This is a response to an “Ask Steve” question.
Today’s question comes from Peter. He asks, how do I make a windmill that uses an alternator to generate electricity?
How an Alternator Generates Electricity
In 1831-32 Michael Faraday discovered that an electrical current is created by moving a conduit like copper wire through a magnetic field. You can create a continuous flow of electrons or current by moving a coil of wire through a magnetic field continuously.
Here MrTeslonian explains more:
Why won’t the alternator from your car work?
The alternators used in turbines have solid state magnets in them (which means they have a steady/static magnetic field), but the alternators in cars have electromagnets in them (which have a magnetic field that varies by how much electricity you put in them). This means automobile alternators need power to generate power. Auto manufacturers do this, so that they can turn on or off the alternator as needed, to prevent the battery from overcharging and to control the amount of electricity being generated.
This is done using a voltage regulator. Although some modern automobile alternators come with external voltage regulators, most come with internal ones. Either way they won’t work for a wind turbine without some modification.
In addition to that, the rotations per minute (RPM) required to generate a good current is higher than RPM an average turbine can create. In order to make it work, you would need to add gearing and pulleys which would create friction and loss of efficiency.
Here Dan Rojas explains more on alternators
Converting an Automobile Alternator
I’m not going to say that you can’t use a vehicle alternator for your windmill, but I will say that it is going to require some modification. MrTeslonian has a couple of informative videos on how he converted an automobile alternator or created a generator for use in a turbine. Unfortunately, he didn’t show his finished product or how well it worked.
MrTeslonian tooled the rotating core (rotor) and installed permanent magnets, then retooled the copper windings (stator core) on his own from scratch. Very cool.
If you would like something with a little less custom tooling. Jeff here shows you how to do it with parts he sells at Missouri Wind and Solar. He sells rotors with permanent magnets pre-installed.
You can buy the rotor here or here and you can buy the stator here. But for those prices, you may just want to buy one of these generators: Freedom Hydro, Freedom, Freedom II Hydro or the Freedom II. (I am not affiliated with Missouri Wind and Solar in anyway and do not earn commissions from them)
Make Your Own Generator Converting a Ceiling Fan
Unlike automobile alternators, ceiling fan motors have a static center of wire coils or windings. This center is called the stator. When electrons flow through these coils they create a magnetic field. A circular rotor on the outside reacts to the magnetic field and rotates along with your fan blades. This circular rotor is a series of steel plates organized in a specific geometric fashion, so they will react to the magnetic field created by the stator and spin.
Ceiling fan motors are easier to convert than automobile alternators because of the static coils. In order to convert this to a generator you just replace the steel rotor with a set of permanent magnets. When I get some free time I’m going to try this. Here, Scott Brown gives a pretty good demonstration of how to do it.
Ceiling Fan Class Part 1
Ceiling Fan Class Part 2
Ceiling Fan Class Part 3
Ceiling Fan Class Part 4 (just for notes on rectifiers at 4:23)
Ceiling Fan Class Part 5
Ceiling Fan Class Part 6
Ceiling Fan Class Part 7
Ceiling Fan Class Part 8
Ceiling Fan Class Part 9
Convert an AC Induction Motor to a Generator
AC induction motors are similar to the ceiling fan motors, in that they both use static coils and a rotor consisting of series of steel plates laid out in a specific geometric pattern. They are different, however, because the coils in an AC motor are on the outside and the rotor is on the inside.
When converting this to a generator you, dismantle the motor, drill holes or recesses into the rotor and glue magnets to it. Similar to what MrTeslonian did with his car alternator. Here is a great little video of Scott Brown explaining and demonstrating this. (As a disclaimer, I haven’t met Scott nor does Living Off Grid Guide have any sort of relationship with him and Green Wind and Other Green Energies. I just think he does a good job. Thanks Scott)
Convert a DC Motor into a Generator
DC motors are different from induction motors in that they have permanent magnets in place already. Therefore, you don’t have to do anything to them for them to generate electricity for you. However, they will produce AC current, so you will have to use diodes to rectify or change the current to DC. Another problem with using a DC motor is that the brushes do wear out and you’ll have to do some maintenance.
Here Dan Rojas Demonstrates and Discusses DC Motors as Generators:
Make a DC Generator from Scratch
You can make your own generator from scratch by creating 2 single wire loops and rotating them between to magnets.
Here MrTeslonian demonstrates:
Make your own Generator
You can create your own generator using a similar design as the ceiling fan conversion. Instead of having your coils parallel to the axis of the rotor and the magnets on the outside, you put the coils “flat” or perpendicular to the axis and the magnets “above” them. Here Aceman307 shows you how he built his:
Wrapping the windings/coils
Building your stater coil
Build your bottom rotor
Building your top rotor
Here Aceman307 shows you another build from beginning to end using a serpentine stator instead of a coil stator.
Building the Wind Turbine Itself
Make TV has a great explanation of building a turbine here, he also shows you how to create blades.
Here is a different frame assembly built by Scott Brown. I apologize for the discontinuity of these videos, but if you are patient and watch them all the way through, you will get the idea.
Creating a frame part 1
Creating a frame part 2
Creating a frame part 3
Creating a frame part 4
Creating a frame part 5
You can also create a vertical axis turbine instead of the traditional propeller type. These are supposed to run quieter. Aceman307 demonstrates how he built his vertical axis wind turbine.
Vertical Axis Turbine
I wanted to take a moment to thank Scott Brown, Dan Rojas, MrTeslonian, Aceman307 and Jeff at Missouri Wind and Solar for putting together those videos for the public and for all the work they are doing to help make this knowledge more accessible. Thank you.
I also wanted to thank Peter for submitting his question.
I hope to hear from you as well. What is your question? Go to Ask Steve and leave your question.
Sign up here to get your FREE DIY Wind Power Toolkit with links to detailed instructables and supplies!
Generator vrs Alternator