The main findings in this E-Book can be broken down into two parts:
• Part 1: Lifetime estimation of a wind turbines main bearing using measurement data and physics based models
• Part 2: Information available to wind farm owners in OEM design documentation to make internal component lifetime calculations using physics based models.
First of all, what is a physics-based model? A physics-based modeling approach can be used to establish a relationship between the forces acting on a component and the consumption of the component’s useful lifetime. Physics-based modelling requires intricate knowledge of forces and how the component in question is affected by those forces and what the forces influence is on lifetime. The influence of different forces on the component’s lifetime is often well established during the design engineering carried out by wind turbine manufacturers.
This E-Book investigates the lifetime for a wind turbine’s main bearing. The axial and the radial forces bear the most influence on lifetime of the main bearing. These two forces are combined into one dynamic equivalent force. However, in the measurement data set used in this E-Book, the axial and radial forces were not available. Luckily, they were available in a simulated data set that was made available by the wind turbine manufacturer for this project. By combining the measurement data and simulated data 3 the dynamic equivalent force could be estimated by correlation using the blade root bending moment that was available in both the measurement data and simulated data.
It was found that the design life of the main bearing was significantly lower when actual measurement data was used compared to simulated data. With measurement data, the life of the main bearing was 31 years and with simulated data, it was 79 years. It is a big difference but both are still sufficiently larger than the technical lifetime assumptions that are normally used for wind turbine investments.
Furthermore, the study found that the consumption of main bearing “life” is higher under certain wind conditions than others. For instance, lifetime consumption for the main bearing is highest at the “knick” of the power curve at wind speeds around 12 to 14 m/s, before a turbine reaches rated power.
It was also concluded that it is possible to generalize the approach taken in this project for any wind turbine component provided that sufficient information is available.
In general, to make use of a physical modelling approach requires measurement of different forces acting on the component in question and an in depth understanding or mathematical formula of the effect of these forces on components under consideration. The next step in the project investigated if this information is or can be made available to the wind turbine owner from the OEM. Five owners of various portfolio sizes were interviewed.
Book authors conclude that making lifetime calculations as done in this case is not possible to do at scale because owners do not possess the required information
1. Measurements of forces (without investing in specific measurement equipment)
2. Design documentation detailing the forces effect on components Information above is in most cases considered proprietary to the OEM and hence not readily released to the wind turbine owner.