Covestro Heat Battery

Executive Overview

The Covestro Heat Battery is a 100 MWh Rondo Heat Battery (RHB) under construction at Covestro's Brunsbüttel chemical site in northern Germany, developed by Rondo Energy in partnership with Covestro. Groundbreaking took place in early 2026, with commissioning targeted for end of 2026. The system is the first Rondo Heat Battery deployment in Europe and the first in the chemical industry, backed by €75 million in financing from Breakthrough Energy Catalyst and the European Investment Bank. The battery charges for 6–8 hours daily from surplus grid renewable electricity — Germany recorded 573 hours of negative electricity prices in 2025, a 25% increase from 2024 — and provides continuous high-temperature steam to the Brunsbüttel site. When operational, it will supply approximately 10% of the site's total steam demand and is expected to reduce Covestro's CO₂ emissions at the site by up to 13,000 metric tonnes per year. Covestro has stated a target of Scope 1 and 2 climate neutrality by 2035 across its 46 production sites worldwide.

How It Works & Differentiation

The Rondo Heat Battery stores surplus electricity as heat in ceramic refractory bricks resistively heated to temperatures exceeding 1,000°C. During discharge, the stored heat produces steam delivered continuously to the site's industrial processes, replacing a portion of the current natural gas-fired boilers. The system integrates directly into the existing steam network using standard industrial automation and digital controls. The charging schedule is aligned with the lowest-cost hours of grid electricity each day, taking advantage of Germany's increasing frequency of negative-price renewable surplus periods. Unlike heat pumps, which are limited by the Carnot cycle to relatively low temperatures, the RHB can supply steam at the pressures and temperatures required by large-scale chemical manufacturing.

Commercialization & Traction

The Brunsbüttel deployment matches the 100 MWh scale of Rondo's Holmes Western California project — the current world-record deployment — making them jointly the largest industrial heat batteries in commercial operation globally. The European Investment Bank's participation provides public-sector validation for the economics of the heat-as-industrial-steam model in the European chemical sector. Covestro has stated it will assess the potential for larger-scale deployment at Brunsbüttel and across its global portfolio based on operational experience. Rondo's concurrent deployments — Heineken Portugal (100 MWh, targeted April 2027) and SCG Thailand (33 MWh, operational November 2025) — demonstrate simultaneous multi-continent commercial roll-out.

Scalability & Strategic Context

The chemical industry is Europe's largest industrial energy consumer, and steam generation accounts for a significant share of that consumption. The Covestro Brunsbüttel project demonstrates that a globally significant chemical producer is willing to commit to heat battery technology under real production-serving conditions. If the system performs as projected, it provides an immediately replicable case for decarbonising steam at Covestro's other sites and for competing chemical producers across Germany and Europe. Germany's Energiewende is creating increasing windows of negative-price renewable surplus that make the RHB's charging economics progressively more attractive, without requiring offtake pricing negotiations or grid stabilisation contracts.