Posters

Abstract

One important environmental concern in operating wind farms across Europe is the bat risk of collision with wind turbines' rotating blades. To avoid this, the bat curtailment practise is implemented, in which the turbines are shutdown during bat activity periods. This, however, leads to a decrease in the annual energy production (AEP). A proper assessment of the energy loss due to bats is key to take decisions on mitigation strategies and correctly estimate the wind farm AEP. Following the manufacturer strategy, the industry standard provides a model to estimate the annual energy efficiency due to bat curtailment in wind farms. This is a time domain efficiency model that works with setting the power generation time stamps to zero into the reconstructed hub height power time series used to calculate the AEP following the criteria defined in the strategy (typically temperature, wind speed and time of the day limits that are recognised to be sensitive to the bat activity). The exact values of these limits depend on the turbine control system design choice of the specific turbine model. However, analysis of real operational data of wind farms show that the annual bat energy loss is under/overestimated due to different reasons. In this work, DNV explains and evaluates the discrepancies seen between the bat curtailment losses in operation and the bat efficiencies modelled using the industry standard. Operational data of different wind farms are analysed to evaluate the resulting gaps which are classified in the following categories: yearly windiness, error in the control strategy implementation, inaccuracy of nacelle instrument readings of the ambient parameters and inertia in the control of the turbine. The final purpose is to understand where the current methodology deviations occur in order to improve the process to model the bat curtailment losses while ensuring bat's security in wind farms.