The Light Stuff... Future of wind power turns on composite windmill blades

The idea of capturing energy from wind is not at all new.  But with the growing use of turbine blades made of advanced materials, wind energy — once prohibitively expensive — is becoming more economical than ever before.
If you want proof, check the prices:  Even as fossil fuel costs have risen dramatically, the cost of emission-free wind energy has declined nearly 80 percent over the past decade, settling in recently at just over 4 cents per kilowatt hour.
According to the American Composites Manufacturers Association, much of the credit for the lower cost of wind energy is due to the use of fiber-reinforced plastic for the all-important turbine blade components that capture the force of the wind.
Typically made of durable plastic reinforced by glass fiber or carbon fiber, these “composite” turbine blades offer some of the same desirable characteristics as composites used on aircraft.  They are very light-weight, yet very stiff, and very strong — ideal for efficient performance in wind flow.
  To explain, just as it is easier to lift a light object rather than a heavy one, the low weight of fiber-reinforced plastic composites helps the blades overcome the pull of gravity on the upward cycle of their rotation.  Likewise, it helps the blades resist acceleration during the downward cycle. 
The greater stiffness and strength of blades made of composites is important because of the speed at which the blades often rotate.  Although they may appear to be moving slowly, it is not uncommon for the tips of the blades to be rotating at 100 miles per hour, creating enormous force considering that a 130-foot blade can weigh more than 11 tons.
Windmill blades made of composites also offer what design engineers call “fatigue resistance,” which means they will continue to perform optimally for a long time.  When you consider that a blade can be in near constant use, making millions of cycles, the benefit of this characteristic becomes obvious.
And blades made of composites also make life easier for other key components in a windmill.  Because they are lighter than traditional materials like metal or wood, they transfer less stress to the rotor, bearings, and mechanical components of the windmill, stretching out the service life of these parts.
In recognition of the fact that the world’s supply of coal and oil will not last forever, many nations are quickly ramping up their wind energy production.  Interestingly, these are some of the same countries that first used windmills roughly 700 years ago.  Denmark, Spain and Germany, for example, have posted wind power growth rates of 25 to 35 percent in recent years.       
Globally, wind industry growth is forecast to be in the double digits over the next decade.  Here in the U.S., a recently passed production tax credit to encourage construction of “wind farms” is expected to spur a five-fold increase in wind energy production in 2005 alone. 
    



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