Design of Wind Turbines - Wind Energy: Renewable Energy and the Environment - page 108

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FIGURE 6.7 Twist and planform for Carter 25 wind turbine blade. Blade is divided into ten sections for
analysis, and the station is at the midpoint of the section.

tool: PROP93 [22]. The inputs to the program include the blade characteristics (number, length and
hub cut-out, planform, twist at the section, and pitch), lift and drag coefficients of airfoils for dif-
ferent angles of attack, and operating characteristics, such as tip speed ratio, rpm, and wind speed.
The tabular output, in metric or English units, of PROP93 can be directed to the screen, printer, or
a data file. Notice for the selected input in the example ( Table 6.1 ) , the rotor is predicted to produce
23.3 kW at 10 m/s. Graphs of the standard output parameters can be displayed as functions of blade
station, pitch, wind speed, or tip speed ratio. Calculated values can then be compared with experi-
mental values. These programs, which are steady state, do not predict the high loads seen in the field
due to gusts and in changing the pitch to feather in high winds (dynamic stall).
Graphs of the planform (Figure 6.7) lift and drag data can be produced. Sample output graphs
(Figures 6.8 to 6.10 ) are for a Carter 25 wind turbine, NACA 2300 series airfoil. Smoother graphs

7 m/s 9 m/s 11 m/s 13 m/s

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Blade Station

FIGURE 6.8 PROP93: Prediction of power output for one blade by blade station for four wind speeds, tip
speed ratio 6.1.