Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in buildi...Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.展开更多
Over the past 80 years,dozens of underground coal gasification(UCG)mine field tests have been carried out around the world.However,in the early days,only a small number of shallow UCG projects in the former Soviet Uni...Over the past 80 years,dozens of underground coal gasification(UCG)mine field tests have been carried out around the world.However,in the early days,only a small number of shallow UCG projects in the former Soviet Union achieved commercialised production.In this century,a few pilot projects in Australia also achieved short-term small-scale commercialised production using modern UCG technology.However,the commercialisation of UCG,especially medium-deep UCG projects with good development prospects but difficult underground engineering conditions,has not progressed smoothly around the world.Considering investment economy,a single gasifier must realise a high daily output and accumulated output,as well as hold a long gasification tunnel to control a large number of coal resources.However,a long gasification tunnel can easily be affected by blockages and failure,for which the remedial solutions are difficult and expensive,which greatly restricts the investment economy.The design of the underground gasifier determines the success or failure of UCG projects,and it also requires the related petroleum engineering technology.Combining the advantages of the linear horizontal well(L-CRIP)and parallel horizontal well(P-CRIP),this paper proposes a new design scheme for an“inclined ladder”underground gasifier.That is to say,the combination of the main shaft of paired P-CRIP and multiple branch horizontal well gasification tunnels is adopted to realise the control of a large number of coal resources in a single gasifier.The completion of the main shaft by well cementation is beneficial for maintaining the integrity of the main shaft and the stability of the main structure.The branch horizontal well is used as the gasification tunnel,but the length and number of retracting injection points are limited,effectively reducing the probability of blockage or failure.The branch horizontal well spacing can be adjusted flexibly to avoid minor faults and large cracks,which is conducive to increasing the resource utilisation rate.In addition,for multi-layer thin coal seams or ultra-thick coal seams,a multi-layer gasifier sharing vertical well sections can be deployed,thereby saving investment on the vertical well sections.Through preliminary analysis,this gasifier design scheme can be realised in engineering,making it suitable for largescale deployment where it can increase the resource utilisation rate and ensure stable and controllable operations.The new gasifier has outstanding advantages in investment economy,and good prospects for application in the commercial UCG projects of medium-deep coal seams.展开更多
为明确中深层水热型地热供暖系统的碳足迹特征并提出减排路径,以韩城能源3号站为研究对象,聚焦采灌井组环节,构建“基础支撑-核心设计-保障优化”三层次物理模型及全生命周期碳排放计算模型。模型涵盖材料生产与运输、施工、运行、拆除...为明确中深层水热型地热供暖系统的碳足迹特征并提出减排路径,以韩城能源3号站为研究对象,聚焦采灌井组环节,构建“基础支撑-核心设计-保障优化”三层次物理模型及全生命周期碳排放计算模型。模型涵盖材料生产与运输、施工、运行、拆除与回收共4个阶段的碳排放计算,并针对高碳排放节点提出减排策略。结果表明,该系统全生命周期总碳排放量为93000.49 tCO_(2),单位面积碳排放强度为294.22 kg CO_(2)/m^(2)。其中,运行阶段是核心排放源,占比89.47%;采灌井组前期物化阶段碳排放量为2098.81 tCO_(2),占系统前期总排放量的19.25%,施工阶段碳排放量占比高达81.55%。该研究结果与策略可为中深层水热型地热供暖系统的低碳发展提供技术参考。展开更多
