Austin Colbert/The Aspen Times
Editor's note: This story has been updated to clarify that the Aspen School District received a $78,400 grant from the state government to help fund the feasibility study. The article incorrectly stated that the grant was $74,000.
The Aspen School District is about to drill 1,000 feet underground.
This is intended to test the feasibility of installing ground source heat pumps, a high-efficiency heating and cooling system that would allow the district to use the earth's subsurface temperature to heat and cool its buildings.
“I want to push the envelope a little,” said project leader Joe Waneka, director of operations and facilities for the Aspen School District. “And that’s why we’re trying to use geothermal energy.”
Geothermal heat pumps transport the liquid compound glycol far below the earth's surface. The glycol absorbs the earth's heat before transporting the heat to the surface heat pumps. The pumps then distribute the heat to the buildings.
The heat pumps work efficiently because the earth far below the surface provides a constant temperature for heat extraction, unlike air pumps that draw heat from fluctuating air temperatures. The geothermal heat pumps also transport existing heat instead of generating new heat by burning fossil fuels like traditional gas heating systems.
But whether the district can install geothermal heat pumps all depends on the feasibility study later this month. The study will test the Earth's thermal conductivity and measure how easily boreholes can be drilled. If the ground beneath the school district is not suitable, the project will be abandoned.
Once construction company McKinstry attempts to drill the six-inch-wide, 1,000-foot-long hole on school grounds, it pumps glycol into the bottom of the hole to measure the soil's thermal conductivity — or the extent to which the soil can efficiently change the glycol's temperature — if everything goes according to plan.
“We may not be able to drill more than 200 feet, we may be sitting on a granite slab,” Waneka said, “or the conductivity is poor.”
However, if contractors can drill to the desired depth and the earth is sufficiently conductive, the school district will move forward with the geothermal heating system, which Waneka said would be an estimated 88 to 90 percent more efficient than its current gas- and electric-powered heating and cooling system. If all goes according to plan, he estimated the district would begin drilling wells for the system in the spring of 2027.
The feasibility study and perhaps the project itself will not rely on taxpayer money. The district received a $50,000 grant from the Community Office of Resource Efficiency (CORE) and a $78,400 grant from the state government to fund the feasibility study, which is expected to cost Waneka between $92,000 and $98,000.
If the study goes well and the county decides to use geothermal heat pumps as its primary heating source, he estimates the county would drill 180 to 220 holes 1,000 to 500 feet deep. The number of holes depends on the depth that contractors determine is best for heat transfer. The shallower you drill, the more holes you need. The deeper they drill, the less.
Although he was hesitant to give a cost forecast, he estimated the project would cost between $28 million and $30 million – $35 million on the high end.
“I’m definitely putting the cart before the horse, so be careful,” he said of making a prediction so early.
The district could expect to have 40% of the project cost covered by a federal tax credit under the Inflation Reduction Act, which took effect in 2022 under President Joe Biden to invest in part in clean energy. The district also plans to fund the project with grants “and any other public-private partnerships we can develop,” Waneka said.
If geothermal heat pumps are successfully installed as the district's primary heating and cooling source, they could expect to save $860,000 a year on gas and electric bills, which is 90% less than they currently pay, he said. In the future, the district could also pursue “Tri-Gen” production – an advanced geothermal heating and cooling process that also generates electricity.
“If we can get to tri-gen production, where we generate electricity, then we get money back for the excess electricity that we sell,” he said.
Tharyn Mulberry, superintendent of the Aspen School District, said developing geothermal systems will help the district reduce its carbon footprint in the valley and could potentially provide it with revenue, depending on how the feasibility study goes.
Reach Skyler Stark-Ragsdale at 970-429-9152 or email him at sstark-ragsdale@aspentimes.com.