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Old 22-07-2014, 16:02   #76
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Re: Are Wind Generators even worth it?

Add wind when you are full of solar.

Upgrade/repair windgen when it breaks.

Don't set your expectations too high for windgen. It's part of the 3 legged stool.

If you can get 50 amps a day out of a windgen, it's still 50 amps you didn't have.
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Old 22-07-2014, 16:12   #77
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Re: Are Wind Generators even worth it?

I'm better than you so there?

Wow, I am just trying to have an intelligent discussion about why it is that way. Wind turbines aren't the only product rated against a theoretical perfect example.


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Old 22-07-2014, 17:16   #78
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Re: Are Wind Generators even worth it?

I suspect that one big source of discontent with wind gen claims is that most folks don't measure the wind strength at the location of the WG. They have the typical wind instrument mounted in clear air at the masthead. The WG is on a short pole or on the davits or arch at the stern of the boat, 40 or 50 feet lower than the masthead, and most definitely not in clear air.

Even in a free field, the wind velocity at the masthead will be significantly higher than at the wind gen site. Add in the frictional losses and the turbulence generated as the air passes over the forward parts of a yacht and there is considerably less available energy where you are trying to extract it with your turbine. Remembering that the available energy varies with at least the square of wind velocity, it is not surprising that folks are disappointed with what they get when their (uncalibrated) wind instrument says "20 knots" and the turbine is actually experiencing 15 or less, and that flow turbulent as well.

It is unrealistic to expect the vendors to spec their units to reflect this situation, for every installation is different. The only rational metric is to spec with ideal conditions of laminar flow of constant velocity. PErhaps a few words of caution (YMMV) would help reduce the customer discontent and these endless discussions on the internet.

Finally, the idea that an automatic regulator is required for our usage on cruising yachts is a bit naive. In the "old days", many of us used home built wind generators that were hoisted in the foretriangle when at anchor, and were directly connected to the mattery bank via a diode. We used such a system for years and never had issues of overcharging. Simply monitoring system voltage avoided any serious repercussions. This level of awareness is not an unreasonable expectation for a cruiser IMO. BTW, those units swung fairly heavy blades, usually of five or six foot diameters, and they were lethal if encountered accidentally. Much care was required when striking the systems if the wind picked up... not OSHA approved at all!

Cheers,

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Old 22-07-2014, 18:58   #79
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Re: Are Wind Generators even worth it?

+1 Jim, the voice of reason. And Yachties always seem to overestimate windspeed anyway, reading the highest speed seen as an average.

One other problem with windgens that cuts lots of juice at sea is the precession as the boat rolls. When spinning the gyroscopic effect and precession causes them to rotate away from the wind as the boat rolls. Often thought mine would have put in 30% more if I simply locked it in one angle in rougher reaching and downwind conditions, but then maybe I would put heavy loads on the mount and bearings?
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Old 22-07-2014, 19:40   #80
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pirate Re: Are Wind Generators even worth it?

I'd prefer to read posts only from folks that own wind gens, Scot.
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Old 22-07-2014, 20:26   #81
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I don't expect much from my windgen when I'm going down wind. On several occasions the wave height and period were perfect to send my windgen spinning 360 degrees. And I mean round and round and round. If I really needed electricity I could have tied it pointed in the right direction
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Old 22-07-2014, 20:39   #82
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Re: Are Wind Generators even worth it?

We have an AeroGen and the boat behind us has something else, can't recall. There is a big difference in the noise with the AeroGen being much quieter. I suspect the other unit is making more juice but I can't tell for sure. I know when the wind gets up to 30 knots even the AeroGen sounds like a C-130 taking off.

Another bloke has two identical wind gens. They are funny to watch. You would think they would track one another, but no way. One will spin like crazy while the other is pointing 90 degrees off doing squat. Then it will reverse. Or maybe they will both go. No obvious rhyme or reason.
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Old 22-07-2014, 23:39   #83
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Re: Are Wind Generators even worth it?

As Jim correctly points out, wind gradient will have a huge impact on your perceptions of your wind generator efficiency.

