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Could superconducting cables play a role in urban power grids? A project led by the UK’s National Grid Electricity Transmission aims to find out.

Transport, heating and industry will all need to be electrified in the coming years if net zero goals are to be achieved. Cities will see the biggest increase in electricity demand, so finding ways to boost urban power supplies is a priority. 

Superconducting cables make it possible to transmit massive amounts of electricity in a very small space, making them the perfect candidate for congested urban grids. So how and where could they be used? 

To answer these questions, National Grid Electricity Transmission has launched SCADENT (Superconductor Applications for Dense Energy Transmission) – an innovation project to identify applications for superconductors in cities. Nexans, a global leader in superconducting solutions, is participating in the project.

Upgrading electricity supplies in cities presents grid operators with a number of complex challenges:

Ageing infrastructure – cable networks in some urban areas are more than 50 years old and capacity is limited. Adding new loads accelerates the cable ageing process, making replacement essential if extra demand is to be accommodated. 

Cost and disruption – deploying new conventional cables is a lengthy and expensive process in terms of obtaining consents and carrying out construction work. It can also be disruptive and unpopular with the public.

Space constraints – conventional cabling needs a lot of space (including space between cables) because factors such as heating and electromagnetic interference must be taken into account. On top of this, there is often a need to build new substations, which is expensive in cities.

Superconducting cables pack a huge punch. To put this in context, you can channel the power of three nuclear power stations through a superconductor just 17cm in diameter. In addition, superconductors generate neither heat nor electromagnetic fields. 

Although superconducting systems are more expensive than copper or aluminium cabling, the additional cost is compensated for by the reduced need for civil works, real estate and substation equipment. Indeed, overall cost is potentially lower compared with conventional cabling solutions.

Smaller footprint – corridors for superconductors are up to ten times narrower than those for conventional cables and lines. This not only saves money, but also minimises disruption and dramatically accelerates the deployment of new infrastructure.  

Trenches not tunnels – cables do not require special infrastructure and they can be run just about anywhere, without the need for dedicated tunnels.

Fewer substations – superconductors make it possible to transmit electricity at lower voltages, but with the same power. So instead of supplying electricity at 400 kV through copper, you can use 132 kV superconductors instead. Equally, conventional 132 kV cabling can be replaced by 33 kV superconductors. Bringing power into cities at a lower voltage reduces the need for step down transformers – a big saving in land acquisition and civil works costs. 

Go-anywhere cables – superconducting cables do not generate a magnetic field, so you can run them safely alongside other electrical cables, telecoms infrastructure and even pipe networks. 

Energy savings – superconductors offer almost no electrical resistance. This means transmission losses are minimal, particularly at 33 kV AC. 

Resilient grids – aside from boosting the power of urban grids, superconducting systems have the potential to enhance the reliability of electricity supplies –  for example, by linking multiple urban substations on a superconducting loop to create an urban bus bar.

Power without limits – there is no length limitation with superconducting cable systems. This makes them the perfect solution for both citywide distribution and nationwide transmission.

The benefits outlined above are not just theoretical – they are already proven in projects carried out by Nexans. Our references include the LIPA 138 kV AC cable project in Long Island in the US, the Resilient Electric Grid (REG) 12 kV AC project in Chicago in the US, and the AmpaCity 10 kV AC link in Essen in Germany – the world’s longest superconducting cable, in operation for seven years.

The benefits outlined above are not just theoretical – they are already proven in projects carried out by Nexans. Our references include the LIPA 138 kV AC cable project in Long Island in the US, the Resilient Electric Grid (REG) 12 kV AC project in Chicago in the US, and the AmpaCity 10 kV AC link in Essen in Germany – the world’s longest superconducting cable, in operation for seven years.

Maximum transmission capacity and near-zero losses

Jean-Maxime Saugrain is the Machines, Cryogenics & Superconductors VP. He was previously Corporate VP Technical and High Voltage Business Group CTO. He held different positions at Alcatel cable in the field of optical fiber manufacturing, both in France and in the United States, before joining in 2000 the division which became Nexans.

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