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Oct 6, 2021 9:00 AM

Re-using depleted mines for energy storage: thyssenkrupp Uhde South Africa wins study and signs an agreement with Pumped Hydro Storage Sweden AB

  • Storage of renewable energy at low cost with high efficiency

  • Pre-feasibility study for a project together with Wismut GmbH

thyssenkrupp Uhde Africa together with Wismut GmbH has been appointed to execute a pre-feasibility for study for a “Renewable Underground Pumped Hydroelectric Energy Storage” (RUPHES) project on a specific site with a South African mining company. thyssenkrupp Uhde South Africa is collaborating with international specialist companies to facilitate mine repurposing.  Already last year thyssenkrupp Uhde had signed a cooperation agreement with mining rehabilitation specialist Wismut GmbH in Germany.  The international cooperation was now recently expanded by an agreement with Pumped Hydro Storage Sweden AB. 

With the increase in renewable energy generation there is an increased need for energy storage.  Renewable Underground Pumped Hydroelectric Energy Storage (RUPHES) in repurposed mines – coupled with solar and wind power – can reliably provide green energy when it is needed.  Repurposing of depleted gold mines for RUPHES enables short construction schedules and significantly reduced costs. The main reason: Gold mining has already created the underground water storage reservoirs that commonly are the mostly costly components of pumped hydro plants. They just have to be adapted to their new purpose.

This is exactly what Pumped Hydro Storage Sweden does. It is part of the company Sustainable Energy Solutions and is currently developing a 2 MW / 8 MWh underground pumped energy storage project in an abandoned iron mine in Aland, Finland.  The project has the support of both the European Commission and Swedish Energy Agency, and they are looking to commission the project in December 2023.  This project demonstrates the reduced construction schedules and costs associated with utilizing mine tunnels for pumped energy storage as did a similar project at the Kidston gold mine in Australia.

Well-proven, cost-competitive solution serving a major trend in Africa

As probably the most mature energy storage technology currently available, pumped hydro accounts for 97% of the global storage capacity.  Exceptionally high hydraulic heads and stable hard rock geology render ultra-deep gold mines ideal for implementing the concept, and for producing internationally cost-competitive, reliable green electricity as well as green hydrogen and green ammonia. Just for comparison: In June 2021, a South African gold mining company announced that they are able to produce electricity from solar power at USD 1.1c/kWh.  This pricing is nearly on par with the best international solar pricing USD 1.04c/kWh, achieved in competitive bidding in Saudi Arabia.  The fact that South Africa has world-class solar and wind resources is gaining traction in both government and industry, and the fact that it is cheaper to provide electricity from South African renewables than it is to provide power by importing foreign gas.  

About thyssenkrupp Uhde:

thyssenkrupp Uhde combines unique technological expertise and decades of global experience in the engineering, procurement, construction and service of chemical plants. We develop innovative processes and products for a more sustainable future and thus contribute to the long-term success of our customers in almost all areas of the chemical industry. Our portfolio includes leading technologies for the production of basic chemicals, fertilizers and polymers as well as complete value-chains for green hydrogen and sustainable chemicals.

 About Wismut GmbH:

Wismut GmbH was established in 1991 to remediate uranium-mining sites in southeast Germany left behind by the SDAG Wismut as world’s largest single uranium producer during the cold war. Fully owned by the Federal Government of Germany Wismut GmbH to date has spent close to €7bn on one of the world’s largest and most complex remediation programmes. As a leader in the field with projects across the globe, Wismut increasingly focuses on developing innovative and sustainable solutions to mine closure and post-closure development and remediation. For more information visit:




thyssenkrupp Uhde
Christian Dill
Communications Manager 
Phone: +49 231 547 3334 


Wismut GmbH
Frank Wolf
Head of Public Relations
Phone: +49 (0) 371 8120-150