Elsevier

Renewable Energy

Volume 198, October 2022, Pages 1193-1209
Renewable Energy

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

https://doi.org/10.1016/j.renene.2022.08.071Get rights and content
Under a Creative Commons license
open access

Highlights

  • Reuse of dry and depleted abandoned wells to boost geothermal energy production.

  • Deep closed-loop heat exchanger (DCHE) as innovative technological solution.

  • Computational numerical approach for DCHE performance optimisation.

  • Sustainable closed-loop configuration for synthetic and real case studies.

  • Long-term DCHE thermal performance improvement by monthly rotation practice.

Abstract

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 temperatures. 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 resources, 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. Furthermore, circulation rates of 0.02–0.04 m3 s−1 are cost-effective, and the system's efficiency and sustainability increase when a fluctuating and periodic heat extraction strategy is employed. When efficiently operated, DCHEs are a viable solution for renewable energy production and should be integrated into the local heat market and distribution network infrastructure.

Field of research

Earth and Planetary Sciences; Energy; Environmental Sciences

Keywords

Geothermal energy
Deep closed-loop system
Borehole heat exchanger
Numerical simulation
Sustainability

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