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Old 24-07-2017, 03:37   #1
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Hydrogenerator yes or no?

Good day, Not sure if to get a Hydrogenerator before i start cruising the world.

Plan is to sail a new Beneteau 41 from UK to caribbean(stay for 1 or 2 years) then head of to USA for a while.

im struggling to understand if the Hydro will do much when im sailing aound the Caribbean? or should i get a wind turbine? i will have solar. will solar be enough to run basics off?

your advice much appreciated, as this is all new to me, as based in UK and not done much cruising.
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Old 24-07-2017, 04:55   #2
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Re: Hydrogenerator yes or no?

Hydro requires a high average speed to work. Basically they have a cut in speed of about 5kn to generate meaningful amounts of power. So you need a boat that will average 120nm a day... which is right about where most cruising boat will be. This explains why they are so universally inconsistent in their reviews.

Personally I would spend the money first on as much solar power as you can fit, then see where you stand.
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Old 24-07-2017, 12:29   #3
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Re: Hydrogenerator yes or no?

I have no personal experience with them, but from what I've read a hydro-generator is an excellent choice for boats doing significant sailing (if you sit in port most of the time it doesn't do much for you, obviously). The problem is that the commercial units are insanely expensive. The good news is that it's not very difficult to build your own, at a much lower cost, though it depends on the layout of your boat. Basically you just connect an alternator to your prop shaft (details depending on boat layout). It works; many people do it. If you do a search of the forums you'll find several threads on the subject.

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Basically they have a cut in speed of about 5kn to generate meaningful amounts of power.
5 knots?! Did you mean 0.5 knots? There's a drop in speed, of course, but I've never hear of anyone experiencing anywhere close to that much of a drop - I doubt that's even possible given the size of the props in question.
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Old 24-07-2017, 13:27   #4
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Re: Hydrogenerator yes or no?

KISS what he means is that for the average unit to produce a significant amount of power, the boat needs to average about 5kts, minimum.

For the OP, their are generators which can produce electricity both from wind & water power, such as the one by Hamilton Ferris. Though you have to convert it from one mode to the other. And when you want to use it as a wind generator, it needs to be hoisted up the rigging. This as opposed to most wind gen's, which you mount on a pole, & don't have to fiddle with them after that.
http://www.hamiltonferris.com/categories/Wind_Power/17
http://www.hamiltonferris.com/categories/Water_Power/16

To some degree, generating power via the wind is a bit of a conundrum. As in order for it to work well, you need to be anchored where there's a good strong breeze. Which is kind of the opposite of where most folks prefer to anchor. Rather, it's common to seek out a spot that's pretty much as sheltered as possible. And of course a hydrogenerator does you no good at anchor.

Wind generators were a lot more popular when solar availability was much lower, & immensely more costly. And back then, panels didn't have quite the output that they do now. But over time the price of solar has come down quite a bit, & it's efficacy has increased.
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Old 24-07-2017, 13:38   #5
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Re: Hydrogenerator yes or no?

Quote:
Originally Posted by UNCIVILIZED View Post
KISS what he means is that for the average unit to produce a significant amount of power, the boat needs to average about 5kts, minimum.
Ah, that makes much more sense. As I understand it, that problem results from people using standard alternators and is solved by using a low rpm alternator such as for wind turbines. Then you get a gradual increase in amps from lower speeds, instead of nothing below a certain threshold. I take it this is what the commercial units do.

For the WattNSea:



Of course, "significant amount of power" is in the eye of the beholder.

For me, just 1A (24AH/day underway) would be very significant.

That's about equivalent to 100W of solar.
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Old 24-07-2017, 14:13   #6
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Re: Hydrogenerator yes or no?

EDIT: Wind gen's were also popular at a time when boats had FAR less average energy usage. There just weren't anywhere near the amount of power hungry systems onboard. So the charging requirements were lower. As, for example, gensets on anything smaller & less expensive than a 50' sport fisher, were fairly unheard of. Not even on big Swans & other high dollar, fancy yachts.
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Old 24-07-2017, 14:21   #7
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Re: Hydrogenerator yes or no?

I'd love to have a water-gen while on passage. It would mean that we would not need to run the genset for an hour or so every other day or sometimes every day depending on how much solar is raining down. I just can't justify the high expense. I'd have to do 3 or 4 circumnavigations before it paid itself off.

I don't like wind gens, but if your destination is the eastern Caribbean then this is one place where they work really well because of the continuous tradewinds during the sailing season.
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Old 24-07-2017, 14:22   #8
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Re: Hydrogenerator yes or no?

If you are only sailing to the carib/USA maybe the return on investment will not be sufficient to warrant buying one... if you do plan to 'cruise the world' ie cross the Pacific etc then -yes - I think it is a worthwhile investment.

Mine is an Aqua4Aerogen... yet another good product killed off by Lewmar.....

5 knots 5 amps 24 hours a day..... combined with my modest solar array keeps my 350 A/h battery bank in good shape when at sea. Mind you I do not have a freezer or other heavy power loads, just lights, fridge, radios, nav computer etc . I only deploy it when on a passage of more than 48 hours or so .

Above 5 knots life just gets better and better....
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Old 24-07-2017, 14:25   #9
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Re: Hydrogenerator yes or no?

Quote:
Originally Posted by KISS View Post
Ah, that makes much more sense. As I understand it, that problem results from people using standard alternators and is solved by using a low rpm alternator such as for wind turbines. Then you get a gradual increase in amps from lower speeds, instead of nothing below a certain threshold. I take it this is what the commercial units do.

For the WattNSea:



Of course, "significant amount of power" is in the eye of the beholder.