U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The co...U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The conclusions indicate a discernible deterioration in the thermal performance of U-MDBHE attributed to heat extraction attenuation.The thermal performance deterioration leads to the oversize of U-MDBHE and hinders the widespread application of U-MDBHE.This study introduces a novel idea that the long-term thermal performance of U-MDBHE should be evaluated considering climate change(CC)and verifies that the favorable effects of CC on the thermal performance of U-MDBHE can effectively mitigate the adverse effect of heat extraction attenuation.The favorable effects of CC include reducing the heating demand(due to the reduced building heating load(BHL)caused by CC)and improving the heating supply capacity(due to the enhanced outlet temperature caused by CC).In addition,the reduced BHL under CC enhances the inlet temperature of U-MDBHE,thereby improving its operation safety.CC mitigates the heat extraction attenuation of U-MDBHE,with the strongest effect in the ascending well,followed by the descending well,and then the butted well.Case studies using experimentally validated simulations on the 30-year operation of U-MDBHE demonstrate that by mitigating the adverse effect of the heat extraction attenuation,CC reduces the accumulated energy consumption by 14.31%–26.59%and improves the operation safety by up to 100%in Harbin(severe cold region)and Beijing(cold region).This study significantly contributes to improving the long-term thermal performance of U-MDBHE.展开更多
基金support by the Shanghai Engineering Research Center for Shallow Geothermal Energy(DRZX-202306)Shaanxi Coal Geology Group Co.,Ltd.(SMDZ-ZD2024-23)+4 种基金Key Laboratory of Coal Resources Exploration and Comprehensive Utilization,Ministry of Natural Resources,China(ZP2020-1)Shaanxi Investment Group Co.,Ltd.(SIGC2023-KY-05)Key Research and Development Projects of Shaanxi Province(2023-GHZD-54)Shaanxi Qinchuangyuan Scientist+Engineer Team Construction Project(2022KXJ-049)China Postdoctoral Science Foundation(2023M742802,2024T170721).
文摘Geothermal energy,a form of renewable energy,has been extensively utilized for building heating.However,there is a lack of detailed comparative studies on the use of shallow and medium-deep geothermal energy in building energy systems,which are essential for decision-making.Therefore,this paper presents a comparative study of the performance and economic analysis of shallow and medium-deep borehole heat exchanger heating systems.Based on the geological parameters of Xi’an,China and commonly used borehole heat exchanger structures,numerical simulationmethods are employed to analyze performance and economic efficiency.The results indicate that increasing the spacing between shallow borehole heat exchangers can effectively reduce thermal interference between the pipes and improve heat extraction performance.As the flow rate increases,the outlet water temperature ranges from 279.3 to 279.7 K,with heat extraction power varying between 595 and 609 W.For medium-deep borehole heat exchangers,performance predictions show that a higher flow rate results in greater heat extraction power.However,when the flow rate exceeds 30 m^(3)/h,further increases in flow rate have only a minor effect on enhancing heat extraction power.Additionally,the economic analysis reveals that the payback period for shallow geothermal heating systems ranges from 10 to 11 years,while for medium-deep geothermal heating systems,it varies more widely from 3 to 25 years.Therefore,the payback period for medium-deep geothermal heating systems is more significantly influenced by operational and installation parameters,and optimizing these parameters can considerably shorten the payback period.The results of this study are expected to provide valuable insights into the efficient and cost-effective utilization of geothermal energy for building heating.
