**
****
Wind
Energy
Laboratory** (part 2)

**Cp-landa
curve of**** Wind Turbines**

Lift type wind
turbines are widely used in modern wind energy conversion systems.* *

The lift forces are generated by different air pressures between the upper side and the lower side of the blades, and rotate the blades.

**The rotating forces ( **
**
red lines
on above figure ) would generate rotational torques. The sum of all
rotational torques is the total rotating torque. This torque (
t ) depends on the wind speed ( V
) , the pitch angle of the blades , and the rotational speed of blades (
w ). 'V', the wind speed is
assumed to be constant over the surface area (the blade generated circle).**

**The torque multiply by 'w'
is the power. hence the 'P' vs. 'w'
curve can be introduced;**

**The efficiency of a wind turbine is the mechanical power
generated divided by the power of the wind available at the hub.**

**That is; 'Pmech.'/[1/2
r A V^3}. The
efficiency is known as power coefficient, 'Cp';
Because 'w' and 'V'
are both variable, there are more**

** than one curve involved. The curves can be
converted to one curve, using a parameter known as 'Tip Speed Ratio' or 'l'.**

**'l'
can represent a point of reference for the resultant of all angles of attacks.**

**only the wind turbine image extracted from; ref:
http://inhabitat.com/painting-wind-turbines-black-could-prevent-thousands-of-bird-deaths-every-year/**

**This results in one curve; Cp vs 'l'.**

**Variable pitch results in more than one cp-l
curve;**

https://www.researchgate.net/figure/279750690_fig6_Fig-9-C-P-vs-l-TSR-for-various-pitch-angles-b

&

http://usuaris.tinet.cat/zefir/pitch.htm

**---------------------------------------------------End of part
2----------------------------------------------------**

**
send
comments or questions to
gholam@aut.ac.ir**

**
****Copyright
© Center of Excellence - EE Department
- Amirkabir University of Technology-all rights reserved- **

*
maintained by
Gholam H. Riahy,
*

https://www.linkedin.com/in/gholam-h-riahy-53a38431/?ppe=1

http://scholar.google.com/citations?user=V8oRgnAAAAAJ&hl=en

https://www.researchgate.net/profile/Gholam_Riahy

http://amirkabir.academia.edu/GholamRiahy