Research status and development trend of key technologies for enhanced geothermal systems

Gong, Liang; Han, Dongxu; Chen, Zheng; Wang, Daobing; Jiao, Kaituo; Zhang, Xu; Yu, Bo

doi:10.1016/j.ngib.2023.01.011

Cited by 15 publications

(5 citation statements)

References 98 publications

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“…Taking into consideration the physical properties and distribution characteristics of hot dry rocks, as well as the regional distribution of geothermal resources in China, granite samples from Xuzhou, China were selected as the experimental rock samples for this study. Granite, an elastic igneous rock with minimal porosity and limited permeability [35], bears close resemblance to hot dry rocks in terms of these physical characteristics. Thus, granite serves as an appropriate representative sample for investigating hot dry rocks.…”

Section: Preparation Of Test Rock Samplesmentioning

confidence: 99%

Experimental Study on Mode I Fracture Characteristics of Granite after Low Temperature Cooling with Liquid Nitrogen

Wang,

Xue,

Cao

et al. 2023

Water

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Liquid nitrogen fracturing has emerged as a promising technique in fluid fracturing, providing significant advantages for the utilization and development of geothermal energy. Similarly to hydraulic fracturing in reservoirs, liquid nitrogen fracturing entails a common challenge of fluid–rock interaction, encompassing the permeation and diffusion processes of fluids within rock pores and fractures. Geomechanical analysis plays a crucial role in evaluating the transfer and diffusion capabilities of fluids within rocks, enabling the prediction of fracturing outcomes and fracture network development. This technique is particularly advantageous for facilitating heat exchange with hot dry rocks and inducing fractures within rock formations. The primary objective of this study is to examine the effects of liquid nitrogen fracturing on hot dry rocks, focusing specifically on granite specimens. The experimental design comprises two sets of granite samples to explore the impact of liquid nitrogen cooling cycles on the mode I fracture characteristics, acoustic emission features, and rock burst tendency of granite. By examining the mechanical properties, acoustic emission features, and rock burst tendencies under different cycling conditions, the effectiveness of liquid nitrogen fracturing technology is revealed. The results indicate that: (1) The ultimate load-bearing capacity of the samples gradually decreases with an increase in the number of cycling times. (2) The analysis of acoustic emission signals reveals a progressive increase in the cumulative energy of the samples with cycling times, indicating that cycling stimulates the release of stored energy within the samples. (3) After undergoing various cycling treatments, the granite surface becomes rougher, exhibiting increased porosity and notable mineral particle detachment. These results suggest that the cyclic application of high-temperature heating and liquid nitrogen cooling promotes the formation of internal fractures in granite. This phenomenon is believed to be influenced by the inherent heterogeneity and expansion–contraction of internal particles. Furthermore, a detailed analysis of the morphological sections provides insights into the structural changes induced by liquid nitrogen fracturing in granite samples.

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Section: Preparation Of Test Rock Samplesmentioning

confidence: 99%

Experimental Study on Mode I Fracture Characteristics of Granite after Low Temperature Cooling with Liquid Nitrogen

Wang,

Xue,

Cao

et al. 2023

Water

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“…Moreover, granite is widely distributed in the Earth's crust and easily accessible. In light of the regional distribution patterns exhibited by hot dry rock-type geothermal resources in China, a granite sample obtained from Xuzhou City, located in Jiangsu Province, was selected for the experiment [28].…”

