The Center for Land Use Interpretation Newsletter

Letting Off Steam

Geothermal Power in the USA
The CLUI exhibit Venting the Earth: Looking at Geothermal Energy examined geothermal power plants in the USA, like this one owned by CalEnergy, near California’s Salton Sea. CLUI photo
CLUI photo
The CLUI exhibit Venting the Earth: Looking at Geothermal Energy examined geothermal power plants in the USA, like this one owned by CalEnergy, near California’s Salton Sea. CLUI photo

WHILE THE SUN SPRAYS THE planet with free energy from above, another fire rages beneath us, at the center of the earth. Pressure from the planet’s core, burning at the same temperature as the surface of the sun, pushes molten rock and heat outwards and upwards. Volcanoes demonstrate this in dramatic ways, but at other locations, like hot springs and geysers, this internal heat escapes more passively. In these places, and even in others where surface activity is hardly visible, geothermal heat is harnessed and converted into electricity.

Shallow, temperate geothermal wells are in widespread use to warm (and cool) individual buildings, simply by drawing the consistent temperature found underground to the surface to help offset the seasonal variations above ground. However, producing electricity at a large scale generally involves turning heavy turbines, requiring higher geothermal temperatures and pressures to be tapped.

Geothermal plants at the Geysers. CLUI photo
CLUI photo
Geothermal plants at the Geysers. CLUI photo

Regions with abundant tectonic activity and thin crustal areas in the US are widespread, especially in the West. Despite this, less than half a percent of the total supply of electricity in the USA is produced by geothermal plants (and the USA leads the world—with around 25% of the global utility-scale geothermally-produced electricity). To say there is room for growth in geothermal is, so to speak, an understatement.

Though the Department of Energy and the Environmental Protection Agency consider geothermal energy a renewable resource, there are side effects from drilling dozens of wells thousands of feet into the earth and letting the steam and pressure out (even if most of the water is re-injected into the aquifer, which it tends to be). These effects include a net loss of water through steam, diminishing and cooling the aquifer (even though some of the steam is collected by condensation); the collection of potentially harmful minerals at the surface (extracted from the water as it passes through power plants); and the effect on the subterranean stasis, including lowered pressures, possibly problematic along active fault lines where the risk of earthquakes already exists.

A proposed form of geothermal production, known as enhanced geothermal systems, involves drilling deeper wells and stimulating them with fracking technologies. While this might open up nearly the entire nation to geothermal energy, not just the relatively thin parts of the earth’s crust, its deployment is controversial.

Distribution pipes at the Geysers. CLUI photo
CLUI photo
Distribution pipes at the Geysers. CLUI photo

Nonetheless, and for the time being, current methods of producing geothermal energy are among the least destructive means of producing electricity at grid-scale, and are relatively easy to build quickly. They are something to look at, at least.

Geothermal plants in the continental USA
CLUI photo
Geothermal plants in the continental USA. CLUI map

Geothermal: Where It’s At
At the moment there are around 75 utility-scale geothermal facilities in the USA that convert the internal heat of the earth into electricity, with 70% of that production in California, 25% in Nevada, and the remaining five percent coming from five other western states. Some are scattered around, but most are found in clusters, often at places that were developed as hot springs resorts more than a century ago.

The largest geothermal energy production site in the nation, and likely in the world, is the Geysers, in Northern California. The Geysers geothermal area, in the rolling hills north of Santa Rosa, was a famous hot springs and tourist attraction, visited by the likes of Mark Twain and Theodore Roosevelt. The first geothermal well was drilled in 1920.

Overlook display at the Geysers. CLUI photo
CLUI photo
Overlook display at the Geysers. CLUI photo

In 1960 the first modern utility-scale geothermal electricity plant opened there, and many soon followed, totaling more than 30 at the peak. By 1987 the site produced more than 2,000 megawatts of power, similar to the output of the largest coal-fired power plants.

When the reservoir of heated water diminished, output declined. By the mid-1990s, output was at less than half of its peak, but even then the Geysers was still the largest geothermal complex in the world.

Today the subterranean geothermally heated water is being replenished by two pipelines, more than 40 miles long, that bring wastewater from nearby communities. This water is injected into the ground, enabling 15 plants to make a total of more than 1,000 megawatts of power at the Geysers.

CalEnergy geothermal plant near the Salton Sea. CLUI photo
CLUI photo
CalEnergy geothermal plant near the Salton Sea. CLUI photo

With 15 plants producing as much as 760 megawatts collectively, Imperial County, in the southeast corner of California, is the second largest concentration of geothermal energy production in the nation. Ten of the facilities are near the southern end of the Salton Sea, where all but one of them are owned by CalEnergy, a subsidiary of Berkshire Hathaway.

The gate to Coso geothermal plants. CLUI photo
CLUI photo
The gate to Coso geothermal plants. CLUI photo

The third largest geothermal energy production site in the nation is at Coso Hot Springs, in the eastern part of California, on the edge of the China Lake Naval Weapons Station, where four plants are operated by a private company, producing up to 275 megawatts.

Geothermal plants at Mammoth.  CLUI photo
CLUI photo
Geothermal plants at Mammoth. CLUI photo

Further up the Owens Valley, the Mammoth Geothermal Complex, near Mammoth Hot Springs, has three plants, with another on the way, and produces up to 40 megawatts.

Nevada, the second biggest geothermal energy state, has around 25 plants, scattered in the northwest part of the state, producing as much as 750 megawatts total. The largest plant, McGinniss Hills, produces 138 megawatts, with the rest averaging around 40 megawatts. The remaining five percent of national geothermal output, outside of California and Nevada, are from less than a dozen small plants in Utah, Oregon, Hawaii, Idaho, and New Mexico. ♦

Signage at the Brady geothermal area in Nevada. CLUI photo
CLUI photo
Signage at the Brady geothermal area in Nevada. CLUI photo
Video portraits of geothermal plants were featured in the CLUI exhibit Venting the Earth: Looking at Geothermal Energy. CLUI photo
CLUI photo
Video portraits of geothermal plants were featured in the CLUI exhibit Venting the Earth: Looking at Geothermal Energy. CLUI photo