Intro: Seeing Green Energy - the Wind Turbine Myth
When it comes to MAKING GREEN ENERGY, we need to know which green energy systems work and which ones don't. We also need to know how well those systems work. If making electricity is your priority and you don't live in an area that gets a lot of wind then you need to forget about building a wind turbine and invest in a solar system. As for me, I have always been fascinated by wind operated devices like windmills, whirligigs and wind turbines. I decided to build myself a wind turbine just for the fun of it. I did not expect to get a lot of power out of it since I live in a relative low wind location. However, I figured I could at least use it to charge my cordless power tool batteries. My expectations and excitement started to rise dramatically while researching the project. I read dozens of internet DIY posting and watched twice that many YouTube videos of people showing how they built their systems and the huge amounts of power they were producing. I saw voltage outputs from turbines that ran as high as 45+ volts. I saw one guy that had two 500 Amp Hour deep cycle marine batteries being charged by a wind turbine not too different from mine. He claimed he ran half his house off that turbine. I knew if my system could produce even a small fraction of the power others said their systems were producing I could not only charge my power tool batteries but I could also power my energy efficent shop lighting system. I was seeing Green Energy Stars.
The stars in my eyes quickly vanished when my turbine was all built and operating. I found out that even my cordless power tool battery charging expectations were as inflated as the power production claims I saw all over the internet. It is apparent that gas mileage and fish sizes are not the only things people tend to exaggerate. My system produces enough power to charge my cell phone battery (occasionally) but that is about all it will do. I am not complaining. My power expectations were low when I decided to build the system. The fact is I did not build it to produce power. I built it because I wanted to. That is what makers do; we build stuff just for the fun of it. I don't get a lot of power from it but I got a lot of satisfaction out of building it. I also enjoy watching it spin in the wind. If I add the small amount of power I get to the huge satisfaction I experience then my wind turbine is well worth the effort and money I put into it. If you are building for power alone then follow my suggestion and invest in solar panels instead.
A PERSONAL NOTE - I realize that I am going to catch a lot of flack in the comments section from people that either have never built and operated a wind turbine or that know nothing about ohm's law and how to calculate power. All I can say to them is to show us the numbers.
Step 1: The DC Generator
I read a lot of bad stuff about turbine blades made of PVC pipe breaking and decided I would buy myself a set of shiny aluminum blades. Six 15 inch blades cost me about $20 and gave me a turbine that measures about a meter in diameter. I had a permanent magnet DC treadmill motor. It seems these type motors and some select automobile alternators are what most people use in their wind turbines. This all looked pretty simple and easy until I discovered the odd size left hand threads on the treadmill motor shaft. I could not find a nut anywhere that would fit that thing. A review of the internet resources showed that everybody with a treadmill motor had to solve this problem but nobody I saw chose to share how they did it. To get around this little problem I decided I would just drill and tap holes in the big cast iron flywheel on the motor and use it as a hub for the blades. That idea was quickly abandoned when I discovered that the flywheel had 13 really thick metal fins cast into its backside. 13 fins means there are also 13 flat spots. There was no way to divide those 13 flat spots and evenly space any number of blades on it (other than one or 13 blades). No matter how i tried to figure it I was going to end up trying to drill and tap one of those blasted fins. Without a nut to fit the shaft and a flywheel I couldn't use as a hub I decided to buy a flat steel hub (another $15) and modify the flywheel so I could use it as a nut.
To accomplish the flywheel to nut conversion I drilled 1/4 inch holes all around the edge of the belt hub on the flywheel. I drilled the holes as close together as I could. I then went back and ran a 3/8 inch drill bit through those same holes. That took out the metal between the holes and left me with a motor shaft nut with really ragged edges. I used a belt sander to smooth the rough drilled edges of the nut. I drilled and taped two 1/4 inch holes in the nut so I could lock it to the shaft. There are other ways one could accomplish the conversion from flywheel to nut but this worked great for me and didn't require machine shop tools I don't have.
Step 2: Adding the Turbine Blades
I bolted the turbine blades to the steel hub I bought and put the whole assembly on the motor shaft only to discover another problem. When I tightened the nut against the hub it locked the hub against the motor case. To solve this problem I ordered 6 special 17mm bore x 1mm thick thrust washers ($3) from Amazon and used them as spacers between the motor shaft bearing and the turbine hub.
ADDED NOTE: I had read that the fewer blades you put on a turbine the more RPMs it will turn. They say the ideal is one blade. I tried 3 blades but it took 12 mph winds to start the thing turning. When I went to 6 blades it started turning at around 5 mph. If I ever have to take it down I may go to 12 blades so a mild breeze will turn it.
Step 3: Untangling the Wires With a Slip-Ring
I was amazed at how people that built wind turbines failed to provide a method of keeping the power wires from getting tangled up as the wind turbine turned on top of their towers. Most didn't mention this issue in their instructions and simply ignored any questions about it submitted in the comments. I was not about to put up a wind turbine without a way to prevent the tangled wires. I decided to use a slip-ring. A special 30 amp slip ring for wind turbines cost anywhere from $35 to $75. I found a really small one on Ebay for $10. It has 10 tiny wires coming out of each of the two ends. I divided the wires into bundles of 5 wires each. The specifications say each wire will handle 2 amps so the total power capacity with the wires bundled into fives is 10 amps. I figured that would be plenty for my turbine. A little heat shrink tubing on each bundle of wires kept the everything neat looking.
