To reduce carbon emissions, colleges dig deep
Princeton is latest choosing to use earth to heat, cool
When administrators at Princeton University decided to cut the carbon emissions that came from heating and cooling their campus, they opted for a method that is gaining popularity among colleges and universities.
They began drilling holes deep into the ground.
The university is using the earth beneath its campus to create a system that will keep buildings at comfortable temperatures without burning fossil fuels. The multimillion-dollar project, using a process known as geoexchange, marks a significant shift in how Princeton gets its energy and is key to the university’s plan to stop adding greenhouse gases to the atmosphere by 2046.
The drilling makes an almighty muddy mess, but when all is said and done, the more than 2,000 boreholes planned for the campus will be undetectable despite performing an impressive sleight of hand. During hot months, heat drawn from Princeton’s buildings will be stored in thick pipes deep underground until winter, when heat will be drawn back up again.
The change is significant. Since its founding in 1746, Princeton has heated its buildings by burning carbon-based fuels in the form of firewood, then coal, then fuel oil, then natural gas.
“This moment is singular,” said Ted Borer, director of energy plants at the school. “This is when we’re switching to something that doesn’t require combustion.”
Geoexchange is not new, but it’s increasingly a choice made by colleges and universities, particularly in the northern United States, that are seeking to decarbonize. Geoexchange is one type of geothermal system. Other types extract heat from deep in the earth but do not return it.
Lindsey Olsen, associate vice president and senior mechanical engineer at Salas O’Brien, a technical engineering firm, said that five years ago, the company was working on two or three campus geothermal projects at one time. That figure has grown to between 20 and 30 projects, she said.
“It really feels like it is doubling every year,” Olsen said. “For institutions in the northern climate that have heating demands, geothermal is one of the most economically viable technologies for producing low carbon heating.”
Among the colleges where geoexchange or geothermal systems are being tested, installed, or are in use: Smith, Oberlin, Dartmouth, Mount Holyoke, and William & Mary. Cornell University has dug a 2-mile test geothermal borehole at its Ithaca, N.Y. campus and is using geoexchange at one of its buildings on Roosevelt Island in New York City’s East River. Brown University drilled test holes to gauge heat conductivity this past fall, and Columbia University secured a special state mining permit to drill an 800-foot test bore on its New York City campus.
Many of the colleges are using their projects as a classroom, conducting educational seminars and tours.
Geoexchange (also known as ground source geothermal district heating and cooling) works like a heat storage bank. In summer, heat is drawn out of warm buildings, cooling them, and transferred to water that is sent into pipes in a closed loop network deep underground. The heated water is stored beneath the frostline, warming surrounding rock. In winter, that heated water is pumped back up through piping and into buildings.
The systems work in tandem with heat pumps, and because it’s all run by electricity, are generally greener than steam boilers that operate by burning natural gas, oil, or propane.
Geoexchange especially suits colleges because they usually have lots of buildings close together, the space needed for borehole fields, and their own stand-alone heating, which makes the adoption of new heating and cooling technology easier. They also tend to have the resources for long-term investments: The systems require significant upfront costs but are projected to save money in later years.
“Institutions operating for a hundred plus years are willing to invest a lot of money, and thinking long term, and paying attention to the benefits this is going to have,” Olsen said. Also, she said, “they have students that are demanding it.”