Time Series Analysis of Subsurface Heat Exchange due to Geothermal Heat Pumps

A large-scale geothermal heat pump system was installed at Missouri University of Science and Technology in 2013. This research characterizes the long term performance of the system in terms of the thermal response of the well field and the surrounding area to the operation of the heating, ventilation, and air conditioning system. Temperature data from a production well located in the center of the well field, a monitoring well located approximately 20 feet from the well field, as well as energy exchange data from the physical facilities are collected to allow comparison of the ground temperature of the well field to the undisturbed (background) ground nearby. Data thus far shows minimal increase in the ground temperature as the system cycles through heating and cooling. This study focuses on the pulses of heat energy propagating from the well field towards the monitoring well, lag time, and ultimately the effects on the overall surrounding ground temperature over time. A time series analysis of the temperature and energy data from the wells is used to characterize the time lapse associated with the migration of heat energy from the production field to the surrounding subsurface during both heating and cooling cycles.