French Consortium Launches €16M RHODÉ Project to Develop Floating Offshore Substations for Deep-Water Wind

A consortium of French companies has launched the RHODÉ research and development project to develop and validate floating offshore substation concepts for wind farms in water depths exceeding 100 metres, supported by a €16 million grant from the French state under the France 2030 programme operated by ADEME. The project will deliver two floating substation designs rated at 320 kV and 525 kV and is expected to take seven to eight years to complete, covering the full value chain from technical specification through to offshore trials.

 

Strategic Significance of Floating Substations

 

Floating offshore substations are a critical enabling technology for the next generation of deep-water offshore wind, where conventional bottom-fixed substations on monopile foundations are not technically viable. As offshore wind development extends into deeper waters in the Atlantic, Mediterranean, and other high-wind deep-water regions, the absence of commercially proven floating substation technology is one of the most significant gaps in the supply chain for floating wind. The RHODÉ project directly addresses this gap by bringing together the core technology domains required for floating high-voltage direct current substations, including transformer technology, gas-insulated substations, AC/DC converter stations, and dynamic HVDC cables, and validating them through a structured programme of laboratory testing, hydrodynamic basin trials, and at-sea validation.

 

Consortium Composition and Expertise

 

The RHODÉ project assembles a consortium with complementary capabilities across the full floating substation value chain. Chantiers de l'Atlantique contributes expertise in the design, construction, integration, and commissioning of substation topsides and foundations, drawing on its established role in large-scale offshore fabrication. France Energies Marines provides expertise in mooring design, digital twins, decision-support tools for offshore substation operations, and environmental impact assessment. Fondation OPEN-C manages five offshore test sites in France, providing access to real-world marine environments for at-sea validation activities. GE Vernova brings knowledge of AC/DC substation design, transformers, gas-insulated substations, and associated control and protection systems. Nexans contributes design, testing, qualification, manufacturing, and installation expertise for dynamic HVDC subsea cable systems, which are a critical and technically challenging component of floating substation infrastructure. RTE provides grid development, maintenance, and operation expertise from the French electricity transmission network. SuperGrid Institute contributes SF6-free insulation technology, dielectric stress simulation, and HVDC metal-enclosed substation design expertise, reflecting the industry trend away from sulphur hexafluoride-based insulation systems.

 

Technical Scope and Programme Structure

 

The project is organised into multiple work packages covering the entire value chain from use case definition and technical specification through to offshore trials. Advanced design work and numerical modelling of the floating HVDC substation and its components will be combined with laboratory tests, hydrodynamic basin trials on scale models, environmental impact studies, and at-sea tests to validate the feasibility of installation, maintenance, and decommissioning concepts. The dual-voltage delivery, with designs at both 320 kV and 525 kV, ensures that the programme addresses the range of voltage levels currently under consideration for large-scale floating offshore wind projects, providing commercial flexibility for developers evaluating different project configurations.

 

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France 2030 Grant and Policy Context

 

The €16 million France 2030 grant reflects the French government's recognition of floating offshore substations as a strategic technology for the country's deep-water offshore wind ambitions. France has significant floating wind resources off its Atlantic, Mediterranean, and Channel coastlines, and the development of domestically anchored technology capability in floating substations supports both the country's energy transition objectives and its industrial strategy for the offshore energy supply chain. The involvement of major French industrial groups alongside specialised research institutions reflects a coordinated approach to technology development that seeks to retain intellectual property and manufacturing capability within the domestic supply chain.

 

Implications for the Floating Wind Market

 

Floating offshore wind has been identified globally as one of the most important growth vectors for renewable energy over the second half of the decade, with projects in development across Europe, Asia-Pacific, and the Americas. However, the commercial scaling of floating wind depends on the resolution of several critical technology challenges, and floating substations are among the most significant. A cost-effective, reliable, and maintainable floating substation capable of operating at the voltage levels required for large-scale power export is a prerequisite for floating wind farms at the gigawatt scale. The RHODÉ project, by targeting both 320 kV and 525 kV designs and by covering the full supply chain from component development to offshore validation, provides one of the most comprehensive research programmes to date on this critical enabling technology.

 

Outlook for the RHODÉ Programme

 

The seven to eight year programme timeline reflects the technical complexity of the challenge and the rigour of the validation pathway required before floating substations can be deployed commercially. The structured progression from design and modelling through laboratory testing, basin trials, and at-sea validation ensures that the resulting designs are grounded in operational evidence rather than purely theoretical performance assumptions. For the broader floating wind industry, successful completion of the RHODÉ programme would substantially advance the technical readiness of floating substations and provide a validated design basis that developers, grid operators, and financiers can use to underwrite the next generation of deep-water offshore wind projects. The French consortium model also provides a potential template for similar collaborative technology development programmes in other countries with deep-water offshore wind ambitions.