PERFORMANCE

 

The following information starts with a few key terms followed by a description of possible property types and finishes with an approximation of the annual production from a Jacobs 31-20 in Kilowatt-hours (Kwh) for the most common ranges of wind resources compared against common terrain types.  Please be sure to use the charts conservatively and follow the descriptions provided. 

Please note that this information is not a guarantee of production and should never be used lieu of a professional wind site assessment.

Annual Average Wind Speed:
The "Annual Average Windspeed" for a wind turbine should be calculated at the hub height and it is the average of all  the varied wind speeds through out the year.  A related term to annual average wind speed is "Wind Speed Distribution"; it is the percentage of time throughout the year that the wind is observed at different binned velocities.

Terrain and Turbulence:
Turbulence which is typically caused by the type of terrain surrounding a site is considered to be the enemy of any wind turbine system (even of those products that claim otherwise); any wind system that is exposed to high turbulence will see reduced production as well as a higher frequency of required maintenance.  The following chart gives typical site descriptions and and their approximate turbulence levels.

Site Description:

Low Turbulence
          - Well Exposed
          - Open farmland with short row crops
          - Flat Terrain
          - Strong prevailing wind direction
Average Turbulence
          - Good Exposure with some obstacles
          - Some ground clutter,
          - Scattered vegetation and buildings
          - Light rolling terrain with open exposure

High Turbulence
          - Marginal Exposure
          - Many trees and or buildings,
          - Lower elevation than surroundings
          -Rolling terrain with scattered vegetation
          -Wind comes from many directions
Very High Turbulence
          - Very compromised sites
          - Suburban Sites
          - Densely wooded sites
          - Sharp differences in elevation (turbine base is lower)

Compare the descriptions above to the chart below assuming that a higher turbulence means lower production for the given annual average wind speeds.  This is a simplification of the production estimate process as many other factors are used in professional assessments; these descriptions are intended to give the user a general idea of possible production.