A plastic 400W alternator for smalll wind-turbine

Description

The world has began to move towards home-energy storage solutions that can partly offset your power bills and charge your electric vehicle. We are looking at small scale wind-power generation that can be home-grown, based on simple designs that can be easily assembled to provide a micro-scale energy source that can cover basic needs.
We propose a design for a permanent magnet alternator tuned towards wind-turbine applications that is built out of machined plastic.

The alternator is designed to give 3-phase power output, using two sets of 9 coils on each stator. Once the alternator design is completed, then a set of wind-turbine blades will be designed. This 20cm diameter generator we estimate can reach power output of 400W, depending on factors such coil winding, blade design and wind.
Join us on our venture to empower people!

Details

The project's drive is to empower people by allowing them to have access to energy through a community driven project and a low-cost design.
To this aim, this project's will explore the potential of building a low-cost alternator out of industrial plastic. This alternator should be tuned towards a wind-turbine application. The main aim is to design a turbine that can be manufactured out of cutting plastic-sheets, easily assembled and low-cost (<250 euros) so anyone can laser-cnc cut his own. Our design philosophy is to minimize the diversity of materials and constuction techniques as much as possible to reduce the cost of harvesting aeolic energy at this micro-scale. Thus, there may be various efficient turbine designs out there, as for example the 3 blade horizontal axis turbine, but implementing such designs with our means may reduce the cost/output ratio. We therefore seek to optimize the use of our plastic-sheet cutting process for the construction of a working wind-turbine + generator.

The pictures shown are of a 3D rendering of our design of a single rotor and dual-stator (3-phase 9-coils each), made out of acrylic plastic (perspex). The diameter of the design is such so the parts can be cut-out of A3 sheets (20cm diameter of rotor and stator). This particular size makes the design suitable for constructing with the abanduntly available CNC or laser cutters of A3 size. Our design aim is to achieve simplicity in construction & assembly, beauty and an acceptable efficiency (output/cost) ratio. We would like to achieve 400W at moderate wind speeds , but such output will depend on the turbine design as much as the alternator (more on the design spec will follow).
Further, due to the nature of this open-design project we aspire that this project will generate community driven revisions to improve the initial design.

At this stage we are building a prototype out of acrylic. Although acrylic is low cost and has low creep and water absorption, it cannot sustain temperatures beyond 80 celsius, and its quite fragile. Thus acrylic is used here only for prototype, and stronger plastic would probably make it into the final design.

The project is shared under a Attribution-ShareAlike 4.0 International license

Components

1 × A3 Acrylic sheet 12mm

2 × A3 Acrylic sheet 3mm

1 × A3 Acrylic sheet 10mm

1 × enamel wire 0.7mm

20 × Teflon Ball bearings

Project Logs

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Project frozen - Back to the drawing board
Kostas Lagogiannis • 08/29/2017 at 16:10 • 0 comments

Hello all,

thank you for your interest in this project. I am sorry I 've failed to update you to say that I have put this on hold for a while now as I've started (and finished this time!) with new projects.

My quick update is that the custom bearing design is not adequate or comparable to what a commercial bearing could give, and also there is wobble on the rotor, unless ball bearings are added on the sides. With the current design these side facing bearings (four teflon balls on the rotor facing the stator coils) are producing too much friction if the made tight enough to stop the wobble.
I believe the ball bearing part of the design needs to be re-evaluated from the beginning, most likely consider off the self bearing solutions (Open to suggestions).

I attach a few more pictures of the a prototype (acrylic) assembly,
free spin tested to satisfaction
Kostas Lagogiannis • 10/29/2014 at 09:32 • 0 comments

Trimmed edges holding axle ball bearings, this did the trick and allow rotor to freespin. So we have modified the design accordingly.
Further, the magnets where added and checked that loading does not impair spinning
Pic: most magnets added top stator liftedin this picture)
Further we added the small rotor extension wings that can be used to attach blades. Here the design needs to be modified so as to fasten these extensions more securely. Otherwise the 3 rotor laminates can be split appart by forces parallel to the axis of rotation .
(Pic of assembled rotor with magnets on both sides, ball bearings and extension wings)
Intented use - wind-turbine design
Kostas Lagogiannis • 10/27/2014 at 13:50 • 0 comments

The alternator design has not yet been bound any particular wind-turbine type. However, if the alternator is going to be directly driven by a wind-turbine, different types of turbines from horizontal axis (HAWT) to vertical (VAWT) and their respective variations will require various modifications to the rotor design. We've been trying to consider which design may be more appropriate using our existing construction methods. Considerations that we have taken into account is:

*the limitation of A3 sheet size, if long blades are required the turbine design should allow these to be incrementally extended to increase the turbine area.

*Laser cutting is suitable for flat material and thus designs that really depend on air-foil shape should be avoided.

A VAWT flat blade Darius type turbine is simple when it comes to mechanisms, as the wind-turbine does not need a tail construction or to rotate to point towards the wind, further they seem to be references saying that such designs are more silent. Additionally, the turbine area can be extended in a modular design that adds sets of 3 blades vertically on the pole where the turbine is mounted.

On the other hand they seem to heavily depend on air-foil blade shape in order to generate torque, or even begin to rotate for that matter.

The picture from a Darius flat-blade turbine designed by Chad Maglaque called the Jellyfish. Such a design could allow a modular expansion of the turbine.
fastening rotor and test free-spin
Kostas Lagogiannis • 10/24/2014 at 00:58 • 0 comments

went to my local hacklab tonight to drill new tapered holes to join the three rotor plates and check the rotor friction against free spinnininh by hand. These can be welded by acrylic cement but for the prototype I need to be able to disassemble.
After some slow drillling I got 3 spaced around the rotor nut/bolts through to hold them together. I then grinded the end of the screw (scalded my finger as the screw got really hot!) .
The overall friction on the rotor is quite low and the gap against stator narrow to approx 1.5mm without scratching and axle fit quite tight. But the rotor doesn't quite free run when I spin it by hand.. There is friction that seems to come from the bearings, perhaps because some of the balls don't roll. I need to check this and perhaps file the ball cages a bit.
So for now, I need to troubleahoot the ball bearings. The design seems right but due to the limitations of laser cutting perhaps some of the balls are locked when I tightened the rotor plates together. Once solved, Then we move on to adding the magnets and coils.
acrylic parts have been laser-cut and test-assembled
Kostas Lagogiannis • 10/23/2014 at 05:33 • 0 comments

1st test of using a laser cutter to manufacture the stator and rotor parts was completed with success. Made minor corrections to the design, fixing the outer rotor plates ball bearing diameter. There a few simple things to learn about laser cutting in the process as this was my first experience with one. Cutting 12mm on 60W laser can be done in 2 passes setting speed to speed to 2%,power 100% freq.100%., but on the 2nd pass refocus 3mm closer. Avoid engraving as it is not very accurate when going to depth and makes the process very slow.
The good news is that once the parts were cut the assembly, adding the ball-bearings and the sequence of the parts through central tube, took a couple of minutes before I could test that the prototype actually rotates easily! However, I still haven't joined the 3piece rotor sandwich so there was some friction that did not allow it to spin. The sandwich could be glued but for the prototype I am going to add 4 or 6 through screws with nuts and taper the holes. It feels great to hold what once was a few sketches on paper!
big thanks goes to to A.S. and Dylan