Roseboom, Matthew (2023-04). A Remedial Approach to Reduce Residual Heat Left Behind By Shutdown Aquifer Thermal Energy Storage Systems: A Numerical Modeling Study. Master's Thesis.
Thesis
Utilizing aquifer thermal energy storage and recovery systems (ATES) and groundwater heat pumps (GWHP) for seasonal space heating and cooling in public and commercial spaces is one solution to reduce fossil fuel consumption for energy and heat production. ATES applications are a form of thermal energy storage that integrates an open or closed-loop well system in groundwater aquifers where warm and cold-water are injected and extracted for heating and cooling purposes in residential and public spaces depending on energy demand. Since this is a low-enthalpy system utilizing shallow groundwater aquifers, temperatures for this study are limited to a range of 5?C-30?C based upon previous environmental work. From an environmental standpoint there are limited studies that assess methods for reducing thermal energy stored in groundwater aquifers to achieve pre-ATES deployment conditions as it is important to understand subsurface conditions once these systems are not in use anymore. This research aims to take a remedial approach by developing numerical models for simulating long-term transient temperature distributions in porous media after the shutdown of a pre-existing ATES system for 30 years. Additionally, it serves to investigate the most effective method to reduce thermal energy stored in an aquifer through cold-water injection push-pull testing to bring the aquifer back to steady-state equilibrium conditions where the temperature remains within 5?C of the initial ambient groundwater temperature (uncertainty is due to changes in surface temperatures over time). Results from evaluating the long-term effect of the shutdown ATES system after five years of operation indicate that thermal energy stored near the warm-well decreases at a faster rate within the first 10 years after the shutdown and proceed to gradually slow as temperatures between wells approach within 2?C to 3?C above pre-ATES deployment conditions. Findings from cold-water injection indicate that the aquifer can be remediated within 5-years given flowrates of 200-300 m^3/d to reduced temperature distributions to below 1?C above pre-ATES deployment conditions, ensuring the longevity and health of the aquifer.
ETD Chair
Zhan, Hongbin Holder of Endowed Dudley J. Hughes '51 Chair in Geology and Geophysics
