Rotor Blades: The use of composites in rotor blade design


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Rotor Blades: The use of composites in rotor blade design

  1. 1. The use of Composites in Rotor Blade DesignThe wind power industry in Europe is expected to grow significantly in the comingyears to coincide with EU targets for the reduction of carbon emissions by 2020 andbeyond. The development of technology towards deep water installations of windfarms is the vital step towards achieving the target of 20% of Europe’s energydemands by 2020. Harnessing stronger and more consistent winds in deeper waterwith larger turbines rated at 8-10MW and higher, is key to providing cost-efficientelectricity. To realise the production of energy at prices competitive with energyfrom fossil fuels, turbines will need to be cheaper to manufacture, to install, and tomaintain.Turbine blades conventionally have been constructed with glass-fibre or carbon-fibrecomposite materials, and are designed to have a lifetime of twenty years or more.One of the important aspects of turbines installed on deep water farms is the cost ofservicing and maintenance. Due to their location and the difficulty and costs ofworking at sea, it is essential that the larger turbines designed for offshore farmsare highly reliable to reduce downtime for servicing and repairs.The industry as a whole and blade manufacturers in particular, are looking forcomposite materials with a variety of characteristics to suit this purpose. Thematerials must be strong enough to cope with the excess load caused by high windson much longer blades. The reduction of the weight of the blades is also important,as the extra weight and fierce weather conditions could cause failures in othercomponents of the turbine, thus creating extra downtime. Cost-efficiency is anotherdriving factor; manufacturing and production costs should not adversely affect theultimate target of producing cheaper electricity en mass.ResearchIn 2010, The Danish Council for Strategic Research’s Programme Commission onEnergy and Environment awarded funding of DKK 38 million for the establishment ofThe Danish Centre for Composite Structures and Materials for Wind Turbines------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  2. 2. (DCCSM) (1). The research centre involves several industry partners including RisøDTU (National Laboratory for Sustainable Energy), The Department of MechanicalEngineering at Aalborg University, Siemens Wind Power, LM Glasfibre, FiberlineComposites, and Bach Composite Industry.The project is intended to carry out extensive research into the development ofexperimental methods of producing and monitoring blades at various lengths. It ishoped the research will give a greater insight into the characteristics required ofcomposite materials in terms of controlling damage evolution and crack growth. It isalso aiming to develop new methods of analysing and predicting the extent ofdamage and crack growth.Wind turbine blades for offshore installation are expected to be 60 metres or more,and it is vital that the turbines are able to withstand small amounts of damagewithout coming to a complete standstill and causing downtime. It is also anticipatedthat the turbines of the future will incorporate a range of sensors to detect andassess damage as and when it occurs. This research will be invaluable for blademanufacturers as it will enable designers to develop larger, lighter blades, while theintegration of sensors will facilitate damage detection and analysis so that decisionscan be made quickly and efficiently as to what type of action is required.ManufacturingMost turbine blades are manufactured from some type of glass-fibre material, andthe development of these composites as well as research into the implementation ofcarbon-fibre composites is on-going throughout the industry. The aim of developingthese composites is to create blades with high tensile strength to cope with theconditions offshore, while retaining a light-weight and cost-efficient design. Onemanufacturer embracing both technologies in the design of its blades is Gamesa,who have introduced carbon-fibre composites into the construction of their latestblades, including the G10X-4.5 MW sectional blade (2).------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  3. 3. Source: GamesaManufacturing of the internal beam of the blade uses both glass-fibre and carbon-fibre materials which have been impregnated with epoxy resin as a base. Severalpieces of cloth are cut and placed into the mould before undergoing a curing process(shown above). The shell of the blade is constructed via the same method, withglass-fibre placed into a mould after a protective coating of paint. Once both shellshave been produced, the beam is bonded between the two, and the blade is passedthough a kiln to form a compact unit. Finally the blade assembly is completed bythe finishing of the leading and trailing edges to meet specification.The challenge for designers and engineers is one of cost versus benefit of usingcarbon-fibre for blade manufacture. While it has the potential to be stronger andlighter than glass-fibre materials, the technology and manufacturing processes arenot in place yet to deliver cost-efficiency and reliability in mass production for theentire blade structure. Many manufacturers are using carbon-fibre composites forcomponent parts of the blade to increase strength in specific areas, but it remainsto be seen what the ideal composite material will be for large turbine bladeconstruction.Composites for the Wind Energy Industry3B Fibreglass Company is one of Europe’s leaders in the development and supply offibreglass products for the wind industry, and produces several composite materialswhich can be used for blade manufacture (3). One of their products which may beparticularly well suited to the manufacture of longer blades for offshore applications------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  4. 