Small Wind Turbine Design Notes
Notes based on a session during the Centre for Alternative Technology Windpower Course
Notes written and taught by Hugh Piggott with input from Claus Nybroe.
Hugh Piggott writes:
The first time I did this talk at CAT they threw me in with no preparation, "Just come as you are!"
and I had to wave my arms about a lot. Since then I have done it countless times, but I still get more
than a few blank looks. It©s probably the most obscure bit of the course. Finally after about ten
years, I have produced a full set of notes. I am so pleased, I asked Ian to put it on his site, and he
has! Thanks Ian. Sorry I did not explain Betz©s theorem, or ©p speed ratio©. Buy my book
ti
©Windpower Workshop© and read the whole story :-)
Content
Defining drag vs lift forces page 2
Finite element blade design page 3
The maths of lift and drag page 4
Setting the best blade angle page 5
Shape of the apparent wind page 6
Optimising the chord width page 7
©Back of an envelope© design page 8
Factors affecting power coefficient page 9
Ideal shapes and practical limits page 10
Pros and cons of high speed rotors page 11
Variation of size and twist windmill blade page 12
Defining drag vs lift forces
Finite element blade design
The maths of lift and drag
Setting the best blade angle
Shape of the apparent wind
Optimising the chord width
©Back of an envelope© design
Factors affecting power coefficient
Ideal shapes and practical limits
Pros and cons of high speed rotors
Variation of size and twist in a 2.3mdiameter wooden windmill blade