Superconductors beneath the waves: Powering the energy transition
Renewable energies
07 October 2025
6 min
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Powering the future: grids under pressure

Electricity is increasingly seen as the most viable path to reduce greenhouse gases, improve efficiency, and strengthen energy security. In fact, achieving national energy and climate goals requires global electricity use to grow 20% faster over the next decade than it did in the previous one. But today’s grids are struggling to keep up.

Demand is rising rapidly due to electric vehicles, heat pumps, and digital services. At the same time, renewable sources such as wind and solar are expanding at a record pace – but often in remote locations far from consumption centers. This combination creates a single, big challenge: move far more sustainable electricity, much farther, much faster. Meeting it requires not only new renewable plants but also grids that are smarter, stronger and more sustainable.

One promising answer lies beneath the waves: subsea superconducting cables, capable of transporting gigawatts of power with minimal losses, shrinking offshore platforms and simplifying grid infrastructure. 

+20%

electricity use must grow 20% faster in the next decade to meet climate goals

80m km

grids to be added or refurbished by 2040

>80%

share of wind and solar in global
power capacity increase by 2040,
up from <40% today

Connecting renewables at sea

Offshore wind power capacity is growing rapidly in Europe, Asia, and the United States. Yet this potential comes with mounting technical and economic hurdles.

Conventional transmission technologies, based on high-voltage alternating (HVAC) or direct current (HVDC) cables, present significant obstacles. They require large offshore platforms to convert power before it reaches the grid, adding both expense and environmental impact. They are also subject to supply chain bottlenecks, which risk delaying projects just as governments raise their targets for renewable integration.

By 2050, the majority of Europe’s electricity is expected to come from renewables. Meeting that goal means upgrading or modernising around 300,000 km of transmission lines and subsea cables. Tomorrow’s energy networks must not only carry greater volumes of power, but also deliver flexibility to cope with fluctuating renewable generation.

Key components of infrastructure transformation will include offshore wind farms, hydrogen pipelines, and long-distance transmission corridors – and crucially, technologies that allow massive amounts of electricity to flow reliably over long distances.

subsea cable for offshore wind farm

Subsea superconducting cables

Superconducting grids could speed up the integration of large-scale renewables—offshore wind farms and remote solar plants alike—by offering an alternative to conventional technologies for bulk power transmission, with lower environmental costs and quicker deployment.

Most new power assets, especially wind and solar, are built in remote locations, demanding vast new grid infrastructure in previously untouched areas. The most complex and time-consuming element of long-distance transmission is the offshore HVDC conversion platform. Superconducting cables offer two ways to bypass it, carrying several gigawatts of power over distances of 50 km or more.

Option 1: DC high-power transfer at medium voltage

Superconductors can carry very high currents without electrical losses. This makes it possible to transfer large amounts of power at lower voltages, while still maintaining—or even increasing—the capacity of the system. In renewable energy, both wind and solar power naturally produce direct current (DC) at medium voltage during their conversion process. This DC is collected and concentrated into medium-voltage direct current (MVDC) export cables for transmission. The Horizon Europe project SCARLET is focused on developing this approach.

Option 2: AC high-power transfer at medium voltage

Superconductors can also extend the reach of HVAC export cables. Future wind turbines are expected to generate alternating current (AC) power at 132 kV, a voltage suitable for medium-distance transmission. Conventional HVAC cables face a key limitation at this voltage: to reduce energy losses over long distances, they require higher voltages and multiple parallel lines, and their insulation capacitance steadily drains energy along the route.

Superconducting cables, by contrast, can carry much higher currents with less capacitance, which means they can deliver more power efficiently at lower voltages. This solution is now viable thanks to the convergence of three mature technologies:
– Cryogenic pipelines that keep superconductors at the required low temperature
– High-temperature superconducting (HTS) cables, refined over 20 years by Nexans
– LNG-based cooling systems developed by Air Liquide

The benefits of superconducting cables

Beyond technical feasibility, superconducting cables deliver tangible advantages for grids under pressure:

  • Carry far higher currents than copper or aluminium, allowing bulk electricity transmission at lower voltages over long distances
  • Offer an unmatched power density: a single 17 cm cable can deliver 3.2 GW – roughly the output of three nuclear reactors
  • Emit neither heat nor electromagnetic fields, avoiding interference with nearby power, telecom or pipeline systems
  • Are compact and unobtrusive, reducing infrastructure footprint in sensitive marine environments
  • Simplify offshore schemes and shrink conversion platforms by at least 75% by replacing resistive HVDC systems.

 

How will this help electrify the future?

Superconducting technology is emerging as a critical enabler of the energy transition. By combining HTS cables with fault current limiters, grids can achieve unprecedented levels of efficiency, capacity and sustainability. These systems expand network flexibility, simplify offshore connections and ease the integration of renewables at scale.

As global demand rises and climate pressures mount, superconductors offer a compact, modular and resilient alternative to conventional infrastructure. By reducing grid losses and supporting long-distance transmission, they align directly with the goals of electrification and decarbonisation. HTS cables, refined by industry pioneers, such as Nexans, are designed to meet this demand.

Picture of Arnaud Allais

Author

Dr. Arnaud Allais is Chief Technology Officer Machinery, Cryogenic and Superconducting Systems at Nexans. Arnaud is a globally recognized authority in advanced electrical grid technologies and high temperature superconductivity (HTS). With over two decades of experience, he leads innovation and strategic development in advanced superconducting systems that are shaping the future of energy transmission.

Arnaud earned his Ph.D. in Materials Engineering from the School of Mines of Paris, in collaboration with Alcatel, where he focused on modeling Powder-in-Tube Bi2223 superconducting wires. He also holds an engineering degree in Energy and Materials from the School of Engineering in Orléans, France. Throughout his career at Nexans, Arnaud has held several key leadership roles, including: Director of the Nexans Research Center, and R&D Program Director at the SuperGrid Institute – a joint R&D venture with GE, Alstom, EDF, and leading French universities.