In 2026, electrical customers in the west could receive some of their power directly from the earth’s core.
OK, not directly, since the heat of the earth’s molten iron core exceeds 10,800 degrees Fahrenheit. But their electricity could be provided in some part by Fervo Energy’s new Cape Station geothermal energy project, located on 631 acres in Utah. 148 acres of that 631 are public land, of which the Bureau of Land Management has approved Fervo’s use.
Earlier this year, Fervo announced two executed purchase agreements with Southern California Edison for 320 megawatts (MW) of energy. That total includes the initial 70 MW output the plant expects to achieve when it becomes operational in two years. Businesswire reports that 400 MW were contracted as of September 10, 2024, but also suggests the plant won’t be online to produce that amount until 2028, so there is some disagreement on Cape Station’s construction and capacity end date.
Fervo, based in Houston, is privately held, so there are no budgetary amounts available on the project. However, the average cost to produce a single kilowatt hour of geothermal power is $4,500, and The University of Michigan’s Center for Sustainable Systems estimates the cost of a gigawatt at $3.75 billion. Extrapolating those figures, one could estimate the cost of the Fervo geothermal plant at approximately $8 billion.
That price tag won’t be shouldered all at once, according to reporting from Engineering News-Record, which speaks of a phased capacity build-out. Fervo’s Chelsea Anderson said that construction is active and ongoing, but “at this time we aren’t able to comment on any specifics regarding suppliers and procurement.”
Geothermal Power Production Explained
Simply speaking, geothermal energy is produced by harnessing the heat of the earth’s core. As mentioned earlier, the core, made up entirely of molten iron and has a temperature of 10,800 degrees Fahrenheit – roughly the same temperature as the surface of the sun. The core is 1,500 miles in diameter and is insulated by a cooler outer core of magma that is 1,500 miles thick, and another 1,800 miles of outer core, also known as the mantle, made of magma and rock. When a volcano erupts, it is the cooler magma core that spews up and out, which we call lava.
Why is Geothermal Energy Considered Renewable?
According to the U.S. Energy Information Administration (EIA), geothermal energy is considered a renewable resource for heat and electricity because the earth’s core is continuously producing energy. Scientifically speaking, the earth’s core will one day cool, but scientists place that “end date” for the earth’s core at five billion years from now.
How Does Geothermal Energy Work?
Obviously, we have not created tools that allow us to extract anything simmering at more than 10,000 degrees, and that’s why geothermal energy does not – strictly speaking – harvest anything from the core itself. Instead, geothermal energy plants extract hydrothermal energy (steam) and/or hydrothermal energy (superheated water) from wells that can reach depths of up to two miles into the earth’s crust.
With both the steam and superheated water ranging in temperature from 300 – 700 degrees Fahrenheit, extraction requires a great deal of care and planning. Geothermal power plants generally utilize both hydrothermal and geothermal sources by piping either the water or steam to the surface and using it to power one or more turbines to generate electricity.
These geothermal power plants generally fall into one of three categories: Dry steam, flash steam, and binary cycle.
The U.S. Energy Information Administration has defined and explained each plant category as follows:
• Dry steam plants use steam directly from a geothermal reservoir to turn generator turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy, where natural steam erupted from the earth.
• Flash steam plants take high-pressure hot water from deep inside the earth and convert it to steam that drives generator turbines. When the steam cools, it condenses to water and is injected back into the ground to be used again. Most geothermal power plants are flash steam plants.
• Binary-cycle power plants transfer the heat from geothermal hot water to another liquid. The heat causes the second liquid to turn to steam, and the steam drives a generator turbine.
Businesswire reports that Fervo has drilled 15 wells at Cape Station thus far, “achieved record-breaking commercial flow rates at the site’s first well test,” and has secured a $100 million loan from X-Caliber Rural Capital to expand and accelerate its operations. Its well test achieved a maximum flow rate of 107kg/s at high temperature and reached more than 10 MW of electrical production, which bodes well for the project.
Speaking as part of Businesswire’s reporting on Fervo, Jesse Jenkins, Assistant Professor and leader of the Zero-Carbon Energy Systems Research and Optimization (ZERO) Lab at Princeton University said:
"Clean firm resources are critical to complete the carbon-free electricity portfolio and provide decarbonized energy around-the-clock. Fervo's technical success commercializing advanced geothermal brings us one step closer to a clean, reliable grid."
Drilling Geothermal Energy Wells Safely
Among the practical considerations with geothermal power is the ability to safely and efficiently drill extremely deep wells to harvest the core’s heat. To do that, geothermal power companies are turning to the fossil fuel industry, whose workforce has supplied more than 90% of the labor hours at Cape Station thus far. Who better to drill into the earth at high depth better than those who have been doing it – in search of oil and gas – for generations? By partnering with local oilfield services firms, Fervo is reported to have slashed the time to drill a geothermal well by 70% year over year.
The other major practical consideration is making sure to not hit existing subsurface utility or pipeline infrastructure when digging or drilling. For that, geothermal companies must turn to professional private utility locators – like GPRS – to fully map the existing underground conditions and utilities on site before they break ground.
Fervo received official DOE approval on October 17, 2024, which will repurpose the protocols and tools used in shale fracking to inject water into subsurface heat pockets to generate hydrothermal steam for electricity generation. If Cape Station meets its stated 2 GW goal, it will tie the record set in 1987 by the world’s largest geothermal field in California, knowns as The Geysers.
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GPRS Project Managers use their knowledge and experience to employ a variety of complementary technologies like ground penetrating radar and electromagnetic locators to pinpoint the location of underground facilities. They are highly trained in Subsurface Investigation Methodology (SIM) so that they can interpret the data from these technologies to create an accurate map of the underground infrastructure, which is then uploaded via GPS or RTK positioning to our SiteMap® platform (patent pending) for customer use. In most cases, your utility map is available online within minutes.
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