by a sealing caprock which precludes injection waters affecting the ground water
supply." The wastewater is tertiary-treated and suitable for human consumption. The is also a Salton Sea geothermal field, but it has been harder to develope because it produces hot salt water rather than steam. "Some estimates put the total
potential for the field at 2,000 megawatts. Development at the Salton Sea geothermal field has
been slowed by the high up-front costs involved with brine-based geothermal power, and the lack
of power transmission capacity from this isolated region to Los Angeles and San Diego." [california]
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