Step 4: Let It Turn
I needed a mechanism that would allow my wind turbine to turn into the wind as it changed direction. I saw where someone else had used a swivelling wheel caster turned upside down. I just happened to have one of those so I used it. I drilled a 1/4 inch hole through the center of the caster pivot and ran my slip-ring wires through the hole. I mounted the body of the slip-ring assembly inside the hole I drilled in the 2x4. I mounted the caster to a 4 foot treated 2x4 stud and drilled a couple of holes in it to route the wires out the side of the stud as shown in the pictures. I used the original caster axle bolt to attach the caster to the 2x4 board.
Step 5: Adding a Tail Fin
A tail fin is required to keep the whole assembly facing into the wind. I used a couple of plastic signs to make my fin. My signs are just like the political signs you see on the side of the roads around election time. My wife has a stack of them she had made before she knew the city where we live won't allow such signs for advertising. I cut two of the signs to the same size. Using a circular saw I cut a 12 inch long slot into the end of the 2x4 and slid the doubled up fins into the slot and secured them with screws through the 2x4. A small bolt and nut on each corner of the plastic keeps them held tightly together.
Step 6: Attaching the DC Motor
I didn't want to have to buy the really large hose clamps most people use to attach their motors to the 2x4 beam so I cut part of the heavy steel motor legs off and used a really big hammer to bend the remaining metal down so it would wrap around the wooden 2x4 beam. I secured the motor with screws, added a plastic electrical box and metal cover from Lowes ($3) and hooked up the wires in the box. I ran CAT-5 cable from the bottom slip-ring wires and left enough extra to run it inside the garage. A little white paint over everything made it look really nice.
Step 7: Getting It in the Air
I have an old unused light pole beside my garage that made a perfect mount for my wind turbine. I bought a 16 foot treated 4x4 and some large lag bolts from Lowes ($25) and mounted one end of the 4x4 about 3 feet from the top of the light pole with a single lag bolt. This bolt would act like a hinge when putting the pole up or taking it down. I put another lag bolt off to the side of where the pole would be when it is raised up. This bolt is to keep the 4x4 from going past center when I lifted it up vertical. I attached a 3 foot long treated 2x4 to the 4x4 with a door hinge so that the 2x4 would serve as a leg for the long 4x4 to sit on while I attached the motor and tail fin assembly to the end of the 4x4. When I lifted the pole up vertically the 2x4 would lies flat against the 4x4. With everything attached I simply walked the 4x4 up straight and ran a second lag bolt through it and into the light pole near the top. The light pole and 16 foot 4x4 put my wind turbine at 32 feet off the ground.
Step 8: The Output
Unlike everything I read and every video I watched before starting this project I am showing both the volts (the mechanical meter) and amps (the digital meter) so you can see my true power output.
The picture shows 53.7 mA at 6.3 volts with a 100 ohm resistor load. That comes out to 0.34 watts of power with a wind speed of 25 to 30 mph. That is about 3 kWh of power per year. Where I live that high wind speed comes only with a storm and isn't something I can depend on for more than a few hours per year.
My turbine doesn't turn at all until the wind gets up to about 5 mph. That means it is not turning at all about half the time. The other half of the time it is turning slowly and producing <1.2 volts at about 17 mA in 5 to 10 mph wind. That is about 0.02 watts or 0.1 kWh per year. It takes 5 volts at 200 mA to charge my cellphone battery. That is 1 watt of power. That comes out to about 4.4 kWh of power per year. That is not a lot of power but it is a lot more power than my system will generate even with high winds. At that rate it would take more than 40 wind turbines like mine just to keep my phone charged.
Step 9: The Truth About Wind Turbines
The truth of the matter is, regardless of what you hear or read, wind turbines are pretty useless for generating electricity in any place that doesn't have constant high winds. Knowing what I know now I would still build mine simply because I enjoyed the build and I love watching it spin in the wind. If I had paid more attention when initially researching this project I would have noticed that everybody talked about the voltage output of their system but not one person mentioned the power (watts). Watts is the true measure of how much electricity is being produced. Volts alone means nothing. My system can produce over 40 volts in moderate wind with no load but when I add a load the voltage drops drastically.
When I saw the extremely low output of my system I went back and did more research to try and find out why my power production was so much lower than the systems I saw on the internet. This time I stayed away from YouTube videos and the DIY blogs. What I found that time was amazing. There are literally thousands of reliable websites that explain the physics behind the low output my system. As it turns out there is nothing wrong with my system. It is operating properly. When it comes to wind turbines; unless you have a commercial wind unit hundreds of feet tall on a mountain or in a windy desert or coastline you just are not going to get a lot of power. Do the research yourself. I am including two links below to help you understand the simple principles behind all of this. There are thousands more reliable sites that provide even more valuable information.
THE WARWICK TRIALS - This report summarises the full findings from the Encraft Warwick Wind Trials Project covering 168950 hours of operation of 26 building mounted wind turbines from five manufacturers across the UK during 2007-2008. This study actually found one wind turbine that used more electricity to power its controls than it produced. A simple digital readout would put my turbine in that same category.
THE TRUTH ABOUT SMALL WIND TURBINES - This information, from a company that sells commercial wind turbines, makes it very clear that wind turbines work efficiently in only a very few cases. This site provides extensive charts and information to help you estimate how much electricity you can expect to produce with a wind turbine. Just remember the figures are for commercial systems. If your turbine is under-engineered as mine is you can count on getting a lot less power than they do.
Step 10: Forget Wind Turbines - Go Solar
The price of solar systems continues to drop dramatically. Harbor Freight sells a three panel 45 watt solar system for about $150 when on sale. With that much power you could charge several cell phones and cordless power tool batteries and still have plenty of electricity left over to power the 12 volt light bulbs included with their system. A small system like this one would produce 1000 times more power than my wind turbine. That is something to consider if you are seeing Green Energy Stars.
If you gotta go - go solar.