RHODÉ Consortium Launches Floating HVDC R&D Project
A consortium of seven French and international organisations has launched RHODÉ (Raccordement HVDC Offshore Distant Électrique), a collaborative research and development project dedicated to developing future high-voltage direct current (HVDC) floating electrical connections for large-scale offshore wind farms located in deep waters and far from shore.
Announced in Nantes on 19 May 2026, the consortium brings together Chantiers de l'Atlantique, France Energies Marines, Fondation OPEN-C, GE Vernova, Nexans, RTE and SuperGrid Institute. The project has been awarded a €16 million grant from the French State as part of the France 2030 programme operated by ADEME.
RHODÉ aims to prepare the way for the first 320 kV and 525 kV floating HVDC connections in France, with deployment anticipated from 2040 onwards. The partners will deliver two floating substation designs at these two voltage levels, targeting offshore wind sites at depths greater than 100 metres and several tens of kilometres from the coastline. Under these conditions, traditional fixed-bottom substation solutions may reach their technical and economic limits, with floating substations emerging as an alternative or complementary approach to enable continued offshore wind development.
The project pursues two strategic objectives. The first is to develop and validate the key technological building blocks of a high-voltage floating HVDC electrical connection, including the transformer, gas-insulated substation, offshore AC/DC converter station and dynamic HVDC cable. The second is to support the emergence of a French industrial sector specialising in high-power offshore floating electrical connections, competitive in both domestic and export markets.
RHODÉ is organised into several work packages covering the full value chain, from defining use cases and technical specifications through to the first offshore trials. Activities include advanced design and numerical modelling of the floating HVDC substation and its components, laboratory test campaigns, environmental impact studies on the floating substation in the marine environment, hydrodynamic basin tests on reduced-scale models, and at-sea unit tests to validate installation, maintenance and decommissioning concepts.
Each partner contributes complementary expertise. Chantiers de l'Atlantique covers the design, construction, integration and commissioning of offshore substations, including topside and foundation. France Energies Marines focuses on mooring design, digital twins, decision-support tools for offshore substation operation and environmental impact assessment. Fondation OPEN-C manages five offshore test sites in France and brings expertise in hosting prototypes at sea, including grid connection, operations, maritime safety and environmental monitoring.
GE Vernova contributes 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 leads on the development, maintenance and operation of the public electricity transmission network. SuperGrid Institute focuses on SF6-free insulation solutions, the simulation of dielectric stresses associated with HVDC metal-enclosed substations and their interfaces with floating substation components, and dielectric and power testing of the equipment.
