A project carried out at NSIRC founder member TWI’s Cambridge laboratories involved a company with interest in developing a structural monitoring system for wind turbine structures. Using the resources available to NSIRC, TWI carried out a literature review and identified six degradation mechanisms relevant to wind turbine towers and foundation structures, as well as four condition monitoring systems that were potentially appropriate for such structures.
The team of engineers used finite element analysis to simulate the change of response of the wind turbine structure with and without defects.
The project work involved four objectives, which were to:
- perform FEA simulations of a monopile wind turbine tower and foundation to predict the response of a damaged structure and compare the response to that of a similar intact structure.
- determine the minimum defect size required to produce a change in natural frequency/ mode shape/ amplitude of strain or displacement.
- compare the magnitude of the structural response due to this minimum defect size with the minimum measurable response of the condition monitoring systems, the aim being to determine whether defects of this size could be detected.
- compare the minimum detectable defect size to the maximum tolerable defect size (from fracture mechanics analysis available in the literature). This was required to determine whether the condition monitoring systems would be capable of detecting defects before they reached the critical size which could cause catastrophic failure of the wind turbine structure.
The results and conclusions of this work remain client confidential. However the engineers at TWI concluded that the finite element model of the wind tower could be used to predict the effect of various damage mechanisms on the structural response of the tower under wind and wave loading.
The final report informed the client about on the feasibility of these potential new condition monitoring systems which would allow the structural response of offshore wind turbine towers to be understood.
To learn more about conditioning monitoring for wind turbine towers and foundations, and indeed finite element modelling at NSIRC please contact us.