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Forum Index : Windmills : Looking for more RPM
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| Marcus20VT Regular Member  Joined: 02/09/2008 Location: WalesPosts: 49 |
Hi All, I have just completed my homemade wind turbine and it is up and at it!! However, I have had to make it a bit descreet as I have no planning permission! So it is not as high as I would like to catch all that lovely wind. At the moment I am getting between 6 and 12 volts from it - I really need double that for anything useable. My generator is from a treadmill motor - 1.5hp 230Vdc at 4800 rpm. Its not ideal, but I should be getting 23V at 480 rpm yes? So how to increase RPM - 1 idea I had wast to cut the meat off the 6mm hub, just leaving enough to fix the blades, thus making it 30% lighter. Another idea was to replace the blades with bigger ones. The original blades are made from the 4 inch soil pipe. Woul;d I get a significant rpm increase if I made some out of 6 inch pipe? Or is there some sort of electronic solution to my problem? Thanks in advance for your help, marcus  |
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MacGyver Guru  Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Marcus20VT Merely increasing the rpm will not do the trick. You need rpm AND power; you need more wind! You can trim out the angle of attack and get the rotor spinning faster, but it will be at a cost of torque and as soon as your genertor loads, it'll eat up all that momentum and you'll be right back where you started. Sorry. 
. . . . . Mac Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Marcus20VT It is a waste of effort to lighten the hub as that will not increase the speed. You need a bigger set of blades that are more efficient to do any good, I have tried the poly pipe blades in the past and found them useless below 10 ms wind speed. For your setup I would suggest a set of windy nation 80 inch blades or similar. You will find that better design blades run quiet and attract less attention. paint the whole thing in a light blue grey color dove grey is the one I use and it will reduce the visual impact, try for a minimum of 26 ft high to get a bit more wind. All the best Bob Foolin Around |
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fillm Guru Joined: 10/02/2007 Location: AustraliaPosts: 730 |
Marcus-Bob , in my opinion by "just looking at the windy nation blades" they provide a no better airfoil section than cutting blades out of large dia PVC except they are cut out of large dia Aluminium tube . Obviously they will be stronger, but as for producing higher RPM and torque, I would be hesitant to say that these would be the answer to your problem to make a generator reach a cut-in of 380Rpm+ in 3m/s where most wind-gens start to make power. I would recomend trying to find an alternator that is more suitable to a wind application. Trying to get it to spin up to 400+ RPM to make 24V would definately not be discrete sound to your neighbours if you are trying to fly under the radar. PhillM ...Oz Wind Engineering..Wind Turbine Kits 500W - 5000W ~ F&P Dual Kits ~ GOE222Blades- Voltage Control Parts ------- Tower kits |
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| Marcus20VT Regular Member Joined: 02/09/2008 Location: WalesPosts: 49 |
Thanks for your replies, all. I'm afraid I completely ignored the laws of "torque" and "momentum" !! - typical sparky!! I'm not quite sure if I can put 80 inch blades on it in its current location - and moving location will be a pain. I have a 4 blade hub, and that would make it massive!! My immediate neighbours are ok - but my next door but one is a bit of a moaner, so I want to keep it quiet from him. It is painted a light green with maroon and white blades and maroon fins like a rocket - not stylish and not discreet I know - but they were the only paints I had available. oh, and then the kids covered it in skateboard stickers! Also worth mentioning, it is pretty quiet when spinning, so I'm not worried about the noise. I am always on the look out for better suited generators, but I am trying to work to a budget, so cannot just buy buy buy for this project. I want to use the power generated for some 12v lights in my shed and to power an "optimate" trickle charger for my bike battery - so no heavy draw or high useage. I'll make some more blades from the 6 inch pipe - they'll be about 40 inches long. Do you think this will make a significant difference, or am I just wasting my time? Thanks again Marcus - in sunny North Wales, near Chester, UK. |
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Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
Hi,Marcus; Marcus Wrote; My generator is from a treadmill motor - 1.5hp 230Vdc at 4800 rpm. The problem you have will continue until You find a different design for your generator. The voltage and power size are fine but the RPM is the Killer, You should have a Motor in the range 1200-2000 RPM for use as a generator. A wind turbine does not operate at 320 rpm, in average wind This is 5.3 turns per second. A larger blade will give you more torque but will not increase your RPM. Note; The 1200-2000 rpm motor will need more torque to drive under load than the 4800 one. Torque is easier to get from a mill than speed. Best of luck on this project. Cheers---Roe EDIT; change "in normal wind". to read "in average wind" Time has proven that I am blind to the Obvious, some of the above may be True? |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Ideally you should probably look for a more suitable motor, but there is some hope if you are willing to do a little experimentation. Recently one of the forum members ( Bob I think ) was playing around with DC step up inverters. These can take a voltage like 6 volts and put out 14 or so volts, enough to start charging a 12v battery. This might be worth looking into. Does anyone remember the link? I think they were an ebay item. You could also play around with gearing up the RPM using a angle grinder gearbox or something similar. While the two idea's above are not the best approach to a long lasting reliable easy windmill, they can be made to work if you give them a go. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
