Abstract
An underground thermal energy storage (UTES) system is designed to store excess thermal energy in the ground during periods of low demand and retrieve it when demand is high. This can be done through circulating water in porous or fractured rock (ATES) or through heated boreholes (BTES). UTES systems can address seasonal mismatches in heat supply and demand, such as in waste incineration plants used for district heating. However, there is limited data on commercial-scale solutions, and challenges have been encountered in actual system performance.
To optimize the performance of an integrated UTES system, it is important to consider both the behavior of the geothermal storage system and the larger energy system. Numerical simulators can model the behavior of the reservoir, but the entire system needs to be considered for profitable utilization. The proposed approach in this study combines numerical simulation with mathematical optimization to optimize the operation of a UTES system. A simplified, modular, representation of the system as interconnected loops allows for practical simulation and optimization based on user-defined goals. A hypothetical example is provided to demonstrate the proposed approach, qualitatively inspired by a real system.