The wind energy market is predicted to grow at dramatic rates, particularly offshore with the opening up of new areas, for example by the British Crown Estates. The industry itself is constantly changing with mergers and acquisitions. For example, in 2009 STX Corp. of Korea joined with Harakosan in the Netherlands to form STX Europe. Wind turbine manufacture is a global business and production is commonly located close to the end-use sites, involving new factories for new market development.
Vestas (Denmark) is currently the biggest global manufacturer of large wind turbines. Other leading players include: Goldwind and Sinovel (China); Enercon, REPower, Nordex and Siemens (Germany); Suzlon (India); Gamesa and Acciona (Spain); GE Energy and Clipper Windpower (USA).
Wind mills are growing in size, with each company announcing that it has a bigger blade span. Gamesa has a 4.5MW turbine in development with up to 135m in diameter. There is great potential for very large turbines offshore. The EU Upwind research project has a long-term vision of 20MW turbines, with blades of 125m, using aerospace grade carbon fibre, according to Povl Brondsted of Riso-DTU, who leads this work. This leads to constant new research into blade aerodynamics and structure, including materials. In addition, the manufacture of such large composite structures is very labour intensive and time consuming. The longer blades need a longer curing time, which can increase quality problems. Industry is crying out for automated processes to ensure repeatability, cut costs and increase output, while ensuring consistent quality. According to the US Department of Energy technical workshop in 2009, the key could be "robotics and process controls for lamination, blade finishing, trimming, grinding, painting, materials handling, pultrusion and inspection". One example of work in this field comes from GE Global Research, which is examining automated carbon composite manufacturing and inline inspection. Blades also require a large amount of material, which is putting demand pressure on the global supply markets for resins, fibres and cores.
Some turbine companies manufacture blades in house and others buy in. One of the independent blade manufacturers, LM Glasfiber in Denmark, has just announced a rebranding to LM Wind Power in a company press release on 20th April 2010. It is also opening a fourth manufacturing plant in China later in 2010. There are a series of other independent composites companies worldwide manufacturing blades. Companies like Gamesa are looking to use solely glass fibre in their latest blades. In other cases, carbon fibre is being used at the most demanding points in the blade structure particularly spar caps, although the costs are high. Tecsis Tecnologia e Sistemas Avancados (Brazil) is studying the effects of out-of-plane fibre waviness on performance, comparing both carbon and glass fibre epoxy laminates.
There are issues with weathering of turbine blades from UV resistance to marine exposure, and lightning performance (a key issue for an electricity generating system). Another key point for study is surface coatings to reduce ice build up. Sensors can be built in to allow remote monitoring of condition. LM Wind Power is working on a new research project incorporating LIDAR (Light Detection And Ranging) optical remote sensors into blades to measure real time wind conditions, which will allow the blade and turbine to adapt. Fatigue load is a key factor in design and there are discussions on the use of smart structures at the Sandia National Laboratories in the USA. Testing and certification is carried out by organisations such as Germanischer Lloyd.
AMI is organising a global conference on Wind Turbine Blade Manufacture to be held 7-9 December at the Maritim Hotel, Dusseldorf, Germany, to discuss blade production from design, through materials and processing, to weathering and testing. Offers of papers should be sent to Dr Sally Humphreys before 28th May 2010.