By David Nutt, Cornell Chronicle, Original source
Cornell is one step closer to determining the feasibility of using deep geothermal energy to heat the Ithaca campus.
Drilling for the Cornell University Borehole Observatory (CUBO) began June 21 and is expected to last about two months. The borehole, located on a Cornell-owned gravel parking lot near Palm Road, will be subjected to a battery of tests, both during and after the drilling, to determine the temperature, permeability and other characteristics of the rock up to 10,000 feet below the earth’s surface.
These findings will help the university determine whether to move forward with a proposed plan to warm the Ithaca campus with Earth Source Heat (ESH), a process that would extract naturally heated water after it’s pumped underground, transfer its heat to a separate supply of water flowing within the campus’ heating distribution pipeline, and return the original water to the subsurface, where it warms back up and begins the cycle again.
Such a system would enable the university to meet its goal of carbon neutrality by 2035, while providing a blueprint for similar renewable energy efforts throughout the northeast and other parts of the U.S. where geothermal heat has not previously been utilized.
“This well will provide scientific information, but it will not be a production well,” said Jeff Tester, the David Croll Sesquicentennial Fellow and professor in the Smith School of Chemical and Biomolecular Engineering and principal investigator for the project. “Measurements made in the well will validate the temperatures and other properties at certain depths. This information will tell us a lot about the characteristics of the rock in a range where those temperatures could be useful for geothermal heat production, and will help us design and build an actual energy extraction process in the next phase.”
An energy project of this scale has not been attempted at Cornell since the implementation of Lake Source Cooling 22 years ago, Tester said. That five-year effort was one of the most significant sustainability initiatives undertaken by an American university.
The borehole drilling is being overseen by Facilities and Campus Services in collaboration with university faculty, staff from the National Renewable Energy Laboratory and experienced geothermal consultants.
At the same time, other universities have expressed interest in Cornell’s approach and are waiting to see the results. “Everybody is very happy for us to demonstrate the feasibility of such a project,” said Steve Beyers, the lead ESH engineer.
The official start of CUBO construction comes a decade and a half after the idea emerged when the university was putting together its Climate Action Plan, which was adopted in 2009.
“We were asking: what kind of resources do we have on campus? We didn’t have sufficient local wind, hydro or solar resources. So we kept looking,” Beyers said. “We hit upon geothermal after reading a pioneering report that Dr. Tester helped co-author before he came to Cornell. It became a critical driver of our Climate Action Plan.”
Most expansion of U.S. geothermal energy has been to generate electricity in locations where plate tectonic or volcanic conditions generate high temperature rocks at a shallow depth, like in California, Nevada and Idaho.
One of the major shifts came when the Cornell team realized that by integrating centralized heat pumps they could make an ESH system function at cooler temperatures, around 70 degrees Celsius, or approximately 160 degrees Fahrenheit, and still be effective.
“We added innovation and expanded the potential for how this could work,” Beyers said. “But we still need the right hydraulic conditions.”
Gathering knowledge, ensuring safety
Geothermal energy can heat a campus, but the challenge is the natural limitations of the rock. To move forward, geological information is needed to enable engineering design.
A $7.7 million grant from the U.S. Department of Energy announced in August 2020 effectively establishes Cornell as a national demonstration site for Earth Source Heat. By that point, university researchers had already been brainstorming ways to gain as much knowledge as they can from a dedicated exploration and monitoring borehole like CUBO.
The diameter of the hole is 36 inches, becoming progressively smaller with increasing depth. The final 2,300 feet will be only 8.5 inches in diameter without a casing – and the focus for acquiring the most important data and testing the capacity of the rocks to transmit water.
While drilling, the researchers will use geophysical instruments to measure rock properties and identify fractures and stress conditions. They’ll collect rock cuttings throughout the borehole, and rock cores in short intervals. Once the hole is completely drilled to a depth of 10,000 feet, a small amount of water will also be pumped through the system to locate permeable zones. After drilling and testing are completed, a fiber optic cable will be installed in the borehole to allow temperature measurements across those deepest rock layers and long-term monitoring.
To reduce the risk of unwanted side effects and to monitor environmental conditions, five water-monitoring wells were installed around the CUBO site and seismometers were placed around the county. Water quality and seismic activity during drilling are being tracked and early alert warning systems are in place.
The researchers also plan to collect water samples within the borehole for a separate microbiology study funded by the National Science Foundation. “What lives down there at 3 kilometers depth, in rocks deposited 400 or 500 million years ago, or in rocks metamorphosed a billion years ago?” said Patrick Fulton, assistant professor of earth and atmospheric sciences in the College of Engineering, and a co-PI on both projects. “If there is life, it’s living in an extreme environment. Improving our knowledge of the diversity of intraterrestrial life and how it survives can potentially provide insights into the origins of life and what is possible elsewhere in the universe. In many ways, the warm, briny water and rocks expected within CUBO are similar to environments on other planets and terrestrial bodies of particular interest to astrobiologists.”
The Cornell team – which includes engineers and geologists from faculty and professional staff, as well as graduate students – is hopeful it will find the highest permeability in the several layers of sedimentary rock and the upper part of crystalline basement between 7,500 and 10,000 feet, especially in layers that are naturally fractured. The more porous or fractured the rock, the better, so that in the future water can absorb heat and flow through the rock between wells.
“The rocks under Ithaca have some predictable properties, and one key prediction is that they will not have the open pore space within them to hold a lot of fluid. However, there are a few depth intervals where existing cracks and fractures may allow for water to flow through,” said co-PI Terry Jordan, the J. Preston Levis Professor of Engineering. “It’s very natural that the rocks under us will have cracks, but we don’t know which of them will have cracks through which water can pass and which of them have grown new minerals and sealed off potential flow paths.”
If the CUBO project shows that natural water flow is not sufficient, the team will explore other methods for improving water flow in geothermal systems.
An educational experience
If the university moves forward with Earth Source Heat, the next phase would entail drilling a separate pair of wells to act as an injector and producer. Hot geothermal water would be pumped from the production well and sent through a heat exchanger. The water would then be reinjected into the second well to circulate through the network of naturally hot underground pores and crevices to be reheated and complete the cycle. At the heat exchanger, the heat would be transferred to a district heating system that runs through campus and connects to individual buildings. Geothermal water and campus heating water would not mix.
The university is converting the Ithaca campus energy distribution system from steam to water heat, which is more efficient and accommodates the lower temperatures associated with geothermal and other forms of renewable energy. Parts of campus, including the newly constructed buildings that are part of the North Campus Residential Expansion, have already been converted into hot-water subdistricts, and East Campus conversion is underway. The plan is to convert the entire system by 2035, Cornell’s goal for achieving climate neutrality.
“A hot water distribution system is cheaper, more reliable, more sustainable, loses less heat, and can accept renewable energy of any kind,” Beyers said. “And we hope Earth Source Heat provides the lion’s share of that renewable heat in the next 10 years or so.”
While other alternatives for renewable energy have been proposed, from heat pumps to solar, Tester says nothing comes close to the cost savings and environmental benefits of Earth Source Heat.
The CUBO team has been engaged in a range of educational outreach efforts, including hosting open houses, assembling and engaging with a community advisory team, and participating in a workshop for K-12 teachers. In that spirit, the team is inviting community members who want to learn more about CUBO and ESH to visit the borehole site on Tuesdays, from noon to 1 p.m., when staff and faculty will be available to talk about the process.
“We want this to be a rich educational experience for our students and for the community,” Beyers said.