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Generators could be made from superconducting magnets […] offering significant savings in size and weight. ‘We can make a machine that will deliver the same amount of power for roughly half the weight and half the volume of a regular wind turbine,’ says Marc Dhalle, materials scientist at the University of Twente in the Netherlands. The EU-funded project, EcoSwing, was coordinated by Danish turbine company Envision.
The new generator is 4m in diameter, 1.5m smaller than a conventional one. It sits inside an 88m high 3.6MW turbine in Thyboron, Denmark.
What’s new is the use of magnets made from a composite tape with a ceramic superconducting layer: gadolinium–barium–copper oxide (GdBaCuO). The superconducting layer sits on a steel ribbon for flexibility and strength. The tape was made by Theva in Germany.
The superconducting tape is also protected from metal poisoning by layers of magnesium oxide and silver. The magnesium oxide also acts as a template for the precise crystalline structure needed by the GdBaCuO. An outer copper layer offers electrical and thermal stabilisation. Tens of kilometres of this tape sits inside the new wind turbine.
‘When groups initially started trying to put this superconductor on a flexible metal substrate, people considered them to be – let’s be polite – overly optimistic,’ says Dhalle. ‘A lot of technical details needed to be mastered, but they turned out to be visionaries.’
‘A wind generator making 1MW of power will contain roughly a tonne of neodymium in its magnets. In our generator, we use about 1kg of [the rare earth] gadolinium, so we use orders of magnitude less of this relatively rare and expensive material,’ says Dhalle. Gadolinium, which replaces neodymium in the turbine, costs just $18.70/kg (£14.50/kg) of gadolinium oxide, compared with $45.50/kg of neodymium oxide, according to Roskill and Asian Metal.
Off-the-shelf cryo-coolers from SHI Cryogenics in the UK chill the superconductor to –240°C. These coolers are similar to those used in ordinary refrigerators, although they’re far more powerful.
A video showing the EcoSwing project in action with Envision was posted in October. Envision is one of the partners in the consortium making this possible.
Fundamentally, the news is that EcoSwing's actors have fulfilled an objective to install a superconducting drive train on an existing wind turbine in Denmark, on the Danish west coast. This is a large-scale wind turbine.
"Superconducting drive train" may be a mouthful but the three words highlight what is special about this effort in wind power. "Superconductivity" is now in focus. For the first time ever, a superconducting generator is about to be installed, said the video narrator, in a functioning wind turbine. The equipment was described as a multi-megawatt direct-drive superconducting wind generator.
The project is claimed to be "the world's first" such drivetrain, showing "a piece of engineering history."
Another EU project called EcoSwing aims to prove that a superconducting generator can compete at more modest scales, and its engineers have nearly done it. By March 2019, the €14 million ($16.3 million) project plans to have installed such a superconducting generator inside a modified 3.6-MW turbine on land, where the installation and maintenance are easier.
Unlike the high-megawatt offshore projects, EcoSwing is aiming for the middle of today’s onshore market. Superconductor technology has let the designers double the turbine’s power density, allowing for a 40 percent smaller turbine generator and a 15 percent cost reduction over those of market leaders, says Jürgen Kellers, EcoSwing’s director at ECO 5, an engineering company that’s one of the nine contributors to the project.
Apart from its size, the EcoSwing generator differs from the InnWind and other offshore designs in that EcoSwing uses a single large cryostat instead of many modular ones. It also relies on a high-temperature superconductor—yttrium barium copper oxide—instead of MgB2. The company chose the former despite the cost, because it’s easier to cool YBCO. “You might say MgB2 is already at a cost that YBCO wants to be in the future,” says Kellers. “On the other hand, cryogenics is not as straightforward and rugged as with YBCO.”