Geothermal deep closed-loop heat exchangers: A novel technical potential evaluation to answer the power and heat demands

This paper investigates and optimises the thermal performance of deep closed-loop heat exchanger (DCHE) systems by applying a computational numerical approach. The investigated DCHE configuration accounts for two deep vertical boreholes, an injection and a production well, connected by a horizontal borehole at depth and an insulated pipeline at the surface, establishing an effective closed-loop system. First, a parametric sensitivity study explores the effects of the environmental, design and operating variables on the production temperature. The simulation uses realistic geological and geothermal conditions, depths, circulation rates and injection temper- atures. Two complex numerical models are then solved for site-specific DCHEs in different geological scenarios: a foreland basin and a convergent margin hosting low-to-intermediate and high-temperature geothermal re-sources, respectively. Production temperatures beyond 40–60 ◦C and 100 ◦ C, sustainable for both heat and electric power generation, are obtained, depending on the geothermal conditions and closed-loop dimensions.