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3D PRINTED PORTABLE WIND TURBINE

A small Portable Wind Turbine, mostly 3D printed!

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A wind turbine mostly 3D printed , which houses a Nema 17 stepper motor as an electric generator. Foldable and no larger than a 2L soda bottle. Simple to replicate and with a low manufacturing cost. CAD, STL and how to make it included.

Generally when I want to get away from the city and camp, I take some kind of power source with me. Within my preferences are the Power Banks. With a small and light one, of approximately 40 Watt hours (Wh), I can charge my cell phone about 2 or three times and that is fine if I am only going to spend a day and do not need to power other equipment such as my camera, for example. If I want to spend more time then I usually take a 222Wh “Solar Generator” with a 60W portable panel. For the energy needs that I have in this type of excursion, it is generally enough for me.
About a month ago I made an excursion of several days and to my surprise at the end of the second day my energy sources had been completely exhausted, also no Sun . I have discarded fuel generators because they are very noisy, polluting and can cause fires. There was a small stream near where I camped and there was also wind that I could have taken advantage of, but I really wasn't prepared for it. I promised to find a solution and include it in my new adventures. I am sure that there are several people around the world with this type of need, that is why I carry out this project so that they can also benefit.
In this project I show you how to make a small portable wind turbine, mostly 3D printed, capable of providing about 12W of power and with dimensions similar to a 2L soda bottle when folded. Although its generation capacity is limited, having it can be beneficial during emergencies or when access to more convenient energy sources is zero or very limited.
Although the initial motivation to carry out this project was not linked to teaching at school, I consider that it constitutes an excellent opportunity to link this type of technology with the teaching-learning process. To be able to present a product of this type at School Science Fairs, which harnesses the energy of the wind wherever the conditions exist, small, very portable and easily installed, should be striking and interesting. Students could answer questions and present the results of electrical measurements of their performance at different wind speeds. I think it would be an enriching experience for everyone.

DESIGN CONSIDERATIONS
For some time the idea of designing a portable wind turbine had crossed my mind. From my experience and for it to be useful I knew it had to be small, maybe the size of a soda bottle, able to fit inside a backpack. Its mass should also be as low as possible.
Since the plane of rotation of the propellers in typical wind turbines is perpendicular to the position of the electric generator, they are initially inconvenient to transport and store once assembled, even when small. I also didn't want to have to use tools to mount and dismount the propellers every time I was using it. Folding propellers, that was the idea, but how to implement it? It took me a while to come up with the answer. Have you seen the way bats sleep? The wings are folded towards the body, that could be the answer. Nature is an excellent source of inspiration, millions of years of evolution support it.
Taking the previous idea as inspiration, I designed this wind turbine.
Since on my travels I usually carry some kind of lightweight tripod to take pictures when the light conditions are low or to make time-lapses, perhaps also using it to support the wind turbine would save the need to carry other equipment. There are thousands of possibilities to support a camera and make it compatible with those pre-existing technologies, I think it would be convenient.
Regarding the generator to use, it was another difficult part to decide. Ideally it would have been to design and build a customed one, but  unfortunately, I did  not have the possibility of building a quality one as I did not have the required manufacturing technology at hand. That is why, a NEMA 17 stepper motor has been selected as generator due to its availability. Another reason to consider when selecting a stepper motor is that ...

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AutoCAD DXF - 25.50 kB - 05/01/2022 at 16:20

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Standard Tesselated Geometry - 2.37 MB - 05/01/2022 at 16:13

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Standard Tesselated Geometry - 1.84 MB - 05/01/2022 at 16:12

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Standard Tesselated Geometry - 1.32 MB - 05/01/2022 at 16:12

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Standard Tesselated Geometry - 1.39 MB - 05/01/2022 at 16:12

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  • FROM STEPPER MOTOR TO BLDC GENERATOR

    adriancubas3 days ago 0 comments

    I have been experimenting with different motors (generators) in order to increase the generating power of the wind turbine. As I presented earlier during my measurements, the nema 17 stepper motor is only capable of delivering 0.65A of maximum short-circuit current even though the RPM is notably increased. I know I can get more than that.

    My first intention was to design a new permanent magnet rotor for the stepper motor and I did so but the results I got were still poor, plus it required modifying the stepper which could be challenging.

    I also rewound a 12 pole BLDC motor, salvaged from a LASER printer. This motor initially had 35 turns per pole and I was able to rewind it to 50 turns per pole. In the measurements that I made, I obtained acceptable values of current and voltage to charge lithium ion batteries of the 18650 type. In the end, I discarded it since it has a high mass due to having ceramic magnets in its external rotor.

