# Q&A: How would you calculate the theoretical power output of a Savonius wind turbine?

How would you calculate the theoretical power output of a Savonius wind turbine?
I built a small scale Savonius style wind turbine for a project. I can easily measure the power it puts out in a wind tunnel using a wattmeter, but how would I calculate the theoretical maximum power output? I want to use these two values to find the turbine's efficiency. Thanks!

According to measurements done in a wind channel3, the maximum power of a 1-barrel Savonius rotor can be calculated with the following formula:
Pmax = 0,18 · H · D · v³ [W]
If we take into consideration all the efficiencies of the system (rotor approx. 50%, transmission device approx. 90%, car alternator approx. 50%), the maximum power of a 1-barrel Savonius wind generator will be (H·D = 0,94 m²):
Pmax = 0,08 · v³ [W]
Note: to get the power in watts [W], the wind speed v has to be introduced in meters per second [m/s] and the height H and the diameter D in meters [m].
The following table shows the maximum power and the optimal rotation speed of a Savonius wind generator for different wind speeds:

Ref: http://www.amics21.com/laveritat/savonius_generator_english.pdf

### One Response to Q&A: How would you calculate the theoretical power output of a Savonius wind turbine?

1. Rudydoo

Hey Drew, Gatorbait is on the right track, but the formulas in Mr. Voneshen’s publication cannot be used for a savonius turbine.