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Old 15-07-2012, 10:22   #1
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Water Generator Concept Thread

Now that I have installed a Simrad electric-hydraulic AP system on my 48' steel cutter, I'm trying to come up with some creative energy production ideas, to supplement my solar panels and wind generator. I've been doing some google research, and the only commercially available water gennie seems to be the Duogen in water mode. This seems to be a clumsy approach, to essentially swing a big wind gennie down into the water.

It occurs to me that the same companies that produce electric trolling motors could, with a bit of modification and retooling, produce simple transom-mounted water gennies for ocean sailors. (Yes, I understand that "as is," trolling motors would not run backwards to produce energy.) To get the RPMs required to spin an alternator is a big part of the problem, but this does not seem insurmountable.

I'm not interested in belting an alternator off of the free-wheeling main prop. I'm interested in a simple device I can swing down or lower into the water from my transom. It seems to me that if the engineering could be worked out, there would be a tremendous market for a simple water gennie roughly the size of a trolling motor. All of that ocean passing below our transoms, there just HAS to be a way to use it to charge the batteries while underway!

Has anybody played with this idea? Thanks.
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Old 15-07-2012, 10:29   #2
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Re: Water Generator Concept Thread

There is a commercially available sail drive type leg which generates electricity but it looks like a fixed solution for ocean racers and probably not cheap either. How about a small outboard engine leg less the engine, at least that would lift clear of the water. It would need a big fly wheel to get the revs necessary for an alternator.

Edit:

http://www.myboatsgear.com/mbg/product.asp?prodID=2210

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Old 15-07-2012, 10:45   #3
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Re: Water Generator Concept Thread

For the average boater who is under sail less than 1% of the time, propellor driven generators are not a practical investment. There have been a number of very well designed tow-ables that have long since gone out of business.
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Old 15-07-2012, 11:10   #4
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Re: Water Generator Concept Thread

One would think that some kind of "PogoStick" like device using the boats motion from wave action could be built,,,kinda like a lever,,but vertical and sent through some gearing.
I am thinking an average boats weight say,,five tons or more,,used as a lever against the seas motion should count for a lot of working effort, then transferred to a type of generator should make plenty of power...No?????
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Old 15-07-2012, 12:05   #5
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Re: Water Generator Concept Thread

Solar Power Marine | Products - Hydro Generators
Wind Powered Generators

The above are two sources of towed generators. Water towed generators will provide the most power for a boat that is moving. If you've got refrigeration and a hungry autopilot, they will provide the power at a reasonable cost. The AquaAir generator is listed 775gbp which is less than a good wind generator. supposedly will produce over 150 amps a day at reasonable boat speeds. they are simple to mount, just tie them to some fixed object on board, run the charging wires to the battery or regulator and throw the towed prop in the water.

They are really only practical/economical for those making relatively lengthy passages. Still, if you have a thirsty autopilot to supply power to, the towed generator seems the best solution. The faster the boat goes, the more the autopilot will have to work and eat more electrons but the towed generator will produce more juice in concert with the increased speed.

The DuoGen is a nice set up but way expensive for most of us.

Yves of CapeHorn self steering fame used a water driven alternator on his around the world cruise. Worked fine except attracted a few large fish and he had to make repairs to the towed prop when one of them mangled it. Biggest problem with a towed unit is retrieving it at speed. Line will apparently tangle up real quick. Have seen simple cones that people slide down the line to stop the prop from turning while it's being retrieved. From experience towing a Walker Log, you don't want to get these things tangled up. Managed to get a fishing line and the log line together once and that was a lesson it only took one iteration to convince me not to let happen again.
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Old 15-07-2012, 12:40   #6
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Re: Water Generator Concept Thread

I was thinking that the trolling motor solution might actually work. I had an old trolling motor that had a burned out speed control so I took the prop off and attached a 600 rpm drill to the shaft and an ammeter to the wires coming out of the motor. When I spun it up I got about 8 amps out of it. I figure if one could put a prop on it that would spin it between 600 and 1000 rpm one could get useful power from it. I have not calculated what size or pitch prop would be needed to turn those RPM at 5 or 6 knots.
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Old 15-07-2012, 12:45   #7
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Re: Water Generator Concept Thread

Duogen is not the only option. I know at least two other:

1) there is a conversion kit that attaches to (examples: Wind conversion kit AQUAIR-100 by AMPAIR / AQUAIR at Toplicht, Wind Powered Generators, GENERIC),

2) there is the new generation waterturbine as used in recent Vendee Globe (Boat Hydrogenerator by Watt and Sea).

