Super-conductors boost extrusion efficiency
Super conducting materials, which conduct current without resistance, are currently the subject of research, with considerable resources being utilised to find techniques that can transform these materials into good energy conductors in technical components.
Magne Runde and Niklas Magnusson at Sintef, the Norwegian research organisation, study super conductivity and are testing super conductors in the huge induction heaters utilised by the aluminium industry.
Currently the industry preheats huge metre-long aluminium billets in induction heaters with copper conductors. When the temperature reaches 500 degrees C, the billet is extruded to profiles.
Runde says: "This heating process leads to large losses in energy. Only half the energy supplied is used to heat the billet. The remaining 50 per cent is waste energy. This is something super conductors can improve."
The researchers have now replaced the copper conductors in the induction coils with super conductors. As the conductivity is significantly improved, a much higher proportion of the energy is transferred to the billet. The researchers have conducted laboratory tests that confirm the energy efficiency is increased to 80-90 per cent.
In their laboratory, Magnusson and Runde have been working on two large super conducting coils, 1.5m in diameter. The super conducting material, magnesium diboride, is in thin, brittle filaments enclosed by a nickel matrix.
Runde states: "These will be the world's largest super conducting coils made from this special material."
In 2007, the German company Zenergy Power licensed a patent based on Sintef's basic idea. The company has acted quickly and produced two heaters, which it has sold. The concept of super-conducting induction heaters was awarded a prize worth EUR100,000 at the 2008 Hannover trade fair. Magnusson and Runde have continued with the research in parallel with - and in competition with - Zenergy Power. In an EU project with eight other partners, Sintef now has a model under construction that is expected to be cheaper than the German model. In this model, the Trondheim research scientists designed and built the super conducting coils.
Magnusson comments: "We have deliberately kept a low profile to see if Zenergy Power succeeded in building a complete model. We now believe the time is right to mark that it is in fact a Sintef invention behind the product."
With around 500 extrusion lines in Europe, the super conductors will be a typical niche product. However, given that the industry stands to make energy savings of up to NOK1million (around EUR118,000) for such induction heaters, the researchers believe there is a market for the product.
Sintef
