Key Takeaways & Executive Findings
- •• Cold energy accumulation during storage induces formation temperature decline, with heat recovery rate decelerating as the cold domain contracts inward. • Increasing groundwater velocity enhances thermal regulation efficiency but reduces production temperature; effective radius and thermal power initially increase then decrease. • Higher injection temperatures slow thermal recovery, and thermal regulation efficiency is more sensitive to permeability and thermal conductivity than other factors. • Levelized cost of electricity is 0.1203 $/(kWh) during cold storage, with annual profit primarily driven by cooling benefits during heat recovery.
Abstract
As mining activities expand deeper, deep high-temperature formations seriously threaten the future safe exploitation, while deep geothermal energy has great potential for development. Combining the formation cooling and geothermal mining in mines to establish a thermos-hydraulic coupling numerical model for fractured formation. The study investigates the formation heat transfer behaviour, heat recovery performance and thermal economic benefits influenced during the life cycle. The results show that the accumulation of cold energy during the cold storage phase induces a decline in formation temperature. The heat recovery phase is determined by the extent of the initial cold domain, which contracts inward from the edge and decelerates the heat recovery rate gradually. With groundwater velocity increases, the thermal regulation efficiency gradually increases, the production temperature decreases, while the effective radius and thermal power increase first and then decrease. The injected volume and temperature significantly affect, with higher injection temperatures slowing thermal recovery, and the thermal regulation efficiency is more sensitive to changes in formation permeability and thermal conductivity. The heat extraction performance is positively correlated with all factors. The levelized cost of electricity is estimated at 0.1203 $/(kW h) during the cold storage. During the heat recovery, annual profit is primarily driven by cooling benefits.
1. Introduction
As the economy progresses, the energy system reliant on fossil fuels, such as coal, minerals, and oil, has significantly advanced human society. Ensuring energy access remains a crucial aspect of a nation’s sustainable development [1,2]. However, as shallow mineral resources become increasingly exhausted, mining operations, both domestic and international, are shifting toward deeper earth strata [3]. Energy demand has received extensive attention in the context of deep development [4]. The increasing depth of mines exacerbates the high-temperature environment, which poses severe risks to the physical and mental well-being of personnel and sharply escalates the accident rate [5], thereby threatening the safety of mining operations.
A range of cooling strategies is essential to meet the temperature requirements of deep mining operations [6,7]. However, traditional refrigeration methods suffer from significant cold losses and low efficiency, with high energy consumption resulting in substantially increased mining operational costs [8]. In contrast to shallow mines, deep mining operations contend with greater heat release from the surrounding rock mass. High-temperature rock formations, as a primary heat source, are the key factors limiting the advancement of mining engineering into deeper strata [9]. Consequently, thermal hazards posed by high-temperature rock present an urgent challenge for deep mineral mining. Nonetheless, high-temperature rock strata can also be viewed as a valuable geothermal resource, offering renewable energy with the advantages of a stable supply and no climatic limitations [10]. Theoretically, the thermal energy stored at a depth of 10 km within the Earth’s crust is equivalent to approximately 2.6 billion tons of standard coal. With a conservative exploitation rate of 50%, the technically feasible geothermal potential could reach up to 40 1020 J [11]. Ensuring the green, low-carbon, and sustainable development of global mining operations hinges on capturing heat from high-temperature rock strata. This approach could transform detrimental thermal hazards into beneficial factors, facilitating the integration of safe traditional energy extraction with the development and utilization of new energy resources.
The underground space created by mining operations emerges as the most suitable candidate for geothermal mining, significantly reducing costs and environmental impact. This study aims to investigate the dynamic formation temperature response and thermal energy extraction performance of a mine geothermal system considering groundwater flow, providing insights for sustainable deep mining and geothermal utilization.
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LI Xibing, CHEN Zhiying, HUANG Linqi, LI Botao, YAN Jingyi, ZHANG Peilei, LIU Zhixiang (2024). Life cycle dynamic formation temperature response and thermal energy extraction of mine geothermal system considering groundwater flow. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2024.12.011
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Frequently Asked Questions
What is the main objective of this study?
The study aims to investigate the formation heat transfer behavior, heat recovery performance, and thermal economic benefits of a mine geothermal system considering groundwater flow, using a thermos-hydraulic coupling numerical model for fractured formations.
How does groundwater flow affect the mine geothermal system?
Increasing groundwater velocity enhances thermal regulation efficiency but reduces production temperature. The effective radius and thermal power initially increase then decrease with higher groundwater velocity.
What is the estimated levelized cost of electricity (LCOE) during cold storage?
The levelized cost of electricity is estimated at 0.1203 $/(kWh) during the cold storage phase.
What factors significantly influence thermal recovery?
Injected volume and temperature significantly affect thermal recovery; higher injection temperatures slow thermal recovery. Thermal regulation efficiency is more sensitive to changes in formation permeability and thermal conductivity.
What are the key findings regarding heat extraction performance?
Heat extraction performance is positively correlated with all factors studied, including groundwater velocity, injection parameters, and formation properties. Annual profit during heat recovery is primarily driven by cooling benefits.
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