Item 2) above got good reviews from IMOCA skippers.

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Old 15-07-2012, 13:30   #8
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Re: Water Generator Concept Thread

AMPAIR also makes a submerged unit which an be mounted on DIY swing arm based on their mounting pole for use on a boat--scroll down to page 18

http://www.ampair.com/downloads/CD%2...%282010%29.pdf
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Old 15-07-2012, 13:50   #9
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Re: Water Generator Concept Thread

Somewhere out on the www there are descriptions of a DIY water genny...basically a line over the taffrail with a shaft & old outboard prop welded to it, hooked to a alternator with rare earth magnets in place of the field windings. Not sure about how well that really works out, but at the minimal prices vs the benefit I'll be plaing with the idea.

Another wild & wacky idea out of left field, was to put the batteries in a gymbal mount so rolling & pitching generates power...minimal, but constant. Powerbudgets are better run by reducing consumption than increasing supply. Not sure how well this would work, either, but having gymballed batteries that don't spill acid in a knockdown or, gulp, a 360, is something I've never heard of on a boat but seems to have merit.Wouldn't need slip-ring (anti-KISS), just a bit of slack in the cables and a plug connector....it's not like the boat will be doing somersaults all the time.

With electric drive for confined maneuvering on the think-list, there is an option of freewheeling generation...still at sea on that one.

Wishing you all the best on your quest for water-power, keep us posted?
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Old 15-07-2012, 18:52   #10
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Re: Water Generator Concept Thread

Thanks everybody. Some great ideas upthread on the comments and at the links you provided. All said and done, none of the ideas now seem as practical as mounting a pulley wheel around the main propulsion shaft freewheeling in neutral. I'm going to explore that a bit.
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Old 15-07-2012, 19:32   #11
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Re: Water Generator Concept Thread

Here 's a great article by a guy who installed his own propshaft gennie:

The Propshaft Alternator - SailNet Community

A propshaft alternator seems to be the ticket. Here's a good article. Short version: A ten-inch pulley on the shaft, going to a two-inch pulley on a 25 amp alternator, generates ten amps of 12v power at 7 knots speed. Sounds good to me, that is what I am going to do.
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Old 15-07-2012, 20:21   #12
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Towed water generators are in my direct experience very poor generators. They tend to produce far less then advertised. Solar is by far the best IMHO

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Old 15-07-2012, 21:27   #13
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Re: Water Generator Concept Thread

I've been researching micro hydro systems for some time as I was going to install one in the creek by the house. Now my plans have changed I an looking at something for the boat.
I think the issue for the boat, for me anyway, is a system that will work while the boat is at anchor or moored rather than just when moving.
As I see it, if I were prepared to put in a supply feed below the water line, there should be enough pressure to drive a small pico inline turbine. Without studying what pressure would be produced it;s hard to determine what power would result.
For now I'm sat researching small turbines and pressures to see if this is feasible. A couple of years ago I was reading of an inline unit that fits into a household water supply and supplies 12v at a pretty low but useful amperage. I'm sure these would be useful on a boat with a pressured water system. Not much use on mine of course.
Ok back to reading and plotting. If anyone is involved in microhydro and would like to move this idea forward and has some capital to move it along do give me a pm. We might just invent the most useful power supply for boating yet.
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Old 15-07-2012, 22:26   #14
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Re: Water Generator Concept Thread

Trying to produce power while at anchor... If there is enough tide to spin the generator I really have to question why you are anchored there? In a slow tidal area you could do it, it would just take a huge prop that would have to be swapped out for undersail.

Seems like a lot of work to avoid solar, which has a much better track record to be honest.
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Old 15-07-2012, 22:50   #15
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Re: Water Generator Concept Thread

I'm a little confused about how you are going to generate power from the pressure water system. It takes electricity to generate the pressure which has got to be more electrical draw than any electricity generated. In our case it would be a total waste as we almost never use the pressure water system while out cruising because it's such a water waster.
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