Functional Failure Mode, Effects and Resilience Analysis (FMERA) to Determine Functionality Gaps of Today's Rotor Blade On-Site Inspection and Repair

Already today average rotor blade length of newly installed wind turbines is beyond 80 m in industrialized countries. Geometrical challenges furthermore comprise large circumferences close to nacelle, large differences between circumferences until the rotor blade tip and nacelle heights reaching and much beyond 150m. Thus, the rated power generated per average operation day increases further reaching the order of 4MW even for slow wind rotor blade turbines with their comparatively large rotor blades. However, along with generated electric power revenues of the order of, e.g., 10k€ a day in Europe, ever increasing standstill time costs arise. Thus, the ambition is to strongly minimize and control inspection and maintenance downtimes and costs. The present article presents a novel functional failure mode and effects and resilience analysis (FMERA) analytical approach on extended system level that includes on on-site inspection and repair capabilities to identify key missing functional capabilities. Missing capabilities are assessed using in addition the resilience dimensions preparation, detection and prevention, absorption, response and recovery, and adoption and learning to assess the criticality of the identified capability gaps analytically. The article identifies main physical access technology as well as inspection gap capabilities of today's solutions as well as potential future technological solutions that are expected to close these gaps. Solution space includes operational technician teams, main operation, and inspection times of wind turbines, as well as site access considerations including offshore. Furthermore, technologies much beyond state of best practice are assessed, e.g. glass fiber reinforced plastics, carbon fiber materials, and alternatives to traditional steel ropes. It is discussed how the proposed FMERA system analytical assessment and optimization process could be further improved for the present sample domain of assessment of rotor blade inspection and repair capabilities as well as further application options.

Keywords: Failure mode effects and resilience analysis, Rotor blade inspection, Wind energy, Analytical assessment of maintenance and repair, Ultra-lightweight physical access and inspection technology.