wind generator experience in 10 knots or less

[Paul Cossman]

Anybody out there with real-world experience with wind generators that produce output in winds of 10 knots or less? What wind generator do you have, and what is the amp output at winds in the 8 to 10 knot range?

I have a circa-1992 fourwinds unit, and I cruised with it for about 8 years, all in the Central and South Pacific. Although it had good output at 15 knots, it had lousy output in the 8 to 10 knot range. And that is the "average" wind strength in areas where I try to anchor. So for most of the time, the fourwinds was close to worthless.

For my upcoming voyage, I am going to be replacing my fourwinds with a unit that has an output "targeted" for 10 knots, rather than a unit that targets a higher output at 15 knots+. I am looking for real-world experience from people who have such a unit. I would hope to find one that puts out 3 amps or so at 10K.

Anybody out there have such a unit?

 

[Ross]

The force of the wind varies as to the square of the velocity. Therefore wind at 15 has a bit more than twice as much energy as wind at 10. Therefore in 10 knots you shouldn't expect more than half what you get at 15 and about a third at 8 knots.

 

[Steve Kamp]

Paul,
I'm using a 2006 purchased AIR-X on my H-38. When winds are light and variable (most of the time) I get between 2 and 5 amps on the meter.With winds between 5 and 10 kts I get a variable output of 4 to 8 amps, because even in this range the wind speed is not constant. My primary source of "green power is two 85 watt solar panels mounted on the top of the dinghy davits. These give me on a clear to partly cloudy day 5 to 10 amps per hour for about 8 to 10 hours. The combination of solar and wind is enough to keep up the house bank (Currently a 4D lead acid) running the fridge 24/7, anchor light all night and cabin lights, instruments,running lights,VHF, and water pump as needed. This was sufficient for a 6 month winter cruise in the Abacos. Of course conditions are more than likely different where you are.

 

[John]

I could swear that Practical Sailor had a review of different generators recently. Included in this review was a comparison of those generators that provided maximum amps vs. those that did better in lower wind speeds. I just did a search of their web site, but couldn't find any record of this review. Maybe if you called them they could tell you when it came out and how to get it.

 

[sailaway78]

Wind generator outputs

I remember the practical sailor test, and unless my memory has totally failed, the new air breeze unit from air x outperformed all others at very low wind speeds. It is only rated at 200 watts, but worked very well at wind speeds under 10 knots. Before Katrina got it, I had a 250 watt unit built by a guy up in the NW somewhere, and loved it. It was very good at low wind speeds, and very quiet. Apparently he is no longer making these, as I can not find him or any info at all. I would think that if you can live with 200 watts or less, I would certainly look closely at one of the smaller units on the market.

 

[Bill Roosa]

Design factors

To capture the wind you need to consider the amount of "wind" that your blades intercept. While the power you get goes up as the square of the wind speed (an uncontrollable variable) the power goes up linearly as you increase the diameter of the blades. Less so by the number of blades. So you would be looking for the genset with the largest diameter blades and the largest number of blades. Course larger is noisier.
Now if you could have a blade the size of your main sail..... hey, why couldn't I just drag a propeller in the water and use the entire sail plan to power my boat both forward and electrically?
Just a thought.

 

[Paul Cossman]

Guys, thanks for all the replies thus far.

Steve, you really get 4 to 8 amps on your AIR-X when the wind is only between 5 and 10 knots?! That is excellent, and is way beyond the performance I thought any wind generator could produce in only 10 knots. What is the noise level like?

John and Nice N Easy, Practical Sailor did do an article in July 2007 on wind generators. Unfortunately, they performed the testing over four days, and based output upon an average wind speed (which was 12.6 knots), with two of the days being "more blustery". That test provided no data on the specific information I seek: which wind generator has the best output in the 8 to 10 knot range, and what is that output in amps. Practical Sailor only said that in that wind range that Ampair and the Rutledge 916 were the best performers. I love Practical Sailor, but that information is hardly earth shaking news, nor is it useful in determining the amp-hour output of these units in 8 to 10 knots of breeze.

