Environmental Engineering Reference
In-Depth Information
Figure 13-1.
Scale model of the Altamont Pass used in wind tunnel tests.
Source:
Lubitz WD,
White RB. Prediction of wind power production using wind-tunnel data, a component of a wind
power forecasting system. Proceedings of AWEA WindPower 2004.
the wind varies across the site. The relative speeds between points are then usually
related to a mast where the speeds have been measured in the field.
Although studies comparing experimental methods to other methods are scarce,
there is no reason to think this type of approach cannot work well under many condi-
tions. It may even provide unique insights in areas where numerical wind flow models
are prone to fail, such as near the edge of a steep cliff. However, few wind resource
analysts adopt this method because of the time and special skills required to build an
appropriate model and the need for access to a wind tunnel. In addition, the method
has some limitations (such as the difficulty of modeling thermally stable conditions
and the challenge of appropriately matching atmospheric parameters to the physical
scale).
13.1.3 Statistical Models
Statistical models are based on relationships derived entirely or primarily from on-
site wind measurements. Typically, one tests different predictive parameters, such as
elevation, slope, exposure, surface roughness, and other indicators, to find those that
appear to have the strongest relationship with the observed wind resource at several
masts. In principle, any parameters can be used, although in practice it makes sense
to focus on those for which there is a reasonable theoretical basis for believing a
relationship should exist. This is one place where a good conceptual understanding is
helpful.
It is probably easiest to explain this approach by example. Suppose one has mea-
sured the mean wind speeds at several different towers at different points within a
wind resource area. Suppose the speeds are plotted against, say, elevation, and a strong
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