Empirical Validation and Numerical Predictions of an Industrial Borehole Thermal Energy Storage System

To generate performance predictions of borehole thermal energy storage (BTES) systems for both seasonal and short-term storage of industrial excess heat, e.g., from high to low production hours, models are needed that can handle the short-term effects. In this study, the first and largest industrial BTES in Sweden, applying intermittent heat injection and extraction down to half-day intervals, was modelled in the IDA ICE 4.8 environment and compared to three years of measured storage performance. The model was then used in a parametric study to investigate the change in performance of the storage from e.g., borehole spacing and storage supply flow characteristics at heat injection. For the three-year comparison, predicted and measured values for total injected and extracted energy differed by less than 1% and 3%, respectively and the mean relative difference for the storage temperatures was 4%, showing that the performance of large-scale BTES with intermittent heat injection and extraction can be predicted with high accuracy. At the actual temperature of the supply flow during heat injection, 40 degrees C, heat extraction would not exceed approximately 100 MWh/year for any investigated borehole spacing, 1-8 m. However, when the temperature of the supply flow was increased to 60-80 degrees C, 1400-3100 MWh/year, also dependent on the flow rate, could be extracted at the spacing yielding the highest heat extraction, which in all cases was 3-4 m.Funding Agencies|Swedish Energy Agency [40531-1]; Linkoping University