• Commissioning planned for end of 2026

• Ten percent of steam at the Brunsbüttel site can be generated with renewable energy thanks to the heat battery

• Breakthrough Energy Catalyst and European Investment Bank support the project

BRUNSBÜTTEL, Germany — January 19, 2026 — Together with guests from politics and business, Covestro and Rondo Energy celebrated the groundbreaking for an innovative heat battery at Covestro's Brunsbüttel site. The Rondo Heat Battery charges when there is a surplus of low-price renewable energy in the grid, stores that energy in bricks, and delivers continuous high-temperature steam for on-site production processes. This offers a sustainable alternative to steam generation using fossil fuels, which are used in continuously running industrial processes, as the available amount of renewable energy at affordable prices fluctuates.

For Schleswig-Holstein, the project represents an important step on the path to climate-neutral transformation of the state. This was emphasized by Tobias Goldschmidt, Minister for Energy Transition, Climate Protection, Environment and Nature of the state, at the groundbreaking ceremony: "The energy transition is Schleswig-Holstein's project of our time. The rapid expansion of renewable energies is a booster for our business location Schleswig-Holstein and makes future-oriented projects like the heat battery possible in the first place. Covestro and Rondo impressively demonstrate how they are driving the energy transition forward with innovative strength, technological know-how, and full confidence. Projects like this contribute significantly to energy sovereignty and to achieving our climate neutrality goals."

The 100 MWh Rondo Heat Battery (RHB) is scheduled to go into operation by the end of 2026. Breakthrough Energy Catalyst and the European Investment Bank (EIB) are supporting the project. The battery will produce ten percent of the required steam at the site, saving up to 13,000 tons of CO2 emissions per year.

"As an innovation company, we are always excited when we can further develop and test promising ideas that can bring us closer to our goals of a circular economy and climate-neutral production," says Dr. Thorsten Dreier, CTO of Covestro. "The heat battery is such an idea: a new technology that enables us to take another step forward on our path to a sustainable future."

The Rondo Heat Battery combines centuries-old materials with modern automation: electrical energy is stored in the form of heat – with the help of bricks that have been used as heat storage in steel mills for centuries. The heat drives an ordinary boiler that delivers emission-free steam. With electricity from renewable energy sources, a constant amount of steam can thus be continuously generated.

“This project shows how two of Europe’s central challenges can be solved together,” said Eric Trusiewicz, CEO of Rondo Energy. “As renewable power expands, it increasingly creates daily periods of abundant, low-cost electricity. At the same time, European industry needs reliable, affordable energy to remain competitive. Together with Covestro, we are demonstrating that clean industrial heat can be both highly reliable and a powerful tool for balancing the grid — while building the energy infrastructure needed to strengthen Europe’s industrial base and energy security.”

For Covestro, steam generation is an essential part of the production process and accounts for a large portion of energy consumption. The steam at the Brunsbüttel site is currently still generated with natural gas. Based on the experience with using the Rondo Heat Battery in Brunsbüttel, Covestro is evaluating whether deployment on a larger scale is possible.