Universities are digging very deep to reduce CO2 emissions
When administrators at Princeton University decided to reduce carbon emissions from heating and cooling their campus, they chose a method that is becoming increasingly popular among colleges and universities.
They started drilling holes deep into the ground.
The university is using the earth beneath its campus to create a new system that keeps buildings at comfortable temperatures without burning fossil fuels. The multimillion-dollar project, using a process known as geo-exchange, marks a significant shift in the way Princeton gets its energy, and is key to the university's plan to stop adding greenhouse gases to the atmosphere.
The drilling creates a huge muddy mess, but ultimately the more than 2,000 planned boreholes for the campus will be undetectable despite an impressive magic trick. During the warm months, heat from Princeton's buildings is stored in thick pipes deep underground until winter, when the heat is extracted 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 unique,” said Ted Borer, director of power plants at the school. “This is when we switch to something that doesn't require combustion.”
Geoexchange is not new, but it is increasingly a choice of colleges and universities, especially in the northern United States, as they seek to decarbonize. Geoexchange is a type of geothermal system. Other species extract heat from deep within 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 five years ago the company was working on two or three geothermal projects on campus at the same time. That number has grown to between 20 and 30 projects, she said.
“It really feels like it's doubling every year,” Ms. Olsen said. “For northern climate settings in need of heating, 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 in use: Smith, Oberlin, Dartmouth, Mount Holyoke and William & Mary. Cornell University has dug a two-mile geothermal test hole on its Ithaca campus and is using geoexchange in one of its buildings on Roosevelt Island in New York City's East River. Brown University drilled test bores last fall to measure thermal conductivity, and Columbia University obtained a special state mining permit to drill an 800-foot test bore on its New York City campus.
Many of the colleges use their projects as classrooms and provide educational seminars and tours.
Geoexchange (also known as geothermal district heating and cooling from the ground) works as a heat storage bank. In summer, heat is extracted from warm buildings, cooled and transferred to water that is sent into pipes deep underground in a closed network. The heated water is stored below the frost line, heating the surrounding rock. In winter, the heated water is pumped back to buildings via pipes.
The systems work together with heat pumps and, because they all run on electricity, are much greener than steam boilers that run on natural gas, oil or propane.
Geoexchange is particularly suitable for colleges as they usually have many buildings close together, the space required for borehole fields and their own stand-alone heating, which makes the adoption of new heating and cooling technology easier. They also typically have the resources for long-term investments: the systems require significant upfront costs but are expected to save money in later years.
“Institutions that have been in business for more than a hundred years are willing to invest a lot of money, think long-term and pay attention to the benefits that this will bring,” Ms. Olsen said. She also said, “There are students who are asking for it.”
Carleton College in Minnesota spent $42 million on its geo-exchange, which was completed in 2021 and expects to break even within 18 years. The system has reduced the school's annual natural gas use by about 70 percent and shaved 25 years off the university's plan to be carbon neutral, which is now expected by 2025, Sarah Fortner, Carleton's director of sustainability, wrote in an email .
Ball State University in Indiana has what its administrators say is the largest geoexchange system in the country, with about 3,600 boreholes. The project, which unfolded in two phases and was completed in 2012 and 2015, cost $83 million and has already paid for itself, said James W. Lowe, the school's vice president for facilities planning and management. The school's carbon footprint has since dropped by 60 percent, he said.
On a recent crisp and clear day in Princeton, Mr. Borer and a few colleagues offered a tour of Poe Field, a three-and-a-half-acre recreational space on the southern edge of campus. It was surrounded by building siding and completely turned over, a sea of mud.
“This is what saving the planet looks like,” Mr. Borer said. “It's extremely chaotic. It's messy. it is disruptive.” But he added, “A year from now, kids will be playing Frisbee here.”
Five oil rigs were working noisily, making their way to a depth of 800 feet. Each hole will take two and a half days to complete, and will include vertical pipes made of high-density polyethylene, folded back on themselves like a giant bending straw. This pipe has a closed loop (no fluid enters the ground) and is attached to a thicker horizontal pipe that acts as an artery, a channel for water and heat. Mr Borer explained what will happen next. In the summer, heat is drawn from buildings into water and also warmed by heat pumps to about 90 degrees Fahrenheit. The hot water will be sent to the underground pipes, gradually heating some of the billions of pounds of surrounding underground rocks from about 57 degrees to about 70 degrees. In cold weather the school can withdraw the heated water. Instead of being around 55 degrees, as groundwater normally might be, the geoexchange water is expected to be somewhere between 60 and 75 degrees Fahrenheit, Mr. Borer said.
“We're not talking about extreme temperatures, but there will be a huge resource that we can get heat from and then deliver it to the buildings in the winter,” he said.
It is expected that all 2,000 geo-exchange drillings will be installed by 2033.
The heart of the entire operation is a new energy control center. It houses two huge heat pumps, with room to add more as the system expands, along with two giant water storage tanks, one for hot water, the other cold, each filled with 2.2 million liters of water, which will be used for heating and heating. cool the campus.
A plant operator will monitor heat needs and generation in real time and, like an energy efficiency DJ, can respond to what is happening and manage heat and cold, deciding when the heat in one of the tanks needs to be saved or put back into the geo-exchange. water wells and when heat must be extracted for showers and kitchens.
Princeton's project is expected to cost several hundred million dollars; university officials could not provide a more precise estimate. In a recent column, Princeton President Christopher Eisgruber said the school would have spent nearly as much to maintain or replace the 150-year-old steam pipe system. Water consumption is also expected to drop by 20 percent.
Across the country, geo-exchange systems are generating something that is increasingly rare on campuses these days: enthusiasm from students, faculty, staff and alumni.
“I've never seen this level of consensus behind a project,” said David DeSwert, executive vice president for finance and administration at Smith College, where a geothermal heating and cooling system is being installed. The school's carbon emissions are expected to be reduced by 90 percent.
“I am not always the person who is cheered at a faculty meeting,” Mr. DeSwert continued. “When we presented this, they were extremely happy. And it is an infrastructure project.”