Wind

A wind resource atlas has been developed for South Africa which estimates mean annual wind speeds in ms^-1 at a 10 m height above ground level for approximately 67% of the country.The Wind Atlas Analysis and Application Programme (WAsP) model, developed by RISO National Laboratory (www.wasp.dk) in Denmark, was used for the estimations of all the provinces within South Africa except the Eastern Cape.The Eastern Cape province wind estimates were derived from a previous study ¹ and incorporated into the final wind atlas for South Africa. Input parameters to the WAsP model included: 

• data from automatic weather measuring stations, managed by the South African Weather Service 
  (+/- 100 stations in total);
• roughness values, derived from the 1996 National Land Cover database; and
• 20 m contour elevation information, obtained from Surveys and Mapping 1: 50 000 map sheet series.

The WAsP model was run for each automatic weather station with a specific extent or modelling area that was based on the terrain of the area.  Radii of 40, 50, and 75 km from the station site were used to define the model area: flatter areas having a larger radius, and more mountainous areas a smaller radius.  The model did not perform well in mountainous terrain, where excessively high mean annual wind speeds have been estimated at certain sites.  The downloadable document below provides an indication of the statistics associated with each station and it¿s surrounding modelled area.   The minimum statistic therefore shows for example the smallest mean annual wind speed estimated for a station and its surrounding modelled area.