"Shaun Van Poecke" wrote in
:

Taking a different approach then, If you were looking for usable amps
for immediate consumption, say, to run a big electric motor, or many
big electric motors ..... do you think youd get more bang for your
buck with a big generator, or with a big stationary motor hooked up to
a bunch of alternators?



If you're looking for electric motive power, 12 volts isn't going to do it.
For instance, the hybrid electric cars are over 400 VDC to keep the
conductor size something reasonable. They have small cells and lots of
them to get that voltage. Trolling motors use either 24 or 48 volts for
the same reason. Low voltage systems are awfully inefficient. That's why
we went from the stupid 6V cars to 12V. They screwed up. They should have
gone to above 30 volts while they had the chance, but I'm sure there some
profit motive why they didn't. Copper wasn't priced like Platinum at that
time, like it is, now. Big diesel engines use 32VDC, which came from the
steam locomotives on the trains. They've been 32VDC since the headlights
were converted from gas to electric.

On the boat.....if you want to run big electric motors, you need a AC power
plant of sufficient size to start them. None of the DC systems have much
available power and the power to weight ratio is terrible. You just get
lots more electrical power from a genset, instantaneous, no hours of
charging batteries, turn it on and it works power. Of course, under sail,
there's a social problem. Sailors dream back to the 1800's. They're
playing buccaneer and want nothing to do with engines, but want modern
electronics and the conveniences electric power provides, like
refridgeration, lighting, cooking, etc. Playing buccaneer is only for
sailing. They don't eat gruel cooked over a woodstove, a more correct
effect. The social problem occurs when someone cranks a genset to provide
the needed power. It, of course, makes a noise and ruins the fantasy.
They'll be called "stinkpotter" by other wannabee buccaneers back at the
dock. So, they buy big batteries to power it, solar cells, windchargers
and play greenie...while sitting in the dark, all hot because the batteries
will only power a little fan, not airconditioning, which the genset can
provide.

Speaking of air conditioning, dear to our hearts here in the South,
"marine" AC manufacturers take advantage of the buccaneers by making units
to hide in the cabin, taking up all kinds of valuable storage space boats
don't have to spare. They have to duct the cool air away from the unit,
taking up more storage space. A guy at the marina I was talking to had a
catamaran sailboat. He was trying to figure out where it was going to be
installed on his cat. He made the mistake of asking me. It was August,
very hot, and I suggested instead of wasting all that space and putting the
HOT AC unit INSIDE the air conditioned space making all that noise, that he
just take off a hatch on one of the pontoon cabins and install a Coleman RV
unit, say 18,000 Btu...heat pump...with soft start kit so it could be run
from a much smaller genset like RVs use. At first he recoiled, buccaneer
style, that I dare suggest such a thing. "Look on the commercial boats and
you'll see lots of them.", I retorted. All the tugs around here and dredge
boats use RV rooftop AC units...no strainers and seawater pumps to clog and
clean...no seawater rotting out water-cooled condensers...no heat INSIDE
the cabin as the RV AC fans and compressors are OUTSIDE the spaces we're
trying to cool. I shrugged and walked off.

I walked the dock and saw him a couple weeks later. He wanted to show me
what he'd done...that wasn't gonna make him any points with the other
buccaneers on the dock, for sure. He'd installed it...(c; "We turned the
thermostat up too high the first day and like to froze to death.", he said.
RV units are much more efficient as they don't spend half their Btu cooling
themselves...hee hee.

Nothing beats a genset for generating power in a boat. It's noisy, but
they've quieted them down a lot with quiet cabinets around them. Exhaust
must always be downwind and in such a way it doesn't come swirling up the
back over the stern....like your outboard or propulsion diesel does. If
it's a gas engine, it's also dangerous to sleep running as there is always
Carbon Monoxide fumes to kill you. These must also be considered.

The finest, quiet genset I ever owned is:
http://www.hayesequipment.com/eu3000is.htm
I have one mounted on the back door of my service truck stepvan that powers
my whole shop, with two 8000 BTU wall AC units, all summer.

This genset, and the other little suitcase gensets Honda makes (EU1000i and
EU2000I) operate completely different from the normal gensets. There is no
50/60 Hz monster core alternator! The alternator in it resembles the PM
rotor flywheel around the stator coils on an outboard gas motor. There's
just more coils and more magnets. It's part of the engine. This is
actually a high frequency alternator, around 1000 Hz at low speed, more as
speed changes. Yes, speed changes with load! We don't care about
frequency. It's output is 3-phase, providing much smoother power, same as
the multiphase alternator on your engine. The 400VAC, high frequency
output from this little 6.5hp gas engine, turning only 1200 RPM until you
get to around 1900 watts of load when the computer speeds it up for more
power, is rectified into high voltage DC. This HVDC is fed to a 3KW
modified sine inverter, which turns the HVDC from the engine into 50 or 60
Hz, 120 or 240 VAC, depending on what country it's sold to. Turning two
8000 Btu Korean regular window ACs, it runs about 8.5 hours on 3.5 gallons
of gas in the metal tank on top of it. The cabinet is so quiet around this
slow-turning engine, people constantly ask me to look at it because they
have a noisy 3600 RPM beast emergency genny at home.

Only thing wrong for your application is there's no way to mount it in a
boat! It's air cooled and the air cooling cools the big muffler, mixing
the exhaust with the hot air pouring out of it so you can't isolate the
exhaust for overboard discharging.

SOMEONE needs to dump the WW2 technology fast turning noisy engine directly
coupled to the massive low freq alternator with only marginal regulation
and build THIS genset in a BOAT cabinet/exhaust/cooling.

If you're ever near a Honda Power dealer...ask him to start one for you.

For your boat? Here's my answer:
http://www.nextgenerationpower.com/
The Kubota diesel it runs on will run 20,000 hours before overhaul if you
stop it and change the oil every 100 hours. Two of them have run
faultlessly, here, on small trawlers. Don't forget to clean the seawater
strainers and once a year the water pump and drive belt would be a good
idea. The diesel runs a constant speed, but it's SLOW because they use the
belt drive to raise the speed to 1800 RPM, or for Oz 1500 RPM (50Hz).
Turns slow, lasts longer...that's easy...(c; It needs an exhaust hose,
diesel fuel line and a seawater source to suck its cooling water from.
It's exhaust is water cooled and is the outlet for the cooling water.

3.5KW is 30" by 18" by 16" and 160 pounds in the quiet cabinet. That's
pretty small. It runs on a trickle of diesel fuel really cheaply.



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