Stilow converter system

A converter is a technical installation that converts direct current (DC) into alternating current (AC) or vice versa. Converters are used wherever electricity is transported using high voltage direct current (HVDC) technology. DC technology makes it possible to controllably transmit large volumes of electricity across large distances while minimising energy losses in the process. For technical reasons, transmission takes place between two defined grid connection points. The line route does not branch off at any given point, nor is electricity injected or discharged along the line.

As part of the Ostwind 4 project, an onshore converter is now planned at the Stilow site in the German municipality of Brünzow to convert the direct current that is generated offshore into alternating current onshore. In a neighbouring substation at the same site, the converted alternating current will then be injected into the transmission grid.

The converter at a glance

The planned converter is to be installed on the Stilow substation site (located in the municipality of Brünzow, in the Vorpommern-Greifswald district). The expansion area for the converter will cover around 6 hectares, expanding the area beyond the existing Stilow substation, erected for Ostwind 3, to the west of the existing site. As such, the total area of the site will increase from what was originally 10.5 hectares to around 16 hectares following the planned installation of the converter.

Technical equipment such as switchgear bays, transformers and disconnectors will be visible from the outside of the converter. The actual system responsible for converting direct current into alternating current is set to be housed in two inner halls, intended to protect the system against adverse weather conditions, abate the generated noise as well as to shield off electrical and magnetic fields.

Additionally, the system includes six single-pole transformers, which are each equipped with noise hoods.

The Stilow site

This site had already been chosen in the scope of the previous Ostwind 3 project following an extensive assessment of various alternative sites. The explicit goal of the search was to find a site that could be expanded to a total area of 16 hectares to accommodate future projects, such as Ostwind 4.

In all, eleven alternative large-scale sites were considered for the substation.

Stilow was eventually preferred for several reasons:

• The Stilow site offers the closest overhead line connection to the existing transmission grid.
• Compared to the alternative sites taken into consideration, Stilow has the lowest adverse effects on humans and the environment.
• There are sufficient surrounding expansion areas so that no new sites need to be created, existing infrastructure can be bundled and the use of additional space is minimised.
• The access roads that were already created for Ostwind 3 can be used following only minor adjustments to the existing transport routes.
• Synergies can also be established with the route for Ostwind 3. The cable conduits for the Ostwind 4 cable system, for instance, were already laid along the onshore route during the Ostwind 3 project.

The permit procedure

The approval of the planned converter in Stilow is now subject to an ongoing planning approval procedure. The application for planning approval for the Ostwind 4 onshore cable route, and with it approval for the planned Stilow converter and tap point, was submitted to the competent German Ministry for Economy, Infrastructure, Tourism and Labour of Mecklenburg-Western Pomerania in February of 2026.