The Estimator is a useful tool to calculate a rough estimate of the electricity production of a wind farm or of a single wind turbine. It is based on the Weibull distribution model of the annual wind speeds, which will give a reasonable distribution for many parts of the world.
The information required for input to do a calculation is the following:
Rated Power of Turbine: This is usually close to the maximum power output in kilowatts of the turbine.
Number of turbines: This is the number of wind turbines in the wind farm.
Mean wind speed at hub height: This is the mean annual wind speed at hub height. If no measurements are available at the location this will have to be estimated. This could come from a wind map if one is available for the region. There are a number of other sources for this early stage estimate of the mean annual wind speed. The supplier can make a regional wind map for a specified region and for a particular height above ground. These wind maps or point location wind estimates come from global wind databases from multiple measurement sources combined with complex modelling. These are an excellent source for the annual mean wind speed, if used with an understanding of their scope and limitations.
Shape Factor: This is a feature of the Weibull distribution. It ranges in value from about 1.5 to 3.0. If no information is available for a value for a particular region it can be set at 2.0.
Losses: This will cover the deductions that need to be made for various factors that need to be accounted for, including array losses due to the presence of wakes from individual turbines reducing the output of turbines, down time for maintenance, electrical losses within the wind farm, and other losses. Typical values for wind farms 10% to 20%. Typical value for a single turbine 5%.
The other remaining input, the Power Curve of the individual turbine, is put in the form of a table in the lower part of the Estimator. The existing figures are for a typical one megawatt turbine. It is best that a specific power curve is put into the table from the actual turbine under consideration. The data will normally be available directly from a manufacturer or their website.
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