An Approximate Solution for Predicting the Heat Extraction and Preventing Heat Loss from a Closed-Loop Geothermal Reservoir

Wu, Bisheng; Ma, Tianshou; Feng, Guanhong; Chen, Zuorong; Zhang, Xi

doi:10.1155/2017/2041072

Cited by 16 publications

(10 citation statements)

References 45 publications

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“…Recently, with the increasing depth of mining, the mechanical characteristics of the coal and rock around roadways at high pressure, high gas pressure [36,37], and high temperature [38,39] have been systematically researched. Yang et al [40] obtained the failure mechanisms and stability control technology for a deep roadway with some soft rocks in the Xin'an Coal Mine in Gansu Province, China, and one new useful "bolt-cable-mesh-shotcrete+shell"-combined support was proposed to support the ventilation roadway.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on the Brittle-Ductile Response of a Heterogeneous Soft Coal Rock Mass under Multifactor Coupling

et al. 2019

Geofluids

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After a gas drainage event causes different degrees of initial porosity in the coal seam, the heterogeneity of the coal mass becomes much more obvious. In this paper, soft coal testing samples with different degrees of heterogeneity were prepared first by a new special experimental research method using hydrogen peroxide in an alkaline medium to generate oxygen. Then, a series of mechanical tests on the soft coal mass samples were carried out under multiple factor coupling conditions of different heterogeneities and confining pressures. The results show that with a low strength, the ductility failure characteristic and a kind of rheology similar to that for soft rock flow were reflected for the soft coal; i.e., the stress-strain curve of the coal mass had no apparent peak strain and residual strength. An interesting phenomenon was found in the test process: there was an upwardly convex critical phase, called the brittle-ductile failure transition critical phase, for the heterogeneous soft coal mass between the initial elastic compression phase and the ductile failure transition phase in the stress-strain curve of the coal mass. An evolution of the brittle-ductile modulus coefficient of the soft coal was developed to analyze the effect of the internal factor (degree of heterogeneity) and external factors (confining pressure) on the transition state of the brittle-ductile failure of soft coal. Further analysis shows that the internal factor (heterogeneity) was also one of the essential factors causing the brittle-ductile transition of soft coal.

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Section: Introductionmentioning

confidence: 99%

Experimental Study on the Brittle-Ductile Response of a Heterogeneous Soft Coal Rock Mass under Multifactor Coupling

et al. 2019

Geofluids

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“…Since the early 1970s, the United Nations (UN) has played an important role in promoting the exploration and exploitation of these resources [1]. Since then, exploratory work has intensified in various parts of the world [2][3][4][5], and numerous innovative research and implementation projects have been undertaken, primarily to produce electricity and heat [6][7][8][9]. The global utilisation of geothermal potential is increasing, and new statistical data in this respect have been supplied by Bertani [10] and also Lund and Boyd [11], whose papers have been presented during cyclic global conferences.…”

Section: Introductionmentioning

confidence: 99%

Review of the Low-Enthalpy Lower Cretaceous Geothermal Energy Resources in Poland as an Environmentally Friendly Source of Heat for Urban District Heating Systems

et al. 2020

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The paper presents a review of the geological and hydrogeological data of the Lower Cretaceous aquifer in the Polish Lowlands and discusses the possibilities for the utilisation of geothermal water resources in existing and new district heating systems. Based on experience related to the use of thermal waters in existing geothermal systems, and using data from the literature, assessments have been made of the energy and environmental effects of the application of low-enthalpy geothermal resources from the Lower Cretaceous aquifer as a source of heat for urban district heating systems. The authors concluded that the implementation of such solutions could result in the production of approximately 4 PJ of geothermal energy annually. To date, these resources have only been developed in three locations—Mszczonów, Uniejów and Poddębice—with the total amount of energy generated annually reaching 100 TJ/year. Similar district heating networks in 120 nearby localities have been also identified. Here, specified geological and hydrogeological conditions enable the extraction of heat from the investigated Lower Cretaceous aquifer, with the aim of using this for heating purposes. To achieve this goal, multiple measures are required, including the following: raising public awareness through appropriate education programmes aimed at the youngest school children; systemic, efficient energy management measures at the central, regional and local levels, and providing financial support and ensuring regulations and laws aimed at improving the development of geothermal resources.

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“…Therefore, the renewable geothermal energy becomes a promising alternative to achieve thermal comfort due to its low cost, high availability, stability, and minimal environment impact and can be utilized by various geothermal subsurface earth structures such as geothermal energy piles (GEP), ground source heat pumps (GSHP), earth-air tunnel heat exchangers (EATHE), borehole thermal energy storage (BTES), geological carbon dioxide sequestration and storage, and geothermal heated pavement [3][4][5][6][7]. The basic principle of these projects is simple: a cold fluid (CO 2 or water) is injected into the buried pipe, absorbs heat from hotter surrounding soil, and then is pumped out [8]. The geothermal-related system represents an important mean to extract heat from below the earth by fluid circulation, and study on maximizing its output performance is very important.…”

Section: Introductionmentioning

confidence: 99%

Laboratory Investigation and Modelling of the Thermal-Mechanical Properties of Soil in Shallow Mineralized Groundwater Area

Zhao

Liu

2019

Geofluids

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The capillary rise of shallow mineralized groundwater can contribute to the salinization of the soil layers. The excessive salt amounts adversely affect soil physical and mechanical properties, as well as the heat transfer performance, all of which are key factors with regard to the design of geothermal-related earth structures such as geothermal energy piles (GEP), ground source heat pumps (GSHP), and earth-air tunnel heat exchangers (EATHE). Therefore, in this study, the thermal-mechanical properties of saline soils are systematically investigated. A series of thermal and mechanical response tests were carried out under different salinity conditions, and the shear wave velocity-stress behavior of saline soil was measured using a modified oedometric cell coupled with an anchored bender element pair. Experimental results showed that saline soils generally have higher dry density and lower optimum moisture content at higher salt contents. The shear strength of saline soil increased about 5% while the salt concentrations of bulk solution increased from 0 mol/kg to 6 mol/kg, and the shear wave velocity increased by 50% to 83% when the normal load increased from 12.5 kPa to 250 kPa for sodium chloride- (NaCl-) treated soil and 39% to 52% for calcium chloride- (CaCl2-) treated soil. In addition, the thermal conductivity decreased by 0.121 W m-1 K-1 for NaCl-treated soil and 0.129 W m-1 K-1 for CaCl2-treated soil on average when the salt concentration increased from 0 mol/kg to 6 mol/kg. Finally, an elastic shear modulus (G0) model and a thermal conductivity (K) model were formulated for saline soil for the first time, and the effectiveness and feasibility of the proposed models were validated by comparisons of the model predicted values and experimental data.

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An Approximate Solution for Predicting the Heat Extraction and Preventing Heat Loss from a Closed-Loop Geothermal Reservoir

Cited by 16 publications

References 45 publications

Experimental Study on the Brittle-Ductile Response of a Heterogeneous Soft Coal Rock Mass under Multifactor Coupling

Experimental Study on the Brittle-Ductile Response of a Heterogeneous Soft Coal Rock Mass under Multifactor Coupling

Review of the Low-Enthalpy Lower Cretaceous Geothermal Energy Resources in Poland as an Environmentally Friendly Source of Heat for Urban District Heating Systems

Laboratory Investigation and Modelling of the Thermal-Mechanical Properties of Soil in Shallow Mineralized Groundwater Area

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