Marine generator

[BustedKnuckle]

I am interested in installing a generator setup similar to the one described in the post below by "Portager". My question is, is there a difference in generators for marine applications. I am worried about this because I have a gasoline engine and I would not want to cause a condition that might ignite any vapors. My plan was to hook up the pump to the engine and run the hydraulic lines up to the cabin away from the engine compartment, then run the generator off the Hydraulic motor.
One other option I would like to consider, but would be worried about because of open sparks, is the addition of a clutch much like the ones used for an air-conditioning unit on a car to engage the pump.
Thanks for the input.

[cyclops]

You are right to worry. Do the marine generator. Same reason we use a marine alternator. KAABOOOM.

[marshmat]

What Cyclops said.

For some things marine, land-based equivalents are fine replacements. Not so with mechanical or electrical gear. The marine generator, like a marine engine, starter, blower, whatever, is designed to be corrosion and explosion resistant. The land-based one will work just fine- until the one day you don't run the blower quite long enough and a wisp of gasoline vapour touches the generator armature. Goodbye engine, and likely half the boat with it. The marine one is a far better bet.

You can get alternators and generators desgined to run directly off your engine in a boat environment. But if you can afford it (and have space), get a marine genset with its own engine and a few BIG mufflers. It'll be more fuel efficient, quieter, and produce 'cleaner' power. The hydraulic thing sounds like added, unnecessary complexity, and it wouldn't be of any safety benefit- gasoline vapours, heavier than air, can circulate through the whole boat and can sometimes reach flammable levels before you can smell it.

[PowerTech]

It only goes Kaboom if it is a gas boat.If you have a diesel boat i am shure you would have no problem hooking up a industrial generator to a hydrolic motor.you could probably find one in the granger catolog that would suit your needs.just keep it dry.Marine generators canot get wet eather ass long as you keep them dry they last.I do think your hydrolic generator idea is sort of retarded though.

[MattZ]

The generator heads found on small (<25 kW) portable generators are brushless. As far as an ignition source is concerned, they should be safe. Many of them are wound with mildew resistant insulation, but ask the manufacturer to be certain.

The high current alternator -> inverter route may be a more cost effective option than hydraulics.

[Busted Knuckle]

Thank you very much for the post. That's the kind of information I was looking for. The reason I would go with the Hydraulic system is because I have most of the parts for the system, just wanted to know the down sides. I know this may not be a conventional set up, but I have seen these before and have contacted the manufacture and they said it would be safe for marine use. I would just like to proceed with caution if I decide to go this way.
Thanks again.

[Portager]

Busted Knuckle;

Did you ever install your hydraulic generator and if so how did it work out?

I think the point that PowerTech is missing is the hydraulic system uses a load sensing variable displacement hydraulic pump which allows the generator speed to be independent of the engine speed. This allows the engine to run just above idle at a speed that allows the pump to meet the power demand of the generator instead of holding a constant 1,800 or 3,600 rpm (assuming 60 Hz AC). The hydraulic system reduces engine wear/noise and improves fuel ecconomy. In addition on a small boat the hydraulic generator requires less volume and requires much lower weight than a dedicated engine driven conventional generator.

[MattZ]

I think a dedicated diesel engine for an AC generator would take up less space, weigh less, and cost less then a variable displacement hydraulic pump, hydraulic motor, oil filters, and reservoir.

There are plenty of turnkey marine diesel generators on the market. Save the hours on your propulsion engine. Unless it's a work vessel and the main engine runs constantly then the hydraulic option is not worthwhile.

[StianM]

Originally Posted by Portager

The hydraulic system reduces engine wear/noise and improves fuel ecconomy. In addition on a small boat the hydraulic generator requires less volume and requires much lower weight than a dedicated engine driven conventional generator.

I could hardly disagree more, hydraulic system generate mutch heat(powerloss) so you would nead mutch more fuel to drive the generator.

Iron pipes, pump, engine and hydraulic oil has weight too.

I remember readin about a generator producing the same Hz whatever rpm you where running. This was done by a electromagnetic clutch. When the engine was running low RPM the magnetic field was made strong so it would let the generator runn at about the same speed, once the engine RPM went up a regulator would turn down the power off the magnet causing the generator to not be albe to folow the engine speed.

Inverter or a diesel generator is a mutch bether choice.

[gbob47]

For my application, I'm not concerned about efficiency. I simply object as an engineer not to use the engine I already have onboard. I need approx 20hp to power a generator head with a mechanical couple. I have a 40hp net Perkins (4108m) auxillary.

A diesel genset is now going for $7000 for a 10KW. The head is approx. $1000 of that piece of equipment. I really don't see the point to drop $5k for power that is already on board. I've got to believe there's a system cheaper than that and less redundant.

I would like to hear for those who have installed a hydraulic generator. I'm not terribly interested in 'why it can't be done'. I think there's plenty of reasons why including cost...I want to know 'HOW to do it'.

[MattZ]

Well if you know enough to know it's the right decision then you ought to know enough to do it. Get mechanical power to pump, get mechanical power from hydraulic motor to the generator head, and the rest is just plumbing. You'll need a governor to control the pump displacement ofcourse. The cheapest and dirtiest way to control the speed would be to use a flow limiting valve, but you'll be cooking your oil pretty good.

[theoldwizard]

Originally Posted by StianM

... I remember reading about a generator producing the same Hz whatever rpm you where running. This was done by a electromagnetic clutch ... a regulator would turn down the power off the magnet causing the generator to not be able to follow the engine speed.

Slipping any clutch for long periods of time will cause it to fail !

The Honda/Yamaha home generators vary engine speed depending on load but still output the same voltage. They do this by converting the multiphase, variable voltage coming directly off the alternator head to (variable voltgae) DC and then convert that back to fixed frequency and voltage AC via a built in inverter.

It sound inefficient, but modern electronics do not have big losses. The big win is fuel consumption under partial load.