Robust and reliable Structural Health Monitoring solutions for foundation and tower to optimize operation and increase lifetime of offshore wind turbines
Carsten Ebert, Steffen Pankoke, Bernd Wölfel
Wölfel Engineering, Hamburg, Germany
Since the efficiency of wind turbines (WT) is primarily reflected in their possibility to produce energy at any time, the down times of WTs due to "conventional" inspections and maintenance is costly and unwelcome for investors and operators.
It is for this reason that the Wölfel Group has developed a wide product line-up of Structural Health Monitoring (SHM) solutions especially for offshore wind turbine structures (tower, transition piece and foundation), that allow for an holistic load monitoring, efficient damage detection and comprehensive lifetime assessment to give wind turbine operators the opportunity to optimize inspections, increase availability and yield and have the opportunity of a potential extension of lifetime.
This presentation will present the backgrounds of a vibration-based SHM system and its features. In this context the functionality of the system will be presented. Important aspects such as e.g. system robustness for the harsh environment, sensors types and application, communication with turbine controller, monitoring center, etc. will be illustrated.
Firstly, the great importance of an SHM system for offshore wind turbines will be discussed, taking the requirements and demands of authorities and operators into account.
In the next step, available systems and principles of known in industrial application will be mentioned, followed by the presentation of the functionality, the electronics and software components of the SHM solution.
The centerpiece of this paper is the presentation are the core outputs of such an SHM systems, the importance of the environmental and operational data that have to be integrated and the advantages of a lifetime assessment for the structural components by such a system.
The basis for this approach is a combination of operational modal analysis (adapted to deals with non-linear system behavior and non-stationary time series) and statistical pattern recognition techniques.
Cost of energy is mainly driven by the OPEX in the offshore wind sector, so SHM systems have a special importance. There has been a huge development in the last years in this field and many different SHM systems are already implemented in various windfarms. They have to proof their ability to optimize maintenance and inspection and give valid information for a reliable lifetime assessment. First results have a promising approach to help bring down cost of energy.
The presentation describes the importance of the extraction of valuable and commercially beneficial engineering information out of the huge amount of acquired sensor data, how and by which data processing procedures this extraction is performed and how the extracted information can be used.
At the end of the presentation some examples of long-time monitoring with respect to structural behavior of offshore turbines in different offshore windfarms will be discussed. Further topics regarding economical aspects and the cost-efficiency of the system will be briefly discussed too. Finally an outlook will be given on the future role of SHM systems and its advantages in the field of offshore wind will be given.