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Old 09-09-2017, 14:14   #1
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Two hydrogenerators?

As I understand, hydrogenerators are the most efficient (renewable) means of power generation on board whild cruising. Is there an argument against using 2 generators in good wind (when speed is close to hull speed anyway?). I was thinking about running an electric stove instead of a gas one or add electric cabin heating (~2kW) instead of burning diesel. Solar is not an option, because there isn't much sun where I am sailing.

Or any hydro generators with more than one prop?

( boat: I expect to buy a heavy 40' plastic classic of a steel boat early next year)
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Old 09-09-2017, 15:45   #2
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Re: Two hydrogenerators?

I can't say this from experience, but I'd think that if you were trailing 2 props for hydrogenerators, then there could be a risk of them fouling one another. Unless, that is, you're talking about fixed units, with drive legs which are lowered like OB engines.

The thing about hydrogeneration is that they really only start to contribute significantly when boat speed is good. Such as at 5kts+. So their lack of output at slow speeds should be balanced by other means of generating electricity.

Regarding heating & cooking via electricity, I don't see it as viable if you're only recharging your banks via hydrogeneration. The draws are just too large. At least unless you have a huge, productive, solar farm.
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Old 09-09-2017, 16:09   #3
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Re: Two hydrogenerators?

That's my concern too, the props should be far enough from each other. OTOH heeling limits positioning quite a bit, they can't just be fixed "one starboard one port"...

Btw, there are a lot of water turbine and prop designs, probably not all react the same.

Using the batteries is definitely planned, I just don't want to push all 2kW load to the battery bank. Half from generated half from the bank for 2-3 hours baking could justify an electric stowe.

Besides, it's a bit flexible when to use the owen, one should pick the windiest part af the day...
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Old 09-09-2017, 16:16   #4
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Re: Two hydrogenerators?

So, how will you cook when not under way or during light air periods?

I'm a proponent of hydro, but only as a supplement to other generation methods.

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Old 09-09-2017, 16:18   #5
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Re: Two hydrogenerators?

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Originally Posted by UNCIVILIZED View Post
Regarding heating & cooking via electricity, I don't see it as viable if you're only recharging your banks via hydrogeneration. The draws are just too large. At least unless you have a huge, productive, solar farm.

Speaking as some with an 1.8kW induction stove top and electric oven, I believe this is true. My solar set up and large battery bank extends times between running the generator, but they certainly couldn't replace it. Plus you will be cooking at anchor most of the time (i.e., your hydro generators are doing nothing).

As for hydro generators in general, I always felt they'd come after solar, a wind generator, big alt and a diesel generator. That is, last in line of available options. They work well enough for generating while on the way, which is great for racers as it's the only time they need to make power. For cruisers, who spend most of the time on the hook? Eh. Only if solar and wind can't produce enough power for the autopilot/fridge while underway and you're trying to stay green.
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Old 09-09-2017, 16:20   #6
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Re: Two hydrogenerators?

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So, how will you cook when not under way or during light air periods?

I'm a proponent of hydro, but only as a supplement to other generation methods.
Valid point, that's more of a passage-thing.
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Old 09-09-2017, 23:19   #7
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Re: Two hydrogenerators?

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As for hydro generators in general, I always felt they'd come after solar, a wind generator, big alt and a diesel generator. That is, last in line of available options. They work well enough for generating while on the way, which is great for racers as it's the only time they need to make power. For cruisers, who spend most of the time on the hook? Eh. Only if solar and wind can't produce enough power for the autopilot/fridge while underway and you're trying to stay green.
It really depends where you are sailing. In northern Europe solar doesn't make much sense... AFAIK hydro produces more power (when working) than wind, thus for a passage from marina to marina (shore power->shore power) type of sailor hydro might be the best solution.
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Old 10-09-2017, 00:36   #8
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Re: Two hydrogenerators?

GTom

I don't know exactly how much power a electrical stove/oven is using. But for sure a hydro is (as long as you are sailing) the most efficient way to produce power. I think you can use 2 paralell on the stern (each around 20 cm beside the backstay). If you use the watt&sea 600 then they will produce at 7 knots around 1100 watts of power. Which is a lot. For sure you'll need for calm periods a genset to bridge these times....
However - hydro generators are also from a esthetic point of view the better solution, I can't understand how sailors can roofing their whole boats with solar panels....
You can check the setup under lifgun(dot)com.
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Old 10-09-2017, 02:26   #9
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Re: Two hydrogenerators?

Big picture they are probably the least efficient way to generate electricity.
- If you are just popping from marina to marina coastal sailing, you really don't need much of anything beyond the engine alternator used while going in and out of port.
- With an older full keel, even under way, you can't expect much power output as you will often be going too slow. Of course if you crank up the engine to go faster, you can just use the alternator.
- It provides no benefit while at anchor but you still need power and doesn't provide benefit if in a marina with shore power.

Even in northern Europe, solar will put out a surprising amount of power with wind generators a viable alternative.

Reality is while it puts out a lot of power during ideal conditions, ideal conditions are so rare that it's not very useful. I think you see this reflected in the fact that very few cruisers use them.
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Old 10-09-2017, 03:38   #10
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Re: Two hydrogenerators?

