[Phys-l] Wind generator output versus wind speed.

[Rick Tarara <rtarara@saintmarys.edu>]

Here is a physics/engineering question.

> From various texts, the theoretical maximum power transfer from wind to 
electrical power is cubic in wind speed and also depends on the area swept 
by the rotors.  The cubic part comes from the KE which is of course 
quadratic in speed but with the added linear factor of wind mass.  All 
that's fine, but when you look at the power curves of real wind turbines, 
you see 'S' curves, with little power generated at low speed and levelling 
to some max power at high speed.  However, the curves look pretty linear 
from the 'cut in' to the 'cut out' wind velocities--slopes greater than one. 
We have the Pasco Energy Transfer Generators and are putting together a wind 
energy lab, but we're also seeing a linear dependency (using a three speed 
fan).  Not sure I understand the linearity and certainly not sure how to 
approach my Energy class (gen-ed students) with anything other than 'turbine 
design is complex and the actual power transfer is a function of each 
individual device'.  Any insights would be appreciated.

http://www.clemson.edu/scies/wind/Poster-Schmidt.pdf

Slide 11 above shows some typical power curves--many others can be found 
on-line.

Thanks,

Rick

***************************
Richard W. Tarara
Professor of Physics
Saint Mary's College
Notre Dame, IN
rtarara@saintmarys.edu
******************************
Free Physics Software
PC & Mac
www.saintmarys.edu/~rtarara/software.html
*******************************