Mitigation measures for preventing collision of birds with wind turbines

Bird collisions with wind turbines is one of the major environmental impacts of wind energy. To decrease the number of avian fatalities in wind farms, several studies have been done to understand, evaluate and apply measures that reduce the risks of collisions. Overall, mitigation measures during the operational phase of wind farms are based on either active or passive procedures, depending on the need (or not) for an external source to trigger an action for preventing a possible collision. The aim of this work is firstly to provide an overview of mitigation measures that have been demonstrated in-situ, including the overall procedures of the tests, results, as well as advantages and disadvantages of the measures. Subsequently, a new patented control concept to avoid collisions (SKARV) is described. Four measures that have been tested at wind farms in Spain, Norway, and USA are summarized: habitat management and painting (passive measures), turbine curtailment and deterrents (active measures). Estimations from these tests indicate an average reduction of 33%-86% in annual bird fatality for specific targeted species. The SKARV concept is not yet tested, but may be a benign alternative.