A Systematic Review of the Design and Heat Transfer Performance of Enhanced Closed-Loop Geothermal Systems

Abstract

Geothermal energy is one of the primary sources of clean electricity generation as the world transitions away from fossil fuels. In comparison to enhanced geothermal methods based on artificial fracturing, closed-loop geothermal systems (CLGSs) avoid seismicity-induced risk, are independent of reservoir permeability, and do not require the direct interaction between the fluid and the geothermal reservoir. In recent years, the development of CLGS technologies that offer high energy efficiencies has been explored. Research on coaxial closed-loop geothermal systems (CCLGS) and U-shaped closed-loop geothermal system (UCLGS) systems were reviewed in this paper. These studies were categorized based on their design, modeling methods, and heat transfer performance. It was found that UCLGSs had superior heat transfer performances compared to CCLGS. In addition, UCLGSs that utilized CO2 as a working fluid were found to be promising technologies that could help in addressing the future challenges associated with zero-emission compliance and green energy demand. Further research to improve the heat transfer performance of CLGS, especially with regards to improvements in wellbore layout, equipment sizing, and its integration with CO2 capture technologies is critical to ensuring the feasibility of this technology in the future.

Thermodynamic Analysis of an Increasing-Pressure Endothermic Power Cycle Integrated with Closed-Loop Geothermal Energy Extraction

“…The need for fossil fuel-based energy has grown due to the world's expanding population and growing reliance on modern technology [1]. The extensive use of fossil fuels has led to many climate problems and much environmental pollution, which are constantly changing our living environment.…”

A comprehensive review of deep borehole heat exchangers (DBHEs): subsurface modelling studies and applications

“…Alimonti et al (2018) reviewed modelling of DBHE systems with a focus on their design and performance for heat and/or electricity generation. Advanced Geothermal System (AGS) technologies, to which DBHEs belong, have been reviewed by Budiono et al (2022), but their work does not include deep BTES. This work therefore aims to provide a comprehensive review on numerical and analytical modelling of closed-loop conventional (vertical) DBHEs and their various applications in heating, cooling and storage, including those not captured by Sapinska- Sliwa et al (2016).…”

Technical Performance Comparison between U-Shaped and Deep Borehole Heat Exchangers

“…Since 2000, research has focused on geothermal energy production and avoiding brine extraction using CLG as the deep borehole heat exchanger. Budiono et al [2] reported a substantial growth in papers during the period 2016-2021. This growth is the result of searches for new technologies and technical solutions to increase geothermal applications.…”

“…Their systematic review studied different CLG configurations, as reported by [2]. Two main types emerged: The first is the concept of a coaxial exchanger, which can be vertical (DBHE) or developed with a horizontal terminal part (DBHEh); and the second is the U-loop scheme, which includes a geometry composed of two pseudo-vertical sections joined by a horizontal branch (ULHE).…”

“…Researchers in China developed more significant literature on ULHEs and worked on experimental plants with different designs. The Budiono et al [2] review concludes by highlighting the main parameters characterising heat extraction, identified as the temperature, heat extraction rate, pressure differential and thermal power. These key parameters are used in our work to compare the two heat exchangers.…”