Assessment & Inspection for Continued Operation of Wind Turbines
Calculation of the possible total service life for a safe continued operation of your wind turbine!
The lifetime of a wind turbine is a minimum of 20 years according to IEC 61400 [1]. However, differences between the design loads and the actual loads on-site can lead to the possibility of operating the WEC longer than the design life. Using an aero elastic simulation the individual overall lifetime can be calculated per main component.
Objectives
Each WEC has an individual lifetime which is affected by the on-site wind conditions. Using an analytical approach, the lifetime of each WEC main component can be calculated (Table 1). Consequently, the weak points of a WEC can be determined and the risk of damage caused by fatigue can be reduced. Knowing the overall lifetime serves as a basis for reliable organisational and financial decisions.
Applications
Different settings for the calculations are imaginable. The simulations can be carried out during the planning process of a wind farm if an advanced planning reliability is needed.
Moreover, the analysis helps to estimate financial and structural risks when the conditions on-site change e.g. in the case of new WECs built in the direct vicinity of existing WECs. The new wind turbines influence the turbulence on-site and cause a wake effect. This might lead to lower energy yields of the existing wind turbines and even influence the structural safety in a negative way. The analysis offers a direct comparison between the two settings.
In addition, the results of the simulation can be used to give advice on how to operate a WEC more safely and adjust it to the individual on-site conditions.
Also, the individual maintenance plan can be adjusted according to the lifetime of the main components and repairs of critical components can be planned in a long-term schedule. In the regular inspections it is possible to check the weak points, e.g. the rotor blade connection (Table 1), more closely and notice anomalies at an early stage. To extend the lifetime of the wind turbine it is possible to
- adjust the operation mode and / or
- renew the affected component.
Results
So far, more than 30 projects show that the simulated WECs can be operated past their design lives.The results lie between 23 and 41 years of overall lifetime for a design life of 20 years each.
In most cases a retrofit or renewal of the weakest component can easily be carried out after a few years of operation. That way it even prolongs the overall lifetime for several years.
Table 1. Examples of the minimum lifetime in years per component for different wind turbines