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Windmill:
Is there any merit to a squirrel cage design, which could be either horizontal or vertical shaft? (Is there a way to calculate the optimum angle for flat blades, or the optimum curvature for "U" shaped blades? Does it matter if the ends of the blades are capped or left open?) One of the advantages
of using a vertical shaft is of course that it doesn't need to be steered into the wind, but then again it cannot be easily furled either. Further, there is the consideration that the top of the "U" shaped blades catch the wind while the bottom returns back against the wind at twice the velocity, which must cause appreciable drag and a resulting loss of efficiency. Is it worth the extra expense to build a shroud that (1) captures and directs the wind onto the energy generating half of the blades, and (2) shields the "drag" side of the returning blades, so that they're returning through static air? (Great! I just reinvented the automobile fan!) Nevertheless, has anyone ever done the math on this design before, or at least does anyone know how? If the inlet of the shroud has 4x the area of the outlet, have you captured four times, or (4^3 =) twelve times as much power? (And yes, the shroud would need to be steered into the wind, but now it can be "furled" too.) Does anyone know why there doesn't seem to be any published designs anywhere using 4x8 sheets of 1/4" plywood in some sort of a metal or wood frame for this configuration? (I've seen plywood used for a windmill tail assembly, and the waterproofing issue is handled with a coat of epoxy.) I see merit in the low cost, large surface area, and with the shroud it can be furled. Low RPM can be boosted by the simple use of an automobile axle and/or manual transmission, at junkyard prices. (What am I missing here?)
Inverter:
Then there's the question of generating "useable" power. Rather than trying to get exactly 3600 rpm (or 1800 rpm with a 4 pole generator) from the wind by adjusting the furling and/or load, I've wondered about using the same 120vac or 240vac generator, but full wave rectifying the output, and "slicing" the output cycles with an scr directly across a bank of 12v batteries. (Appreciable power is generated at low RPM? Power transfer is easily and efficiently controlled over a very wide range? Is it a fact that 12v batteries actually require 40v+ across them for high amperage charging?) Then what? Does everyone just accept the low quality of "modified sinewave" inverters or the high price of pure sinewave inverters - not to even mention the hideous cost of grid-tie inverters? Are there any public domain designs for the latter two devices? Are they really that hard to design from scratch? I realize that the grid-tie inverter is fairly complicated, since it must exacty match the line frequency, phase, and voltage, and THEN decide how much power to inject back onto the line, plus continuously check for a "power off" condition to prevent "islanding". (How? Unless it disconnects itself periodically? Or can it continuously check to see if the load - and consequently the voltage - changes dramatically in either direction?) Operation of the output stage power transistors or FETs in the linear region wastes half of the available power in the form of unwanted heat that must then be handled. (Has anyone ever heard of a 12vdc to 120vac "switching A/C power supply" that is frequency and phase controllable, and better yet would have a "constant current" mode?) Ok, how about this? Has anyone heard of a cheap inverter design using a 120vac to 12vac transformer, which generates a "24 step" sinewave by connecting the battery cells in timed succession to the 12v side of the transformer, from 0 to 12v (in 2v steps) for the first 90°, reversing the order for the next 90°, then inverting with an "H" bridge and repeating for the next 180°? (It would really need to be an 8.5vac transformer due to the RMS issue.) Could the input/output waveforms be smoothed with some simple combination of inductors/capacitors? (Has this been done already? Is it patented?) Sure, the first battery cells will discharge faster. But that issue can be resolved by designing the charger to charge each cell proportionally. Final question. Do standard utility meters detect the direction of power flow? (If one injects power into the line, what's to say their power meter won't just add that to their bill? If these meters CAN detect direction, then how do they do it?)
Comments?
Bath tub thinking
http://www.parliame...ech/999/4032406.htm
[PainOCommonSense, Oct 21 2004]
A vertical axis windmill
http://www.newenerg...h/product/windmill/
[phoenix, Oct 21 2004]
Another vertical windmill
http://www.sigurnos...culjak/windmill.htm
[phoenix, Oct 21 2004]
And another (Darrieus) vertical axis windmill
http://purrfectcats...8080/james/darrius/
[phoenix, Oct 21 2004]
Overbaked
http://groups.yahoo.com/group/overbaked/
Perhaps a better place for the [WindPwr] brainstorm. [Worldgineer, Oct 21 2004]
[link]
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thats a whole heap of questions! |
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Yeah Po. Is this a question or an Idea. I think someone needs to click help. As far as i know these sorts of windmills have been prehistory baked. You might like to look at Darius Windmills while you are at it. |
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Forgive my attention span defecit: please distill that into a single, easily comprehensible idea. |
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Yes, yes, yes, yes, yes! No! No, line breaks. Yes, yes, no! Secret, no, ain't tellin', yes and no, fight the power, maaaaaybe,could be, sure it can, nope, sure, yes, yes, chivalry, I dunno. |
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The trouble with the drag coefficient being used in tandem with a verticle side'plex as in traditional windmills, doubled with the horizontal stretchbeam being placed tower then the main crank, is that the area covered by each blade, coupled with the open 'air vents' at the ends, can make co-agdulant and indefienct speed gainings when compared against a 'Guerand' rotations flip-shield doubling-up strategy. |
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Thats what I think anyway. |
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Well, let's be positive and consider the good news. (1) I found this site in the first place. (2) I successfully posted a discourse. (3) I found my way BACK to the site. (4) People actually found, read, and RESPONDED to my post! Now the bad news. I wrote a monolith. (But give me a break? I was merely hoping to provoke intelligent discussion, and at least we have a start!) |
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Shall I start over? (But first. Bath tub thinking - I couldn't get your link to work. po - yes. PainOCommonSense - sources please? FloridaManatee - yes. thumbwax - I lost you at the "line breaks". britboy - um, sure.) |
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(1) Has anyone ever used 4x8 sheets of plywood in a windblade design before? (1a) Squirrel cage with either flat or "U" shaped blades? (1b) Set at an angle and mounted on something like a wheel rim, similar to conventional fan blades? (1c) If not, why not? (1d) If so, are the results documented anywhere? |
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[Wind] Welcome the HB. You're close getting the concept, you are just coming in a bit early in your design. You're still at the "what should I design?" phase. Come back to us when you've picked a design and can describe it concisely or in an entertaining way, and we'll help you refine it or toss it out. |
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If you'd like help with the "what should I design" stage, or would like to chat about anything else in the world, try overbaked (link). |
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[WindPwr], I think I can help you with some of your questions. It might be easier if the questions were numbered or something.
