City of Aspen officials have identified five spots in town where an exploratory geothermal well could be drilled.
The city has also applied for geothermal water rights for underground stores of water that would be used in the system, making Aspen the first municipality to take advantage of a new state law: The Colorado Geothermal Act.
The city hopes to create a public utility that would harvest geothermal heat from under ground and distribute it to downtown Aspen buildings. Preliminary studies show that as much as 1 million square feet could be heated “at a cost competitive with natural gas,” according to a city press release.
Geothermal heat takes advantage of warmer underground temperatures, which increase in proportion to the distance from the Earth’s surface. The warmer underground air, where the average temperature 5 feet below the surface is 55 degrees Fahrenheit, is pumped to the surface and then heated — using an electric current — to the desired temperature. The system works in reverse to provide air conditioning in the summer.
As a network of 19th century mining tunnels runs underneath Aspen’s streets, and as those tunnels are filling up with water, a proposed city geothermal system would tap into those waters, which provide a more efficient heating source than solid ground.
The five sites in town identified for potential geothermal wells include a section of Rio Grande Park, Heron Park, the “Millionaire Property” at the foot of Aspen Mountain, Wagner Park and the “Cowenhoven Vent” on Smuggler Mountain.
All of the proposed geothermal sites are on city property or in the public right of way except for the Cowenhoven Vent.
At a work session last week, Aspen City Council told the city’s public works department to forge ahead with its geothermal studies. The public works department will come back with a more solid proposal to drill on one of the sites, along with a contract for the work, which the council will have to approve.
Drilling a geothermal well, between 1,500 and 3,000 feet deep, can cost as much as $500,000 — a figure city officials project would be recouped in about seven years, thanks to energy savings.
The city is seeking a financing partnership on the geothermal system with Gov. Bill Ritter’s Energy Office, which is seeking to develop more geothermal capacity in Colorado. There is only one geothermal public utility in Colorado, despite the fact that, according to one study, the state has the sixth-highest geothermal potential in the nation.
Aspen also sits on top of a geological phenomenon called the “Aspen Anomaly,” which refers to an area stretching from approximately Leadville to Paonia where the earth’s crust is thinner than in other areas. Thinner crust means warmer underground temperatures than might be expected otherwise.
curtis@aspendailynews.com