25 June 2018 - We could easily integrate superconducting power cables into our grids within the next five years, says Christian-Eric Bruzek. The French engineer works for the cable manufacturer Nexans and is currently coordinating a team of ten European partners within the EU project Best Paths. In the demonstration project “Superconducting cables for very high power transmission” they have developed a cable system that is designed to transport electric powers of up to 3.2 GW. The team has manufactured a 30-meter-long prototype. As yet, there are no standards for this new technology, but the team has set up some benchmarks in terms of material performance and system security. We talked to Bruzek about the achievements and challenges of the project.
Could you explain the major advantages of superconducting cables for electricity transmission?
There are two major advantages. First of all, with superconductivity there are no transmission losses, because there is no electric resistance. In conventional energy transmission, this loss accounts for up to five per cent of the transported energy. Superconducting cables do, however, require a constant energy supply for the cooling fluids that keep them below -200°C. But the energy needed for cooling purposes is still smaller than the energy lost in conventional resistive cables.
The second benefit is the compact size. Our cable design would require underground corridors that are just one metre wide. To transport the same amount of energy, conventional systems would need a corridor up to 10 metres wide with eight resistive cables installed side by side. Besides this advantage, superconducting cables do not heat the ground and are therefore less harmful to the environment.
Several projects are currently testing superconducting cable technologies in the grid. What is the added value of the Best Paths project?
We have for the first time designed a high-voltage cable system capable of operating in direct current. All the other projects deal with alternating current only. To name a few, in the Long Island project in the United States, a 0.6 GW AC cable is operating in the grid, and in Japan, a prototype AC cable with the capacity to transmit 1.4 GW has been installed in a substation. These projects are all based on high-temperature superconducting materials, which are manufactured in a complex and very costly process. Within Best Paths we have developed a cable that uses the superconducting material magnesium diboride, which is very economical to produce.
Which project achievements are you most proud of?
Firstly, we are very happy with the performance of the wires. With a transported current of 700 Amperes, magnesium diboride has proven its ability to carry huge amounts of electricity – 500 times more than a simple copper wire! It is exceeding our expectations. Our project partner Columbus Superconductors has already produced hundreds of kilometres of this wire. Secondly, we were able to develop an innovative and safe high-voltage insulation, which consists of lapped paper impregnated with liquid nitrogen. In case of an electrical breakdown, the nitrogen will automatically fill any gap in the paper and the insulation properties will be recovered. We have published our test results in a top-tier scientific journal.
And what did you find most challenging?
Technically, one of the most challenging tasks is to manage the connection between the superconducting cable and the existing grid using high-voltage terminations. For me, this is the one of the most important insights of our demonstration. Other aspects need to be discussed further, for instance the question of how superconducting links would impact on the way we operate the grid.
What applications do you propose for high-power superconducting cables?
In the short term, the most suitable applications would certainly be those where we make the most of the size advantage. Examples would be areas where civil work is expensive, but also urban areas where space is limited. Another application could be to pass below rivers. In these examples a short superconducting cable could serve as a ‘bridge’ connected to resistive cables or overhead lines. This is why we are carefully examining possible links to the existing network.
So to summarize, short links would be the next application, but then of course we could go further and cover long distances. For instance, we could reach remote wind farms, where several gigawatts – huge amounts of power – are generated and need to be transported to consumption centres.
What are the next steps for this technology?
The next step would be to develop testing guidelines for high-voltage direct-current superconducting cables to ensure safety and quality standards. A consortium of manufacturers would need to be formed and agree on the testing procedures. We have to include transmission system operators (TSOs) in this process because they are still cautious. So we are now calling on policymakers to create economic incentives for TSOs to invest in superconducting cable systems.
What efforts are you making to overcome the information gap regarding this technology?
New technologies are often met with scepticism – as the Best Paths coordinator Vincente Gonzáles from Red Elétrica said, people are reluctant to be the ‘first movers’. Although research on superconductors has made great strides, the dissemination to the ‘power grid world’ is very limited and we want to change this.
We are planning a dissemination workshop on 5 July in La Spezia in Italy on the premises of the ASG superconducting fusion magnet factory, where we want to show how the cable is produced. We will also present the project results to the Best Paths consortium and Members of the European Parliament on 19 and 20 September in Brussels. We still have quite a way to go, but I am optimistic that within the next five years we will see superconducting cables entering the real grid.
Learn more about the demonstration project here:
You can register here for the workshop “Superconducting cables for very high power transmission” which takes place on 4 and 5 July 2018 in La Spezia, Italy:
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