As a simple example, if your wind instrument is mounted at the top of your mast at, say, 100' above sea level (yep, you have a big boat) and your wind generator is mounted on a pole at, say 15' above sea level, then wind gradient might well be such that although your wind instrument might read 12 knots at 100' up, your wind generator might only be getting 3 or 4 knots at 15' above sea level.
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Old 23-07-2014, 00:00   #84
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Re: Are Wind Generators even worth it?

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Originally Posted by Weyalan View Post
As Jim correctly points out, wind gradient will have a huge impact on your perceptions of your wind generator efficiency.

As a simple example, if your wind instrument is mounted at the top of your mast at, say, 100' above sea level (yep, you have a big boat) and your wind generator is mounted on a pole at, say 15' above sea level, then wind gradient might well be such that although your wind instrument might read 12 knots at 100' up, your wind generator might only be getting 3 or 4 knots at 15' above sea level.
That's all good and true....but when I strap a wind generator on a tripod and drive down the road at 10kts, 15kts, and 20kts and get barely 1/2 to 3/4 of the rated output for some brands of generators while others hit their advertized values...well there is some BS marketing going on. This isn't rocket science to design and execute a test protocol folks...its fun and easy really...and that's why my boat projects never get done. I'm too busy having fun collecting and crunching data. Once a scientist always a scientist I guess.
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Old 23-07-2014, 00:21   #85
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Re: Are Wind Generators even worth it?

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That's all good and true....but when I strap a wind generator on a tripod and drive down the road at 10kts, 15kts, and 20kts and get barely 1/2 to 3/4 of the rated output for some brands of generators while others hit their advertized values...well there is some BS marketing going on. This isn't rocket science to design and execute a test protocol folks...its fun and easy really...and that's why my boat projects never get done. I'm too busy having fun collecting and crunching data. Once a scientist always a scientist I guess.
Indeed. I wasn't suggesting that there aren't some "shonky" marketing claims getting thrown around (air generators are by no means alone in this respect), merely pointing out a quite commonly overlooked fact. Surface friction wind shear gradients are fascinating - in lighter breezes, it is a good reason to twist off your mainsail as the apparent wind changes over the height of your mast...
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Old 23-07-2014, 04:24   #86
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Re: Are Wind Generators even worth it?

Had a wind gen once...it was really quiet...when you used it as a sea anchor...thats all it was good for anyway...bloody piece of sh**t
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Old 23-07-2014, 05:08   #87
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pirate Re: Are Wind Generators even worth it?

Well in defence of wind gens... I cruised for 4yrs down the Atlantic coast and around the Med in a 31ft Westerly.. full time live aboard with just an Aerogen.. admittedly she had no watermaker/washing machince/AC/fridge freezer and 8CD player to cope with..
Just the usual.. Instruments/VHF/lights/TP and a small invertor for charging and a coffee grinder..
Never suffered a flat battery once.. not that it would have bothered me any... as the Volvo MD2B could be hand cranked..
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Old 23-07-2014, 05:50   #88
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Re: Are Wind Generators even worth it?

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Na....me no understand.....you help me please....

Me no science man just ignore the 9 US patents that let me retire at 38 and go cruising...

Thanks for the fun.
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Old 23-07-2014, 07:01   #89
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Re: Are Wind Generators even worth it?

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Another bloke has two identical wind gens. They are funny to watch. You would think they would track one another, but no way. One will spin like crazy while the other is pointing 90 degrees off doing squat. Then it will reverse. Or maybe they will both go. No obvious rhyme or reason.
It seems the most wind generator oscillations away from pointing into the wind can be cured by putting on a bigger tail fin. I know a few people who have done this with excellent results. They can still get thrown off at sea of course but a bigger tail fin helps a lot in marinas and at anchor.
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Old 23-07-2014, 09:30   #90
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Re: Are Wind Generators even worth it?

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Originally Posted by Jim Cate View Post
I suspect that one big source of discontent with wind gen claims is that most folks don't measure the wind strength at the location of the WG.
I bought one of these specifically to measure wind speed at the WG. Its been a great tool in that I now have a much more accurate measure of how fast the wind is moving at the wind generator.

Vaavud - Wind Meter for Smartphones

For me, it was great at diagnosing that I really did have a bad wind generator and that it really wasn't starting up at the claimed speed, nor was it producing the claimed output.
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