12 April 2007
12 April 2007
A study commissioned by AGY found that the company’s ZenTron roving should produce up to 25 percent mass reduction in the unidirectional spar cap and trailing edge components of wind turbine blades.
This will provide up to 11 percent total blade mass reduction in 62.5 meter blades compared to standard E glass. The study was commissioned through KC-WMC (Knowledge Centre - Wind Turbine Materials and Constructions, Holland), and unidirectional spar material was modified to include various fibres. ZenTron roving was used as an alternative to E-glass and carbon. To provide accurate input for the design process, AGY commissioned the Compositec composite materials resource center in France to generate composite data regarding the mechanical performance of a vacuum infused unidirectional ZenTron roving in NCF epoxy composite.
“Our objective was to demonstrate that AGY ZenTron roving could fit into the cost/performance model of material selection for wind turbine applications,” said Ed Mahoney, New Business Development Manager, AGY Europe.
“The results show that ZenTron roving can give wind turbine designers an option to replace or retrofit E-glass spar structures on current blades with a stiffer material, therefore enabling longer blades to be manufactured for the same weight as their current E-glass blade,” continued Mahoney. “This gives them the potential to extract more power from an existing turbine.”
Mahoney said the reduction in blade weight with ZenTron roving was primarily achieved from its 28 percent higher stiffness-to-weight ratio compared to E-glass fibre. This is based on the principle design criteria of achieving tip deflection, static strength and fatigue strength allowable.
Current state-of-the-art blades for 3 megawatt turbines are around 50 meters in length and are reported to be reaching the limit of designs possible with E-glass fibres in the spar cap. There is currently a trend to longer blades for wind turbines, but increased length also brings new challenges to be overcome. For example, longer rotors require more mass for the greater lengths and increased cross-sectional thickness to resist the higher bending loads from wind and rotational inertia. For turbine blades limited by tip deflection, the blades require greater bending rigidity to prevent hitting the back tower at the highest wind speeds.