CompositesWorld

FEB 2018

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FEBRUARY 2018 32 CompositesWorld WORK IN PROGRESS ยป LM Wind Power's (LM, Kolding, Denmark) sole product is wind turbine blades. From 1978 through 2016, the company had produced more than 195,000 blades. Recently, LM stretched its skills to produce its first 88.4m wind turbine blades (Fig. 1, above). Almost as long as a 100-yd American football field, they are the longest blades yet built by any manufacturer. e swept area of a turbine rotor fitted with 88.4m wind blades is large enough to cover three soccer fields and power a small town. e blade in question, designated LM 88.4 P, is nearly 15m longer than LM's previously longest blade, the LM 73.5 P, but only 6 MT greater in mass (see Fig. 2, p. 33). is was accomplished by introducing the lightweight strength and stiffness of carbon fiber into the spar cap laminate. Other wind blade manufacturers have leveraged the benefits of carbon fiber for more than a decade โ€” primarily through pultruded and carbon/epoxy prepreg spar caps โ€” justifying its higher price through realized performance benefits that enabled competitive levelized cost of energy (LCoE) per megawatt hour. LM, however, is now taking a different approach, embedding a hybrid carbon/glass fiber main spar cap along the length of its standard glass fiber base shell laminate. Saving time and money, the blade shell and spar cap are built in the same tool, with the shell serving as the mold for the hybrid-carbon spar cap. "e LM 88.4 P is the first hybrid blade to be built in this way, using a dry hybrid-carbon layup with a vacuum-assisted resin transfer molding (VARTM) infusion process," says LM's Michael Lund-Laverick, director composite technology projects. is hybrid design enabled LM to stretch its core competence to a 88.4m blade within its existing resin-infusion process, without adding another manufacturing process. is strategy met LM's customer's design specifications within established cost and schedule targets. "We chose the solution that was closest to the concept we usually apply, thereby reducing risk and enabling faster development for the customer," Lund-Laverick says. e design process for the 88.4m started with the question LM's engineers ask first on every project: How windy will it be? Customers select one of four wind classes established by the Inter- national Electrotechnical Commission (IEC, Geneva, Switzerland), based on the destination wind farm site and on calculated loads (Fig. 3, p. 33). LM's customer for the 88.4m blade, Adwen (Bremer- haven, Germany, now part of Siemens Gamesa Renewable Energy, Zamudio, Spain), specified Wind Class I (high wind) for offshore sites. LM, accordingly, designed the blade for 50 m/sec (112 mph) Reference Wind Speed and other Class 1 requirements. Carbon/glass spar cap enables world's longest wind blade LM Wind Power goes long with a resin-infused hybrid carbon composite strategy. By Donna Dawson / Senior Writer Emeritus FIG. 1 LM Wind Power's 88m blades, installed One set of 3 LM 88.4 P blades, installed by Adwen and running in Bremerhaven, Germany, on this single wind turbine, are said to be capable of powering around 10,000 homes โ€” a small town. Ten similar turbines might power a city. Source (all photos) | LM Wind Power

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