Superconductor power lines for transmission
The cables could make it easier to integrate new renewables into the grid
When certain materials are cooled below a ‘critical’ temperature, they exhibit no electrical resistance. This phenomenon is known as ‘superconductivity’, and although it was first discovered in 1911, scientists still don’t fully understand how it works. Nonetheless, it has underpinned a range of world-changing innovations – from MRI machines to the Large Hadron Collider.
The ability to conduct electricity without losses has self-evident benefits for TSOs, but the challenge for engineers wishing to harness superconductivity is getting the materials below their critical temperature – which can be very cold indeed. Until the 1980s, the superconductive materials known to science (low-temperature superconductors, or ‘LTS’) required liquid helium to get down to temperatures below -243 degrees Celsius. This made superconductors impractical and uneconomic for applications like power transmission and distribution.
"‘High temperature’ in the context of superconductivity is still extremely cold in everyday terms – around -180 degrees Celsius."
In 1986, however, IBM researchers discovered superconductive materials with much higher critical temperatures, known as high-temperature superconductors (HTS). ‘High temperature’ in the context of superconductivity is still extremely cold in everyday terms – around -180 degrees Celsius. But increasing the temperature from -243 to -180 degrees is extremely significant, as it enables the use of affordable liquid nitrogen for cooling. This has unlocked a whole range of use cases for superconductors, including in power cables.
From the 2010s onwards, first-generation superconductive cables have been used in distribution to ease congestion in cities such as Essen, Chicago, and Munich. Now, however, Irish startup SuperNode is developing next-generation technology to bring superconductivity to long-distance transmission.
"A superconducting cable consists of an inner ‘cryostat’ through which the liquid nitrogen is piped. This is surrounded by the superconducting material, and the whole cable is housed within an outer cryostat – a vacuum-insulated container that prevents outside heat from disrupting the superconductivity."
"A superconducting cable consists of an inner ‘cryostat’ through which the liquid nitrogen is piped. This is surrounded by the superconducting material, and the whole cable is housed within an outer cryostat – a vacuum-insulated container that prevents outside heat from disrupting the superconductivity."
A key factor determining the suitability of superconductive cables for transmission is the distance the liquid nitrogen can travel before it needs to be re-cooled. And SuperNode’s technology includes two key innovations that address this point.
A superconducting cable consists of an inner ‘cryostat’ through which the liquid nitrogen is piped. This is surrounded by the superconducting material, and the whole cable is housed within an outer cryostat – a vacuum-insulated container that prevents outside heat from disrupting the superconductivity. In the superconducting cables operating today, the inner cryostat is made of corrugated steel, which enables the expansion and contraction of the materials as temperatures fluctuate. However, this corrugated design also increases the friction, turbulence, and pressure drop within the cryostat, reducing the distance the liquid nitrogen can flow. SuperNode’s cable, by contrast, has a smooth inner cryostat made from novel materials that expand or contract very little in response to temperature changes. This extends the range of the cable.
The company has also developed record-breaking soft vacuum insulation that prevents heat from leaking into the inner cryostat, further extending distances between re-cooling.
While working to develop a prototype and prove the technology, SuperNode is also planning for future scalability. The company has a facility in Dublin focused on producing samples and prototypes, and, in 2024, it opened a plant in Northumberland, which will produce cables for pilot projects and demonstrations. Following the development of a continuous manufacturing process, the startup hopes to have commercial products ready by 2028.
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The value proposition for SuperNode’s cable is relatively simple: the startup claims it can carry five to 10 times more energy in a single line than conventional transmission technologies. Because of this, the company’s cables could one day transmit power over large distances, including in underwater applications to connect offshore wind farms to the grid. Due to its very small size compared to conventional copper cables, the technology is also ideal to increase power flows in densely populated cities or to provide data centres with bulk power. Beyond pure performance, the cables are compatible with conventional techniques and equipment, making it quick and easy for them to be integrated into the grid. SuperNode therefore pitches itself as a solution for enhancing grid capacity rapidly.
Development stage Development
Innovator website supernode.energy
Innovator contact info@supernode.energy
Making superconducting cables cheaper, longer, and more robust
Making superconducting cables cheaper, longer and more robust
A startup is changing how superconductors are produced for enhanced operational resilience
SuperNode is optimising cooling systems for its superconducting cables. Meanwhile, another startup, Denmark’s SUBRA, is focused on how the superconducting wires within the cables are produced. Today, high-temperature superconductors are produced as a ‘flat tape’, a technology that has inherent limitations in terms of cost, capacity, and – crucially – length.
SUBRA’s innovation is to move on from flat tape technology by producing superconductors as bundled wires, a radical departure from existing technologies. By using these wires, the startup’s SUBRACABLE solution can be scaled to extremely long lengths, in excess of 100 kilometres, unlocking new applications in long-distance transmission.
Larger companies are already experimenting with superconductors through demonstration projects and shorter transmission circuits. However, current flat tape technology depends on hundreds of high-quality joints made by specialised tape-to-tape soldering, which is expensive. Power density is also limited in flat tape cables for operational protection purposes.
SUBRACABLE solution can be scaled to extremely long lengths, in excess of
The bundled wire technology in SUBRACABLE, by contrast, has greater operational robustness, enabling much higher operational limits. SUBRA also claims its technology has the potential to be delivered at a lower cost than conventional superconductors, in part because it eliminates the need for soldering.
The company’s goal is to become a preferred supplier to cable manufacturers, who will incorporate the SUBRACABLE component into full cable solutions (which will also include insulation and nitrogen cooling systems).
To develop its technology, SUBRA has previously received funding from the European Innovation Council (EIC) Accelerator programme. In December, it announced a convertible loan from Novo Holdings in preparation for a planned Series A funding round in 2025.
Did you know?
SUBRA is addressing some of the existing obstacles to applying superconductors to transmission, targeting large-scale production to drive down costs. In doing so it hopes to contribute towards the goal of ramping up a pan-European energy grid, while also providing an efficient means of connecting wind turbines and solar panels. Superconductors using today’s technology have already been successfully demonstrated in key distribution points and electrical transformer stations. SUBRA is hoping that its SUBRACABLE will facilitate full grid integration.
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