Iron flow battery firm ESS Inc to build 50MW/500MWh system for LEAG in Germany

June 15, 2023
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Iron-saltwater flow battery company ESS Inc looks set to deploy by far its largest project to-date, a 50MW/500MWh system at a renewables hub from German energy firm LEAG, with potential for more.

The NYSE-listed firm is partnering with LEAG on a new renewables hub located at the site of the Boxberg Power Plant, a 2.5GW lignite-burning facility.

A ten-hour duration system using ESS Inc’s (full name ESS Tech Inc) iron and saltwater electrolyte long-duration energy storage (LDES) technology will be commissioned at the site in 2027. The firm offers durations generally of 6-12 hours.

The system is expected to become a standardised building block in LEAG’s plan to deploy 2-3GWh of energy storage as part of the transformation of its legacy power plants. The process will also involve the deployment of 7-14GW of renewable energy generation and 2GW of green hydrogen production, although the announcement did not say how much was planned for the Boxberg site specifically.

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The project still requires definitive agreements and normal financial close which are anticipated to conclude in the third quarter of this year. LEAG and partners plan to invest €200 million with further support anticipated from additional investors and stakeholders, the announcement, made at Ees Europe today, added.

LEAG and ESS Inc have also joined the Energy Resilience Leadership Group (ERLG), an initiative led by Bill Gates-founded Breakthrough Energy and Siemens Energy, founded at the 2023 Munich Security Conference to enhance Europe’s energy resilience by bringing clean energy tech to scale. LEAG and ESS Inc’s project is one of those that the ERLG is working to accelerate.

“A key requirement for our transformation into Germany’s Green Powerhouse is the deployment of cost-effective Long-Duration Energy Storage. We are energised to demonstrate the value of iron flow battery technology at scale,” said Thorsten Kramer, CEO of LEAG.

“The Energy Resilience Leadership Group and Breakthrough Energy have provided an ideal framework to drive rapid technology development and deployment to meet emissions goals as soon as possible.”

Eric Dresselhuys, CEO of ESS, added: “The deployment of renewables and long-duration energy storage will not only deliver reliable, clean energy to effectively replace the baseload power currently provided by coal, it will deliver economic opportunity and a cleaner environment for Germany.”

If it goes ahead it will be by far the company’s largest deployment to-date. It is fairly early on in its path to large-scale commercialisation, with just under US$1 million in revenue last year and recent projects in the kWh range. It finished 2022 with a production capacity of 800MWh.

LEAG until recently had the largest battery energy storage system (BESS) operational in Germany, the 66MW Big Battery Lausitz.

15 September 2026
Berlin, Germany
Launching September 2026 in Berlin, Energy Storage Summit Germany is a new standalone event dedicated to Germany’s energy storage market. Bringing together investors, developers, policymakers, TSOs, manufacturers and optimisation specialists, the Summit explores the regulatory shifts, revenue models, financing strategies and technology innovations shaping large-scale deployment. With Germany targeting 80% renewables by 2030, it offers a focused platform to connect with the decision-makers driving the Energiewende and the future of utility-scale storage.

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