Bill, I once used your propeller dragging idea. I had two "fourwinds" generators: one wind generator mounted on a dedicated permanent pole installation, and the second "water tow" generator mounted on my stern. To the stern mount I attached 80 feet of very stiff line, a four foot stainless steel rod, and then an outboard-type propeller on the end of the rod. At four knots of boat speed it put out about five or six amp-hours. On one passage where we were beam reaching in about 12 to 15 knots of breeze, the two generators provided our entire energy budget for about ten days of that passage. (Our consumption at anchor is about 125-150 amp hours per 24 hour period, and under way is more like 200+ due to electronic auto-pilot use). BUT I got tired of not being able to fish, as the two lines invariably tangled behind the boat. Plus it sometimes created a safety hazard as it would be difficult to retrieve the line in heavy weather conditions. Not to mention the constant overhauling of the generator due to water intrusion . . . .

Anybody else with experience in 8-10 knot winds, who can give me info on amp output with their unit at that wind speed?

 

[Rich Stidger]

I installed an Air-X last year and kept output vs wind data. Give me a day to dig it out and summarize the info and I will post.

 

[Steve Kamp]

Paul,
I was sitting at the nav desk today and glanced over at the amp-meter connected to the Air-x. It was jumping between 3 and 6 amps as the wind gusted from the south between 4 and 12 kts. The Air-x makes a low frequency moan begining at around 3 kts and increases with wind speed. This moan is audible inside the cabin. Outside, in the cockpit it is a light brushing sound. On the finger pier I don't hear a thing, but then again my wife says I have selective hearing. In any case what I do hear is the sound of free electricity.

 

[Ross]

I just googled Air-x systems and this is what I learned: they seem to cost about 1400 dollars for a power head and a tower. After that the electricity is free.
Grid electricity costs 11 cents per KWH. My diesel engine can turn my alternator and generate 600 watts even if the wind doesn't blow. Air-x is rated at 400 watts at 28 mph wind but that speed is unusual. 14 is much more likely. Diesel fuel cost me about 40 cents per hour just to run the alternator. At 14 mph the Air-x will probably put out 100 watts max.

 

[Paul Cossman]

Steve, thanks for the info. The low frequency moan and brushing sound really don't bother me, so I am glad to hear that report. You say you got 3 to 6 amps w/winds from 4 to 12 knots. That could mean that the 3 amp reading starts at 10 knots, or starts lower. Do you have a feel for when the Aix-X starts to generate 2 or 3 amps?

Ross, thanks for your input. I understand your outlook on the economics of power generation. For me, however, there are other factors far more significant than economics. I lived on my boat in the tropics for years. My diesel generator set-up is likely less insulated than yours, so I have an issue with sound and heat. If I want to block off more sound, that means less air flow and more retained heat in the engine (and battery) compartment, which is already significant in the tropics. When I run my genset for the requisite two hours/day (a five HP Kubota running a 130 amp alternator), it gets very hot in the cabin. So it becomes a real chore to find the right two hours. We generally settle for one hour in the morning, and one in the evening. Then we have to tolerate the sound while it runs. And we have to remain in the boat, so it limits our activities. The money expended is not important to me; the time and comfort are important. I lived with a fourwinds generator for all those years, so I am also quite experienced with the output of wind generators at various wind speeds, and understand the trade-offs. I have anchored hundreds (thousands?) of times, and have sometimes selected my anchorage based upon wind speed for power generation purposes. I now am ready to anchor solely for comfort, and hence my queries about low wind speed generators.

Anyway, just thought I'd let you know why the monetary economics are not important to me; comfort and aesthetics are.

 

[Ross]

I think that I would invest in some serious ventilation for my machinery spaces.

 

[tc0nn]

I would think you could attach a two/three speed gear box on the front of the generator to compete with slow wind speed. You might consider getting a second wind generator with higher pitched blades and a lower output just to trickle when the conditions are less than favorable.

I'm actually looking for suggestions on how to attach a permanent spoiler like hard mount for my various toys. I don't want to get in the way of the bimini, or lose much/any headroom when in/egressing out the aft. This is a 1996 MacGregor 26x btw.

Toys:
1. Marine VHF Ant. (1/4 wave)
2. Ham VHF/UHF (5/8 wave)
3. GPS ant.
4. Solar panel (up where nobody will step on this one!)

