3 Bladed Savonius Wind Turbine

By Joseph Ellsworth 2008
info-@-correctenergysolutions.com (remove dashes to make email work)

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Prototype of new design for 2008. Intended to improve efficiency and reduce fabrication costs.

Video of turbine in 2.5 MPH winds More videos below or see components

This 3 bladed Savonius design runs faster with a TSR of approximately 0.9 TSR than my previous design of opposing buckets which had a TSR of 0.55. This unit provides better lift characteristics off the back side of the blade provides better secondary thrust off the trailing blade.

Benefits of this Savonious Design

Great low wind performance
Self starting in all wind conditions without aiming.
Highly tolerant of turbulent winds
Easily survives 100+ MPH winds without damage, brakes, yokes or aiming.
TSR approx 0.9 to 1.1
Completely silent in all wind speeds tested.
Compatible with Extrusion based fabrication
Can use wide range of plastics
Easily adjusted for a wide range of sizes
Easy to add braces as needed to accommodate wide range of materials
With Savonius turbines a higher speed generally means higher efficiency and it also makes electrical generation more cost effective.

This turbine was made from scrap PETG which I had to glue end to end. As a result ended up slightly out of balance. This can cause a slight wobble. This is not a problem is production units since the plastic is all brand new and fully balanced. The frame was made from light weight aluminum which is not sufficiently rigid and ends up amplifying the wobble unless braced. Production units normally use a heavier gauge steel tube frame but the aluminum is nice to carry around for local testing.

PETG is not long term solar stable so it would have to be painted for long term outdoor use. We can use Polycarbonate if long term outdoor use with the clear material is desired.

5 MPH Closeup Dbl-Click on Image to play video
Running in 7MPH Wind DBL-Click on Image to play video	7MPH Closeup DBL-Click on Image to play video
Up to 11 MPH DBL-Click on Image to play video	11 MPH closeup very fast DBL-Click on Image to play video
Short 3 blade prototype

Components

Airfoil pattern

This is the shape of the plastic after bending and before assembly.

Horizontal brace and End cap

Top down Views

Notes / Disclaimers

The turbine may appear in some photographs to have a helical spiral. This is not the case as you can see from the top down pictures above. Our digital camera is slow enough it's scan of the CCD image sensor is slow enough so that when the turbine is spinning it travels far enough in a single picture to make it appear as if the blade was twisted but it is really an artifact of slow CCD processing in the camera.

We have not tested in wind tunnel TSR is calculated by taking multiple readings with hand wind meter and comparing those readings with current wind speed and then averaging the readings. The wind meter responds to changed in wind speed rapidly while the turbine spins at the higher speed for longer and is less sensitive to changes in wind speed so in turbulent winds high confidence TSR readings are problematic.