Numerical modelling of a deep closed-loop geothermal system: evaluating the Eavor-Loop

Joseph J. Kelly; Christopher I. McDermott; Joseph J. Kelly; Christopher I. McDermott

doi:10.3934/geosci.2022011

AIMS Geosciences

2022, Volume 8, Issue 2: 175-212. doi: 10.3934/geosci.2022011

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Research article

Numerical modelling of a deep closed-loop geothermal system: evaluating the Eavor-Loop

School of GeoSciences, The University of Edinburgh, Edinburgh, UK

Received: 29 November 2021 Revised: 18 January 2022 Accepted: 09 February 2022 Published: 23 February 2022

Conventional geothermal energy systems are limited by hydrogeological conditions and environmental risks, and wind/solar solutions have issues with intermittency and the need for grid storage. Deep closed-loop geothermal systems such as the Eavor-Loop are championed as scalable, dispatchable, zero-emission alternative energy technologies, but as yet they are largely untested. A series of numerical models are created using the finite element method to evaluate the power output claims made by Eavor. The models use typical parameter values to create a simplified study domain. The modelling results show that the power output claims are plausible, although the upper range of their predictions would likely require production temperatures in excess of 150 ℃. The technology is shown to be scalable by adding additional lateral wellbore arrays, but this leads to a reduction in efficiency due to thermal interference. It is demonstrated that the presence of groundwater can improve power output at relatively high hydraulic conductivity values. Doubt is cast on the likelihood of finding such values in the deep subsurface. Flow rate is shown to increase power output, but the practicality of using it to follow energy demand is not established. Various limitations of the study are discussed, and suggestions are made for future work which could fill in the remaining knowledge gaps.
- deep closed-loop geothermal,
- heat transport,
- numerical modelling,
- baseload power,
- multilaterals
Citation: Joseph J. Kelly, Christopher I. McDermott. Numerical modelling of a deep closed-loop geothermal system: evaluating the Eavor-Loop[J]. AIMS Geosciences, 2022, 8(2): 175-212. doi: 10.3934/geosci.2022011

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Abstract

Conventional geothermal energy systems are limited by hydrogeological conditions and environmental risks, and wind/solar solutions have issues with intermittency and the need for grid storage. Deep closed-loop geothermal systems such as the Eavor-Loop are championed as scalable, dispatchable, zero-emission alternative energy technologies, but as yet they are largely untested. A series of numerical models are created using the finite element method to evaluate the power output claims made by Eavor. The models use typical parameter values to create a simplified study domain. The modelling results show that the power output claims are plausible, although the upper range of their predictions would likely require production temperatures in excess of 150 ℃. The technology is shown to be scalable by adding additional lateral wellbore arrays, but this leads to a reduction in efficiency due to thermal interference. It is demonstrated that the presence of groundwater can improve power output at relatively high hydraulic conductivity values. Doubt is cast on the likelihood of finding such values in the deep subsurface. Flow rate is shown to increase power output, but the practicality of using it to follow energy demand is not established. Various limitations of the study are discussed, and suggestions are made for future work which could fill in the remaining knowledge gaps.

References

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