An analysis of the discrepancy in availability and production at a wind farm in Sweden

Eolus recently developed, sold and now manage a wind farm consisting of four 2 MW wind turbines located in the northern half of Sweden. Soon after commissioning it was noticed that they were underperforming in terms of production and availability. It was suspected that one turbine was underperforming relative to the manufacturers’ power curve. Furthermore, the de-icing systems were discovered to be problematic, causing a lot of unplanned downtime. The main goals of this project are to determine the causes of the discrepancies in availability and production at the wind farm. As part of the investigation, the malfunctioning de-icing systems are also investigated. Initially, the background of the wind farm was researched. Important contracts, maintenance reports and other documentation was reviewed. Moreover, interviews were performed with four people involved with the wind farm. These revealed that problems first began during the construction phase. Delays and poor construction quality in general led to problems being carried over to the operations stage. Complications with the de-icing systems and blade drainage holes contributed to underperformance during the first year of operation. The second year of operation was marked by the de-icing system electrical cabinet detaching in the hub of turbine 2. Analysis of the turbine data and status files confirmed and elaborated on the information provided by the qualitative analysis. Investigation of the production and lost production figures revealed that the main problems have been related to the pitch systems, low temperature kits, sonic anemometers, PT-100 sensors, and the software for the controllers. Furthermore, a significant proportion of the lost production and downtime in years one and two can be attributed to tests and repairs performed on the de-icing systems. However, early indications in year three suggest that the single active de-icing system in turbine 3 is functioning as it should. Year three began with a significant improvement in availability, all turbines have experienced monthly availabilities of at least 90%. Overall, it appears that the fact that only one de-icing system is active has had a significant impact on the availability and production figures. However, organisational issues with the manufacturer still need to be resolved, as do the technical issues.