Emission-Free Energy: Straight From Nature’s Oven

Geothermal energy, dubbed by some as a 'sleeping giant' or renewable power in the United States, appears as one of the most attractive climate-friendly options available.
Publish date:
Social count:
Geothermal energy, dubbed by some as a 'sleeping giant' or renewable power in the United States, appears as one of the most attractive climate-friendly options available.

Solar has always been sexy. Wind is attracting big-name investors. Biomass has the heartland.

And then there’s geothermal energy, what many Americans associate with remote hot springs and quaint old buildings with hot water running through radiators.

But recent research suggests geothermal could be a more abundant, reliable, cost-effective and less invasive energy source than other renewable sources. Who would have thought?

The first clue was a study by the Massachusetts Institute of Technology. About a year ago, an MIT press release began with a sentence that concluded: “The huge amounts of heat that reside as stored thermal energy in the Earth’s hard rock crust could supply a substantial portion of the electricity the United States will need in the future, probably at competitive prices and with minimal environmental impact.”

Then came an announcement from the U.S. Geological Survey: The first assessment of geothermal resources in 30 years showed that development of identified geothermal systems could more than double the electricity currently supplied by the resource and if enhanced geothermal resources (or EGS) were developed, 345,000 megawatts would likely be available. That’s the equivalent of nearly half of the currently installed electric power capacity in the country.

Cheap, But Not Cheap Enough

To be clear, traditional geothermal power is created when steam heat from deep in the Earth’s crust is tapped to provide power to run a turbine, generating electricity. EGS works by drilling and then fracturing hot rock, circulating water through the system, and using the resulting steam to run a turbine.

Last year, the U.S. Bureau of Land Management opened 190 million acres of federal lands for leasing and potential development of geothermal energy, something industry leaders for years had been lobbying for. The BLM approved 18 geothermal drilling permits in 2006; that number doubled in 2007 and nearly quadrupled in 2008.

Although the United States is the world leader in geothermal, with 69 plants currently generating about 2,960 MW, other countries such as Iceland and the Philippines are getting a healthy portion of their power from the resource. The Philippines generates 27 percent of its electricity (about 1,350 MW) from geothermal power. Geothermal plants in Iceland generate about 25 percent of that country’s electrical power; perhaps more impressive is that an estimated 87 percent of Iceland’s buildings are heated with water cycled from geothermal wells through building pipes and heat radiators — one example of what is called “geothermal direct heat.”

Geothermal heat has been used in this country for more than a century, but development of it as an electricity generator has come in fits and starts. Like many renewable energy sources, interest in it peaked in the 1970s, but development slowed after the energy crisis abated.

Raser Technologies, Inc., changed the “slow” part last year when it built a 10 MW geothermal plant 155 miles southwest of Provo, Utah, in six months, and subsequent discoveries at the site have the company expecting to produce 230 MW of power from the field.

Part of the growing interest in geothermal is that it can provide constant power, something neither solar nor wind — intermittent sources of energy — can deliver. Another advantage is the relatively small area required for a geothermal plant compared with the large acreages needed for wind turbines and solar displays.

Geothermal discoveries have been made over a broad range of terrain and regions. All Western states, including Alaska and Hawaii, have geothermal potential. And if new advances in extracting heat from the earth — a wide swath of approaches to enhancing or engineering geothermal systems — power could potentially be tapped across the country.

The “sleeping giant,” as some have called geothermal, already exceeds solar and wind in its contribution the United State’s renewable energy pie. The nation got 7 percent of its total energy consumption from renewable sources in 2006; geothermal sources provided just 5 percent of that pie, dwarfed by biomass (49 percent) and hydropower (41 percent) but well ahead of solar with 1 percent and wind with 4 percent, according to U.S. Energy Information Administration statistics.

A recent USGS study on geothermal focuses on 13 Western states, largely because geothermal reservoirs are generally found closer to the surface in the West — within about 5,000 feet. Typical geothermal wells are drilled up to 8,000 feet into the ground at a cost of $5 million dollars a well. The success rate for drilling is about 50 to 75 percent, according to Lisa Shevenell, director of the Great Basin Center for Geothermal Energy at the University of Nevada, Reno, making drilling costs the main stumbling block to geothermal at this point — exacerbated by the nation’s economic downturn.

