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.
Highlights
Global energy demand and the demand for fossil-based energy are projected to increase through to 2050 as a result of an increasing population and continued economic growth
This paper aims to review all publications associated with the design, mathematical modeling, and heat transfer performance of different types of closed-loop geothermal systems (CLGSs), as well as compare its performance with different working fluids, i.e., water and CO2
The number of articles published in this period increased by 414% compared to the previous period (2011–2015). This reflects the importance of new renewable energy sources as the world transitions to clean energy and suggests that researchers have started to consider the potential of closed-loop Enhanced Geothermal System (EGS)
Summary
Global energy demand and the demand for fossil-based energy are projected to increase through to 2050 as a result of an increasing population and continued economic growth. There has been an increasing amount of discussion regarding the transition from fossil-based fuels to renewable energy sources to achieve zero-emission targets. Unlike other forms of renewable energy such as wind and solar energy, the energy derived from geothermal sources is considered to be more viable as it is not dependent on solar intermittence or weather conditions [2]. Hydrothermal energy is a conventional energy source that can only be utilized in specific regions located in volcanic basins, such as in the United States of America, Indonesia, and Iceland, among others [3]. The MIT report [4] states that an Enhanced Geothermal System (EGS) could be a promising energy source because it can provide an additional 100 GWe by 2050. Several studies have considered a novel use of EGS that utilizes CO2 , which was found to outperform its
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