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Adrian Wilson

Editor's Viewpoint

18th May 2018, UK

Staying ahead in wind power: Vestas and Hexcel

While the lion’s share of its turnover is generated by the aerospace industry, Hexcel was instrumental in developing the first prepreg materials for composite wind blades and its materials have been on the platforms of Vestas for over twenty years.

The two companies announced an expansion of their existing supply agreement last October and at this year’s JEC World in Paris, it was revealed that Hexcel’s Hexply M79 prepreg was being used for the blades of the latest Vestas V136-4.2 MW turbine.

Advanced aerofoil

The V136-3.45 MW combines an advanced aerofoil design with the proven 4 MW nacelle and large diameter steel tower (LDST) technology, to deliver high and efficient energy production in low- and medium-wind conditions.

At this year’s JEC World in Paris, it was revealed that Hexcel’s Hexply M79 prepreg was being used for the blades of the latest Vestas V136-4.2 MW turbine. © Vestas

The aerofoil design applied to the 66.7 metre-long blades, enables a 16% increase in annual energy production while at the same time minimising structural loads. Advanced aerodynamics, particularly at the blade tips, and aero add-ons such as serrated trailing edges, decrease the maximum noise emission level.

Vestas has been optimising carbon blade applications for the past 15 years, and the V136-3.45 MW benefits from the advanced use of carbon pultrusions, resulting in light-weight, highly robust blades with optimal performance.

EUR 350 million installation

Vestas installed its first V136-3.45 MW turbine in December 2016 and after extensive testing and verification commenced full-scale production during 2017.

It has just announced a partnership with Swedish utility Vattenfall, and Danish pension fund, PKA, for a EUR 350 million, 353 MW wind energy project which will see 84 of the V136-4.2 MW turbines installed across the Blakliden and Fäbodberget wind parks located in Åsele and Lycksele Municipality in central Sweden.

The V136-3.45 MW combines an advanced aerofoil design with the proven 4 MW nacelle and large diameter steel tower (LDST) technology. © Vestas

“With wind energy becoming the lowest cost energy solution in many markets, the global wind energy market is expanding and creating new opportunities that involve new customer segments, partnership constellations, technology solutions and financing structures,” said Anders Runevad, president and CEO of Vestas. “As the global leader in wind energy – with 92 GW of wind turbines in 79 countries – Vestas continues to be highly involved in this evolution and is working with key partners developing solutions that address a wind park’s full value chain and maximise return on investment and profitability.”

Turbine delivery is expected to begin in first half of 2021 with full commissioning planned for fourth quarter of 2021.

HexPly M79

The introduction of HexPly M79 prepreg five years ago offered a viable option for manufacturers making blades by infusion to move to prepreg technology and benefit from superior mechanical performance.

It was the company’s response to industry requirements for a lower temperature curing prepreg and for faster curing. For a very low temperature cure, the company recommends a cycle of ten hours at just 70°C but if a more rapid cure cycle is required, the prepreg can cure in only 4-6 hours at 80°C.

There is also much less risk of an exothermic reaction – a 60% reduction on Hexcel’s standard M9G prepregs – yet the prepreg is based on the standard and proven epoxy chemistry. An additional benefit is that the prepreg has an outlife at room temperature of at least two months, which is unusual for such a low temperature curing product.

The aerofoil design applied to the 66.7 metre-long blades, enables a 16% increase in annual energy production. © Vestas

The low cure temperature of HexPly M79 gives the added benefit that the system is totally compatible with any liquid epoxy resin used for infusion processing. This means that the prepreg and infusion processes can be combined in the same blade, combining the twin advantages of stronger laminates and cost-effective processing.

The ultimate in blade performance is achieved when HexPly M79 is reinforced with carbon fibre to provide exceptionally strong laminates that are lighter than those made with glass fibre. HexPly M79 with carbon fibre reinforcements represent an enabling technology for wind blades that are now approaching 100 metres in length.

Polyspeed

At JEC World 2018, Hexcel introduced Polyspeed pultruded laminates for load-carrying elements in wind blades. These continuous cross-section profiles, made from a polyurethane matrix reinforced with unidirectional carbon fibre, provide consistently high mechanical properties, including high stiffness, fracture toughness and shear strength, combined with low weight and durability. A two-metre-diameter coil of pultruded carbon laminate containing 255 metres of the material in a single roll was exhibited at the show.

Working with Hexcel, Vestas has been optimising carbon blade applications for the past 15 years. © Vestas

Also showcased was a new surface finishing prepreg for wind turbine blades and components. This provides a tough, durable and ready-to-paint blade surface without the use of gel coat and results in faster blade manufacture, saving time in production and reducing material costs. The benefits of the new surfacing prepreg were demonstrated via a wind blade exhibit given four different treatments across the blade surface. These included a section with gel coat, a section of standard prepreg without gel coat, and a section where a fleece was added to improve surface quality but still required preparation before painting due to pin holes. The final section made with new HexPly XF2P surfacing prepreg had a ready-to-paint surface, straight from the mould, without any requirement for gel coat, fleece or finishing operations.

“By continuing our long-term partnership with Hexcel, we will continue to bring down the cost of energy through our combined strengths and enhance the competitiveness of Vestas through market-leading blade manufacturing,” said Vestas Wind Systems executive vice president Jean-Marc Lechêne.

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