Concepts and characteristics of a U-shaped docking well geothermal heat extraction system

Li, Li; Liu, Xiantao; Xiao, Dianshi; Huang, Kun; Li, Shuxuan

doi:10.1177/0144598719832712

Cited by 11 publications

(4 citation statements)

References 18 publications

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“…UCLGS refers to a U‐shaped well formed by steel casing in both vertical and horizontal engineering wells. When working, the fluid working fluid completes the heat transfer via the descending, horizontal, and ascending sections and then enters the ground heat exchanger to complete the closed cycle 11 . Sun et al 12 developed a model for simulating CO 2 flow in the UCLGS and proposed two new concepts of critical position and effective distance.…”

Section: Introductionmentioning

confidence: 99%

“…When working, the fluid working fluid completes the heat transfer via the descending, horizontal, and ascending sections and then enters the ground heat exchanger to complete the closed cycle. 11 Sun et al 12 developed a model for simulating CO 2 flow in the UCLGS and proposed two new concepts of critical position and effective distance. Furthermore, Song et al 13 reported an unsteady heat transfer model for UCLGS, which took in account with the change of convective heat transfer coefficient and analyzed influences of important parameters on UCLGS performance.…”

Section: Introductionmentioning

confidence: 99%

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Research on economic length of the horizontal section of downhole coaxial heat exchanger geothermal system based on net present value

Xiao

Cai

Tang

et al. 2021

Intl J of Energy Research

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Summary Hot dry rocks (HDRs) exhibit wide distribution characteristics and have attracted considerable attention because of their considerable potential for geothermal development. A downhole coaxial heat exchanger geothermal system (DCHEGS) with a horizontal well is a novel and effective method for geothermal development and utilization from HDR. To examine the heat extraction performance, a mathematical model of a DCHEGS was established. This model was extremely accurate and consistent with the experimental test results (relative errors were <8%). By analyzing calculation results, we determined that the heat extraction power increased with the horizontal section length; however, the growth rate decreased. Hence, there must be an economical horizontal section length. Subsequently, to identify the optimal length of horizontal section, an economic evaluation model of a DCHEGS with a horizontal well based on net present value (NPV) was established. Finally, the economic evaluation model was applied using the GR1 Well as an example. The results demonstrated that the project can only be profitable when the horizontal section length of the GR1 Well is between 0 and 4009 m, and the optimal economic length is 1466 m. Thus, in this study, the horizontal well length design method proposed can effectively provide a theoretical support for the practical design and operation of DCHEGS.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Research on economic length of the horizontal section of downhole coaxial heat exchanger geothermal system based on net present value

Xiao

Cai

Tang

et al. 2021

Intl J of Energy Research

Self Cite

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“…Recently, closed-loop geothermal systems based on geothermal water recharge technology that consist of injection, horizontal, and production wells have been proposed (Fallah et al, 2021;Li, et al, 2019a;Sun et al, 2018). These systems are efficient and sustainable.…”

Section: Introductionmentioning

confidence: 99%

“…However, several current studies on U-shaped geothermal wells focus on their concept and nature (Li, et al, 2019a). Existing studies have developed mathematical models for flow and heat transfer to determine the relation between the well structure, wellbore size, process parameters, and working fluid physical parameters and the heating power and outlet temperature (Li, et al, 2019a;Liao et al, 2021;Lyu et al, 2020;Sun et al, 2019). The finding of such studies have laid the foundation for developing geothermal energy technology using U-shaped geothermal wells.…”

Section: Introductionmentioning

confidence: 99%

Research on Design Method for Optimal Flow Rate of U-shaped Geothermal Well Based on Exergy Analysis

Xiao

Wang

et al. 2021

Energy Exploration & Exploitation

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Closed-loop U-shaped geothermal wells show great potential owing to their special well-depth structure, which can provide a good flow rate and heat extraction. However, no advanced process parameter optimization method is available for U-shaped geothermal wells. To effectively describe the heat transfer processes of U-shaped geothermal wells, an analytical solution that couples transient heat conduction in the surrounding soil (or rocks) with the quasisteady heat transfer process in boreholes was developed. This modelling approach depends on many common elements, such as the thermophysical properties of the working fluid and series of resistances for various elements in the wellbore. Subsequently, based on the exergy analysis method, the optimal operating flow rate was defined and a design method for the optimal flow rate was developed. Results indicate that to obtain the maximum exergy efficiency, different optimal flow rates for the U-shaped geothermal well are achieved at different stages of the heating period. This findings of this study expand the research ideas of the process parameter optimization of U-shaped geothermal wells and provide a theoretical basis for developing an optimal circulating-flow-rate design for U-shaped geothermal wells.

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Evaluating a large geothermal absorber’s energy extraction and storage performance in a common geological condition

Chen

Feng

2020

Applied Energy

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Concepts and characteristics of a U-shaped docking well geothermal heat extraction system

Cited by 11 publications

References 18 publications

Research on economic length of the horizontal section of downhole coaxial heat exchanger geothermal system based on net present value

Research on economic length of the horizontal section of downhole coaxial heat exchanger geothermal system based on net present value

Research on Design Method for Optimal Flow Rate of U-shaped Geothermal Well Based on Exergy Analysis

Evaluating a large geothermal absorber’s energy extraction and storage performance in a common geological condition

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