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MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329

Posted: 07:27am 06 Dec 2009

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My windmills just pump air and I therefore have absolutely no experience with blades direct-coupled to a generator.

My question is: as the speed of the wind constantly changes, how does one even out the frequency of the electricity produced?

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

oztules

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Joined: 26/07/2007
Location: Australia
Posts: 1686

Posted: 08:00am 06 Dec 2009

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In fancy terms.. we need a frequency converter.

In real terms that means we rectify to DC and bank it in a battery bank, and convert it later (or now) into 110v 60hz or 240v 50hz with our trusty inverter.

Those with grid tie need to do the same thing, with or without the batteries. ie rectify to DC and straight to the grid inverter to make the 50 or 60 hz for the grid, or charge batteries and run the grid tie from there.

There is one other way to get fixed frequency from a variable speed shaft. The induction grid tie is the other one. Here we vary the shaft speed (from the wind), and excite the magnetic field with a fixed frequency (the mains or other low impedance source frequency source.) The output will be in sync with the magnetising source.. (50 or 60hz mains) not the shaft speed.

The proviso is (and there is always a proviso) that we can't move too far from the right shaft speed, or the "slip" will be too great, and the thing will lose the sync field.

This is only useful for larger machines, and with pitch control which is helpful, or fixed chord blades (so they stall more as they overspeed), or where you have enough blade, and a big enough motor that you can drag the TSR down to closer to the right speed, without losing too much power from the blades. The basis of grid tied mills until big converters came along.

........oztulesEdited by oztules 2009-12-07

Village idiot...or... just another hack out of his depth

MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329

Posted: 06:53pm 06 Dec 2009

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Oztules

Thanks for the detailed reply. Unfortunately it zoomed well above my head. Yikes! Now I remember WHY my windmills just pump air.

I guess I'll simply stick to mechanical stuff; levers and cogs and stuff I understand, but now at least I know what lies down that yellow-brick road. Thanks again.

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

Perry

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Joined: 19/11/2009
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Posts: 190

Posted: 10:14pm 06 Dec 2009

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Hey MacGyver,
I'm new here so I probably missed most of your posts. What things do you run with your 'air' turbines? Sounds interesting.
At work I proposed a big utility scale turbine that pumped air. The tubular tower has a big volume and that would serve as an air tank. An air motor and generator are mounted on the ground. They didn't want to pursue patents.

This is the point that many people post that this is an ancient idea anyway.

Perry

MacGyver

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Joined: 12/05/2009
Location: United States
Posts: 1329

Posted: 11:50pm 07 Dec 2009

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Perry

First off, all my air engines are piston or peristaltic (trapped rubber hose). Air turbines are too noisy, dangerous and require way more volume than they're worth.

I usually run a small motorcycle generator with the air engines, but I've been in the process of designing and building my own alternator out of neo-magnets.

All I'm after is to charge batteries. All my machines (lathe, mill, drill press) run off 12-volt d.c. Well, also, I use some of the compressed air in my greenhouse, which power several DWC hydroponic tomato growers.

If you're after using a LARGE tubular tower as a pressurized air receiver, make sure you keep the pressure in the very low range -- 30 to 50 psig or you'll be approaching a bomb. If a large container is under high pressure and it gets punctured, it'll want to take off like a large balloon!

My view on patents: Patents serve only to keep others' hands off. In many instances, very cool things have been invented, patented and locked away. What a waste. I learned to "share" in kindergarten about 55 years ago and it seems to work quite nicely for me.Edited by MacGyver 2009-12-09

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

Perry

Senior Member

Joined: 19/11/2009
Location:
Posts: 190

Posted: 12:21am 08 Dec 2009

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Yes, but we get a big bonus for every patent we have issued.

I think your compressed air turbines sound pretty interesting. I understand the issues with large amounts of compressed air. After some number crunching It became obvious that even a huge turbine tower has nowhere the volume to store enough energy. The commercial plants that do this use enormous salt caverns to store the compressed air.

Any chance that you have any pic's of you turbines?

Perry

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