Probabilistic assessment of wind farm annual energy production

Energy yield (EY) evaluation of a wind farm (WF) is essential for profit estimation and such analysis is usually part of the pre-feasibility study for any WF. Energy output from a WF can vary because of several factors including site location and WF layout. It is therefore essential to estimate EY accurately taking into account as many realistic effects as possible. Both energy output from a WF as well as transfer of energy into the grid are vital information. In this paper, methodologies are provided to calculate losses due to wake effect, internal WF collector system, and a new method to calculate unavailability of wind turbine (WT) and WF components. A novel method to calculate wind energy curtailments due to network transmission bottlenecks is also presented considering internal WF losses for four collector systems. Correlations between incoming wind speed (WS), WT availability and Transmission Line Loading (TLL) are used to determine range of wind energy curtailments for several possible scenarios. Impact of wind resource variation (at a site) on energy output and energy curtailed is also analysed.

► Comprehensive methodology to evaluate energy yield of a wind farm is presented.
► Method for reliability based losses consider unavailability of wind farm components.
► Possible scenarios for energy curtailment due to transmission bottlenecks analysed.
► Impact of wake and electrical losses on energy output determined.
► Sensitivity analysis show effect of wind resource on energy yield and curtailments.