Geothermal energy is clean and renewable,derived from the heat stored within accessible depths of the Earth's crust.The adoption of a single-well system for medium-deep and deep geothermal energy extraction has at...Geothermal energy is clean and renewable,derived from the heat stored within accessible depths of the Earth's crust.The adoption of a single-well system for medium-deep and deep geothermal energy extraction has attracted significant interest from the scientific and industrial communities because it effectively circumvents issues such as downhole inter-well connections and induced seismicity.However,the low heat transfer capacity in geothermal formations limits the heat extraction performance of single-well systems and hinders their commercial deployment.This review covers various enhancement concepts for optimizing the heat transfer within single-well systems,emphasizing critical parameters such as heat transfer area,heat transfer coefficient,and temperature difference.Additionally,it presents the thermo-economic evaluation of different configurations of single-well borehole heat exchangers and super-long gravity heat pipes(SLGHPs).The SLHGP,utilizing phase-change heat transfer,is recognized as a highly effective and continuously productive technology,capable of extracting over 1 MW of heat.Its pumpless operation and ease of installation in abandoned wells make it cost-effective,offering a promising economic advantage over traditional geothermal systems.It also highlights the challenges and potential research opportunities that can help identify gaps in research to enhance the performance of single-well geothermal systems.展开更多
基金supported by the National Key Research andDevelopmentProgramofChina(GrantNos.2021YFB1507300 and 2021YFB1507302)the National Natural Science Foundation of China(Grant Nos.52206126 and 52206287)+1 种基金the Jiangyin Science and Technology Innovation Special Fund,China(Grant No.JY0604A021015210001PB)the Jiangsu Provincial Carbon Peak Carbon Neutralization Technology Innovation Special Fund,China(Grant No.BE2022012).
文摘Geothermal energy is clean and renewable,derived from the heat stored within accessible depths of the Earth's crust.The adoption of a single-well system for medium-deep and deep geothermal energy extraction has attracted significant interest from the scientific and industrial communities because it effectively circumvents issues such as downhole inter-well connections and induced seismicity.However,the low heat transfer capacity in geothermal formations limits the heat extraction performance of single-well systems and hinders their commercial deployment.This review covers various enhancement concepts for optimizing the heat transfer within single-well systems,emphasizing critical parameters such as heat transfer area,heat transfer coefficient,and temperature difference.Additionally,it presents the thermo-economic evaluation of different configurations of single-well borehole heat exchangers and super-long gravity heat pipes(SLGHPs).The SLHGP,utilizing phase-change heat transfer,is recognized as a highly effective and continuously productive technology,capable of extracting over 1 MW of heat.Its pumpless operation and ease of installation in abandoned wells make it cost-effective,offering a promising economic advantage over traditional geothermal systems.It also highlights the challenges and potential research opportunities that can help identify gaps in research to enhance the performance of single-well geothermal systems.
