by Alexandra Chang
Geothermal energy is undergoing a renaissance, says Jeff Tester, Smith School of Chemical and Biomolecular Engineering. Tester has been part of a core group of geothermal researchers since 1974, working to bring this underground renewable energy source into its current form.
“The global geothermal community is small, with an even smaller group of some 300 to 400 research scientists and engineers who have kept their vision together for a long period of time. We maintained interest in geothermal even when it wasn’t popular,” says Tester, who is the Director of the Cornell Energy Institute and Principal Investigator for Earth-Energy Systems Integrated Graduate Education and Research Training (IGERT) program, funded by the National Science Foundation.
Through the years, Tester and his lab have worked on many aspects of evaluating, harnessing, and maintaining geothermal energy resources — from developing new drilling methods that could reduce costs, to modeling heat extraction performance, to providing in-depth analysis of geothermal system lifespans and economics.
Heating a Campus with Geothermal Energy
Today, after working on geothermal projects worldwide, from New Mexico to England to Australia and Iceland, Tester leads a project right on his home turf: Cornell’s campus. An Enhanced Geothermal System is one of Cornell’s Climate Action Plan (CAP) goals as the campus moves toward a more sustainable, low-carbon future. First, researchers are performing a feasibility study in order to best understand how to heat Cornell’s buildings, laboratories, and many greenhouses with geothermal energy. That study in itself is a lengthy project, one that involves many engineering questions.
Tester says that the researchers have to look at everything from the design of the system to issues of the reservoir. “We have to drill a deep hole into the ground,” he says. “We need to learn as much as we can from measurements made before the drilling — the seismicity of the area, the geological column we have to drill through, the current district heating system at Cornell, and more.”
The goal is to design a project that modifies the existing heating system so that it can accept geothermal heating. Once the initial study is completed, the next steps are to study and develop financial metrics; complete a Full Environmental Assessment Form (FEAF) to document the project’s environmental, social, and economic impacts; and draft a white paper to make the project a reality.
“With a growing recognition of the need to transform our energy system to one based on renewable resources, we are confident that geothermal will achieve its potential as a major supplier of heat and electricity,” Tester says.
Heating Cornell with the Earth’s heat is still years away, but Tester says there is a lot of promise, and researchers believe utilizing geothermal energy stored several kilometers below ground will substantially reduce the campus’ consumption of natural gas, lowering costs in the long run. According to current estimates, the system could supply 25 percent of the energy used on campus and reduce the university’s carbon footprint by more than 38 percent. “With a growing recognition of the need to transform our energy system to one based on renewable resources, we are confident that geothermal will achieve its potential as a major supplier of heat and electricity,” Tester says.
Cooling Cell Phone Towers with Geothermal Energy
Also on Cornell’s campus, Tester and his lab are working to understand how geothermal energy can be used to cool cell phone towers. In 2013, Tester’s lab installed a hybrid geothermal heat pump system at the base of a Verizon cell tower building located at the edge of Cornell Plantations that serves the Cornell campus and surrounding region.
“There are at least 40,000 cell phone towers in the country, and all of them use a lot of electricity,” says Tester. “One way of making them work much more efficiently is to use geothermally cooled heat pumps.”
The cell phone towers still run on grid-supplied electricity. By using geothermal, there’s an added benefit of using the ground as a heat sink, which would reduce electricity consumption by around fourfold. But, Tester adds, the problem is that “few people are really aware that the long-term operation of heat pumps can be used solely for cooling.”
Researchers are currently in the process of collecting and analyzing data from the cell tower system with the goal of developing a reliable, predictive model that could be used for the entire country. The estimated data collection period is a few years, in collaboration with Verizon. Once a model is validated with existing data, Tester says the next step will be to locate additional cell towers that are good candidates for geothermal cooling.
Tester is also extending the research toward a related project: cooling data centers. “Data centers are enormous energy sinks,” says Tester. They produce a large amount of heat and need to be constantly and actively cooled since companies such as Verizon (among many others) never want their servers to go offline. Tester and Max Zhang, Sibley School of Mechanical and Aerospace Engineering, are working together with Verizon to examine a few representative data centers for geothermal cooling suitability. Research is in the early stages, but Tester says they expect to be on their way to physical testing within the next year or two.
Drilling for Geothermal Systems
A large portion of Tester’s work throughout the years has focused on developing advanced drilling methods. Drilling for geothermal systems is a process much different from drilling for oil — it requires drilling much deeper and it becomes part of a system that needs to be maintained over decades.
“Our idea is that if geothermal is really going to work, you need to lower the intrinsic cost of drilling, and the more economically accessible the resource becomes,” explains Tester.
His group has looked at less traditional methods of drilling, like thermally cutting rock with a flame or with high-temperature pressurized water. “It’s not a question of doing something we haven’t done before, but doing it better and less expensively by having a better understanding of the fundamental processes involved,” he says.
The Tester lab has already seen success with thermal drilling methods, compiling evidence that shows hydrothermal jet thermal drilling might be up to 10 times better at penetrating very hard rock than using the crushing and grinding mechanism of a traditional drill bit.
Cornell Collaborations in Sustainability Research
Tester oversees many collaborative research efforts at Cornell. It’s through these collaborations that Cornell has been able to achieve real advances in sustainability research, Tester says, be it in geothermal or bioenergy or carbon sequestration.
“We aren’t just writing papers anymore. We’re trying to actually have an impact,” says Tester. “This is the underpinning of Earth-Energy Systems IGERT, the Cornell Energy Institute, and the Atkinson Center, too. We have groups talk and work together in a fundamentally new and different way.”