Geothermal faces the same obstacles as other renewables when oil and gas prices fall, as they have in the last few months. What once looked to be a competitive price — around 5 to 7 cents a kilowatt hour for wind and geothermal — may not be when oil is selling for $45 a barrel.

Geothermal was “just booming,” eight months ago, Shevenell said, saying it was comparable to the excitement and development in oil fields a century ago. At that point there were 45 projects in various stages of development in Nevada, second only to California in geothermal production. Since then, many of the projects that hadn’t secured funding prior to the economic meltdown are having difficulties, she said. Geothermal is “going to remain reasonably risky upfront. It’s a reliable resource because you can have long-term energy. It’s very stable once you get past the initial cost.”

There are a few American investors who have gotten by those costs, including stock market guru Warren Buffett and Google.org, the philanthropic arm of the Mountain View, Calif.-based search engine company, both of whom are putting big money into EGS development. Google.org recently ponied up $10 million to three entities working to map the resource and demonstrate its economic viability.

EGS: Mother (Nature’s) Little Helper
But Shevenell maintains that EGS is a technology for the future even though there are many geothermal sites that could be developed here and now. However, it could be argued, considering the broad definition of what constitutes EGS, that the technology is already in use today.

One person who knows of an example of EGS is Colin Williams, director of USGS Heat Flow and Geothermal Resource Studies and its Earthquake Hazards Team. He cited The Geysers in northern California as one project where a form of EGS has been shown to be successful.

The oldest geothermal producer in the country — and still the largest — The Geysers was discovered around the middle of the 19th century. Hot springs there were enjoyed by luminaries such as J. Pierpont Morgan, Theodore Roosevelt and Mark Twain. A century later, the country’s first large-scale geothermal electrical-generating plant began operating at The Geysers, producing 11 MW of power. Today, the venture, operated by Calpine Corporation, comprises 22 power plants that produce about 725 MW — enough to power 725,000 homes, or a city the size of San Francisco.

But about a decade ago, The Geysers was losing steam, literally. Too much water had been extracted, without replenishment, and questions began to arise as to the viability of the resource. A unique solution was developed — billions of gallons of wastewater from Lake County and the nearby city of Santa Rosa would be pumped to the site and injected into the wells to replenish the underground reservoir. To date, this method has been seen to be quite successful.

Some cite The Geysers as an example of EGS because its system of operating has been “enhanced” or “engineered” by injecting water from off-site into the wells. On the other end of the EGS-definition spectrum is drilling into a promising site, fracturing the rock, and injecting water that will be heated and circulated to create the geothermal resource. This is a much more involved, costly and unknown process, but if some bets pay off, it could some day rival oil and gas as an energy supply — without greenhouse gases.

Shevenell pointed to what she sees as a potentially cost-effective method of using EGS today — 20,000-foot wells that were drilled for oil and gas in the Gulf Coast that could be converted to an enhanced geothermal system. She said the U.S. Department of Energy has received solicitations to study the potential, adding, “I’m pretty hopeful. It’s a great direction to go in. It could prove some of this technology without a whole lot of investment.”

So, what are geothermal’s “faults,” to venture a pun? Other than large upfront discovery and development costs, the main drawbacks are small earthquakes that result from drilling and reservoir movement, and, at some sites, unwanted contaminants, such as mercury, showing up in the water.

Williams said micro-earthquakes could begin to trigger a larger quake, so an EGS should not be built near an active fault and monitoring needs to be done at all facilities to address seismic activity. “If properly managed, seismic activity is not a significant problem. It’s something (geothermal developers) have to plan for and monitor.”

He said unwanted minerals in the water also need to be monitored and usually are “separated off during the power production process.”

Lost in the excitement of geothermal’s potential as a major player in electrical generation is the old-school method: direct use of hot water and/or heat from the earth. Today, direct-use includes a broad range of applications, including space and greenhouse heating, agriculture drying, aquaculture and geothermal heat pumps for space heating and cooling. In 2000, direct-use was credited with providing 5,373 MW of thermal heat in the United States. Shevenell believes that’s just the tip of the iceberg.
She noted there are widespread direct-use geothermal applications in Europe.  “We’re woefully behind on utilizing it,” she said.

“It’s pathetic.”

But that’s another story.

Sign up for our free e-newsletter.

Are you on Facebook? Become our fan.

Add our news to your site.