This paper presents an analytical method for calculating the thermal behaviour of borehole heat exchangers and borehole thermal energy storages under the boundary condition of a constant inlet temperature. An analytical model based on the use of g-functions is set up for this purpose. Due to the small difference in g-functions for different boundary conditions within short observation times, the analytical model can be verified with a simple numerical model. In addition, the numerical model is used to evaluate the thermal capacity of a borehole thermal energy storage with 80 boreholes. The analytical model is coupled to the EBSILON® Professional power plant simulation environment. In future, this connection should make it possible to simulate borehole thermal energy storages with high-temperature heat pumps.
