Fiber optic Blade Monitoring. Final report / public part

"Condition monitoring of wind turbine components is of growing importance. For bearings, gearboxes and other rotating equipment, techniques are available from other applications. For condition monitoring of rotor blades, no suitable techniques are available up to now. However the interest for it is increasing rapidly. Three main reasons can be mentioned for the late development of blade condition monitoring systems. · The sensors to be implemented in the blades were expensive and had a short lifetime expectation. · A measurement system should be mounted in the hub and supplied with power. A data link between the rotor and the turbine that operates independent from the turbine communication system is necessary. Up to now, such a data link was expensive, and sensitive to failures. · Algorithms to predict the remaining lifetime and trigger alarms are available only partly and still need to be validated. With respect to the sensors, reliable sensors become more and more available, particularly the fibre optic sensors. At this moment, measurement instrumentation based on fibre optic sensors, is available but mostly for other branches of industry. Most instrumentation is tailor made for specific applications. The gained experience can be used for wind turbines, however there are several specific requirements that ask for additional developments. With respect to the data link between the rotor and the turbine, more solutions become available. Wireless LAN is one very serious option, which ensures a fast and flexible data link, independent from the wind turbine design. Additionally, the possibility to install instrumentation in the rotor is more and more common practice. Both the sensors and the data communication systems are being developed outside the wind energy community. The implementation of the systems in wind turbines and the development and use of algorithms are wind energy specific. This document gives a summary of the activities as performed during the project as far as the public part is concerned. This includes the feasibility of the application of load measurements for load reducing control strategies for the complete turbine as well as for condition monitoring of the blades. For the condition monitoring application algorithms have been defined which can give the user insight in the loads encountered during operation and the remaining lifetime of the blades. The specifications for a baseline system were also derived which can be used for the development of a specific blade monitoring system for further experiments and algorithm development."