A VIEW INTO FUTURE POTENTIAL ICE THROW POLICIES AND THEIR EFFECT ON THE YIELD OF A VIRTUAL WIND FARM

Sammanfattning: There is a growth of wind power development in icing climates, in which ice accumulation on objects takes place. This leads to specific challenges including ice throw, the detachment of ice from wind turbine blades. The lack of understanding of the ice throw phenomenon among authorities leads to the fact that there is no coherence in the applied ice throw mitigation policies in various countries and regions, which can cause safety- and financial hazards for wind farms in icing climates. This research focusses on ice throw risk mitigation methods and their effect on a wind farms yield. Qualitative research is applied, interviewing six experts in the field of cold climate wind power development. The participants are from academic, public and private research institutions in five countries. The qualitative research focusses on policies that are plausible but non-preferred, as well as preference suggestions from the experts on how to treat the ice throw risks. The non-preferred policies involve shutting down wind farms during icing periods and conditionally allowed operation with applied heating systems. These policy scenarios are applied to a virtual wind farm near Slagnäs, Sweden, in order to indicate the impact on the yield and underline the impact that these policies would have on the turnover of a wind farm in a sever icing climate. The non-preferred policies have a significant impact on the Slagnäs wind farms yield with 2,28% annual yield losses in case of 200 annual icing hours. Apart from the impact on yield, the policies might not reduce the danger of ice throw significantly, as from a standing still turbine, detached ice can still travel a horizontal distance of up to one time the turbine height. Therefore, policies should according to the interviewed experts not focus on limitations, however focus on understanding risks and taking appropriate action for risk mitigation. International guidelines are the best tool to create a deeper understanding of ice throw risk assessments and their limitations, as well as an understanding of risk mitigation methods. In this case, the risk assessment process shall be standardised, however the risk mitigation methods shall be site specific.