    Looking for alternatives, I found 130kV BLDC motors at a good price on Aliexpress. They are motors used in the Matrice M600 drones of the DJI company. Perhaps they were discarded due to bearing wear or because this Drone is already out of production, I don't know but I do know that its capabilities as generators are exceptional.

    Below are the results of the measurements I made. My conclusions from these measurements are as follows:

    • They deliver a lot of current even at low RPM. In the measured range, the short-circuit current had a linear growth behavior as a function of the RPM.

    • It was verified that they are 130KV motors (revolutions per volt) as can be seen in the trend adjustment equation. To obtain voltages of 5 V or more, more than 600 RPM is required, which leads to the redesign of the generator blade to operate at higher RPM.

    • At approximately 840RPM, a charging current of 1A is obtained in an 18650 cell, which exceeds the generation capacities of the stepper motor at the same RPM.

    I can tell you that I have already finished the first variant of the Generator Hub (BLDC M6010) and I am now working on the redesign of the new Blade with the GPL software QBlade 0.96.

    Greetings to all

  • MEASUREMENTS TO THE GENERATOR, RESULTS AND CONCLUSIONS

    adriancubas05/05/2022 at 17:58 0 comments

    During the field tests on prototype 1, the maximum voltage value obtained in the internal capacitor was approximately 22V. The wind speed recorded that day was 22km/h, with gusts of 26-28km/h.

    In the lab, if we spin the generator rotor until we get that 22V, we could measure the maximum RPM reached during the field tests. Other values of electrical magnitudes could be determined to try to characterize the nema 17 stepper motor in its role as generator in this Wind Turbine.
    To carry out the experiments, a three-phase induction motor was used, which could vary the frequency of the supply current with a Variable Frecuency Drive (VFD) and with it, the RPM of its operation. This motor was attached to the chuck of a drill with which the generator shaft would be fixed. Attached to this mandrel was a small magnet that would pass close to a 2000-turn coil of fine gauge wire, when the entire assembly rotate. This coil would be connected to the signal input of an oscilloscope where pulses would be detected. Measuring the time elapsed between pulses with the same phase and determining its reciprocal, the frequency expressed in Hertz (Hz) would be determined. In turn, a multimeter would be placed at the generator output and the voltage and current would be measured based on the RPM. At the end graphs of dependency of these magnitudes based on the RPM would be generated. One area of interest was determining the best series-parallel configuration of 18650 lithium cells to be charged by the generator. Two 1500mAh 18650 cells balanced at a voltage of 3.7V were used in the experiments. Conclusions:
    • The nema 17 stepper motor (generator) apparently is not capable of supplying a short-circuit current greater than 0.65 A. From 500 RPM, a pre-limit value of 0.6A is obtained.
    • The 22V obtained during the field tests correspond to about 870 RPM of the generator. Typical values would be between 500-700 RPM.
    • The open circuit voltage has a linear behavior as a function of RPM. At 600RPM approximately 14.5V is obtained.
    • At typical 700 RPM  you get 0.5A charging current on a 1S2P 18650 system, versus approx 0.26A on a 2S1P 18650 system.
    • It makes no sense to use configurations of three or more 18650 cells in series. High RPMs are required that this wind turbine could hardly reach.
    This is all for now, tell me your opinion!

  • ORGANIZATION OF THE STL FILES TO PRINT

    adriancubas05/01/2022 at 16:07 0 comments

    When I uploaded the STL files to the Files section for the first time I forgot one piece. Now I have named the STL files with letters consecutively. I have also included an image showing each piece and its corresponding letter. Nut I and K are not the same, although they look the same externally, keep this in mind!
    The L part does not necessarily have to be 3D printed. I have found it feasible to cut it with a laser cutter or a CNC. I have included the DXF file of this piece.

    Part G can be replaced by a standard tube of that size and would avoid the need to print it.

View all 3 project logs

  • 1
    DOWNLOAD AND PRINT ALL THE STL PARTS OF THE ASSEMBLY

    You can download the pieces from here in the FILES section. As I make changes to any of them, I will replace the corresponding file so that the most up-to-date ones are the ones that are published.

    I've included a STEP file in case you want to take a closer look at the assembly or change something depending on your interests. If you need any special type of file format let me know and I'll see if I can help.

    I have printed my prototypes in PLA. I will probably end up printing it in ABS or PETG, although PLA has worked very well for me so far.

    In this system, the parts are subjected to relatively high mechanical stress. That is why I have printed all the pieces at 100% infill with the exception of the propellers and tail, that I finally decided to print at 40%. The thickness was 0.28mm in all cases. I used a Longer LK4-PRO printer with a 0.4mm nozzle.

