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Simulated temperature evolution of large BTES - case study from Finland

Korhonen, Kimmo
Leppaharju, Nina
Hakala, Petri
Arola, Teppo
The largest borehole thermal energy storage system in Finland (also one of the largest systems in Europe) is located in Sipoo, Southern Finland. The system produces heating and cooling energy for a large logistics centre and consists of 157 vertical borehole heat exchangers that are grouped into 10 blocks. The temperature of the heat carrier fluid circulated in each block has been monitored since the operation was started. A numerical model of the system was created using the finite element software COMSOL Multiphysics® in order to simulate the temperature evolution of the system and the surrounding rock mass using the monitoring data as input. Simulation results indicate that the temperature within the rock mass embodying the system has decreased as the system is imbalanced but the decrease is moderate. The temperature disturbance created by the system was found to extend 50 metres from the borehole field. Based on the simulation the shallow geothermal reservoir will suffice for the designed lifetime of the system.