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Turbine performance

In an energy production calculation, a power curve supplied by the turbine supplier is used within the analysis.

Generic power curve adjustment

It is usual for the supplied power curve to represent accurately the power curve that would be achieved by a wind turbine on a simple terrain test site, assuming the turbine is tested under an IEC power curve test.  For certain turbine models, there may be reason to expect that the supplied power curve does not accurately represent the power curve that would be achieved by a wind turbine on a simple terrain site under an IEC power curve test.  In such a situation a power curve adjustment is applied.  

High wind hysteresis

Most 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 shut-down 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

Site-specific power curve adjustment

Wind turbine power curves are usually based on power curve measurements, which are made on simple terrain test sites.  Certain wind farm sites may experience wind flow conditions that materially differ from the wind flow conditions seen at simple terrain test sites.  Where it is considered that the meteorological parameters in some areas of a site differ substantially from those at a typical wind turbine test station, then the impact on energy production of the difference in meteorological parameters at the site, compared with a typical power curve test site is estimated.  This may be undertaken where turbulence or up-flow angle are considered to be substantially different at the wind farm site than that which is experienced at a typical test site, and sufficient data is available to inform on the appropriate adjustments.