Superconducting Cables for a Sustainable Energy Transition

The EU project SCARLET (acronym for "Superconducting cables for sustainable energy transition") unites 15 partners from 7 countries around the goal of designing and industrially manufacturing superconducting cables in kilometric lengths. “The cables should be available to purchase from 2027 onwards," says RIFS researcher Adela Marian. The promise of superconducting cables lies in their high efficiency, compact size, and reduced environmental impact, enabling them to overcome the disadvantages of overhead lines and conventional cables.

Until now, there have been no incentives for grid operators to use superconductors, explains Marian: “Grid operators have used copper cables for decades now. And because the entire infrastructure is already in place, they remain the more affordable solution – or at least with respect to the near-term costs. But around 16 percent of the power transmitted via these systems in Europe is lost due to electrical resistance. Grid operators have nevertheless shied away from investing in superconductors. And this despite the fact that they have long since proven themselves in practice – for example in the Ampacity project in Essen, where the technology ran smoothly over the entire test period." In light of this, the SCARLET team is working to achieve both technological gains and to develop policy recommendations that will facilitate the deployment of superconducting cables.

Lossless transmission onshore and offshore

The distinct advantage of superconducting cables is their small size, which makes them ideal for use in substations in densely built areas, for example. But they could also be used cost-effectively to transport electricity over long distances, for example from offshore wind farms to the coast. The cable that the SCARLET researchers want to use there is a so-called high-temperature superconductor. These materials, which are mostly ceramics-based, behave like superconductors at temperatures below minus 183 degrees Celsius.

But superconductors could also be used on land, explains Adela Marian: "We are planning tests with high-temperature superconducting cables that will deliver electricity from the coast and other remote locations to the grid. In addition to their compact footprint, another advantage here is that the cables have a much smaller impact on the landscape than overland cables."

Combined pipeline for electricity and hydrogen

Another cable system that physicist Adela Marian is working on with the SCARLET team represents a milestone in the energy transition. The system will combine a superconducting cable made of magnesium diboride wires with a pipeline for the transportation of liquid hydrogen produced using renewable energies, which will serve as a coolant for the cable. When it is rolled out, the system could be used to supply any facility that requires both electricity and hydrogen - for example, harbours where ships are refuelled with hydrogen, or industrial plants such as steel and cement works.

For Adela Marian, this futuristic concept marks a return to her beginnings in superconductivity research: When she joined the Research Institute for Sustainability (then known as the Institute for Advanced Sustainability Studies, IASS) in 2011, she worked alongside IASS Director and Nobel laureate and physicist Carlo Rubbia on the magnesium diboride superconductor. This relatively inexpensive compound becomes superconducting at minus 234 degrees Celsius. Hydrogen liquefies at minus 252.5 degrees, making it a suitable coolant for this application. Superconductors and hydrogen, the technology of the future and the energy carrier of the future: Marian and her colleagues aim to bring the two together.

“A boost for the energy transition”

Adela Marian on the state of the art and challenges in grid expansion

The expansion of renewable energies in Germany is accelerating once again and electricity grids will need to keep pace with this development. What can superconductors contribute?

Superconducting cables have no losses due to electrical resistance, so using them leads to more efficiently transmitted power and a higher-capacity network. Their use would facilitate the expansion of renewables. Crucially, their transmission corridor is more than 10 times narrower than that of conventional underground cables (this is akin to comparing a footpath to a six-lane highway). This smaller footprint can help to build public acceptance, as it is their impact on landscapes that often gives rise to protest against energy transition projects. Superconductivity would give the energy transition a boost.

The Electricity Network Development Plan 2023-2037/2045 envisages a climate-neutral energy system. Why can’t this be achieved using conventional technologies such as underground or overhead copper cables?

To achieve its targets for integrating renewable energy, Germany will need 25,723 kilometres of new lines, with an investment volume of more than 300 billion euros by 2045. Conventional cables are copper-based and this massive expansion will be susceptible to supply bottlenecks and shortages. Superconducting cables can complement conventional technologies, providing huge savings in copper usage, as their production requires seven times less copper. This would avoid conflicts around the availability of raw materials for the energy transition and secure supply chain resilience.

Superconducting technology has proven itself in pilot and demonstration projects. What can politicians do now to promote investment in superconductors?

So far, superconducting cables have been successfully operated in the electricity grid for several years, for example as part of the AmpaCity project in Essen. Further pilot and demonstration projects of this kind are needed to convince grid operators – who are often risk-adverse – of the benefits of innovative technologies and allow them to gain hands-on operational experience. This can be enabled through innovation-friendly regulations that financially incentivise the initial acquisition of new technologies such as this. Moreover, it should be politically mandated that the superconducting option always be included in feasibility studies and tenders of new transmission projects.

This article was first published on 6 September 2024 in the Tagesspiegel supplement "Wissenschaft im Zentrum. Neues aus Forschung & Lehre in Brandenburg“.