Flooded mineshaft compressed air energy storage in the Witwatersrand Goldmine Complex – case study of a proposed novel energy storage method

15 December 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


With renewable energy sources representing a rapidly-growing share of the global energy mix, their intermittent nature has led to growing interest in mechanisms of storing energy during periods of high availability, for use during times of high demand. Several different types of compressed-air energy storage have been considered, including constant-volume approaches such as salt dome or artificial vessel storage and newer constant-pressure approaches such as submerged cavern storage. This manuscript proposes a novel approach where abandoned, flooded mineshafts are pressurized with air, displacing water downward in the shaft but upward in other hydraulically-linked shafts in the same geological complex. This approach is something of a hybrid between compressed-air storage and pumped storage and is thermodynamically distinct in that neither pressure nor volume are constant. An application to the abandoned goldmine shafts of South Africa’s Witwatersrand geological complex is considered, and thermodynamic analysis indicates that this approach offers around 10% greater energy density than conventional compressed air energy storage, and that a single mineshaft could have isothermal storage capacity exceeding 1GWh, with some operational advantages specific to the Witwatersrand context, meriting further research to design processes.


energy storage
Compressed Air Energy Storage


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.