For me, just 1A (24AH/day underway) would be very significant.

That's about equivalent to 100W of solar.
1a just isn't significant. That 100watt panel will cost you usd100-200. The water gen will be a complicated piece of gear to mount and deploy for a lot lot more.
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Old 24-07-2017, 14:38   #10
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Re: Hydrogenerator yes or no?

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1a just isn't significant. That 100watt panel will cost you usd100-200. The water gen will be a complicated piece of gear to mount and deploy for a lot lot more.
There's a limit to how much solar can fit on a boat.

If that's limit's passed, hydro's a good option IMO.

Also the cost doesn't have to be that high if you DIY.
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Old 24-07-2017, 14:50   #11
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Re: Hydrogenerator yes or no?

Quote:
Originally Posted by KISS View Post
Ah, that makes much more sense. As I understand it, that problem results from people using standard alternators and is solved by using a low rpm alternator such as for wind turbines. Then you get a gradual increase in amps from lower speeds, instead of nothing below a certain threshold. I take it this is what the commercial units do.

For the WattNSea:


Of course, "significant amount of power" is in the eye of the beholder.

For me, just 1A (24AH/day underway) would be very significant.

That's about equivalent to 100W of solar.
Kiss,

It actually has to do with the energy available in a flowing liquid. Because the potential available energy is a function of the velocity^2 even a modest increase in speed has a major effect on available power. Generating more power from a slower moving fluid is possible it just takes a massive increase in the props surface area. Messing about with alternators may help a bit, but not enough.

To generate as much power at 4kn as you generate at 5kn, you need a blade with 156% more surface area. At 3kn you need 277% more surface area.

Of course as you expand the prop size you also increase the drag substantially, and slow the boat down a lot. Which hurts the amount of power produced, requiring a larger prop... and quickly you get to a prop of ridiculous proportions.

This is why hydro-gen manufacturers have pretty much settled on the same prop. Its larger enough to generate reasonable power at moderate speeds without killing boat speed. But the physics just doesnt allow for much better performance than they are getting right now.

So the short answer is if you can average 5kn of boat speed day in and day out then a hydro gen can be a great thing. If you do not hit this then they probably wont work out all that well for you. Either way solar is more reliable and much cheaper.
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Old 24-07-2017, 15:48   #12
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Re: Hydrogenerator yes or no?

They work, but they are not set and forget things, like most things on a boat being made up of irregular lines and angles, customization is required.

If I was you though I'd spend the money on other things, panels and batteries, much less complicated, much more set and forget

I've had two watt and sea since 2013, I mount them both at the same time often because my boat is slow. But it's been a learning curve and not without troubles (and defects)
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Old 24-07-2017, 16:32   #13
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Re: Hydrogenerator yes or no?

Quote:
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Kiss,

It actually has to do with the energy available in a flowing liquid. Because the potential available energy is a function of the velocity^2 even a modest increase in speed has a major effect on available power. Generating more power from a slower moving fluid is possible it just takes a massive increase in the props surface area. Messing about with alternators may help a bit, but not enough.

To generate as much power at 4kn as you generate at 5kn, you need a blade with 156% more surface area. At 3kn you need 277% more surface area.

Of course as you expand the prop size you also increase the drag substantially, and slow the boat down a lot. Which hurts the amount of power produced, requiring a larger prop... and quickly you get to a prop of ridiculous proportions.
I appreciate those physical limitations, but the alternator still makes a big difference. A standard alternator produces zero power at boat speeds at which a low rpm alternator would produce something. That something, over many hours, can add up to a lot.

Quote:
This is why hydro-gen manufacturers have pretty much settled on the same prop. Its larger enough to generate reasonable power at moderate speeds without killing boat speed. But the physics just doesnt allow for much better performance than they are getting right now.
I wasn't trying to suggest that the commercial units could be improved upon (as I said earlier, they no doubt already use the kind of low rpm alternators I'm talking about). Rather I was suggesting that some DIYers get a bad result because they use a standard alternator.

Quote:
So the short answer is if you can average 5kn of boat speed day in and day out then a hydro gen can be a great thing. If you do not hit this then they probably wont work out all that well for you. Either way solar is more reliable and much cheaper.
Again, "significant power" is in the eye of the beholder.

If your energy budget is 500AH/day, 1A is trivial. If it's 50AH/day, it's another story.

Also, again, you can only put up so much solar.
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Old 24-07-2017, 16:44   #14
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Hydrogenerator yes or no?

Note that there are various W&S models and prop sizes to choose from that affect power output. The above graph is their most basic model, it gets better than that - at a cost. We have a 600W W&S, with 280mm prop, and use it only for multiday crossings and it my money well spent, particularly during the night passage drains. In the OPs case I would agree with those above, to put your money into solar ... or more or better batteries, and after you finish your rime in the Caribbean you will be better informed to make a choice for a hydrogenerator.
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Old 24-07-2017, 17:07   #15
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Re: Hydrogenerator yes or no?

Something that the solar fan boys keep ignoring: in some seasons and on some courses, evenif the sky is clear, your panels are shaded by the sails... all day long almost!

EG: recently came up from Tasmania to Queensland, mostly due N +/- 15 degrees. It was early winter, the sun is way north of us,the angles are low and the days are short. We had good following winds, so were often wing and wing. The panels on both dodger and arch were shaded during most of the day. At the times they weren't in the shade, the sun was low in the sky, either E or W of us. The result is bugger all solar power. With winds well aft, the apparent wind was too low for our Air-x to contribute much.

I really missed our old home brew trolling generator. Our boat speed was high enough that we would have been making 10+ amps with that old rig, and that sure would have been a help.



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