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Ted:
Apparently you've spent some time thinking about this topic.
To respond, let's split the boating community into those boats which are cruising regionally, and those which are crusing internationally.
My guess is that 99.9% of power boats never have to deal with more than one power standard. The simplest, and least expensive, solution for these boats is probably a generator that is putting out electricity at the frequency, phasing and voltage that the equipment around the boat expects.
That leaves the boats which are cruising in places where power varies. This situation requires an Atlas, Asea or something similar. You made the comment: "... They should be able to synchronise with generators and shore power units so the power can be managed automatically with little human intervention. The electronics for this is relatively cheap and simple. .." I believe the Atlas does offer this. This will be my first Atlas, so I'm not sure if it is as simple as they claim it is. I shall find out soon. I have a power point presentation by Atlas where they talk about seamless power transfer from the generators to shore power. I'm not having the Atlas provide this, but it can do it.
Indirectly related to your comment about swapping the cruising alternators with one 25kw alternator: I would like to see the hp requirement for a hydraulic alternator based on different loads. Is it straight line? There is a correlation between hydraulic power requirement, and electricity produced. At 25kw, nearly 50 hp is required. What is the hp requirement at 1kw, 5kw, 10kw, etc? I'm just wondering if fuel consumption is really any better by running a hydraulic alternator, versus running a generator. My guess is that your idea of a single 25kw generator does work.
My two hydraulic alternators generate 500 amps of 24v power, or 12kw. As you said, this is not enough to run the a/c. However, it is enough to run a limited amount of A/C. If the boat were used to carry paying passengers, the A/C would have to be on throughout the boat at all times. However, on our boat, it is usually just Roberta and I, and we have no need to waste fuel running air conditioning throughout the boat. If we did have guests, and a higher a/c requirement, the system is installed such that I can dedicate a generator to running just the a/c, and run the rest of the boat off of the hydraulic alternators.
I do not know how difficult it is to find a 25kw hydraulic alternator, or how large one is. If they aren’t monsters, or horribly inefficient at lower loads, I agree with you, it does seem like a good thing.
My comment questioning their necessity was made over lunch with a friend, when the topic came up: “would I do it differently if starting fresh?” In that context, especially if someone else is buying the drinks, sometimes things are said that may or may not make sense when looked back at later. I said that I would consider dumping the hydraulic alternators and the inverters, and just run off the generators while under way. Whether I really would or not, I don’t know. I’d have to do some serious thinking. Here’s why I think it wouldn’t be a totally dumb idea:
- Generators are fairly well defined technology. I can get a mechanic about anywhere to fix a generator, and they are somewhat “black boxes”. I can swap a generator if I want to at any time. They are simple – you just turn it on when you want it, and off when you don’t.
- The hydraulic alternators are a little scarier to work on. You have high pressure hydraulic lines and hydraulic valves to contend with.
- I don’t know this, but I suspect that the hydraulic alternators are not as efficient as a normal generator
- The generators are needed anyhow, because of “at anchor” and low rpm situations. Thus, if I am stuck with the generator, the hydraulic alternator is just something else to be maintained.
My focus in my comment was on simplicity of maintenance. It can be argued that nothing is easier to maintain than something you don’t have. If I can solve the electrical needs through having generators alone, then perhaps all of this other gadgetry could be tossed overboard.
Now, ALL of that said – you look at my boat, and you’ll notice I took the complete opposite approach, and I have no plans to remove anything. This is fun intellectual discussion, nothing more, and as I said before, I don’t know what I would really do if ever faced with starting over.
-Ken W
| Williams, Ken |
2007-07-11 11:59:05
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I was interested in your comment about simplifying the electrical system. From a European perspective the curious American 110/240 volt single phase system adds unnecessary complexity along with all the lighting and pumps on 24 volts DC. In my eyes a boat should be all 240/415 volts AC, the higher 3 phase voltage being confined to the larger loads in the engine room. DC voltages would not figure at all except for emergency lighting and the inverter source.
To this end I agree with you about a large inverter able to supply a good load during the quiet overnight period while at anchor or alongside. It amazes me that the likes of Atlas, ASEA and others do not make a 15 to 18KW unit in a single box similar in size to their shore power units. They should be able to synchronise with generators and shore power units so the power can be managed automatically with little human intervention. The electronics for this is relatively cheap and simple.
With regard to San Souci it seems to me that the invertors cannot run the whole boat including the all the air conditioning while underway, I might be wrong as I have not seen a electrical schematic for the boat. A modification which could be made in the future would be to replace the two cruise alternators with one 25KW+ 110/240 60 cycle alternator. I say 25+ as it should be large enough to power the whole boat including all the air conditioning.
I am sure the hydraulics are up to it as they can power the two large thrusters. The invertors would be used to charge the batteries using their 3 state regulation.
This is not meant in anyway to be criticism of your boat, is just my perspective on an aspect of modern trawler yachts. | Fyfield, Ted |
2007-07-11 07:47:58
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