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US energy firm completes trials on “breakthrough” superconducting tech for next generation wind turbines

GE’s superconductive tech to offer advantages in efficiency, weight and cost reductions and could save energy by as much as 20 per cent on 10MW turbines

GE says its superconducting tech could reduce costs for wind turbine towers and foundations

US power firm GE has completed trials for what it has said is an important step in testing a viable way of producing large amounts of electricity from wind turbines using high temperature superconductors (HTS). The company has successfully completed trials of Hydrogenie, a power generator incorporating "groundbreaking" technologies that enable highly efficient production of electricity in a small space. The technology can also benefit hydropower and marine energy turbines.

Hydrogenie makes use of superconductors instead of copper for the rotor windings on the motor, operating at 43 Kelvin or -230°C. The technology was tested in late 2012 up to, and well beyond, its full rated load 1.7MW spinning at 214rpm and met expectations and design predictions. The tests were carried out at a GE Power Conversion facility in Rugby, England.

Until recently, superconductivity could only be achieved at around 4K (-269°C). But GE said the new HTS exhibit the "phenomenon" at much higher temperatures. Such machines will need less complex insulation systems and less powerful cooling than used hitherto on devices such as medical MRI magnets.

GE has said a superconducting wind turbine generator may permit significant reductions of mass mounted on the tower. This will help to reduce the cost for the tower and its foundations. Recent studies conducted for GE Power Conversion show that the lifetime energy saving for a superconducting wind turbine compared to a conventional machine could be as much as 20 per cent for machines above 10MW.

Martin Ingles, Hydrogenie project manager at GE Power Conversion, said: "This technology is a true breakthrough. It could radically improve the efficiency of equipment producing electricity from water and from wind and may also be suitable for further applications down the road."

The news follows GE's other efforts to cut costs in wind energy. This includes work announced in November 2012 to develop a new turbine blade design, which aims to reduce costs up to 40 per cent.

Efficiency and weight reductions for wind

The latest superconductors are made by depositing a superconducting layer of ceramic onto a relatively cheap base metal. GE said they have virtually no resistance to electrical current when cooled to very low temperatures, so windings can be made with wires having a cross section around two per cent of a conventional copper wire winding.

More windings can be fitted into electromagnet coils, resulting in a higher power magnet that is substantially smaller or lighter than before. GE said superconductivity offers significant advantages in efficiency and significant weight reductions compared with conventional machines. The company said the greatest benefits in terms of size and mass reduction are for applications where high torque machines are typically used, most likely as a direct-drive application in installations, such as wind turbines and run-of-river hydropower plants.

GE said it has overcome significant technical challenges relating to the cryogenic cooling and thermal insulation required to keep the superconductors at the required temperature. Extremely cold helium gas is piped through a rotating coupling into the machine rotor and then circulated around the individual coils. "It's rather like trying to keep ice cubes frozen on a rotisserie in a very hot oven," said Ingles. "Except that our rotisserie is rather high tech."

Setting the framework for wind power

The rotor is located inside a vacuum, but still has some direct contact, via its shaft, with the outside world. This creates issues relating to the massive temperature differences along the shaft.

The machine incorporates a patented method for transferring torque from cold HTS coils to the machine rotor. Low resistance thermal joints and assemblies ensure that low cooling power is required to cool the coils. GE said the machine demonstrates all of the technologies required to make HTS machines a commercial reality.

The company said the successful completion of the Hydrogenie project will "set the framework" for continued research and development in the study of superconducting machines. In addition to wind, one specific area that may potentially benefit in the future is the upgrading of older run-of-river hydropower plants. Coupled with running the machine/turbine at variable speed the benefits could allow efficiency improvements of up to 12 per cent at part load.

GE said: "The technology building blocks developed as part of the project also will be used in other businesses where high torque and slow speed machines are in use. The most immediate areas of demand are in wind power generation and in marine propulsion."