Wind & Wet

DIY wind turbine (2)

PVC wind turbine blades

Pipe blades

Having established the input power required to turn the alternator the blades needed to be designed to provide the power. The wind power calculator was used to match the alternator power curve with values.
Blade radius
580mm
Tip speed ratio
6.5
Coefficent of performance
0.3
This gives the power curve below.
Graph of power against wind speed
The alternator will start charging at around 300 rpm which equates to a wind speed of about 3m/s.
The blades were made using an early version of the pipe blade designer with the following values.
Blade radius
580mm
Tube radius
60
Tip speed ratio
6.5
Angle of attack
4
Offset
15
Number of blades
3
Coefficient of lift
0.85
The coefficient of performance and coefficient of lift values are estimates. The blades were made from semi circular PVC gutter described in the pipe blade design section.
The chord at the tip and root of the blades came out very close to the original Mk1 version. The mounting holes, however, were noticeably further in from the trailing edge, setting the blades at a shallower angle and allowing the turbine to rotate faster.
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