Reference data set for injection and extraction cycle of a borehole thermal energy storage field: A numerical and experimental study

Borehole thermal energy storage systems are utilized across the globe to capture solar or residual thermal energy and store the heat seasonally. Although many borehole thermal energy storage facilities exist and operate, there are few facilities that are equipped to provide data and be used for research purposes. This paper provides an extensive experimental dataset of the operation of a borehole thermal energy storage field. The operating conditions include a constant temperature heat injection cycle followed by a hold period and a stepped-constant temperature heat extraction cycle. The experiment was initiated on November 23, 2021, and concluded on January 18, 2023. It involved a total of 340 GJ of heat injection and 192 GJ of heat extracted. Measurements of soil temperature and fluid temperature are shown, along with mass flow rates and the calculated thermal power. A COMSOL Multiphysics model with simplifying assumptions was used to demonstrate the modelling capability of the code. The results show that the COMSOL model of the borehole field was able to capture the thermal response of heat injection and extraction cycles to within 4.5 % of the experimental results.