Swelling colloids – mixtures, such as milk and paint, in which particles are suspended in a substance and which can grow up to 100 times larger under certain temperatures – could be used to fix flow pathways in underground geothermal systems, a problem that has hobbled investment in geothermal energy.
The technique of swelling colloids was originally developed at Cornell for biomedical applications. The idea to use them in geothermal systems is backed by a $3.45 million grant from the U.S. Department of Energy, and brings together engineers, chemists, materials scientists and geophysicists.
The colloidal suspensions will be tested in the field by Cornell students and researchers on a subsurface well system at the Altona Field Laboratory in Altona, New York, before further field testing is conducted in partnership with energy technology company Cyrq Energy and the City of Boise Department of Public Works, which operates the largest municipal geothermal district heating system in the country.
“The industry needs some innovation in this area,” said Jeff Tester, the Croll Professor of Sustainable Energy Systems in the Smith School Chemical and Biomolecular Engineering and principal investigator for the grant. “The idea of having some non-traditional, non-petroleum engineers thinking about these types of challenges and creating solutions is exactly what has people excited about this grant.”
Deep geothermal systems extract thermal energy from the Earth by circulating water down a well and through a network of underground channels and crevices in hot rocks. The water absorbs heat from the rocks and returns to the surface, where it can be used for direct-use heating or electric power generation.
The early phase of any new geothermal project requires exploratory drilling and reservoir field testing to demonstrate that enough heat can be produced. But this exploratory phase can be financially risky, according to Tester.
“By far, the overall cost of a geothermal project is dominated by thermal energy output of the reservoir as determined by the temperature and flow rates of the injection and production wells in the field,” Tester said.
For commercial development, it is necessary to understand and control fluid flow within a geothermal reservoir to reduce the financial risk. For example, a problem can be encountered if the water’s underground flow path within the reservoir short circuits and doesn’t travel through optimal rock channels. If the water begins to cool the channels too quickly, the geothermal system can fail to produce sufficiently hot water.
“What geothermal operators end up doing is either reducing the flow that they put through the system so they can extend the lifetime, or they have to drill new wells entirely,” Tester said.
A solution proposed by Tester and an interdisciplinary group of Cornell researchers comes in the form of temperature-responsive colloids – with sizes into the micron scale – that can grow up to 100 times larger once they encounter a specifically programed temperature. The swelling colloids would enter a geothermal system, expand within cooled short-circuiting channels to block the pathways, and redistribute water toward hotter flow paths.
Because the temperature-responsive colloids would also shrink in size once the short-circuiting channels exceed the threshold temperature, the process of blocking and redirecting the flow path is intrinsically reversible, effectively extending the lifetime of the well a second time.
“If successful, our methodology will extend the thermal lifetime of a given injector-producer well pair,’ said Adam Hawkins, postdoctoral researcher and co-principal investigator. “From a commercial perspective, this will substantially improve the economics as it will reduce the need to drill additional wells to sustain production.”
The science behind the swelling colloids was developed by Ulrich Wiesner, the Spencer T. Olin Professor of Materials Science and Engineering and co-principal investigator, who has demonstrated he can synthesize colloidal systems to be tailored over a wide range of sizes, topologies and functionalities for applications such as bioimaging, biosensing and drug delivery.
“We realized that my group’s expertise in navigating complex biological environments for cancer diagnostics and therapeutics should be translatable to the complex environments underground,” Wiesner said. “With the help of this grant and our excellent interdisciplinary team, it will be very exciting to explore how far we can push these analogies.” Wiesner said.
The research team will experiment with engineering different versions of swelling colloids with the help of co-principal investigator Christopher Alabi, associate professor and the Nancy and Peter Meinig Family Investigator in the Life Sciences, who also has experience developing engineered polymers and synthetic colloids for biomedical applications.
The team will then test the colloidal suspensions in laboratory and field settings, first by using X-ray and laser-optic equipment developed by Sarah Hormozi, associate professor of chemical and biomolecular engineering and co-principal investigator, to study how well the colloids disperse in a laboratory flow system.
At the commercial scale, the team will rely on the expertise of Patrick Fulton, assistant professor of earth and atmospheric sciences and co-principal investigator, to characterize underground flow and heat transport through advanced monitoring techniques and modeling.
The grant comes on the heels of a separate $7.7 million grant to install the Cornell University Borehole Observatory – a 10,000-foot deep borehole to explore the viability and safety of using geothermal energy to heat the Ithaca campus.
While the swelling colloids won’t be tested in the Cornell borehole, both projects share the ultimate goal of lowering the financial risk of deep geothermal systems in a safe, transparent and environmentally friendly manner.
Syl Kacapyr is associate director of marketing and communications for the College of Engineering.