I got mine from there:DC to DC step up converter Got 3 of them now, one at the windmill, one to drive a 18V battery drill from a 12V battery and one spare. If you do use them near the 150W power range then the heatsinks are not big enough. I found the PCB fits just inside a multifinned heatsink, removing the original bar heatsinks and screwing the power devices (with insulating washer & spacer) to the fins on each side it runs on max power and just gets warm. If you can't picture my heatsink mod let me know and I take a picture of it. Klaus Klaus |
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| Marcus20VT Regular Member Joined: 02/09/2008 Location: WalesPosts: 49 |
Hey that looks a good spot!! I guessed there would be some sort of electronic solution - I am a bit worried that my treadmill motor would fry the circuit, but as I would never get to max power (4800 rpm) I am open to answers on this. Also - stupid question probably - is both the i/p and o/p variable - i.e does this just give you 3v more than you generate? - or is the i/p variable and the o/p set? Thanks for all your posts and help, marcus |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi All I have good success with the up converter, I am now using two on the mill a small one that cuts in at four volts and pumps to 27.5 volts at 2 amps and the larger one that cuts in at 10 volts and pumps to 28 volts at a maximum of 9 amps. On continuous full load it got to hot as tinker said so I made a heat sink from two pieces of 1 1/2" x 1/16" aluminium angle, at full load continuous it gets a bit warm but is still containing the magic smoke. by the time the volts reach 27.5 the voltage across the module equalizes and the power then goes through the main rectifier. Using these modules my mill, one of Phill's Mills now makes power from 2.5 ms approx 40 watts to furling at 15 ms at 1500 watts. Most of the time it spends at slow speed so every watt is a bargain, on my old mill a Chinese 500 watt unit I am getting output from 3 ms up to 1000 watts at 15 ms and more above that as it doesn't furl. I have seen over 50 amps on it in gusts as well. I had some problems when I first put mine on as it caused the mill to grumble and sound bad, I thought it was loading to low but found there was a open circuit diode on the boost module rectifier and that caused uneven phase loading on the alternator, new diode bridge and its as good as new. My mills are delta connected for maximum efficiency but with these modules produce power as soon as the blades are turning over 60 rpm. All the best Bob Foolin Around |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hey Bob, is that the same up converter that Tinker linked too? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Marcus, there is one trim pot. It adjusts the output voltage. In my case I set it to 24V for the drill power supply. Input must be lower than the output but could be anything from 10V up.
You can read the specs on the website, just scroll down a bit. Klaus |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Hi Glenn That is the larger one, looks the same from the photo but with bigger heat sink they will go to 10 amps input. Without a heat sink they let the smoke out over 5 amps continuous. The smaller one may be more useful in the application here as it works from 4 volts with a input of 2.5 amps from memory as the big one cuts in at 10 volts. As mentioned I use two now one to get the lower voltage and the second one comes in at 10 volts. The blue pot adjuster sets the output volts, I connect a little globe across the output for a bit of a load, as it makes the setting a bit more stable and visible, a 30 watt halogen globe fro a spot light works well. The output voltage is the one you set the input is whatever goes in, if the input voltage goes above the output setting it turns off, so you will need a diode direct to the battery to conduct power should your generator get spun up in high winds. It is also a good idea to have an isolating diode on the input and output of the boost module to isolate it. If you are charging a 12 volt battery set the output of the module at 14.2 volts on the battery side of the isolation diode as it lowers the volts by about a half a volt, mine did anyway, or a 24 volt battery set to 28 volts. Item number:190447676555 ebay search number foe smaller one Item number: 200607221396 All the best Bob Foolin Around |
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| Greenbelt Guru Joined: 11/01/2009 Location: United StatesPosts: 566 |
Hi all, This is a interesting little Item, reminds me of the old TV flyback transformer that was used to generate the voltage for the CRT. I saw Bob's and Tinker's Posts some time ago but didn't check it out. This Could be useful on solar arrays that have lost a few cells to keep the volts up to Inverter input. The link is A Schematic of the Voltage converter Cheers----Roe Time has proven that I am blind to the Obvious, some of the above may be True? |
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| charlie_ruizpr Newbie  Joined: 08/07/2010 Location: Posts: 36 |
Does this go from turbine to controller or from controller to battery? |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Turbine to Controller. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Marcus20VT Regular Member Joined: 02/09/2008 Location: WalesPosts: 49 |
Thanks for all the help on this. Unfortunately I have not given Mother Nature the respect she deserves, and I am ashamed of that! During the particularly gusty last but one weekend, I woke to find my turbine on the ground. It has litterally been ripped from the fixings, bending the washers to do so
Luckily the pole missed both cars and the neighbours garage, but 2 blades are snapped, housing broken, tail fins destroyed, but hopefully no damage to the hub and motor shaft. So, I am off the air, or off the wind so to speak for a while. Hopefully will be back up and running soon. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Sorry to hear that Marcus But rest assured, the same thing has happened to most of us. I've had one pull the concrete guy wire anchors out of the ground! Next time I dug a deeper hole and used more than half a bag of cement. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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