CHARACTERIZING THE OBSERVED WIND RESOURCE - Wind Resource Assessment: A Practical Guide to Developing a Wind Project - page 128

Table 10-1. Sample wind resource report statistics

Report products Units

Data recovery (DR) fraction %

Mean and annualized mean wind speed m/s

W/m 2 Mean wind power density (WPD)

Wind shear Nondimensional exponent

Turbulence intensity (TI) %

◦ C

Mean air temperature

kg/m 3 Mean air density

Speed frequency distribution Graph

Weibull A and k parameters m/s ( A ), nondimensional ( k )

Wind rose Graph

Daily and hourly speed distributions Graph

10.1.1 Data Recovery
The data recovery (DR) is defined as the number of valid data records ( N valid ) divided

by the total possible number of records ( N for the reporting period. It is usually

expressed as a percentage. The equation is as follows:

)

N valid
N (

DR = 100 × % ) (10.1)

For example, the total possible number of 10-min records in December is 4464. If
264 records were deemed invalid, the number of valid data records collected would
be 4200 (4464-264). The DR for this example would be

4200
4464

DR = 100 × = 94 . 1% (10.2)

The DR should be determined for each sensor for all levels at each site.

10.1.2 Mean and Annualized Mean Wind Speeds
The mean wind speed is simply the average of the valid speed values for the period
in question:

N valid

1
N valid

v = v i (10.3)

i = 1

However, the mean wind speed can sometimes be a misleading indicator of the wind
resource. If the data span a period much shorter than a full year, the mean will not
reflect the full seasonal cycle of wind variations. Even if the data span a full year,
there may be large gaps in the record that can bias the mean in favor of months with