The hot spot
San Juan Mountains may be tapped for geothermal energy

A man relaxes poolside at Trimble Hot Springs earlier this week. In addition to providing therapeutic and recreational opportunities, the San Juan’s plentiful geothermal reserves are also being studied as a source of alternative energy./Photo by David Halterman

by Allen Best

From the looks of one map assembled by geologists, the San Juan Mountains got into a nasty fistfight. But that’s a good thing if you’re worried about greenhouse gases accumulating in the atmosphere.

The globs of purple and red on the map indicate hot-spots that scientists and engineers say may possibly be used to produce electricity. Most electricity now is produced by burning fossil fuels, mostly coal but increasingly natural gas.

Of course, wind and solar energy are being integrated into electrical grids, but they also pose challenges, because they are not steady, and no large-scale methods of storing the energy have been perfected.

That’s where geothermal energy from the San Juans as well as other parts of the West may come in. The heat would be used to produce steam, which in turn could be used to create electricity. “It is a renewable that has the ability to stay on 24 hours a day. That’s the Holy Grail,” says Matt Sares, of the Colorado Geological Survey.

A 2005 study by the Western Governors’ Association projected total production of 12,558 megawatts of electricity from enhanced geothermal by 2025. Taking a longer view, a 2006 report called “The Future of Geothermal Energy” foresees potential for 100,000 megawatts of base-load generating capacity by mid-century – or 10 percent of U.S. supplies. In contrast, the hotly contested Desert Rock coal-fired plant proposed near Farmington would deliver 1,500 megawatts.

The evidence for deep-underground heat sources in the San Juans has been mostly inferred from deep water wells, mines and assorted other pokes into the Earth’s crust. For example, a survey of 20 wells in the San Juan Basin south of Durango drilled to tap coal-bed methane also reveal temperatures of 250 degrees Fahrenheit at depths of 7,000 to 9,000 feet.

Still, this evidence is tantalizing. The 2006 report found that Colorado altogether is the top region in the nation for potential geothermal heat located at depths of 10 to 13 kilometers (6 to 8 miles).

The temperatures of the hot springs at Trimble, north of Durango, and at Rico, Ouray and elsewhere, are well documented. But the geologists want to go deeper. One such project involves Rico. Sares explains that different minerals can dissolve, or melt, at different temperatures. One such mineral is a type of quartz called silica. If that mineral is found in dissolved form in the hot springs at Rico, it will suggest a certain temperature range at depth.

There are other techniques as well for determining underground heat, tools that Sares calls “geothemeters.” Such detective work is best done first, before the far more expensive test-boring to great depths.

Meanwhile, both the federal government and geothermal entrepreneurs are beginning to take steps to actively develop underground heat. A critical first step being contemplated by the Bureau of Land Management is leasing public lands for exploration of heat sources.

Hot water seeps from the rock formation along Highway 550, norht of Durango. a popular stopping point ofr tourists, the seep and others like it could be the new frontier of alternative energy./ Photo by David Halterman

Of course, underground heat is already used widely in Western Colorado – and in most cases it’s not necessary to go too far toward China. The most common application is a technology called ground-source heat pumping. At 8 to 10 feet below ground, the temperatures remain about 55 degrees year round. Ground-source heat pumps exploit that constant temperature. The key technology is similar to what allows refrigerators to freeze items when it’s hot all around. In winter, the 55-degree heat of the ground can be milked to warm homes. The converse is also true in summer, reducing electrical use for air conditioners.

Better understood, if more rare, is direct use of geothermal heat. An example is Pagosa Springs, where the shallow underground pools of hot water were tapped in 1982 to provide heat for 13 businesses and two homes. Near Buena Vista, at the base of Mount Princeton, hot water is also tapped to heat greenhouses. And in the San Luis Valley, such hot water is used to grow alligators.

Far more rare is tapping these shallow hot-water resources to create electricity. However, the idea is not new. The world’s first such hydrothermal electrical plant went into production in Italy in 1904. Better known today is Iceland’s extensive use of shallow hot water for production of electricity, as well as heating.

But the world’s largest geothermal field for electrical production is in California, northeast of San Francisco. California altogether gets 5 percent of its electricity from these shallow, hot-water sources. Tapping these sources also plays a key role in Nevada’s ambitious goal of quadrupling its electricity derived from alternative sources during the next three to five years.

A new power plant using hot water also went into production during January in Idaho, south of Sun Valley. It produces 10 megawatts of electricity. Existing electrical geothermal plants also operate in Utah, Hawaii and Alaska.

Enhanced geothermal, also called geothermal, is the fourth and most cutting-edge idea in this quest to produce alternative energy. It is defined by great depth, commonly 10,000 feet or more, but also greater challenge in extracting heat, explains Sares.

Rocks found at those greater depths tend to be crystalline, what most people call granite. Unlike sandstones, which are found nearer the surface and are kind of like sponges when examined through a microscope, these crystalline rocks at greater depths and pressures have porosity, or space, that allow passage of water.

As such, water must be pumped down into the hotter formations with the goal of fracturing the rocks, but not too widely. Then the water can be injected to be heated, and then extracted at the surface where, as steam, it can be used to produce electricity before it is returned to the rocks to be reheated.

“It’s relatively new technology,” explains Sares. The technology has been tested in research projects in several places in the world. In many it remains experimental – but in others, including France and Australia, electricity is now being produced.

There is some potential for using existing oil and gas wells for electrical production. In Texas, where some wells have been drilled to depths of 30,000 to 40,000 feet, water produced from those wells comes out at 200 degrees and sometimes hotter.

In Colorado, gas and oil wells drilled between Denver and Greeley have produced temperatures of 200 to 250 degrees. “In Colorado we don’t have to go to 30,000 feet to get some of those temperatures, because the heat flow here is higher,” says Sares.

The state government sees geothermal in Colorado as a resource that needs to be studied, similar to coal, oil and other energy deposits. Enhanced geothermal was also a bright spot in the energy legislation passed last December by the U.S. Congress, which envisioned $25 to $30 million in allocations, compared to $5 million annually in recent years.

But the MIT group led by Jefferson W. Tester, a professor of chemical engineering, sees sufficient potential to warrant an investment of $800 million to $1 billion in research and development, to improve drilling technology. Test’s group found “no major barriers to limitations to the technology.” But, in a speech last October in Montrose, Tester said he sees the need for federal aid to establish locations of greatest potential for development.

Tom Konrad, a Denver-based alternative energy analyst, also sees great potential – particularly given the likelihood of carbon constraints. Already, geothermal from shallow wells competes with the cost of electricity from new coal-fired power plants, at about 5 cents per kilowatt hour.

But will the deeper, enhanced geothermal electricity come on line in Colorado soon? Sares suggests that proof in the pudding remains some years away.