PLANT DESIGN AND ENERGY PRODUCTION ESTIMATION - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 235

16.3.1 Wind Resource Measurements
Wind resource measurements are the linchpin of energy production simulations. Only
direct measurements from within the project area capture with high confidence the
true speed and direction frequency distributions that determine the energy production
potential. Without them, it is rare that financial institutions or investors will risk money
on building a wind project of a significant size.
The wind resource data are usually imported into wind plant design software in the
form of a tabular file popularly called a TAB file . One such file is imported for each
mast in the project area to be used in the energy production simulations. A TAB file
provides the frequency of occurrence of winds observed within specified speed and
direction bins. An example of this format is shown in Figure 16-3. In principle, a time
series of wind measurements could also be used, but only some programs support this
option.
Figure 16-3. An example of a TAB file containing wind measurements binned by direction
and speed. The first two lines contain information about the site, including, in the second line,
the X and Y coordinates and height of measurement. The third line indicates the number of
direction bins or sectors (in this case 12, indicating 30 ◦ -wide sectors), as well as scale and
shift factors used for adjusting the speeds and directions, if necessary. The fourth line indicates
the frequency of occurrence of each direction sector (e.g., in this case, winds come from the
third sector, east-northeast, 2.825% of the time). At the start of each successive line is the
upper limit of each wind speed bin (1 m/s in the first line), followed by the relative number of
occurrences (summing to 1000 in this example) of that speed range within each direction sector.
For example, when the wind direction is in the third sector, the speed falls in the 4-5 m/s speed
bin with a frequency of 119.65 out of 1000, or 11.965%. The total frequency of occurrence in
this bin is therefore 2.825% × 11.965% = 0.338%. Source: AWS Truepower.