HANOVER — Dartmouth College will soon look underneath the Dartmouth Green for a solution to its green energy needs.
A well-digging rig will be on the northeast corner of the green starting Monday as the school tests whether a so-called “geoexchange” system is capable of providing heat and air conditioning to many of its campus buildings. The tests are part of an effort to find a viable alternative to a biomass heating plant the college also is considering.
Dartmouth also will drill in the northeast area of the Dewey Field parking lot Dec. 9, the college said in an announcement posted on its website Wednesday.
Dartmouth said the geoexchange systems, which are powered by electric heat pumps, use a series of underground, closed pipe loops to use the stable ground temperature — about 50 degrees — to heat in the winter and cool in the summer.
“If we find that large-scale geoexchange systems are a viable option for our campus, this could become part of a portfolio of solutions to meet our energy needs,” Josh Keniston, Dartmouth’s vice president for institutional projects, said in the Dartmouth announcement.
The college estimates that 26 heat pumps under the green in the heart of downtown Hanover could provide 75% of heating and almost all of the air conditioning for the nearby Rauner Special Collections Library.
The larger system at Dewey Field could have 300 wells and provide 50% to 80% of Dartmouth’s overall cooling as well as 15% to 30% of its heating.
The technology would not threaten the aesthetics of the green. Dartmouth said geoexchange systems can be built under buildings and under open land, and that once they are in place, the surface land can be returned to its current use.
The heat pumps are a part of the college’s Green Energy Project, a $200 million plan to switch from steam heat to a hot-water heating system and to replace its 121-year-old oil-burning power plant in downtown Hanover.
The effort initially drew criticism from prominent scientists who said plans to build a wood-burning biomass plant could “substantially” increase Dartmouth’s carbon emissions. However, the school said last month it would explore “non-combustion” alternatives.
But a group of Upper Valley residents called on the college’s board of trustees to formally rule out combustion sources.
The Upper Valley Clean Air Committee, which has opposed the biomass project, submitted a letter to the trustees Monday asking them to “find a better way forward for our health and the planet.”
Biomass is still under consideration, Keniston said in Wednesday’s news release. He predicted that heat pumps are unlikely to meet the heat demands of Dartmouth’s coldest days and would require a supplementary system.
The test borings will be 500 feet deep and 6 inches in diameter, according to the college.
Once they’re drilled, liquid-filled piping will be inserted, and the pipes will sit for five days to stabilize the system. Testing would then take two days to determine whether either site could work with the pumps.
The boreholes will be covered after tests are complete. They won’t be visible and both sites will go back to current uses, the college said.
Dartmouth has some familiarity with geoexchange. One such system, with 13 deep wells, was built in 2007 and provides 100% of the air conditioning and 25% of the heat for the Fahey and McLane residence halls on campus.
Keniston and Rosi Kerr, the college’s director of sustainability, will be at the Dartmouth Green test site from 1 to 4 p.m. on Tuesday to answer questions about the project.
Tim Camerato can be reached at tcamerato@vnews.com or 603-727-3223.