The Rheology of Temperature-Responsive Volume-Phase Transition Hydrogels for the Improved Thermal Performance and Lifetime of Geothermal Systems.

With the massive rise in investment towards renewable energy to combat climate change, geothermal energy represents a major economically viable alternative in many parts of the world. Geothermal systems purposely contain many flow paths to maximize heat transfer area, but many paths do not meet desired temperatures or are drained of their thermal energy over time, providing "short circuit" routes that harm thermal performance. Previous models predict plugging these routes and redirecting flow can extensively improve both the thermal performance and lifetime of the system. Volume-phase transition (VPT) particles present an excellent candidate to plug these flows as they expand in low temperatures and contract in high temperatures above a lower critical solution temperature (LCST), drastically changing the volume fraction of the system and thus important parameters such as viscosity and yield stress. Rheological characterization is performed to better understand and compare these properties to obtain an ideal hydrogel recipe that is optimized for temperature-sensitive and plugging capabilities.