Dynamic simulation and economic evaluation of dual-mode borehole thermal energy storage in electrified district energy systems

As the transition to low-carbon energy systems accelerates, long-duration energy storage that balances supply and demand across seasons is becoming essential. Borehole Thermal Energy Storage (BTES) provides a promising solution by storing energy underground for extended durations. Traditionally, BTES has supported either heating or cooling, but rarely both. This study presents a techno-economic analysis (TEA) of an Amplified Grid system that integrates BTES with Ground Source Heat Pumps (GSHP) to deliver district heating and cooling. Representative districts in San Francisco, Houston, and Chicago each with distinct climates and utility pricing are modeled. The system leverages dynamic pricing by charging during off-peak hours when electricity is inexpensive and discharging during on-peak periods when prices are high, reducing costs and improving grid flexibility. Thermal performance is simulated using a validated two-dimensional radial ring model that captures seasonal dynamics in the BTES field. Coupling this model with hourly district loads and electricity tariffs enables evaluation of energy savings and payback periods. Results show dual-mode BTES operation lowers annual utility costs by 40% in San Francisco, 30% in Houston, and up to 45% in Chicago, where large seasonal variations enhance storage utilization. This work demonstrates the potential of BTES as a dual-mode, long-duration storage strategy for district energy. By supplying both heating and cooling from a unified storage system, the approach advances grid flexibility, decarbonization, and resilience, offering actionable insights for utilities pursuing sustainable energy infrastructure.