Introduction: Design a Wind Turbine From Trash
Awhile ago I read a book by William Kamkwamba called The Boy Who Harnessed the Wind about a boy in Malawi who built a wind turbine from trash. Reading that book really fired my imagination and since then I have built a dozen wind turbines all on a lower budget than he had "$0". This is a tutorial, not on how to make a specific wind turbine, but a wind turbine from whatever parts you have available.
I would have had more pictures but I accidently deleated most of them.
- yaw bearing
- rectifier/charge controller
Step 1: Finding a Generator
This is the hardest piece to find, but there are lots of different options.
- stepper motors
- old DC motors
- brushless DC motor
- induction motor PMA
- car alternator
- home brew PMA
You can get stepper motors out of several different appliances including printers, scanners, photocopiers, and fax machines. These are one of my favourite options. They produce usable amounts of electricity, but they do need a rectifier to produce DC.
DC motors are by far the easiest option. But they don't produce much electricity unless they are rotated at pretty high RPMs. DC motors are very common. The two things that you want with a DC motor is low RPMs and high voltage, the higher the better. Good places to get these are in electric lawn mowers, treadmills, and ancient tape players.
Brushless DC motors are probably the best option. You can get them out of newer power tools, HVAC units, smart drive washing machines, and newer ceiling fans. These also need a rectifier to produce DC.
Another option is to convert a regular induction motor into a PMA (permanent magnet alternator) by drilling holes in the core and gluing magnets into them.
Another common option is to use an old car alternator. The reason that they are popular is because are very convenient because they have a built in charge controller and so do not require any external circuitry. The downside is that they need high RPMs to generate electricity so are only suitable for very windy locations.
Home brew PMA is by far the hardest. and probably the most expensive, because you need to buy a bunch of big magnets that cost about $150.
Step 2: Blades
Blades are usually not too hard to come by. Deciding the number of blades is a bit of a trick. Anywhere between 2 and 20 is pretty normal. If you have lots of light wind you probably want 5 or 6. The downside to more than three blades is that they quickly max out their RPMs and so strong winds don't produce much more electricity than light winds. The good thing is is that they start spinning in a lot lighter wind than 2 or 3 blades. 3 blade designs are considered the most efficient but they need higher wind speed to startup. I tend to like using PVC blades. I won't go into detail on how to make them because there are lots of instructables on making them. You can also use regular fan blades. Another option is to carve your own blades, but that requires more work than I have ever had time for. I have heard that they preform fairly well.
Step 3: Yaw Bearing
The Yaw is what the wind turbine rotates on to turn into the wind.
Several good options are:
- bike wheel bearings
- bike fork bearings
- two pieces of pipe that fit together nicely
- misc ball bearings
- office chair swivels
- small wheel bearings like those that are on a moving dolly
I am using the bearing from an old weed wacker that I chopped up.
Step 4: The Body
There are many different sizes and shapes of wind turbines. So I am not going to tell exactly how to build it. If you want ideas go online and search "micro wind turbine" and look at images. And then you can try to model your wind turbine after it. I would suggest that you make it sturdy enough to withstand a good windstorm. Also try to get a good cover over the generator.
Step 5: Tail
Tails also come in many shapes and sizes. As a general rule the larger and further out the tail the better it will turn into the wind, but you still want your turbine to be balanced. So try to find a happy medium. The tail can be any shape or design. It doesn't matter if it is just a plain triangle or shaped like an animal or whatever else you have in mind. You can use wood, metal or plastic. I prefer the latter two options.
Step 6: Tower
Many "professional" wind turbine manuals suggest that you should install your wind turbines at least 30 feet higher than any thing within 200 feet of the tower. This is totally unachievable most DIYers who aren't either in the prairies or pretty rich. The towers I build aren't even thirty feet over the ground. As a rule of thumb the taller the better, but if it is only 10 feet high don't be to worried. The taller your tower is the more dangerous it is. So make sure it is well secured and stay away from it in a wind storm. You can use either wood or metal for your tower. I would suggest aluminum as it is light and easy to work with.
Step 7: Rectifier/charge Controler
The last thing to do is to decide what your turbine is going to power and build/buy the electronics. If you are using a brushless motor or a stepper motor you will have to make a three phase bridge rectifier to rectify the AC to DC. You will also need some sort of charge controller. If you are using you turbine to charge a USB device then you can either make your own charger out of the popular lm7805 or lm317. There are plenty of instructables covering those builds, or you can use a car phone charger. If you are going to charge 12v lead acid batteries there are several simple charge controllers here: https://www.homemade-circuits.com/how-to-make-solar-battery-charger/ . If you know a decent amount about electronics you could also try this: https://www.instructables.com/id/DIY-AUTOMATIC-SOLAR-CHARGE-CONTROLLER/
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