 

[kloudie1]

Newest Practical Sailor (yesterday) has a test of a new wind generator, the Air Breeze, made by the same guys who make the Air X. The other test was in March '07.. They said the Superwind 350 is the pick of the litter.

 

[Franklin]

I just googled Air-x systems and this is what I learned: they seem to cost about 1400 dollars for a power head and a tower. After that the electricity is free.
Grid electricity costs 11 cents per KWH. My diesel engine can turn my alternator and generate 600 watts even if the wind doesn't blow. Air-x is rated at 400 watts at 28 mph wind but that speed is unusual. 14 is much more likely. Diesel fuel cost me about 40 cents per hour just to run the alternator. At 14 mph the Air-x will probably put out 100 watts max.

And your engine cost min $5,000? Running Diesels at low RPMs isn't good for them. So calculate how many hours you get out of your engine and divide the cost of the engine and add that to the fuel cost.

Also, Diesels are loud and require re-fueling. Not many stations in the ocean

 

[sailingdog]

Don't forget to add the costs of maintenance per year multiplied by the percentage of the annual use you run the engine for... For a long-distance cruiser, solar and wind make far more sense, since the amount of diesel you can carry is finite and the wind and sun are free.

And your engine cost min $5,000? Running Diesels at low RPMs isn't good for them. So calculate how many hours you get out of your engine and divide the cost of the engine and add that to the fuel cost.

Also, Diesels are loud and require re-fueling. Not many stations in the ocean

 

[Paul Cossman]

I just read Practical Sailor's review of the Air Breeze. Although it appears to be a good choice for anyone expecting to anchor in winds over 10 knots, it still doesn't address those of us who strive to anchor in winds of less than 10 knots. Based upon Practical Sailor's testing and analysis, it looks like the Rutland 913 is the best bet for low wind power output.

If I had the space on board, I'd stow my Fourwinds and make it interchangeable with the Rutland 913 on my mounting pole, using the existing universal two prong plug running up the center of the pole. But stowage is an issue, and having cruised with boats having both the high-output and low-output wind generators, I just have to stick with my decision to change to the low-wind targetted unit.

 

[Bill Roosa]

Low wind speed generation

So what I hear everybody saying is that there is a market for a wind generator that:
produces in 3-7 knots of wind
has an output of 5-7 amps at that wind speed

It should be quiet and maintenance free of course

How big a prop (ft in diameter) would you be willing to accept?
My initial restaurant napkin estimate is you would need a windmill (lots of blades) type with around a 6' diameter prop.

Thoughts?

 

[Franklin]

So what I hear everybody saying is that there is a market for a wind generator that:
produces in 3-7 knots of wind
has an output of 5-7 amps at that wind speed

It should be quiet and maintenance free of course

How big a prop (ft in diameter) would you be willing to accept?
My initial restaurant napkin estimate is you would need a windmill (lots of blades) type with around a 6' diameter prop.

Thoughts?

If you make it a light weight 6', I'm cool with that. I've always wondered why the blades are so small.

 

[Paul Cossman]

So what I hear everybody saying is that there is a market for a wind generator that:
produces in 3-7 knots of wind
has an output of 5-7 amps at that wind speed

It should be quiet and maintenance free of course

How big a prop (ft in diameter) would you be willing to accept?
My initial restaurant napkin estimate is you would need a windmill (lots of blades) type with around a 6' diameter prop.

Thoughts?

Bill,

Actually, I understand the hyperbole, but my goal isn't really that outrageous. I'm talking about an average wind speed of 8 to 10 knots, which is a pretty common wind speed for a protected anchorage. I have seen the old Ampair wind generators put out 2 to 3 amps in that wind, and make such little noise that it could not be heard over the breeze. At the same time, in the same wind, my fourwinds would not generate any power. Thus, in a 24 hour period, the Ampair would generate 50-70 amp hours while the Fourwinds might generate 4 or 5 amp hours.

So really my objective isn't THAT ridiculous. And I understand the trade-offs involved between high and low output units. This brings me back to my original post. I can read the articles that are out there. What I am after is finding anyone who has had the first-hand long-term experience with the Rutlands 913, the Ampairs, and the like, who can tell us about their experience in the 8 to 10 knot range?