Power dispatching is one of the important requirements for wind power systems. Using energy storage systems, especially the battery energy storage system (BESS) is one of the more effective solutions for overcoming this problem. The required battery capacity depends on the fluctuation level of the output power, which is affected by several factors. In this paper, the object is to estimate the required battery capacity based on wind speed data and turbines position in the design phase of a wind farm. An analytical method is presented to estimate the short-term fluctuation of wind farm power considering wake effect, turbulence, and spatial smoothing. Then, a method for estimating the optimum battery capacity, based on the statistical characteristics of wind farm power including average value and standard deviation over a long-term period, is presented. In addition, a new model is presented to estimate the battery lifetime in the case of non-uniform charge/discharge cycles. The numerical results for a case study, over one-year wind speed data, are presented and the results show the effectiveness of the proposed approach in determining the optimum battery capacity.
