Operational Response of a Soil Borehole Thermal Energy Storage System
AbstractThis study focuses on an evaluation of the subsurface ground temperature distribution during operation of a soil borehole thermal energy storage (SBTES) system. The system consists of an array of five 9 m deep geothermal heat exchangers, configured as a central heat exchanger surrounded by four other heat exchangers at a radial spacing of 2.5 m. In addition to monitoring the temperature of the fluid entering and exiting each heat exchanger, 5 thermistor strings were embedded in boreholes inside and outside of the array to monitor changes in ground temperature with depth. After 75 days of heat injection at a constant rate of 20 W/m, corresponding to 11.5 GJ of thermal energy, the average ground temperature in the array increased by 7degC. However, depending on the storage volume definition, only 2.43 4.86 GJ of thermal energy was stored attributable to heat losses. After a 4 month rest period the heat storage was observed to decrease by 60% owing to further heat losses. The trends in subsurface temp.