SHM.Tower® – Intelligent and Certified System for Monitoring Tower Vibrations and Maximizing Lifetime Extension

Vibration monitoring enables proactive optimization

Depending on the location and mode of operation of a wind turbine (WTG), the vibration stress – especially on the tower – varies greatly. The monitoring system SHM.Tower records these stresses via an integrated sensor. Due to the permanent comparison of the current RMS-values with the applicable standards – e.g. ISO 10816-21 and VDI 3834 – the condition of the turbine is always visible at first glance. Turbine settings and operating mode can be continuously and proactively optimized. The system issues warning messages if predefined threshold values are exceeded. WTGs with excessive loads are thus immediately identified and countermeasures can be initiated.

Reliable lifetime prognosis and optimized lifetime extension

Wind turbines are usually designed for a lifetime of 20 years. However, at the end of this design lifetime there is often a great potential for further operation. The decision on this is made within the scope of a lifetime extension report. So far, these are usually based on historical operating and wind data as well as turbulence reports. However, due to conservative load assumptions and insufficient consideration of the wind direction – and thus the distribution of lifetime consumption across the tower cross-section – the overall potential for a lifetime extension for as long as possible is often significantly underestimated.

SHM.Tower calculates the loads that actually occur and are distributed over the tower cross-section based on the accelerations measured in the tower and thus enables an exact statement to be made about the actual lifetime consumption. Even critical extreme conditions are directly recorded. Thus, the lifetime prognosis is no longer based on assumptions alone. The lifetime extension can be maximized and the entire yield potential can be tapped.

SHM.Tower was already certified as a Condition Monitoring System by WindGuard Certification GmbH in 2019. In 2020, the implemented load reconstruction methodology was also successfully assessed. It could be proven that SHM.Tower enables load measurement with a very high accuracy and is therefore very well suited for use in the context of lifetime extension reports:  

„Now that it was shown that the vibration profiles recorded with SHM.Tower are a very good representation of the system dynamics relevant for fatigue, there are indeed valuable possibilities for assessing the lifetime extension of modern WTGs. On the one hand, the DELs derived from vibrations can be used to validate and optimize the dynamic calculation model in order to minimize conservative safety factors. On the other hand, the measured load distribution in the tower cross section can be used to reduce the determined damage to the foundation and tower. In real terms, this results in a significant lifetime extension beyond the usual service life horizon without any loss of forecasting reliability. We have proven this in the assessment procedure.“

Frank Weise, Managing Director of WindGuard Certification GmbH

Use from the start or as retrofit

Sensors and electronics of SHM.Tower are built into a compact housing and allow for an easy installation in the tower head of the turbine. If the system is used right from the start, the operating status and the consumed lifetime are precisely recorded throughout all phases of use – thanks to the energy-autonomous mode even during construction and in the event of power failures. However, even if SHM.Tower is retrofitted, the system provides significantly improved lifetime assessments compared to conventional methods – even though the vibrations of the first years of operation are not recorded. Extrapolations enable the assessment over the entire service life.

After the initial lifetime extension report, you can optimally accompany the remaining service life of your WTG by continuously monitoring the vibration levels and tower loads.

The advantages of SHM.Tower at a glance:

Maximized
lifetime extension

Optimized
operation

Warning messages
when threshold values
are exceeded

Reliable asset
valuation

Identification of
black sheep

Functions:

Optimization of operation

  • Measurement of vibration stress and output of warning messages when threshold values are exceeded (ISO 10816-21/VDI 3834)
  • Frequency distribution of RMS values (e.g. annual cycle)
  • Wind farm monitoring to locate heavily loaded turbines
  • Monitoring of natural frequencies (tracking, long-term monitoring and trend analysis) to verify structural integrity
  • Unbalance indicator for aerodynamic unbalance and mass unbalance (for wind farm monitoring)

Lifetime prognosis

  • Lifetime prognosis for each tower segment
  • Classification of stresses according to operating conditions
  • Lifetime consumption trend
  • Valid statements for the lifetime extension of the turbine (also in case of retrofit)

Performance

  • Energy self-sufficient monitoring function (recording up to 3 months without energy supply)
  • Connection to the Wölfel monitoring portal MIC.Tower
  • Interface for external sensors (three-channel sensors)
  • Frequency range: 0.1 – 10 Hz
  • Measuring range: ± 2 g

References

White Paper "Maximizing the lifetime extension with SHM.Tower" 1.06 MB
White Paper "Maximizing the lifetime extension with SHM.Tower"

Up to now, lifetime extension reports have usually been based on historical operating and wind data as well as turbulence reports. Due to conservative load assumptions and insufficient consideration of the wind direction, however, the potential for continued operation for as long as possible is often significantly underestimated. Based on the accelerations measured in the tower, SHM.Tower calculates the real occurring loads distributed over the tower cross section and thus allows an exact statement about the actual lifetime consumption. The lifetime extension can be maximized and the entire yield potential can be tapped. This methodology has now been successfully evaluated by Deutsche WindGuard. In our White Paper, you can find out everything about how it works, the validation project and the areas of application.

White Paper "Structural Monitoring to Optimize Lifetime Extension" 1.02 MB
White Paper "Structural Monitoring to Optimize Lifetime Extension"

Structural Intelligence in wind turbines allows for the monitoring and evaluating of the lifetime of the towers during operation. The data collected serves as the basis for lifetime extension assessments: The measured fatigue loads show the actually consumed lifetime of the towers.

White Paper "Lifetime monitoring in turbine towers" 616.89 KB
White Paper "Lifetime monitoring in turbine towers"

A wind turbine is one of the industrial structures with the highest vibration loads within its lifetime. It has to withstand up to 250 million load cycles within approximately 20 years. The vibration loads of wind turbines vary considerably depending on the location and operational mode of the wind turbine.
Even two wind turbines in the same wind farm may differ significantly in their vibration loads. In the design phase, these loads can only roughly be determined leading to potential reserves of turbine’s lifetime during operation.


Please contact us personally

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We would be pleased to support you in solving your problem concerning "Wind turbine vibrations" and advise you on questions regarding our system and service offerings in the areas of structural health monitoring, vibration reduction, sound and noise as well as structural design.

Timo Klaas

+49 40 524715-265
klaas@woelfel.de
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Dipl.-Ing. Bernd Wölfel

+49 40 524715-266
bernd.woelfel@woelfel.de
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Lorena Sproll-Astorquiza

+49 931 49708-761
lsa@woelfel.de
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