Tufts University installed a geothermal system in January 2019. (Cushing and Sons)
Michael J. Daley
When I was assigned the task of investigating the many college and institutional geothermal heating systems being installed or planned for the northeast, I had visions of well drillers probing the Earth for hidden bubbling, boiling reservoirs of water.
“Not so,” Bart Cushing of Keene, New Hampshire-based Cushing and Sons informed me, “It’s pretty much fifty degrees down there.”
The test wells his company and others drill are to determine the rock’s capacity to supply the amount of heat needed by the structures on the surface. The less often used term “geoexchange” is far more evocative of what is actually going on: a watery dialog with the reliability of the 50-degree thermal gradient about 500-800 feet beneath Earth’s surface.
“What happens is we take that fifty degrees and extract twenty, then return the colder water to get reheated,” Bart explained. “It’s perpetual and a good deal.”
His company did a full geoexchange system for the Cheshire County Jail consisting of eighty 400-foot wells that paid back the investment in just five years due to the increase in natural gas prices.
“The system is good for a hundred years and completely invisible, everything is five feet underground.” Bart also notes that since the water loop is completely isolated, these systems can even be installed in brownfields and contaminated water sites.
Heat testing (generator and heat unit with white blanket covering) is done after the tubing and grout is installed. The test is run for 48 hours sending heat into the ground and measuring how much heat the formation will generate. In the northeast region, 160 to 190 feet of borehole per 12,000 Btu per hour is the amount a borehole will sustain using a conventional ground source heat pump. (Cushing and Sons)
Geoexchange heating systems are exploiting that amazing aspect of thermodynamics where any heat differential can be used to produce work with the right understanding and technology. In this case, heat pumps are used.
Founded in 1972 by his father, Bart and Jeff Cushing worked at well drilling in high school and joined the company full time in 1979. In the years since, Cushing and Sons has grown steadily from a one-rig business to their present fleet of three modern high-capacity pneumatic hammer drill rigs. They have installed over 35,000 wells and systems.
Those rigs have been in high demand recently to drill test wells at many regional colleges which hope to exploit the geothermal capacity beneath their campuses to replace their fossil fuel fired heating systems. Each hole can take up to two-and-a-half days to complete. Cushing explained, “Once the test well is dug 500-800 feet, we drop down dr11 pipe forming a U tube. Then we conduct 48 hours of flow and heat measurements. For example, typical results indicate 160 to 180 feet per ton of energy capacity with a recirculation rate of three gallons per minute per ton. For reference a ton of energy is 12,000 Btu/hr.”
From there it’s simply a matter of engineering to determine the linear vertical footage required and number of production wells that are needed to meet the heating needs of the buildings. That number could be anywhere from a few dozen for a residential system to the more than 2,000 holes that are projected for the Princeton University geoexchange project.
“We just lost a bid to do 130 holes on the Green at Dartmouth,” Cushing chuckled. “We did the original test holes there in 2019. You do not win them all.”
When I noted that he did not sound too disappointed, Cushing explained, “There’s so much demand these days I’m running into hard choices about how to deploy equipment. We have only so many drilling rigs and skilled personnel in the region.”
Cushing does not want to shortchange his water well drilling operations because that is where the bread and butter come from. He said, “These geo systems are a one off from the business perspective. They last a hundred years and nothing else is needed. Not so our relationship with our other customers. That’s ongoing and I value the connection.”
“The colleges all have a pact for the climate and they see these systems as the answer,” Cushing said. He quickly ticked off an impressive list of regional institutions currently developing geoexchange heating solutions, including Dartmouth College, UMass at Amherst, Smith College, University of Vermont, Norwich University, and Greenfield Community College.
We are talking about significant change here and really good news for the planet. For instance, Dartmouth College burns 3.5 million gallons of No. 6 fuel oil (the dirtiest kind) in its steam heating plant. The climate action plan introduced by then-president Phil Hanlon in 2017 called for a switch from oil to renewable heat by 2025. The College already heats two buildings with geothermal and in 2022 began investigating four more sites on campus with the hope that this source of clean energy can completely replace the steam plant.
Similarly, Smith College in Northampton, MA uses fossil fuels for heat. Also, in 2022 they committed to replacing their heating plant with a geoexchange system. They have already identified sufficient geothermal resources and begun actual drilling for production fields. The project is proceeding in three phases scheduled for completion in 2028. When the switch is complete, the campus will produce 90% less carbon emissions.
One of the most heartwarming aspects of this surge of interest in geothermal energy is illustrated by an anecdote Cushing related to me with his worldly-wise chuckle.
“We were in the middle of the UMass campus drilling some test holes and people going by were flipping us the bird because they thought we were doing some new construction. So, we put up some signs explaining we were working on green energy and right away those fingers turned to high fives.”
A recent New York Times article on this subject noted that geoexchange systems at colleges around the country seem to be earning a rare commodity on campuses these days: the approval of students, faculty, staff and alumni. The article quotes David DeSwert, executive vice-president for finance and administration at Smith College who said “I’ve never seen this level of consensus behind a project.”
Hearing of this, it dawned on this seasoned fighter from the age when renewable energy was considered a mere pipe dream that a whole new generation of young people are coming of age, not with a promise of a better way but actually seeing that better way materializing before their eyes.
Cushing and Sons has worked at the colleges of UMass, Amherst, Smith, Dartmouth, Williams, Marlborough, and Keene State. They also installed geoexchange systems at the schools of Kimball Union Academy, Eaglebrook, Kingswood, and Oyster River.
Michael J. Daley for some twenty years taught renewable energy on the Great New England Energy Show Van of the New England Coalition which featured the first ever solar-powered ice cream freezer funded by Ben and Jerry’s.
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