Materials for Wind Turbine Blades: An Overview

1. Introduction
The reduction of fossil fuel dependency requires the expansion of the renewable energy sector.The European Union seeks to cover 20% of its energy needs from renewables by 2020. In order toachieve this goal [ 1 , 2 ], the wind energy capacity should be expanded by two orders of magnitude.The EU offshore wind energy capacity is expected to grow by 21% annually [3–5].The history of wind turbines for electric power generation started in 1988 Cleveland Ohio, USA,
1888 by Charles F. Brush [ 6 ] and in Askov, Denmark in 1889 by pioneer Poul La Cour [ 7 ]. In 1941,electricity production from wind was made using turbines with steel blades built by the companyS. Morgan-Smith at Grandpa’s Knob in Vermont in USA. One of the blades failed after only a fewhundred hours of intermittent operation (see Figure 1a). Thus, the importance of the proper choice ofmaterials and inherent limitations of metals as a wind blade material was demonstrated early in thehistory of wind energy development. The next, quite successful example of the use of the wind turbinefor energy generation is the so-called Gedser wind turbine, designed by Johannes Juul, with threecomposite blades built from steel spars, with aluminum shells supported by wooden ribs, installed atGedser coast in Denmark in 1956–1957. After the 1970s, wind turbines were mainly produced withcomposite blades [8,9].
The Gedser turbine (three blades, 24 m rotor, 200 kW, Figure 1b) was the first success story ofwind energy, running for 11 years without maintenance. In this way, the linkage between the success ofwind energy generation technology and the application of composite materials became an issue fromthe beginning: the first turbine, built with steel blades, failed, while the second one, with compositeblades, worked for many years.

Materials for Wind Turbine Blades: An Overview