The sites were selected because of where they sit on the campus’s heating loop, how close they are to additional equipment that may be needed and the amount of space they have nearby for more wells. By drilling in three locations, Brown’s sustainability leaders hope to gain a better understanding of the different geothermal properties that range across campus, including how much heat the rocks can absorb.

“The rock substrate can vary from location to location, and that can impact how effectively the wells in that area can perform,” said David Larson, senior energy engineer for the Office of Sustainability and Resiliency. “High rates of heat transfer would essentially mean we would need fewer geothermal wells to meet our heating needs, while a lower rate of heat transfer would require more wells.”

Data collected at each test-well on the heat storage capacity of the rock below the Earth will help the team put together a feasibility plan that includes financial and logistical details including costs, constraints and impacts to campus from construction. That plan would give University leaders the assessment needed to make a decision on whether or not to move forward with implementation.

If viable, the precise nature of constructing geothermal wells on campus would depend on indicators such as the rate that heat can be injected or extracted at the sites. This will help determine the number of wells needed, which would likely number into the hundreds. Construction would encompass a multi-year effort with wells installed in at least three locations either at or near the current test sites.

From fossil fuels to geothermal energy

The University’s exploration of geothermal energy complements a growing array of campus initiatives to confront the global climate crisis, including launching a thermal efficiency project and renewable energy agreements to offset the University’s on-campus electricity use. The ultimate goal is to achieve net-zero by 2040 with 75% of reductions happening by 2025.

“We’ve aligned our goals with what global climate scientists have identified as a critical tipping point for elimination or reduction of greenhouse gas emissions,” said Jessica Berry, assistant vice president for sustainability and resiliency. “When you're taking on a project as big and complex as this, it's really important to explore all of the technological options that may be available. As new information comes to light and as we continue to study the campus with these test wells, we’ll remain flexible and agile in amending our overall roadmap with the best available information and science to get us to where we want to be.”

In recent years, geothermal energy has gained traction worldwide as a source of emissions reductions. There are many types of heating systems based on geothermal energy, but the idea Brown is exploring would use the ground beneath the Earth as storage for heat in the summer and then as a source for it in colder months.

In the summer, when cooling is needed, waste heat from chillers and air conditioners would heat water (or another coolant), and that water would be pumped into a closed U-shaped pipe in the ground, heating the rocks in the depths beneath Brown’s campus. In the winter, when heat is needed, cool water would be pumped to that depth, where it would be warmed by the previous summer's waste heat and brought back to the surface to heat buildings across campus.

“There's no exchange of anything other than heat energy with the surrounding rock, and no groundwater contamination because it’s a self-contained pipe,” said Porder, who is also a professor of ecology, evolution and organismal biology and of environment and society at Brown.

This movement of heat from one place to another is made possible by heat pumps. Air conditioners and refrigerators are both types of heat pumps and work by taking heat from the inside of a building or refrigerator, respectively, and moving it outside. In a geothermal system, the heat pumps move the heat into and out of the Earth.

“It will work almost like a thermal battery,” Porder said.

Should the University move forward with a full geothermal system installation after the assessment period, the wells will be completely below grade and visibly unnoticeable. The analyses and plans for a potential geothermal system are expected to be complete in 2024.

“Geothermal is a very promising path toward our decarbonization goal, but the reason they’re called ‘test wells’ are because they're just that — tests,” Porder said. “We will know much more in time, but we are hopeful.”