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Reality is while it puts out a lot of power during ideal conditions, ideal conditions are so rare that it's not very useful. I think you see this reflected in the fact that very few cruisers use them.
Typical response from someone who has not used o ne!

Hydro does not fulfill all power requirements, and will not work in the way postulated in the OP. But for passage making, they shine... even when the sun does not.

Perhaps the reason that few cruisers use them is that few cruisers are actually passage makers. For those of us who do, they are a useful adjunct to the energy budget. I really miss the one I had on Insatiable the first.

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Old 10-09-2017, 04:05   #11
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Re: Two hydrogenerators?

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Typical response from someone who has not used o ne!

Hydro does not fulfill all power requirements, and will not work in the way postulated in the OP. But for passage making, they shine... even when the sun does not.

Perhaps the reason that few cruisers use them is that few cruisers are actually passage makers. For those of us who do, they are a useful adjunct to the energy budget. I really miss the one I had on Insatiable the first.

Jim
No I haven't used one but I understand how they work and their strengths and weaknesses. I don't have one because as a coastal cruiser (similar to what the OP describes in his use case), it's almost useless. As a percentage of time under way at 80% or more of hull speed (where they really shine), your average cruiser would be lucky to have those conditions 1% of the hours in a year and may go weeks or even months without seeing those conditions. Even on passage becalmed for a few days, you will need an alternate power source.

Even most passage makers will find minimal use for them if they only do 1 or 2 crossings per year.

If you are under passage for 3-4 months per year, it's a totally different ballgame but those are far from typical cruisers.
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Old 10-09-2017, 04:46   #12
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Re: Two hydrogenerators?

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It really depends where you are sailing. In northern Europe solar doesn't make much sense...
Wow, who told you that. Take a look at this picture with 180w of solar charging my batteries quite nicely thank you. Solar has two advantages in Northern Europe, the panels are cooler so more efficient and the summer daylight hours are really long. Forget 6 hours start thinking about the amps flowing in from sunrise until sunset.

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AFAIK hydro produces more power (when working) than wind, thus for a passage from marina to marina (shore power->shore power) type of sailor hydro might be the best solution.
If all you are doing is sailing from one marina with shore power to another marina with shore power then you don't need hydro. you probably don't need anything for trips of less than 2 days, but some solar or wind to top up the batteries will be nice and won't drop your cruising speed like hydro will. Also yachts spend 6 days week stationary, what are you going to do then, always rely on a marina. Nah there are better solutions to being self sufficient.

Pete based in Gosport UK.
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Old 10-09-2017, 05:01   #13
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Re: Two hydrogenerators?

You need to do some maths, but an electric stove or electric cabin heating isn't going to work, not without a huge generator.

However, you might use a slow cooker. This one was from Argos and is 120w. So that is a draw of 10 amps from the batteries at 12.5v. In practise is takes 20 minutes to come up to hot and then cycles on and off so the actual amount of power needed could be less, but difficult to measure on its own. Solar can support this which is why we carry it on board following a South Western UK gas shortage in 2016 which caused all sorts of problems.

Pete

http://www.argos.co.uk/product/7194816
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Old 10-09-2017, 12:28   #14
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Re: Two hydrogenerators?

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No I haven't used one but I understand how they work and their strengths and weaknesses.
And I suppose you are aware of the different optimized blade size for each speed class? And all this is from a "first gen" manufacturer, who didn't really do much more than use a standard prop, not a special design for power generation.

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If you are under passage for 3-4 months per year, it's a totally different ballgame but those are far from typical cruisers.
1 month passages + 1 month cruising are realistic for me ATM.

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GTom

I don't know exactly how much power a electrical stove/oven is using. But for sure a hydro is (as long as you are sailing) the most efficient way to produce power. I think you can use 2 paralell on the stern (each around 20 cm beside the backstay). If you use the watt&sea 600 then they will produce at 7 knots around 1100 watts of power. Which is a lot. For sure you'll need for calm periods a genset to bridge these times....
However - hydro generators are also from a esthetic point of view the better solution, I can't understand how sailors can roofing their whole boats with solar panels....
You can check the setup under lifgun(dot)com.
Thank you for the reference! Before doing any investment, I'll do my homework, which model does the best for the ("slower than average") 3-6knot speed range.

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...
Even in northern Europe, solar will put out a surprising amount of power with wind generators a viable alternative.

Reality is while it puts out a lot of power during ideal conditions, ideal conditions are so rare that it's not very useful. I think you see this reflected in the fact that very few cruisers use them.
Wind is a valid point, solar - I don't know. Last time we did some 24 hour passages in Scotland, of which we had 10hours night and 14 hours overcast. Very good force 6 wind though!
Besides, I hope for a major improvement in solar tech in the next few years (at least in price...), thus a big investment is solar today would seem silly in 5 years. Meanwhile the sun-independent wind/hydro solutions of today will hold their value well. I do want solar, but not now.
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Old 10-09-2017, 17:01   #15
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Re: Two hydrogenerators?

Found a 2 years old tech review, apparently hydro wins by a large margin if someone uses the boat TO SAIL, not to anchor most of the time...
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