How does the gear ratio affect the power efficiency generated by a wind turbine

[superkaho]

I have a basic question on how the power efficiency of wind turbine affected by the gear ratio.

Suppose there is a generator connected with the rotor through a gear enhancer, a higher angular speed of generator is obtained. Since a higher voltage is produced, we may think that the power efficiency of generator is increased compared with no gear.

However, based on the conservation of power, the equation should be:

torque(rotor) x angular speed(rotor) = torque(generator) x angular speed(generator)

if the angular speed of generator is higher, then it torque should become lower.
if there is no change for their angular speeds, they should have the same torques too.

1) Therefore, is it incorrect to say that the power efficiency of wind turbine is increased when installing a gear enhancer?
2) In the same windspeed environment, should the power efficiency be lower after using gear system? (due to friction)
3) If so, why it is common to install a gear up system in commercial wind turbine? any advantage for it?

I hope you guys can teach me as I have to make a mini-wind turbine for my physics project. =)

 

[russ_watters]

Welcome to PF.

What's "power efficiency"? Is that just the efficiency at which it converts wind power to electrical power?
What's a "gear enhancer"?

The efficiency of any device is dependent on a lot of factors. For a wind turbine, the ability to extract power from the air is based on the aerodynamic properties of the turbine. The efficiency of an electric generator is dependent on its mechanical and electrical properties. Beyond that, for an ac generator, there is a specific rpm at which it must run to generate 60hz power. The desired operating rpm of these two devices does not necessarily match, hence you use gears to ensure that each is operating at the proper rpm.

Gearing for a car is determined the same way. A car's engine operates best in a certain rpm range. But the rpm of the wheels is based on the speed you are going - and it changes. Hence, you use gearing to select an engine rpm in the engine's best operating range that will provide you the speed you want.

 

[superkaho]

The power efficiency of wind turbine refers to the ratio of electical power generated to the mechanical wind power input. For the gear enhancer, it means that a smaller gear. When the smaller gear is attached with my dc generator, it rototes faster and produces higher voltage.

In short, I am pondering if it helps to generate more power when installing a gear system.

Wind turbine with gear system VERSUS wind turbine without gear system, any suggestion from theoretical perspective?

 

[russ_watters]

A wind turbine will produce the most power when the turbine and generator are both operating at the optimal rpm. Gears are how you make that happen. Changing the gear ratio to make them spin at other rpms will reduce the efficiency.

When the smaller gear is attached with my dc generator, it rototes faster and produces higher voltage.

Voltage is not energy.

 

[superkaho]

thanks for your reminder, but how can i know the optimal rpm of my generator and turbine?? the specification of generator is as follow:
http://www.mitsumi.co.jp/latest/Catalog/pdf/motorav_m25e_11.pdf

Also I know that there is something called tips speed ratio(TSR). does it help to the design of the wind turbine??

 

[mawais15]

tip speed ratio is an important in the design of axial flow wind turbines.
this factor determines the number of blades that you need to install on your turbine.