Major Order for Fluence: Vattenfall Awards 4-Hour Large-Scale Storage System at Brunsbüttel Nuclear Plant Site – Commissioning Planned for 2028

Brunsbüttel – Vattenfall has contracted US battery storage provider Fluence to build a turnkey large-scale battery storage system with 254 MW of power capacity and more than 1,000 MWh of storage capacity in Brunsbüttel. Designed for a storage duration of around four hours, the system is scheduled to enter operation at the end of 2028.

As large-scale battery storage is expanded, the market for storage technology, system integration and long-term operating services is growing. Fluence reports rising order backlogs for storage systems and services. At the same time, different applications and storage durations are gaining importance: alongside shifting larger volumes of electricity over time, stabilising the power system plays an important role.

Fluence to Supply Battery Storage with More Than 1,000 MWh of Storage Capacity

Vattenfall's storage system is being built on the site of the former Brunsbüttel nuclear power plant in Schleswig-Holstein, which is currently being dismantled. The energy group took the final investment decision in September 2026. Construction is scheduled to begin in 2027.

Fluence will handle planning, procurement, construction and commissioning, as well as long-term services. The project will use the Gridstack Pro 5000 platform, comprising battery systems, power electronics and an energy management system. A new substation is planned to provide the connection to 50Hertz's 380-kV transmission grid.

At the end of 2025, Vattenfall had still planned a storage capacity of 700 MWh for the project at a power capacity of 254 MW. With the storage capacity now increased to more than 1,000 MWh, the calculated storage duration rises from just under three to around four hours. According to the company, Vattenfall's own battery storage portfolio totals 270 MW, of which 150 MW is in operation and 120 MW under construction. With Brunsbüttel, it would almost double to around 524 MW.

Fluence Expands Order Backlog for Battery Storage and Services

Fluence's global order backlog for battery storage systems stood at 12.6 GW as of June 30, 2026, compared with 8.2 GW a year earlier. This represents an increase of around 54 percent for the US provider. The backlog for long-term battery storage services rose from 4.9 GW to 7.9 GW over the same period, an increase of around 61 percent. The power capacity already under service increased from 5.5 GW to 6.3 GW.

Despite the growing order backlog, Fluence is under earnings pressure. In the third quarter of its 2026 fiscal year, the company posted a net loss of USD 44.3 million, compared with a profit of USD 6.9 million in the same quarter a year earlier, and lowered its full-year guidance.

According to the companies, Vattenfall and Fluence are now working together on eight battery storage projects in three European countries. Fluence says it has completed more than 20 battery storage projects in Germany.

From Home Storage to Long-Duration Storage: Storage Systems with Different Roles in the Power System

Depending on technology, storage duration and application, energy storage systems serve different functions. Smaller home storage systems are used primarily to store self-generated solar power and increase self-consumption. With dynamic electricity tariffs and appropriate control, they also offer additional options for shifting power purchases to periods of low prices.

For large-scale battery storage systems operated on a market basis, by contrast, the focus is on the commercial use of their flexibility. This includes power trading and the provision of balancing power to stabilise grid frequency. Vattenfall already markets large-scale battery storage systems of other operators on the wholesale power market and on balancing power markets. According to the energy group, the planned system in Brunsbüttel is intended to contribute to the integration of renewable energy and to power system stability. With a storage duration of around four hours, the facility can shift larger volumes of electricity over time.

A third application is battery storage held specifically to safeguard grid operation. One example is TransnetBW's grid booster in Kupferzell, with 250 MW of power capacity and 250 MWh of storage capacity. Fluence is also supplying the battery technology there. The facility is currently under construction. According to the Grid Development Plan, commissioning is planned for 2027. Unlike large-scale storage systems operated on a market basis, the grid booster is intended exclusively for grid operation tasks. Use for power trading is ruled out under the approval granted by the Federal Network Agency. The grid booster allows existing power lines to be used more intensively: in the event of a line outage, it feeds in power within seconds and offsets impending overloads for up to one hour.

A fourth group comprises storage systems for longer periods. These include redox flow batteries, in which power and storage capacity can be sized largely independently of each other, and compressed-air energy storage, which can store energy for several hours. For storage over days, weeks or even seasonal periods, hydrogen storage in particular, as well as certain thermal storage technologies, are options.

Source: IWR Online, 16 Oct 2026