PLANT DESIGN AND ENERGY PRODUCTION ESTIMATION - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 237

Figure 16-4. An example of a WRG file containing the gridded output of a wind flow sim-
ulation. The first line indicates the number of columns and rows in the grid, the X and Y
coordinates of the upper-left grid point, and the grid spacing. (Here scientific notation is used,
but it is not required.) The next lines contain the wind resource data for each grid point. The
first two parameters in each line are the X and Y coordinates of the point. These are followed
by elevation above mean sea level (1060.8 m for the first grid point), the height above ground
(80 m), the overall mean Weibull A parameter (9.1 m/s), the overall Weibull k parameter (2.09),
and the mean wind power density (735.3 W/m 2 ). Then there is the number of direction sectors
(12), and for each direction sector, in groups of three, the frequency (in percentage), the Weibull
A (multiplied by 10), and the Weibull k (multiplied by 100). Note: for this example, the table
is truncated to the right after the fourth direction sector. Source: AWS Truepower.

Table 16-1. IEC classifications for turbine suitability for the standard sea-level air
density of 1.225 kg/m 3 .

Wind Turbine I II III

Class A B C A B C A B C

V ref (m/s) 50 50 50 42.5 42.5 42.5 37.5 37.5 37.5

I ref 16% 14% 12% 16% 14% 12% 16% 14% 12%

Source : IEC 61400-1 Third Edition 2005-8.

with a turbine vendor or has already placed a number of turbines on order for this
and other projects. Very often, though, the developer is free to consider any of an
ever-growing selection of wind turbine models.
However, not every turbine is suitable for every site. The question of turbine
suitability should be addressed provisionally early in the process to avoid wasting time
assessing unsuitable models or developing unrealistic expectations of the performance
of the project. (The final decision on turbine suitability is up to the manufacturer, who
must decide whether the turbine will be warranted for the site, and if so, under what
operating conditions.)
The analyst should become familiar with the standard IEC turbine classifications,
which are summarized in Table 16-1. It is common to hear sites referred to as “Class