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.
farmland with short row crops
prevailing wind direction
Exposure with some obstacles
- Some ground
vegetation and buildings
rolling terrain with open exposure
- Many trees
and or buildings,
elevation than surroundings
terrain with scattered vegetation
from many directions
|Very High Turbulence
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.