Numerical Modelling of Deep Geothermal Exchanger and Its Application for the Litoměřice Site, Czech Republic

Abstract

The use of geothermal energy in Czech Republic is still at its very beginning. To accelerate the progress of geothermal energy sphere in Czech Republic, the RINGEN project has been established. Among seven project partners, our team from Technical University in Liberec (TUL) provides the software solution for the estimation of the deep geothermal exchanger behavior. Coupled thermos-hydraulic numerical model has been implemented in software Flow123d (developed in TUL; Březina, 2019), alongside the COMSOL Multiphysics software, serving as a benchmark (Comsol, 2019). The geometry of the fracture network, which constitutes the deep geothermal exchanger, is stochastically generated by our own scrpt in Python language. The algorithm uses the conventional Poisson process with conditions of 1) a network connectivity and 2) a correction of the defect cases (e.g. small intersections or close parallel fractures). The contribution shows scenarios of various site geological structure and geothermal exchanger set up. Using the current knowledge of the (probable) geologic properties at the Litoměřice site, the model results have been used as quantitative estimations of the exchanger output and working life. Both regional and local variants of the model will be considered: the first for the coarse scale, including the wide surroundings of the exchanger; the second for the detailed scale of the exchanger, providing the range of results for different stochastically generated fracture networks. The results are interpreted with an aim to determine (predict) a long-term sustainability of the energy mining based on proposed working regime designs.