Section: Instrumentation and Experimental Designmentioning

confidence: 99%

Investigation of Rock Mechanical Properties under Liquid Nitrogen Environment

Wang,

Liang,

Shi

et al. 2023

Geofluids

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In order to promote sustainable energy development and reduce the impact of fossil fuels on the environment, it is crucial to strengthen the development and utilization of clean and renewable geothermal energy. Liquid nitrogen fracturing, as an emerging waterless fracturing technology, has outstanding advantages in rock fracturing effect and thermal exchange ability with hot dry rock and is more environmentally friendly. In order to evaluate the influence of liquid nitrogen on the mechanical properties, acoustic emission characteristics, and cross-sectional crack propagation characteristics of granite at different initial temperatures, this paper carried out three-point bending tests and acoustic emission detection on granite treated by high-temperature heating and liquid nitrogen cooling. Finally, based on the cross-sectional scanning test, the expansion characteristics of microcracks in granite were analyzed. The results show that the higher the initial temperature of granite, the stronger the cold impact of liquid nitrogen on granite, and the faster the rock’s mechanical performance declines. The acoustic emission ringing count is closely related to the development of microcracks in granite, and as the initial temperature of granite increases, the more ringing counts there are, indicating that the huge temperature difference induces more microcracks inside the rock. In addition, the cold impact of liquid nitrogen can effectively promote the fracturing of granite. After liquid nitrogen treatment, the fractal dimension of the granite cross-section increases, the shape of the cross-section becomes rough, and many micropores appear. This study can provide a scientific basis for the engineering application of liquid nitrogen fracturing technology.

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“…This, after appropriate treatment and stimulation, allows fluid to circulate through the rock, become heated, and then be used to generate electricity or heat at a topside power plant. Around thirty EGS projects are currently either under development or in operation worldwide, with a total installed capacity of about 12 MW [5]. Of these, five are in routine operation and fourteen are currently capable of producing power.…”

Section: Introductionmentioning

confidence: 99%

“…Nevertheless, EGS projects have not yet reached large-scale commercial operation due to a number of obstacles that need to be overcome. In article [5], authors underlined aspects which may cause an impediment to rapid EGS deployment, some of the points mentioned are as follows:…”

Section: Introductionmentioning

confidence: 99%

Environmental Impact of Enhanced Geothermal Systems with Supercritical Carbon Dioxide: A Comparative Life Cycle Analysis of Polish and Norwegian Cases

Strojny,

Gładysz,

Andresen

et al. 2024

Energies

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Low-carbon electricity and heat production is essential for keeping the decarbonization targets and climate mitigation goals. Thus, an accurate understanding of the potential environmental impacts constitutes a key aspect not only for the reduction in greenhouse gas emissions but also for other environmental categories. Life cycle assessment allows us to conduct an overall evaluation of a given process or system through its whole lifetime across various environmental indicators. This study focused on construction, operation and maintenance, and end-of-life phases, which were analyzed based on the ReCiPe 2016 method. Within this work, authors assessed the environmental performance of one of the renewable energy sources—Enhanced Geothermal Systems, which utilize supercritical carbon dioxide as a working fluid to produce electricity and heat. Heat for the process is extracted from hot, dry rocks, typically located at depths of approximately 4–5 km, and requires appropriate stimulation to enable fluid flow. Consequently, drilling and site preparation entail significant energy and material inputs. This stage, based on conducted calculations, exhibits the highest global warming potential, with values between 5.2 and 30.1 kgCO2eq/MWhel, corresponding to approximately 65%, 86%, and 94% in terms of overall impacts for ecosystems, human health, and resources categories, respectively. Moreover, the study authors compared the EGS impacts for the Polish and Norwegian conditions. Obtained results indicated that due to much higher electricity output from the Norwegian plant, which is sited offshore, the environmental influence remains the lowest, at a level of 11.9 kgCO2eq/MWhel. Polish cases range between 38.7 and 54.1 kgCO2eq/MWhel of global warming potential in terms of electricity production. Regarding power generation only, the impacts in the case of the Norwegian facility are two to five times lower than for the installation in the Polish conditions.

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Research status and development trend of key technologies for enhanced geothermal systems

Cited by 15 publications

References 98 publications

Experimental Study on Mode I Fracture Characteristics of Granite after Low Temperature Cooling with Liquid Nitrogen

Experimental Study on Mode I Fracture Characteristics of Granite after Low Temperature Cooling with Liquid Nitrogen

Investigation of Rock Mechanical Properties under Liquid Nitrogen Environment

Environmental Impact of Enhanced Geothermal Systems with Supercritical Carbon Dioxide: A Comparative Life Cycle Analysis of Polish and Norwegian Cases

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