AmpaCity: Power grid revolution without resistance

Can you imagine a world premier taking place – and no one sees it? This is exactly what happened on 30/4/2014 in Essen, when RWE Germany put the longest superconductor cable in the world into operation right in the middle of the city of Essen. Of course there was a lot of media hype, but the superconductor cable especially developed for this location by the Nexans company runs underground between the two substations in Essen, Hercules and Dellbrügge. This is how inconspicuously the power grid revolution can happen.

Superconductors can conduct electricity with virtually no resistance. If the demonstration project "AmpaCity" runs positively, urban substations could soon become superfluous to needs. The 15 cm thick superconductor cable replaces a classic 110 kV cable line along a one-kilometre stretch. The new cable transmits approximately five times as much electricity within the same diameter. Before the start of the pilot project, a feasibility study was carried out. Now practical testing should show that the new technology is efficient, economical and can be integrated.

Engine for progress:

  • the longest superconductor cable in the world in real life operation
  • energy savings of 50% compared to traditional cables
  • efficient use of resources: five times thinner cables with the same power transmission
  • the world looks to Essen: Many delegations from all over the world regularly visit to gain information

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Photo: RWE

The structure of the superconductor cable. The cable is constructed concentrically, with the coolant, nitrogen, cooling the inside and outside of the conductor (shown here in turquoise). At the beginning of superconductor research, materials were only superconducting at very low temperatures close to absolute zero. In 1987, Dr. Johannes Bednorz, together with his colleague Prof. Karl Alexander Müller, received the Nobel Prize in Physics for the discovery of high-temperature superconductors.

It won’t work without nitrogen

The German physicist Johannes Georg Bednorz and his Swiss colleague Karl Alex Müller received the Nobel Prize in 1987 for their discovery of the ceramic materials that make superconductivity possible at relatively high temperatures. In this context, high temperatures mean -196°C, because the superconducting materials must be cooled with nitrogen in order to develop the desired effect. The energy requirement for the superconductor cable consists of the nitrogen consumption and the electric energy for the circulation pumps and vacuum pumps and comes to approx. 50 per cent of the energy accrued in losses during operation of the replaced 110 kV cable. "The AmpaCity project shows us whether and in what way superconductors can sustainably improve the distribution of electricity in our cities and make this process even more efficient. Moreover, the superconductor cable, which is only 15 centimetres thick, requires far less space than a conventional cable. Ultimately, some large substations may in the long run become superfluous to needs", explains Dr. Frank Merschel, project leader at RWE Germany.

Electricity revolution right in the middle of NRW

In addition to energy efficiency, there is also resource efficiency of course: It is not just substations that can be made redundant; it will soon be less crowded under the surface in Essen too, when the five times thinner superconductor cables replace the traditional 110 kV lines. The whole world is now looking to Essen with curiosity, because the power grid revolution just might be starting here.

Photo: RWE

"For Germany, this is a project that will have the signal effect of bringing new technical achievements to the awareness of the public and will lead to an intensive discussion on further developments and solutions in the energy sector."

Dr. Johannes Georg Bednorz, Physicist and Nobel laureate.

Partners and sponsors

  • RWE Deutschland AG
  • Westnetz GmbH
  • Nexans GmbH
  • KIT, Karlsruher Institut for Technology
  • Bundesministerium für Wirtschaft und Energie (BmWi)