Feasibility in developing smart structures for use in wind turbine blades
Blockey, James Craig
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Recently the use of wind as an alternative energy source has developed quickly. The length of the blades is a leading factor in the power output of a wind turbine and as a result, blade length has grown at a similar pace to the growth of the industry. The rapid expansion in use and size of wind turbines is not without its problems, though. As the industry has changed and grown, the overall design of the blades has remained relatively stagnant. This is evident in two primary areas, power control and health monitoring. Power control mechanisms are generally unchanged, utilizing either pitch control or active stall designs. While effective, these systems are neither efficient nor fast acting and can contribute to higher maintenance requirements. Current wind turbine blades also have no sensors built into them. The nacelle and tower utilize many sensors, but the blades themselves have none, leading to blades which are incapable of any real time health monitoring. The application of smart structures will enable the in situ monitoring of the blade and allow the blade to adapt to changing wind loadings Smart structures are those which apply an array of sensors to continuously monitor the state of the structure and are capable of using those sensors to appropriately react to achieve a desired state. This paper will examine the application of smart structures to the wind energy industry. It will be shown that a fiber optic, Fiber Bragg Grating sensor is the best type of sensor for wind energy. One of the main contributing factors is the capability of the sensors to multiplex, which means many sensors can be located along a single optical fiber and different types of sensors can be run on the same optical fiber. The blades will 'react' to changing conditions through the use of an actuated Gurney style flap. The flap will be used to shed the wind loads from the blade in high wind scenarios. These systems working together will provide an effective and efficient method of advancing the design of the wind turbine blade to a level appropriate for the systems expected today and in the future.