Colorado’s geothermal resources may get workoutadmin
June 18, 2006 Filed Under: Mining Services, Oil and Gas
Colorado’s state geologist said that the state rests upon a vast energy reserve, but this time he’s not talking about coal, oil or natural gas.
Vince Matthews, who also heads the Colorado Geological Survey, attended a conference in September where Nevada’s efforts to develop its geothermal resources were outlined ”and I thought, ”˜Gee, we’ve got that. In fact, we’ve got better than what they’ve got.’ ”
Matthews isn’t the only one who thinks so. He says he’s getting increasing numbers of calls from consultants wanting to know about Colorado’s resources. They won’t say whom they represent but interest is strong enough for him to put together a report outlining the state’s geothermal resources along with a map showing where they are.
“The one thing we don’t have is steam at the surface,” Matthews said, and that’s why Colorado traditionally has not been seen as a prospect for geothermal energy.
Geothermal power is nothing new. Many cities have tapped underground steam and hot water as a heat source and people have been using geologic steam vents to run electrical generators for more than century. The world’s largest geothermal power field is The Geysers, a sprawling area of steam vents in coastal mountains north of San Francisco that churns out 750 megawatts of power. Direct geothermal generation has been limited to areas like that, where superheated steam flows out of the ground, but new technologies developed over the past three decades have made it possible to generate power from water that leaves the ground at temperatures below the boiling point.
That could mean that Colorado’s hot springs areas could be used for more than relaxing stiff muscles or raising alligators and tilapia.
Those new binary systems tap the source of hot springs below the surface and the hot water is used to heat coils with a gas like pentane or butane, which have much lower boiling points. Those high-pressure substances then drive turbines that produce power.
That kind of water can be found in many parts of Colorado, Matthews says, including just about all of the San Luis Valley, the Arkansas Valley from Salida to Buena Vista, an area running from Canon City to Florence, and smaller areas around Pagosa Springs, Glenwood Springs, Durango, Hot Sulphur Springs, Ouray and Rico.
In Southern Colorado, people have been aware of geothermal resources for decades and they’ve found a variety of uses for them. There are a number of artesian wells still in use that were hit by unsuccessful wildcatters looking for oil. Oil was found in some areas around Florence and is still being pumped but hot water was also was abundant. Canon City once used artesian hot water to fill a municipal swimming pool and Larry Conrad, who lives just outside Florence uses the water from the Dakota formation to fill the pool at his Desert Reef Beach Club and heat his home and a greenhouse. The surface temperature there is 132 degrees, he said.
Farther east, artesian wells still provide water but the temperature drops considerably. Eric Clark, whose great-great-grandfather Silas was drilling for oil in 1879 in Pueblo’s Grove neighborhood when he hit water, said that the surface output of Clark’s Spring Water is 78 degrees.
Matthews has published a report available on the National Renewable Energy Laboratory Web site that outlines the current uses of geothermal energy and some of the potential benefits from binary generators.
He points out that the provisions of Amendment 37 call for power companies to get 10 percent of their electricity from renewable sources and geothermal energy would be one way to satisfy that. So far, most have relied on contracts with a growing number of wind farms and Xcel recently announced plans to buy power from a solar generator in the San Luis Valley.
Geothermal’s advantage is that it’s also a clean source of energy but one that’s available 24 hours a day, regardless of weather. The water it uses is recycled and the secondary system that runs the turbine is enclosed.
Binary geothermal plants in Nevada provide as much as 250 megawatts of power, just more than one-third the output of the two units now operating at Xcel’s Comanche Station here.
Just the existence of hot springs is not enough to prove the potential for power generation, Matthews cautions, and volume of water also is a major consideration. In his report, he says Colorado fields likely would produce about 5 megawatts, enough to serve local communities.
“One of the criteria you need is about 265 degrees at less than 13,000 feet deep. We’ve registered gas temperatures in the San Juan basin at 320 degrees at 6,800 feet.”
The structure of the rock also is important, he said. “It isn’t just enough to have hot rocks. You have to have porous and permeable rocks down there to allow for good flow. In Colorado, we have young active faults, young volcanic eruptions,” all the conditions that make geothermal power practical.