SCARLET — Superconducting cables for Europe’s clean energy future

Nexans joined a 15-partner European consortium to bring High-Temperature Superconducting cable systems to industrial scale, enabling gigawatt transmission with near-zero losses.

Bridging demonstration and industrial readiness for superconducting grids

Europe’s energy transition demands a fundamental rethink of how electricity is moved across the continent. As renewable generation grows and power flows become more complex, conventional cables are reaching their physical and economic limits.

Funded under the European Union’s Horizon Europe programme, SCARLET (“Superconducting Cables for Sustainable Energy Transition”) is a flagship research and industrialisation initiative. It brings together 15 partners across 7 countries with a shared ambition: to design, manufacture, and validate superconducting cable systems at the gigawatt scale, ready for commercial deployment.

The project targets a paradigm shift in power transmission, moving from High-Voltage Direct Current (HVDC) at very high voltage to Medium-Voltage Direct Current (MVDC) superconducting cables that can carry equivalent power levels in a far smaller physical footprint. A single 17 cm-diameter HTS cable can transmit up to 3.2 GW, a feat that conventional cables cannot match in constrained corridors.

SCARLET addresses the full system lifecycle, from conductor manufacturing and cryogenic engineering to type testing, system protection, and techno-economic assessment. By the project’s conclusion, both onshore and offshore HTS cable systems will have reached the final qualification step before commercial installation.

The initiative also responds to a critical strategic need: as offshore wind capacity accelerates and urban grids face saturation, superconducting cables offer a technologically and economically viable path that conventional HVDC solutions cannot always provide.

The energy transition is not just a generation challenge, it is a grid challenge. Transmitting ever-larger volumes of renewable power raises technical, economic, and spatial problems that conventional solutions are not equipped to solve.

1. Infrastructure corridor saturation
   Urban and coastal corridors are congested. Conventional HVAC and HVDC cables require large right-of-way corridors and significant land use, making grid reinforcement in dense areas increasingly difficult and costly.
2. The cost of offshore converter stations
   High-Voltage DC cables for offshore wind export require large, expensive converter platforms offshore and on land. For remote or deep-water farms, this infrastructure alone can represent a decisive fraction of total project cost.
3. Transmission losses at scale
   Conventional cables dissipate electrical energy as heat over long distances. As transmission distances grow and volumes increase, resistive losses become a measurable drag on system efficiency and carbon performance.
4. Scalability beyond demonstration
   Superconducting technology has been demonstrated in pilot projects. The critical gap is industrial manufacturing at kilometre scale and multi-GW capacity, the step SCARLET is specifically designed to close.
5. Absence of standards and type tests
   No established type test procedures exist for DC superconducting cables or LH₂ cryogenic systems. Without certified qualification pathways, commercial procurement and risk underwriting is effectively blocked.
6. Techno-economic uncertainty
   Grid operators and project developers lack validated data to compare superconducting solutions against conventional alternatives at system level. SCARLET’s assessments are designed to fill this critical gap.

Nexans is not a peripheral contributor to SCARLET, it is one of its central technical pillars. As the only participant combining over three decades of HTS manufacturing experience with the industrial capacity to produce kilometre-length superconducting cables, Nexans was a natural lead for the project’s most technically demanding workstreams.

The company’s role spans the full cable system lifecycle: from the electromagnetic and thermal design of the HTS conductor, through cryogenic envelope engineering for both onshore and offshore environments, to type testing and the development of new accessories enabling distributed cooling along extended cable routes. Nexans also provides the cryogenic envelopes, the vacuum-insulated jacketing that maintains the cryogenic environment, for the MgB₂ cable developed by other consortium partners.

Beyond physical deliverables, Nexans is actively shaping the regulatory and standards landscape, submitting type test recommendations for DC superconducting cables and contributing to the certification framework for LH₂ cryogenic systems, without which commercial deployment would remain blocked.