The inverter set of questions:
Don't try to cut rectified 240vac to 12v using an SCR. The phase angle would have too much error, and the voltage output control would be difficult. Use a transformer first.
Connection to the grid needs voltage and phase synchronisation (assuming same frequency). A voltmeter and phase rotation relay are required. Once synchronised and stable, then connect. Power transfer is controlled by trying to increase frequency a little (which is like trying to increase the frequency of the whole grid). Reactive power is controlled by trying to change the voltage. As you can see, it is quite complex. In a small steam powered turbine (say 10MW), most of these things can be done manually. With an inverter system driven by wind, it would most likely need to be automatic.
Metering is available that can measure in both directions. They measure the direction of current, voltage, and phase angle between V and I. |
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Worldgineer - Thanks for the advice. Ling - I'd like to know if we could carry on this discussion elsewhere? I'd like to learn more about the grid tie interfacing requirements. (I'd never heard of a phase rotation relay!? Did you mean power transfer is obtained by increasing the phase - not the frequency? What is reactive power, and how is it different from the earlier reference to power transfer? Are standard utility meters directional?) I'm interested in your thoughts on my "stepped sinewave" generator idea. Could we maybe continue this discussion via email? |
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Ok. First I'd like to thank everyone for their advice, and let me try rephrasing my questions into ideas, and see if I can get this right this time (before I delete this page entirely and start over...) From the top:
I have an idea for a windmill, with blades made out of epoxy coated 4x8 sheets of plywood. There are three configurations I'd like to consider:
(1) A huge squirrel cage fan with 4x8 flat blades placed at some ideal angle, mounted on top of a car wheel rim.
(2) A huge squirrel cage fan as above, but with the 4x8 plywood bent into ideal "U" shaped blades.
(3) A huge "conventional" fan with four, six or even eight flat 4x8 blades at some ideal angle, suspended from bent steel pipes welded to a car wheel rim.
If data isn't already available for the ideal angles and "U" shapes of the blades, and cannot easily be calculated or estimated, then scale models could be built to gather experimental data. (Wind blades don't have to be 4x8, but this design is intended to catch as much wind as possible.)
In each case, the wheel rim would be mounted on the car hub/axle/transmission or transaxle, which would boost the low RPM/high torque to a higher RPM at the engine side of the transmission, where the generator would be connected. By selecting which "gear" to engage in the transmission, there would be several gear ratios to choose from. (The other differential axle would simply be locked.)
Although perhaps crude, the design would be cheap, and would presumably catch a lot more wind than the other standard two to five blade propeller systems out there. (Admittedly these designs would not be practical to mount on a tower, but in my case there is a phenominal amount of wind at ground level, compliments of living near Chicago I guess...) |
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Sorry, it wasn't a phase rotation relay: should be a Synchroscope! |
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Ling, I hadn't heard of a synchroscope either, but a simple search came up with a description - thank you! (I knew someone that had been in the Navy, that explained to me the process of switching from ship power to land power - basically snapping one huge set of knife switches open while simultaneously snapping another set closed. The person in charge of this operation got so good at it that the ship's lights wouldn't even flicker. But occasionally there would be an awful shower of sparks... However, this was awhile back, and hopefully his successors are using this device now!)
If you have time, I'm still curious what you think of my "stepped sinewave" with 2vdc resolution idea for an inexpensive high power inverter. |
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Note that I've removed the MFD now that you have an idea here. I still think you should either delete this when you're done with it or take your anno and replace your idea with it. |
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Now, for the idea. I think this may work fairly well for an off-the-grid application, such as a house far from power lines. |
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I like the first Vertical Axis Windmill link from Phoenix. (Might anyone know if this design is actually in use anywhere?)
Worldgineer, thanks, I appreciate it. (If I move the idea to the top, then most of the negative comments will be out of sync. Is it cosher to remove them? What happens with the negative votes?) |
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Feel free to delete annos that aren't related to your idea, which will apply to many of the annos once you edit. The fishbones, however, have a mind of their own. |
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Mind you I only got past the first sentence or two. Advantage. Doesn't matter which way wind is blowing no need for windvane etc. Disadvatage.. physics of them poorly understood and complicated and the few prototypes that have been built don't seem to function very well. There might be potential in this design but so far no one has found it. |
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