IN Brief:
- Two German projects will combine 147MW of solar generation with 79MW/237MWh of battery storage.
- Salzgitter Flachstahl will purchase the solar output and control operation of the associated batteries.
- The arrangement links short-duration storage directly to the growing electrical demand of lower-carbon steel production.
Zelestra has signed a hybrid power purchase agreement with Salzgitter Flachstahl covering two planned solar-and-storage projects in Germany, combining 147MW of photovoltaic capacity with 79MW/237MWh of battery energy storage.
The projects will be built in Brandenburg and Thuringia, with Zelestra owning and operating both plants. Salzgitter Flachstahl will buy the solar output and control operation of the associated batteries, giving the steelmaker direct influence over when stored electricity is dispatched against its industrial demand.
Zelestra expects the two solar plants to supply around 158GWh of electricity a year. The batteries will be charged exclusively from surplus solar generation, creating a hybrid arrangement in which generation and storage are commercially linked rather than contracted as separate assets.
The agreement is the first hybrid power purchase agreement in Germany for both companies and the first time Salzgitter will operate battery storage as part of its electricity procurement strategy. For an energy-intensive steel producer, that adds a controllable layer between variable renewable generation and a production process whose electrical demand will increase as the company shifts towards lower-carbon steelmaking.
Salzgitter is developing its SALCOS programme around direct reduction, electric arc furnaces, and hydrogen production. The first transformation stage includes a direct reduction plant, an electric arc furnace, and 100MW of electrolysis capacity, with the group targeting a reduction of more than 95% in carbon dioxide emissions from steel production as the conversion progresses.
That change moves a larger share of the production system towards electricity and hydrogen, increasing both the volume and the timing sensitivity of power demand. A conventional renewable PPA can provide long-term energy volumes and price visibility, but it does not remove the hourly mismatch between solar production and an industrial load that continues beyond daylight hours.
The 79MW/237MWh storage component gives Salzgitter around three hours of nominal discharge at full rated power. Actual operation will be shaped by state-of-charge limits, round-trip efficiency, the shared connection arrangement, and the control strategy agreed with Zelestra, but the configuration is suited to shifting part of the solar output into later demand periods.
Storage can also reduce the need to treat every fluctuation in renewable production as an immediate market exposure. Where the battery has available capacity, surplus solar generation can be retained rather than exported at the prevailing price, then released when the industrial load is higher. That does not provide seasonal firm power, but it can smooth intraday variation and improve the match between generation and consumption.
The commercial structure makes control rights particularly important. Zelestra will own the assets, while Salzgitter will direct battery operation, so metering, dispatch instructions, operating limits, and the allocation of losses will have to be integrated into the PPA. The battery therefore becomes part of the procurement architecture rather than a standalone merchant storage project.
Zelestra has been expanding its German portfolio across solar and storage, including the commissioning of its first operating German solar project at Klevenow. The 27.5MWdc Klevenow plant marked the company’s first operational solar asset in the country and sits within a German development pipeline that Zelestra says exceeds 2GW.
The Salzgitter projects add a different commercial model to that pipeline. Instead of selling solar generation and battery services independently, the developer is packaging both technologies around the load profile of a single industrial customer, while leaving the off-taker with direct control over storage dispatch.
That also changes the way project performance will be judged. Annual solar yield remains important, but battery availability, degradation, round-trip efficiency, response to Salzgitter’s dispatch instructions, and the ability to maintain the agreed operating window will influence the value delivered over the contract term. Long-term service strategy and augmentation planning will therefore sit alongside module performance and plant availability.
That model will still have to operate within the technical limits of the grid connection and battery system. Transformer ratings, inverter capability, protection settings, metering boundaries, and plant controls will determine how quickly the batteries can respond and how much solar output can be shifted without breaching the connection agreement.
For Salzgitter, the arrangement places short-duration flexibility next to a growing requirement for renewable electricity. For Zelestra, it turns two new German solar developments into dispatchable hybrid assets whose value will depend as much on control integration and industrial load matching as on the annual megawatt-hours generated.
