JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009 - 27

unable to develop a follow-up on major innovations. William Abernathy and James Utterback described the evolution of products and processes as a transition from an early ‘fluid’ state where performance criteria are not well defined for new products (less standardization) to a highly ‘specific’ and rigid state where the performance criteria are clearly specified (more standardization) and production volume increases. Today, horizontal axis wind turbines (HAWT) have reached the design status where their major features (such as three-blade structures) have become standardized from supplier to supplier, due to a combination of factors such as aesthetics, dynamic stability, and optimum cost versus power generation. Knowledge depth is what distinguishes market leaders from the rest. Such firms treat technology as a major source of competitive advantage. Patents can be seen as a measure of their explicit form of knowledge, but a firm also keeps knowledge in a tacit form which resides in the people, especially in process technologies, etc. These are reflected in the quality and reliability of the products the firm produces. Vestas wind turbines are one such example, boasting 20 years of outstanding reliability. Dynamic wind turbine systems like these, which operate in all types of conditions with minimal human intervention, constitute a unique engineering product. As noted earlier, the power generated from wind energy is directly proportional to the rotor area, and hence to the square of the blade diameter. Figure 2 represents a typical power curve, which shows that wind power increases cubically with wind velocity. However, beyond a critical wind velocity, the power capture capability of a wind turbine is de-rated to avoid mechanical damage due to material limits. Rotor blade characteristics are related directly to length in a number of different ways, including: 1. Mass x length3 2. Power x length2 3. Resonant frequency x 1/length3 4. Blade cross-section constrained by airfoil requirement. 5. Blade length and cross-section determine large deformation behaviour, thus coupling structural and aerodynamic performance. Fig. 2: Power generated versus total wind speed. Rotors are subjected to wind loads and other steady and unsteady loads that increase non-linearly with length. Two main types of loads are involved: 1) wind loads such as steady mean wind, vertical wind shear, cross winds, tower shadow and wind turbulence, and 2) non-wind loads, including centrifugal forces, gravity forces, gyroscopic forces and ground motion and shock loads. to explain why some species evolve in intermittent leaps. A punctuated equilibrium model can be used to explain how a geographic separation can cause disruption in a new species and a new species to arise. A similar phenomenon can be observed when technology migrates from one application or market to another and must meet a different set of performance criteria/demands, as long as healthy resources are available to allow it to grow with unique characteristics. In some cases, the technology can come back to “conquer” the original application. Such technology drifts are encouraged, to create a surge in the overall technological development. But this can only come about with the collaboration of all partners all along the value chain, including scholars, researchers, and suppliers on the outside, and research and development teams, manufacturing staff, marketing and service personnel, among others, on the inside. We need to focus on both technology development and market application to manage the development of emerging technologies. Intellectual property concerns, legal restrictions, sunk costs may hinder, but are not a reason to abandon an application. Evolution of composite technology An industry’s success clearly depends on the application demands and the technology’s push in what they can deliver. This enables innovation transfers from one industry to another. However, the selection criteria and performance expectations of a technology, as well as the resources it offers, enable enhanced growth in that particular technology compared to before migration. New technologies undergo periods of evolution and revolution and can be created either by convergence or fusion of existing technologies. This can be compared to the evolution process of biological species, where competing views exists. Darwin’s theory assumes that evolution takes place gradually through natural selection, but is unable Composite innovations Composite science is interesting for wind turbine generator (WTG) applications for several reasons. First, it makes it possible to increase the specific strength and stiffness of materials. The length of future blades and the power output of future WTGs can also be increased, even as WTG operating costs are lowered due to improved reliability. The size of components/systems can be reduced, and mass production with consistent quality becomes possible. Wind turbine blade design is predominately driven by fatigue loading, good fatigue performance being essential for blade optimization. As turbine size increases, so does their fatigue loading. In operation, blades are subject to No47 March-April 2009 / jec composites magazine 27

JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #47 - March/April 2009