Wind Turbines - Consumer Rated

Discussion in 'The Projects Forum' started by retched, Jan 11, 2010.

1. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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I am interested in bi-charging a bank of batteries with a small turbine and a solar array.

The question I would like addressed - Wind turbines have a "break-in speed" and an operating speed. The operating speed is much slower than the break-in.

ie. break in speed 8mph operational speed 2.8mph

OK-Break in speed:
Now, Im guessing, its like the larger amp draw when first starting a motor. Getting over the friction and increasing momentum to get things moving. After that, continuing the cycle requires less power.

SO. IF the wind speed is regularly over the OPERATING speed, but under break-in, would it make any sense to use a charged cap ratched solenoid kick-start to get the turbine spinning when wind speeds are above operating but under break-in?

Do you think this is one of those perpetual motion ideas?
If the amount of power required to get the blades moving can be made up for before the wind reached break-in speed, It could work.

Now, I need people who know what they are talking about to set me straight.

Any math would be greatly appreciated.

2. rjenkins AAC Fanatic!

Nov 6, 2005
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I get the impression that the 'break in speed' only applies to some grid-connected systems, where they need to get to a minimum point before the control system decides it's worth syncronising with the AC network.

For a system like that, where it has to switch on & off line, they also have to allow for the generator loading pulling the speed down when it does switch on line and starts providing power.

For a low voltage output system, that will not apply. The generator (or altenator) will just start to provide current as soon as the output voltage exceeds the battery or load voltage, just like a car alternator.

ps. Be very wary of the figures on commercial 'consumer' wind generators - the ratings are often taken with them mounted on a mast clear of all obstructions, and the actual figures in typical domesic use are a fraction of the theoretical output.
One type tested by a UK consumer group worked out to have a cost repayment time of about 20 years, somewhat longer than it's rated life.

Have a look at some of the DIY designs from enthusiast web sites and get some real-world figures and design / location info, before you commit too much cash.

Last edited: Jan 12, 2010
3. jpanhalt AAC Fanatic!

Jan 18, 2008
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@retched, What you suggest makes sense to me. Many devices need a similar "get going" push and require much less push to keep going. Jet and propeller driven aircraft are just two examples.

The get going push often does not need to get anywhere near operating speed. My gut tells me that a capacitor and solenoid would not do it, though. I am not sure how the solenoid would be attached to the drive shaft. No formulas, just a gut feeling. If you ever saw Flight of the Phoenix (Jimmy Stewart), it used a centrifugal engine starter. The starter was spun up to speed with compressed gas, then engaged to the engine.

I suspect your blades barely need to be moving, so I would consider an electric motor with flywheel that would engage with your blades much like a Bendix does in a car. Using gears would produce a lot of stress, so I would look at some sort of hydrostatic coupling.

However, the simplest solution would be if the generator/dynamo in your wind mill can also operate as an motor. If that is the case, then supplying power to it would get the blades moving.

John

4. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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I had a feeling I was wrong. And thanks. ([ed] check the 2nd pdf on next post talking about "start-up rather than break-in") Last night I canceled my order for the turbine to give myself a chance to D-I-Myself.

I have yet to do a decent search for diy plans, but I have started brainstorming and charting my ideas. Gotta get started.

And for my project, its not to suppliment AC but to try to convert a living space to all DC with out loss of DC-AC inverters. So a battery bank charger/desulfer and a whole bunch of revamping AC stuff to DC.

Last edited: Jan 12, 2010
5. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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jpanhalt,
That was my original thought. The idea for the solenoid to cock a kickstart spring. The sprind connected by ratcheted couple could take the inital force and ease the shaft moving then disconnect, like a motorcycle kickstart.

Just to get things moving enough for the pitched blades to grab more wind.

I thought of the alternator idea also, using it as a motor to get things moving, it seemed to me the initial pull would require much more power than the solenoid. I wanted to see if I could use as little power as possible.

here in the info in the vertical:

and in this pdf it shows "start-up" wind speed for a turbine:

Last edited: Jan 12, 2010
6. BMorse AAC Fanatic!

Sep 26, 2009
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If you are looking to do a DIY micro wind generator, check out my project here >> http://www.morse-code.com/windmill_generator.htm, especially, especially my PVC propeller blades, which makes mine spin even at low wind speeds of about 3 to 4 MPH, and also, check your local wind maps to see if a windmill will do you any good in your area..... but then again the wind maps in my area say that my location is pretty poor for a windmill, and mine hasn't stopped spinning since I put it up early last year

Nov 6, 2005
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8. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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Thank you. Thank you. Very good information. Do you find gearing up for maximum RPMs into the generator kills torque too much and starts to kill efficiency?

I suppose it depends on the generator...

Have you found what works best for a generator? Brands? or even car alternators?

9. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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Another idea. Sorry. Thought. When using a car-type alternator to produce power, you can increase output by increasing the current on the stator, correct?

That in turn produces a greater flux creating a greater overall power. This also has the upside of "slowing" the turbine in high wind conditions. Now, If you were to pull the power for the stator from the generated power circuit, you will eventually come to a pass where it is no longer efficient. What if you used an aux micro turbine to power the stator? say, after crunching the numbers, using a smaller generator with a smaller prop size?

I got the idea from seeing many wind speed meters on windmills posts, and thought of addind another small turbine.

Any good that could come of this?

I was told during a automotive class years ago that the ony way to make the alternator more efficient was to power the stator from a seperate power source, I though of a battery, but that would have to be charged, either from the same alternator or ultimately off the engine with another alternator. If you could get "free" power for your stator, you should be able to maximize output from the alternator.

10. BMorse AAC Fanatic!

Sep 26, 2009
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Car alternators can be used, but only if you can drive them atleast 500 rpm's, to produce the 12 to 14 volts to charge a battery, or to rewind it and use different magnets.... The best way I found (I did a lot of research, and hands on stuff to figure this out ) was to use a permanent magnet motor rated for higher voltages but low RPM's. A plus also in using DC motors is that the output is DC, no need to rectify it to charge a bank of batteries, then have to re rectify it back to AC.

or you can make your own turbine generator capable of outputting anywhere from 400 watts to 2 KW.... But then you have to have a larger swept area to produce that kind of power, so then you are starting to get into 50 meter poles and taller for your generator.....

11. BMorse AAC Fanatic!

Sep 26, 2009
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Now you are delving into perpetual motion

A lot has been tried and done by a lot of people, check out sites such as http://www.windstuff.org/, he has a lot of stuff posted on his DIY generators... and this site >> http://www.thebackshed.com/

Last edited: Jan 12, 2010
12. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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Thank you. I need to digest. 500 rpm is about the top of the line I wanted to handle. I will have to finish my turbine sans generator to see about speed/stability.

Have you ever tried a vertical blade design?

6 blades would give you half the height of a 3 blade horizontal design.

Thanks,

13. retched Thread Starter AAC Fanatic!

Dec 5, 2009
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Have you any direct reason for staying with a DC motor against rectifying an alternator?

I just can not find information on choosing one over the other (besides rectifying). Post rectification, what would be the advantage of one over the other?