Lifetime Analysis of a Wind Turbine Component

The design life of a wind turbine is often said to be around 20 years. In practice it is frequently observed that components in a turbine fail earlier and must be replaced before the stated lifetime. Therefore, it is very important for the stakeholders of wind turbines to have a good estimation of the components remaining lifetime and create a suitable maintenance schedule. By possessing that knowledge, preventive measures can be taken to reduce the stakeholder’s losses. The purpose of this thesis was to investigate how the remaining lifetime of a wind turbine component can be estimated based on online measurement data. This included a study on whether the initially designed lifetime of a wind turbine component differed when the turbine had been in operation for some period of time. It was also of interest to find out if turbine owners have enough information regarding their turbines in order to perform similar studies. The project was divided into two parts. In the first part a direct drive multi-MW wind turbine was studied. Lifetime calculations were performed for the main bearing, which is placed on the turbine shaft. However, some necessary measurements were missing and it was investigated whether a correlation to another signal could be found. In the second part of the project, five qualitative interviews were conducted with wind turbine owners with a varied range of installed capacity. A correlation to the measured blade root flapwise bending moment was found and the lifetime calculation was performed. The designed lifetime of the main bearing differed substantially compared to when the turbine had been in operation for some period of time. From the lifetime calculation it was found that different wind speeds affect the wear of the main bearing differently. The highest wear of the main bearing occurred close to the rated wind speed. If similar calculations were implemented for other components the operator of a wind turbine would get a better picture of how different operating conditions influence the wear of different components. As a result, the owner could decide how the turbine should operate during the most destructive wind speeds. From the interviews it was found that the owners do not get sufficient information from the manufacturer in order to do similar studies. Some owners have tried to gain access to more information regarding their turbine, but to little avail as the manufacturers are unwilling to share this information due to competitive reasons.