Design and optimization of a borehole field with 2U and coaxial pipes for an industrial building

TIG SA is planning the construction of a new industrial building in Bulle and relies on surface geothermal energy as an energy source. For this building, GEOEG designed and optimized a geothermal borehole field with thorough consideration of the opportunities provided by different pipe configurations for the boreholes, including 2U and coaxial pipes.

Design and optimization of a vertical geothermal borehole field with 2U and coaxial pipe heat exchangers

Variants with (a) double U and (b) coaxial geometry
The developed design was performed via 3D time-dependent thermo-hydraulic simulations according to the requirements of the SIA 384/6. Surveys allowed to achieve a characterization of the underground from hydrogeological and geothermal perspectives. Numerical thermal response tests were used to determine the critical thermal properties of the boreholes. An iterative process finally allowed to achieve an evaluation of the overall energy performance of the borehole field over a 50-year horizon, with due consideration of the pipe layout characterizing the boreholes, the thermal interactions among such boreholes, the presence and influence of the building basement, and the surface thermal conditions. The ON/OFF operation of the heat pump and the building thermal energy requirements were numerically modeled via a dynamic procedure. The obtained results provided with a thorough definition of the temperature variations within and around the boreholes over time, as well as with a precise quantification of the energy yield provided by the considered solution.
3D temperature field obtained from finite element numerical simulations lasting 50 years. The simulations considered thermal interactions among the designed boreholes and the details of their pipe configurations, among other variables.

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