Grid availability: This factor defines the expected grid availability for the project. It is stressed that this factor relates to the grid being outside the operational parameters defined within the grid connection agreement as well as actual grid downtime. This factor also accounts for delays in the project coming back to full operation following a grid outage. A typical assumption for generic projects in Europe is 99.5 %, however, grid availability in India could have different behaviours and therefore this value should be regarded with caution.
High wind hysteresis losses: Wind turbines will shut down when the wind speed exceeds a certain limit. High wind speed shut down events can cause significant fatigue loading. Therefore, to prevent repeated start up and shut down of the turbine when winds are close to the shutdown threshold, hysteresis is commonly introduced into the turbine control algorithm. Where a detailed description of the wind turbine cut-in and cut-out parameters are available, this is used to estimate the loss of production due to high wind hysteresis by repeating the analysis using a power curve with a reduced cut-out wind speed. Due to the low wind conditions expected at all sites, the FOWIND consortium has assumed these losses to be negligible.
Power curve compliance: Wind turbines will have some sub-optimal efficiencies when considering the power curves provided by the manufacturer. These inefficiencies are due to different factors such as pitch/yaw misalignment, controller performance, etc. For this reason, DNV GL typically assumes a power curve compliance efficiency of 99.5 %.
After consideration of all the factors mentioned above, DNV GL has assumed an overall Wind Farm Performance availability of 98.0% for all different scenarios.
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