文摘Over the past 80 years,dozens of underground coal gasification(UCG)mine field tests have been carried out around the world.However,in the early days,only a small number of shallow UCG projects in the former Soviet Union achieved commercialised production.In this century,a few pilot projects in Australia also achieved short-term small-scale commercialised production using modern UCG technology.However,the commercialisation of UCG,especially medium-deep UCG projects with good development prospects but difficult underground engineering conditions,has not progressed smoothly around the world.Considering investment economy,a single gasifier must realise a high daily output and accumulated output,as well as hold a long gasification tunnel to control a large number of coal resources.However,a long gasification tunnel can easily be affected by blockages and failure,for which the remedial solutions are difficult and expensive,which greatly restricts the investment economy.The design of the underground gasifier determines the success or failure of UCG projects,and it also requires the related petroleum engineering technology.Combining the advantages of the linear horizontal well(L-CRIP)and parallel horizontal well(P-CRIP),this paper proposes a new design scheme for an“inclined ladder”underground gasifier.That is to say,the combination of the main shaft of paired P-CRIP and multiple branch horizontal well gasification tunnels is adopted to realise the control of a large number of coal resources in a single gasifier.The completion of the main shaft by well cementation is beneficial for maintaining the integrity of the main shaft and the stability of the main structure.The branch horizontal well is used as the gasification tunnel,but the length and number of retracting injection points are limited,effectively reducing the probability of blockage or failure.The branch horizontal well spacing can be adjusted flexibly to avoid minor faults and large cracks,which is conducive to increasing the resource utilisation rate.In addition,for multi-layer thin coal seams or ultra-thick coal seams,a multi-layer gasifier sharing vertical well sections can be deployed,thereby saving investment on the vertical well sections.Through preliminary analysis,this gasifier design scheme can be realised in engineering,making it suitable for largescale deployment where it can increase the resource utilisation rate and ensure stable and controllable operations.The new gasifier has outstanding advantages in investment economy,and good prospects for application in the commercial UCG projects of medium-deep coal seams.
文摘为明确中深层水热型地热供暖系统的碳足迹特征并提出减排路径,以韩城能源3号站为研究对象,聚焦采灌井组环节,构建“基础支撑-核心设计-保障优化”三层次物理模型及全生命周期碳排放计算模型。模型涵盖材料生产与运输、施工、运行、拆除与回收共4个阶段的碳排放计算,并针对高碳排放节点提出减排策略。结果表明,该系统全生命周期总碳排放量为93000.49 tCO_(2),单位面积碳排放强度为294.22 kg CO_(2)/m^(2)。其中,运行阶段是核心排放源,占比89.47%;采灌井组前期物化阶段碳排放量为2098.81 tCO_(2),占系统前期总排放量的19.25%,施工阶段碳排放量占比高达81.55%。该研究结果与策略可为中深层水热型地热供暖系统的低碳发展提供技术参考。
基金supported by the Key Research and Development Projects of Shaanxi Province(Project No.2024SF-YBXM-596 and Project No.2024SF-YBXM-604)Special Fund Project of Science and Technology Innovation by Shaanxi Provincial State-owned Capital Management Budget(Project No.31228000000008/011900)+2 种基金Top Young Talent Programme of Xi’an Jiaotong University(Project No.011900/11301224030703)Qin Chuangyuan“Scientist+Engineer”Team Program(Project No.2022KXJ-039)Innovation Capability Support Program of Shaanxi Province(Project No.2021PT-028).
文摘U-type medium-deep borehole heat exchanger(U-MDBHE)is a sustainable building heating technology.Current studies assess the long-term thermal performance of U-MDBHE using typical meteorological year weather data.The conclusions indicate a discernible deterioration in the thermal performance of U-MDBHE attributed to heat extraction attenuation.The thermal performance deterioration leads to the oversize of U-MDBHE and hinders the widespread application of U-MDBHE.This study introduces a novel idea that the long-term thermal performance of U-MDBHE should be evaluated considering climate change(CC)and verifies that the favorable effects of CC on the thermal performance of U-MDBHE can effectively mitigate the adverse effect of heat extraction attenuation.The favorable effects of CC include reducing the heating demand(due to the reduced building heating load(BHL)caused by CC)and improving the heating supply capacity(due to the enhanced outlet temperature caused by CC).In addition,the reduced BHL under CC enhances the inlet temperature of U-MDBHE,thereby improving its operation safety.CC mitigates the heat extraction attenuation of U-MDBHE,with the strongest effect in the ascending well,followed by the descending well,and then the butted well.Case studies using experimentally validated simulations on the 30-year operation of U-MDBHE demonstrate that by mitigating the adverse effect of the heat extraction attenuation,CC reduces the accumulated energy consumption by 14.31%–26.59%and improves the operation safety by up to 100%in Harbin(severe cold region)and Beijing(cold region).This study significantly contributes to improving the long-term thermal performance of U-MDBHE.