    The propellers were printed one at a time. They took about 6 hours each. I used supports and the position was as shown in the picture. The support pattern was CUBIC and I used CURA slicersoftware.


  • 2
    INSTALL THE COLLET PROPELLER ADAPTER IN POSITION

    To do this you must insert it inside the hole that the Central Hub has. On the other side, place and adjust the nut until the assembly is tight. Since the Blades and Hub will rotate in the opposite direction to the tightening direction of the Collet Propeller adapter, there is less risk of the assembly coming loose.

  • 3
    BOLT THE BLADE ENDS TO THE CENTRAL HUB

    All the holes in the designed parts are for M3 screws. Place the pieces as shown in the images, but do not overtighten them. The Blade Ends shall be able to articulate freely 90 degrees.

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Discussions

jeff.crown wrote 3 days ago point

When you're closer to a finalized version I'd definitely be interested in purchasing it from Tindie!

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adriancubas wrote 3 days ago point

:)

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goldrick31401 wrote 05/12/2022 at 00:19 point

So I guess using gear reduction would be in order?

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adriancubas wrote 05/12/2022 at 01:21 point

I'm trying to avoid using gears, but it might be a workaround. I have already gotten a bldc motor to deliver 6V at 600RPM with a short circuit current of 2.6A (had to rewind that motor). With those values i can use a boost converter and stabilize an output voltage. I keep experimenting. Greetings

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tomasfarken wrote 05/10/2022 at 07:46 point

I like the project very much!!!! :-)

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adriancubas wrote 05/10/2022 at 15:35 point

Thank you, I really appreciate your comment!!!

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Todd Medema wrote 05/10/2022 at 00:36 point

What wind speed range will this work in? Would love to see a wind speed vs watts graph!

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adriancubas wrote 05/10/2022 at 15:34 point

Right now I am trying to improve the generation efficiency of the stepper motor. Apparently, when the RPM exceeds around 800 RPM, the increase in the frequency of the alternating current generated leads to a notable increase in impedance, which greatly limits the output current. I work on two solutions: A new permanent magnet rotor for the stepper motor and a rewound BLDC motor. When I get an acceptable output power, I will publish the dependencies between magnitudes, including the one you suggest. Greetings

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cr15 wrote 05/08/2022 at 03:07 point

Can you be a little more specific on the collet adapter? When I click on the link it's just pulling up an amazon search.

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adriancubas wrote 05/08/2022 at 03:42 point

You need a "prop adapter" that is capable of holding the 5mm shaft of the stepper motor(generator) and has a thread length of 12mm or a little more. The thickness of the screw is 6mm. The one I used is out of stock. i think this can work https://amzn.to/3vVjOeh

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cr15 wrote 05/13/2022 at 15:43 point

Got it. Will post something when I get everything put together. 

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Alexey Vazhnov wrote 05/03/2022 at 17:54 point

Adriancubas, amazing project!

Could you please share it under some opensource license?

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adriancubas wrote 05/03/2022 at 21:10 point

Sure, no problem! How do i do it?

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Alexey Vazhnov wrote 05/03/2022 at 21:19 point

If you have already selected a license, then just add a file like "LICENSE.txt" to the files and maybe add a note into "details" or "description" chapter.

If you didn't select a license yet, then I can suggest something like "CC-BY 4.0 or newer" or a "public domain", but this choice is completely up to you, of course.

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tazelaar wrote 05/01/2022 at 18:52 point

more interested in a belt wind turbine like humdinger 

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adriancubas wrote 05/02/2022 at 20:45 point

Yes I will definitely do one of those in the future!

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dzuljo wrote 04/30/2022 at 05:48 point

Hello,thanks for the project,I like a lot. 
Maybe is my printer problem or dimension on the printed file is wrong. 
Extremo de Hélice inside hole is 14mm. 
Hélice is 15mm. 
Not possible to fit together.
Kan you please check?
Thanks

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adriancubas wrote 04/30/2022 at 12:09 point

I'll check the model as soon as I get home. If I have any interference in this part of the assembly I will correct it and let you know. I know others have already started printing the parts. Has anyone else encountered this problem? Glad you liked this project!

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adriancubas wrote 04/30/2022 at 13:47 point

I just checked and I have no interference in the design. The pieces between each other have a gap of 0.2mm. The Blade 15mm cylinder would go into the 15.2mm hole in the other part. I just uploaded some pictures of this in step 4 of the instructions. Send me a close up photo of the problem to see if I can think of a solution.

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SirDezzy wrote 05/14/2022 at 08:49 point

Hi, this is a very good project but I am also having printed size issues. So far, none of the propellers are fitting into Part B. Also D does not fit onto A. Very odd.

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