Superconducting cables for sustainable energy transition

Project Information

SCARLET

Grant agreement ID: 101075602

DOI

10.3030/101075602

EC signature date 23 August 2022

Start date 1 September 2022

End date 28 February 2027

Funded under

• Climate, Energy and Mobility

Total cost

€ 19 602 668,75

EU contribution

€ 14 999 959,75

Coordinated by

SINTEF ENERGI AS
Norway

Periodic Reporting for period 2 - SCARLET (Superconducting cables for sustainable energy transition)

Reporting period: 2024-03-01 to 2025-08-31

Summary of the context and overall objectives of the project

Superconducting wires have reached performance levels suitable for high-current cables, and research on superconducting cables, including technology validation, has laid the ground for final development steps of the technology. At the same time, an increasing number of prospective renewable energy generation sites are in remote areas with the need of high-power transmission to existing electricity grids at low cost.
SCARLET takes the important step of developing superconducting cables, utilizing their benefits by operation under DC conditions, at high currents and medium voltages, perfectly suited for transmission of electric energy from many renewable energy generation sites. A key feature is the medium-voltage operation, enabled by the high-current capability of superconductors, which eliminates costly high-voltage converter stations, thereby allowing for significant overall cost reductions. Additionally, the energy losses, the footprint, and the environmental impact of the cables are much lower than in their conventional counterparts. The SCARLET superconducting cables will be industrially manufactured in processes prepared for multi-kilometre lengths, and will be demonstrated, including undergoing cable type tests.

The exploitation will start during the project to raise awareness of the benefits of superconducting cable systems among industrial customers, while also preparing the ground for a standardisation framework. The market penetration will be driven by cost reductions (offshore applications), environmental protection in pristine areas (onshore), and synergies between electricity and LH2 transport (new application area).

The technical report has been updated after comments from The Commission

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

A cross-technology identification of relevant use cases to be studied and evaluated throughout the project has been developed.

Three potential cable structures have been identified for HTS MVDC applications and will be studied further in simulations to determine their benefits in a complete onshore or offshore system. These structures could be used in 1 or 2 GW applications at voltage levels of 50 and 100 kVDC, respectively.

Several designs of MgB2 cable system in liquid H2 have been proposed and investigated. It includes the cable, the termination and electrical joint. The study also includes the conception of different test facilities required for the development processes such as measurements of critical current of wires and cable conductors and the characterization of the voltage breakdown of the cable insulation in LH2. Extensive analysis of voltage breakdown and of the MgB2 properties have been started clarifying the cabling and operational specifications. Cryogenic envelopes have been proposed for the different uses envisioned. A concept of re-cooling machine for LH2 has been proposed and different solutions for circulation pump are under discussion. These works are carried out while considering the safety rules for the use of liquid H2.

Setup of a realistic electrical system and protection options into a full electrical model of a long MVDC connection with the various SC cables technologies. Simulation of a set of fault scenarios to size the protection devices and assess the response of the SC cable. Start of the RSFCL design with the specification and selection of one HTS tape supplier and the design of the cryogenic 50 kVdc bushings.

Our first thermal and hydraulic studies show that the cable systems considered can be cooled on one side with one cooling station for lengths of 20 to nearly 40 km, with the distance depending strongly on the sea depth and the choice of cable cryostat.

Elpipes, an alternative to SC cables and traditional power transfer technologies, based on hollow conductors with a large cross section to reduce losses, have been studied. A preliminary conclusion is that the proposed technology faces many practical challenges, making it unfeasible.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

A small cross-section MgB2 cable with a conductor of a diameter below 20 mm can be designed to transport more than 20 kA DC while resisting transient phenomena in the grid. With this very compact cable design, it has been verified that a sufficient space is left in the cryogenic pipes to transport the bulk mass flow of liquefied hydrogen up to several tons per hour, conforming with requirements of end users. The MgB2 wires have also been found mechanically robust and flexible toward the stresses from the cabling and installation operations.

Modelling methods for overcurrents and transient phenomena have been developed for superconducting cables.


The high current MVDC connection seems feasible. The main lock is the SC cable for which the feasibility demonstration will be the main outcome of SCARLET. For the rest of the system, no technological lock appears.