4. is Advantex®. It is a boron-free E-CR glass with corrosion resistance propertieswhich could be ideal for the aggressive weather conditions experienced in deepwater installations. It offers several benefits over traditional E-glass, including a 9%higher tensile strength, optimised sizing for improved processing and enhancedfatigue performance, and a cleaner environmental footprint.The removal of boron from the glass composite stops the creation of dust particles,which are associated with partial volatilisation when exposed to high temperatures.The removal of added fluorides also helps to reduce the creation of dust particles.The use of modern melting technologies results in a significant reduction ingreenhouse gas emissions, and increased energy efficiency also aids the reductionof carbon emissions.Further developments by 3B have seen them introduce another composite, HiPer-texTM, resulting from manufacturing developments in their own technology. The fibreis based on a new patented glass formulation, which 3B say respects theenvironment with optimised melting and sizing technologies. Key to the wind energyindustry is that this material may facilitate the production of longer blades with upto 30% higher tensile strength than E-glass, up to 17% higher tensile modulus, andup to 40% increased fatigue strength, and crucially up to 8-10% weight savings.The potential for this new type of composite is that engineers may be able to designlonger blades without any increase in weight, which are able to cope with higherloads from wind speed. The increased fatigue strength may also prolong a blade’slifetime and reduce the frequency of service and maintenance visits; somethingwhich is essential to the development of deep water offshore wind farms. Thematerial also retains the anti-corrosive properties which will be required for offshoreinstallations.------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  5. 5. SummaryWith EC regulations dictating that renewable energy should supply 20% of Europe’selectricity by 2020, the wind power industry is undergoing continual development ata rapid pace. The most viable way of achieving the target is for the wind industry todevelop deep water offshore wind farms with future turbines to be rated at 10MW ormore. There is substantial investment in all aspects of wind farm design, fromfoundations to turbine development to grid integration; and there is a need forinnovation in all areas to design turbines which can be mass produced cost-effectively.Blades can account for 20-25% of the overall cost of a turbine, and are therefore asignificant component in terms of cost reduction. Despite the requirements toreduce overall cost, blades will need to be produced which are in excess of 60metres to be able to supply enough power to meet demand. The contradiction ofincreasing size while reducing cost is a complex design issue for blade and turbinemanufacturers, and one which must be assessed at component level. Manufacturingprocesses are being continually developed to streamline the production of suchblades, and material selection is a key issue for manufacturers as they look toimprove strength and durability, while lowering the cost of production.The use of composites in the construction of turbine blades is commonplace already,but the development of newer glass-fibre and carbon-fibre materials offers thepotential to improve upon existing designs as manufacturers look towards largerand larger turbines. Some manufacturers are already integrating carbon-fibrecomposites into the construction of their blades, while others are further improvingthe characteristics of glass-fibre materials. At this stage there is no ‘ideal’ compositematerial for the construction of turbine blades, and it is likely that several years ofresearch and development will be required, along with experience of turbines underreal installation conditions, before the best possible types of materials becomeuniversally accepted. Colin Pawsey------------------------------------------------------------------------------------------------------------------- ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences:
  6. 6. References: (1) AFM_DCCSM.aspx (2) (3) content/themes/3b/pdf/brochures/Brochure-Wind_UK.pdf Want to know more about advances in wind rotor blades? Check out our Download Centre, where you will find more articles, white papers and interviews regarding this topic: ---------- IQPC GmbH | Friedrichstr. 94 | D-10117 Berlin, Germany t: +49 (0) 30 2091 3330 | f: +49 (0) 30 2091 3263 | e: | w: Visit IQPC for a portfolio of topic-related events, congresses, seminars and conferences: