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DIY Savonious Wind Turbine

A small wind energy harvesting system for charging batteries to power your projects when solar is not an option

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Sometimes you have a project in a remote location without good sun exposure for powering it with solar cells. Wind is a potent source of alternative energy. This project explores using a small wind turbine system to replace solar cells for powering remote IoT projects.

A Savonious windmill design was chosen for its ability to work in gusty conditions and easily handles wind coming from any direction. It does not need to be mounted on a tall tower like the large three-bladed horizontal-axis wind turbines used for commercial electric power generation.

The windmill blade design will be flexible in size, to accommodate different project's requirements for power. The generator will be an easy to construct axial-flux design. There will be 5 and 12 VDC output options to match the requirements of the IOT system.


Academic research has shown that a Savonious windmill design with: 2:1 aspect (height:width); 10% blade overlap; and a stack of 3 sets of half-cylinder blades offset by 120 degrees is within a few percent of the efficiency of more exotic shapes for Savonious windmills that would require 3D printing of the entire blade structure. Recycled round containers are an easy source of cylindrical material for the blades.  3D printing structures for the ends of the blades makes for easy assembly, but does limit the diameter of the windmill.  This design allows for easy scaling of the windmill to match the requirements of various projects.

12coil0.25IN_C.brd

Stator rev C Eagle layout.

brd - 36.84 kB - 06/27/2018 at 05:54

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12coil0.25IN_B.sch

Stator rev C Eagle schematic.

sch - 75.91 kB - 06/27/2018 at 05:53

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12coil0.25IN_C-Gerbers.zip

Stator rev C gerber files.

x-zip-compressed - 332.16 kB - 06/27/2018 at 05:52

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12coil0.25IN_C.pdf

Stator design with key dimensions. Rev C is the first version released to fab, untested at this time.

Adobe Portable Document Format - 134.08 kB - 06/27/2018 at 05:50

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  • Fusion 360

    Laen08/01/2018 at 16:18 0 comments

    This has been the biggest project I've done yet with Fusion 360, and I've learned quite a lot.

    • Always start each new document with "Create -> New Component".  This lets you separate your model into pieces-- each with its own history-- and move them around separately.
    • Copy and paste components to make multiple copies of a component.  This allows you to make design changes to the original component, and have all the copies of it update automatically.
    • Use the CAM tool to output profiles for laser cutting.  That's what I did for the "plates" between the blades.
    • McMaster Carr puts 3d models of their entire catalog online, which you can easily import into Fusion 360.  This is amazing. 

    I still have a bunch to learn.  When doing a design, do you put the nuts and bolts in, or is that too much detail? Should I be setting up joints?

    Also, Fusion 360 has a really nice rendering engine:

  • New Blade Design

    Laen07/30/2018 at 04:09 0 comments

    Greg says Savonious blades work best when they can "spill" from one to the other through the axle, so I made a new blade design which allows the some overlap between the blades.  Another advantage of this is that it lets you print larger blades if you want.

    The blades are self-symmetrical, and interchangeable. 

    Like before, they're parametric:

    • Blade Diameter
    • Blade Height
    • Blade Thickness

  • Parametric Blades

    Laen07/13/2018 at 20:50 0 comments

    Since the limiting factor for the size of the blades is the size of your 3D printer's print bed, I designed this parametrically as well. 

    It supports these parameters:

    • Blade diameter (from tip to tip)
    • Blade height
    • Shaft diameter
    • Thickness of the blade.

    As our savonious design requires three of these, I figured it would be smart to design it such that 

  • Parametric Rotor

    Laen07/13/2018 at 01:45 0 comments

    One of our goals for this project is to make it as parametric as possible, so we can easily adjust the specs as we experiment to get the power output we need.

    So, I designed a Parametric Rotor in Fusion 360.  It has several parameters:

    • Number of Magnets
    • Size of Magnet (assumes square magnets)
    • Diameter of the magnet ring
    • Diameter of the hole for the shaft.

    For flexibility, I've been designing this with both laser cutting and 3D printing in mind, and this file can be used to generate a DXF for lasercutting, or an STL for 3d printing.

    I don't think my key system there will work well for actually tightly securing this to the axle.  I need something with a setting screw. 

  • First stator and rotor prototypes have arrived

    Greg07/13/2018 at 00:44 0 comments

    Laen has designed a 16 magnet rotor to work with the original PCB stator.  He designed it in Fusion360 and cut it out on his laser in an afternoon.

    The initial stator design, "Rev C", PCB has arrived from OSHPark. I need to test the performance of this design so I have an order of magnitude guess on what the design parameters should be for the next version.

    The initial order of mechanical parts has arrived from McMaster-Carr.  Gluing the magnets into place and attaching the rotor to a shaft is easy, but I only bought 2-foot shafts, so its a bit unwieldy for a lab bench setup.  I am working on a 3D printed structure to hold the stator in place above the rotor. When that is done, I can do some initial tests of performance by turning the shaft by hand and measuring the resulting voltage across a known load.

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