New Superconductive Material for Long-Distance Energy Transmission

The energy landscape in Europe is changing rapidly and the percentage of renewables is steadily increasing. For example, in Germany solar and wind power provided an average of 33% of the total electricity production in 2015. And the phase-out of nuclear power, as part of the country’s energy transition or Energiewende, will result in the expansion of the local electricity grid.

However, renewable energy depends on local weather conditions, on the possibility of electric power being shunted from one region to another, and also on the construction of a new, long-distance network of transmission lines linking countries in Europe.

 © Photo credits: Trevor Prentice

With the existing technology, high-voltage DC overhead lines are the cheapest option today. However, the rural population and environmental groups strongly oppose this solution with its unsightly pylons.

An alternative is to bury copper or aluminium high-voltage lines underground, a solution used in populated areas, but which is unlikely to be applied over long distances due to the much higher cost than overhead lines.

Another drawback of present energy transport through copper or aluminium lines is the transmission losses caused by the electric resistance of these wires. This resistance causes the heat up of wires, and energy is then lost. For long lines, energy loss can be as much as 10% of the transmitted energy. On a European level, that is the equivalent output of 3 to 5 large power plants.

In 1911 the Dutch physicist Heike Kamerling Onnes identified the so called “superconductors”. He discovered that when some metals are cooled down to temperatures close to absolute zero, they lose all electrical resistance. For example, a current flowing in a closed loop of niobium held at practically absolute zero will flow forever. The scientist suggested that superconductive wires might be a good idea for energy transport.

The first practical proposal was formulated 50 years ago by the American physicist Richard Garwin. He proposed that a transmission line of 1000 km, transporting 100 Gigawatt (at that time all the energy produced in the US) could be transmitted through a single underground superconductive cable, just a mere 30 cm wide including its cooling system. The drawback was that cooling the wire down to a few degrees above absolute zero, would have been too costly.

During the 1980s scientists discovered new ceramic materials that become superconductive at much higher temperatures, up to 70 degrees above absolute zero. Although cooling would be much cheaper, these high-temperature superconductors are difficult to manufacture and too expensive for use over long distances. Because of the high cost, utility companies have remained sceptical about their use in energy transport.

But in 2001 researchers in Japan discovered that a quite simple compound, magnesium diboride (MgB2), becomes superconductive at a temperature of 39 degrees above absolute zero (39 K). In 2011 at the Institute for Advanced Sustainability Studies (IASS) in Potsdam, Germany, the physics Nobel Laureate Carlo Rubbia initiated a research cluster investigating the application of superconductive lines for energy transport.

Magnesium diboride is only available in powder form, but researchers at Columbus Superconductors in Genoa, Italy, found the material could be manufactured in long strands by filling copper or nickel tubes with the powder and sintering them. “High costs barred the way for the energy transportation over long distances with superconductors. MgB2 really changed the game”, says Giovanni Grasso, Director General and co-founder of the company.

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by Alexander Hellemans
youris.com