A seven-partner French consortium has launched a major research and development initiative aimed at building the technological foundations for floating high-voltage direct current electrical connections capable of linking deep-water offshore wind farms to the national grid, with the first commercial applications envisaged from 2040 onwards.

A Consortium Spanning the Full Value Chain

The RHODÉ project, an acronym for Raccordement HVDC Offshore Distant Électrique, brings together Chantiers de l'Atlantique, France Energies Marines, Fondation OPEN-C, GE Vernova, Nexans, RTE, and SuperGrid Institute. The project has received a grant of USD 18.55 million from the French State as part of the France 2030 program, operated by ADEME.

Each partner contributes distinct expertise to the consortium. Chantiers de l'Atlantique brings its experience in the design, construction, system integration, and commissioning of offshore substations, covering both topside and foundation elements.

France Energies Marines contributes 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 across France and holds experience in hosting prototypes at sea, including grid connection infrastructure, maritime safety, and environmental monitoring.

GE Vernova contributes its know-how in the design and construction of AC/DC substations, transformers, gas-insulated substations, and associated control and protection systems.

Nexans provides expertise in the design, testing, qualification, manufacturing, and installation of dynamic HVDC subsea cable systems. RTE, which develops, maintains, and operates France's public electricity transmission network, is also a consortium member.

SuperGrid Institute rounds out the group with expertise in SF6-free insulation solutions, simulation of dielectric stresses in HVDC metal-enclosed substations, and the performance of specific dielectric and power tests on relevant equipment.

The Technical Challenge of Deep-Water Wind

The project is a direct response to the anticipated expansion of offshore wind development into waters exceeding 100 meters in depth and locations several tens of kilometers from the coastline.

At such depths and distances, conventional fixed-bottom substation solutions are expected to reach their technical and economic limits. Floating electrical substations are being positioned as an alternative or complementary solution to allow offshore wind development to continue while managing costs, environmental impacts, and coexistence with other maritime uses.

RHODÉ is described by its partners as the missing link between research projects already underway and the industrial realization phase of the first floating HVDC connections operating at 320 kilovolts or 525 kilovolts. The project will deliver two floating substation designs rated at those respective voltage levels.

What the Project Will Develop and Test

The program targets the key technological building blocks required to make a high-power floating HVDC connection viable. These include a transformer, a gas-insulated substation, an offshore AC/DC converter station, and a dynamic HVDC cable.

The work is organized into several packages that cover the entire value chain, beginning with the definition of use cases and technical specifications and extending through to initial offshore trials. The R&D work combines advanced design and numerical modeling of the floating HVDC substation and its components with laboratory test campaigns.

The program also encompasses environmental impact studies examining the floating substation within the marine environment, hydrodynamic basin tests conducted on reduced-scale models, and unit tests at sea intended to validate the operational feasibility of installation, maintenance, and decommissioning concepts.

Two Strategic Objectives

The consortium has articulated two overarching goals for the project. The first is to develop and validate the technological building blocks of a high-voltage floating electrical connection operating in HVDC at either 320 kV or 525 kV.

The second is to help establish a French industrial sector specializing in high-power offshore floating electrical connections that is competitive in both the domestic French market and in export markets.

The partners state that the project is intended to support France's broader offshore wind ambitions while also contributing to international efforts in the sector. The industrial and technological groundwork laid by RHODÉ is aimed at enabling the first commercial-scale floating HVDC connections to be realized from 2040 onwards.

Funding and Institutional Backing

The USD 18.55 million grant awarded to the RHODÉ project is channeled through the France 2030 investment plan, with ADEME serving as the operator for this funding stream.

The involvement of RTE, as the operator of France's public electricity transmission network, underscores the project's alignment with national grid development priorities.

The participation of Fondation OPEN-C, which administers dedicated offshore test infrastructure, provides the consortium with access to the physical facilities necessary to move from laboratory validation to real-world sea trials.

Powering Smarter Decisions Across France's Energy Landscape

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