Just my luck, I get to talk a little about what I know....... I am an electro-mechanical
engineer.
Have to remind all the planners and schemers if it's too good to be true, then it IS!
The motors generate a LOT of heat. Lower voltage worse than higher voltage. Current is
culprit, resistive wiring is the cause. All the motors will shut themselves down once a
temp limit is reached. Some will protect themselves by slowing you down versus a
complete stop. Motors are rated at peak & continuous. Many companies don't distinguish
the difference in their literature or specs. Some only report only peak output. They run at
peak, overheat and slow down to some fraction of their rating. Good for a short burst.
Not good to run all day ! Re-e-power derated themselves after some experience. Water
cooling is a WHOLE lot better than air cooled, since it has more thermal conductivity. Most
electric marine motors are water cooled. Be persistent with checking specs on any air
cooled motor. Likely their results do not reflect extended performance. Only OSSA has
solved getting water cooling inside the motor. All the pods heat internally and are thus
self limiting in their true output.
Same goes for generators. Lightweight e-cycle is intended for short runs and shut down.
IF you need to move some distance they cannot output 10KW peak except for a limited
period and may not be up to running continuously at all. This applies for these other
lightweight units, like Phasor, Nextgen & Ample. OSSA purposely derates their generators
to give buyers a clear understanding of continuous output. That means 10kw is more
likely 160kg not pounds.
The motor controllers are also heat sensitive. They need a LOT of air if you plan to run a
significant amperage. SEaled boxes have all those heat fins for a reason. They will shut
down as well. The golf cart stuff was never intended to run 24 hours. It works for a
while. Good for in/out of the marina, but not necessarily a 100% solution for long term
run. I can also tell you even good controllers are problematic. They are computer
controlled devices with a digital pulsed current output. They don't have a NASA chipset,
thus failure can happen at any time. Have spares of all boards. These controllers are
managing a lot of info, accel, decel rates, current, voltage, temp feedback of motor and
controller and a host of fault conditions. Even the biggest of companies, OSSA, Solomon
Tech, etc. have controller problems which they don't care to publicize. Repair parts are a
FAR away !
Size the motor, controller, battery and genset combo for how fast you want to go at max
cruise speed. Generally hull speed is the proper design spec. Takes twice the power to go
1 knot faster, waste of energy.
Also do be fooled that this is any more reliable than the iron genne. In simplest terms
think of your car. How many times did it start when you turned the key. When it didn't
start what was the most likely cause ? NO battery power ? Batteries require more
stringent management than most foresee. Battery bank has to be sized based first on
max CONTINUOUS current output. COld cranking amps is unsustainable for more than a
few seconds. Combine RE loss of motor, batteries, genset, motor controller, battery
controller/charger and you can see the failure rate climb.
I am not holding my breath for ANY new technology. All of this is old stuff being
reapplied with some degree of success. hybridized/ fuel cells and new battery technology
will not be available or affordable in the near future. For now electric auxiliaries will
weigh more, perform worse, and be less reliable overall.
Still may be a good fit for the proa just because of the unique design and propulsion
needs. Plus you can put the motor, controller and power source wherever they can fit.
When the genset is off, nice and quiet too unless it's a Torqeedo. Their controller humms
annoyingly at max output.
My general guidance is seek a professional if you are making a cruiser for offshore work.
They will assist and insure no disappointment or malady in design. If just coastal cruising
then have fun with whatever you can source and bring backup parts!
Questions & comments ?
Yes you can always size the system as minimal acceptable for inshore use. Just then have
less flexibility when bad things happen.
JT
--- In harryproa@yahoogrou
>
> -I can't imagine the price staying that way for long. Also methanol
> does need to be handled with care because of the potential to cause
> nerological effects. This can include excessive handling and breathing
> of fumes ( not to mention drinking it). LOng term, there is a
> reasonable chance that it can be manufactured reasonably cheaply from
> plant waste such as straw and tropical grasses.
> Robert
> -- In harryproa@yahoogrou
> >
> > diesel is problematic in fuel cell since fuel cell uses hydrogen
> only. Diesel contains much more carbon and less hydrogen than most
> other fuels so it must be processed more and waste more than fuels
> with higher hydrogen content, such as methanol. Methanol is used
> because it has highest hydrogen content of all alcohols used as fuel.
> Methanol price depends on how much you order at one time. Small
> quantities may cost 10-20 euros a litre but thousand litres may push
> the price down to 40-50 euro cents a litre.
> >
> > Arto
> >
> > --- On Tue, 6/17/08, Mike Crawford jmichael@ wrote:
> >
> > From: Mike Crawford jmichael@
> > Subject: [harryproa] Re: Idle thoughts on electric drives
> > To: harryproa@yahoogrou
> > Date: Tuesday, June 17, 2008, 6:14 PM
> >
> >
> >
> >
> >
> >
> >
> > In terms of future options, we're supposed to have diesel
> fuel cells within five years. If this were to happen, we could
> do away with the genset weight, yet still go all-electric.
> would be an ultra-quiet and clean system, without the weight of a
> generator, that could still used regenerative props. There are
> methanol-based fuel cells now, but the cost of the fuel is ridiculous,
> so they are best used for powering lights and electronics.
> >
> > The only problem is that five years away is often more than
> five years away. Thus, my goal would be to build a
> future-compatible system where the boat could start with a genset and
> then swap it out for a fuel cell.
> >
> >
> >
> >
> > Rob Denney wrote:
> >
> >
> > G'day,
> >
> > Electric drive is certainly getting popular. Your scenario would
> > certainly work, but i am not yet convinced about recharging. There
> > are smaller volume electric motors than the Solomon and we are looking
> > at a variety of ideas including mounting them on the rudders on lift
> > up brackets so they are steerable and out of the water when not
> > required. Electric motor and battery technology is still getting
> > better and cheaper so no one is buying them until they have to,
> > although Blind Date now has an electric auxillary to aid with
> > steering. Should have some feedback on this by the end of the summer.
> >
> > regards,
> > Rob.
> >
> > On Tue, Jun 17, 2008 at 1:27 PM, oceanplodder2003 <dana-tenacity@
> usa.net> wrote:
> > > I was cruising the Solomon Technologies site. I like the idea of
> > > electric drive. I don't like internal combustion engines, I don't
> > > motor very much. I don't like the idea of dragging those bloody
> great
> > > props around.
> > >
> > > So I thought about recharging with the props till the batteries are
> > > nearly full, then getting them out of the water and using
> solar/wind
> > > to top them off.
> > >
> > > Would this work. A Single (or double) Solomon drive mounted on the
> > > centreline of the boat with a shaft that drops down to the
> water when
> > > in use. The drive unit is hinged. The hinge allows it to rotate
> 180 so
> > > it can pass through vertical (don't do this in shallow water) and
> > > "shunt" so you can motor/recharge on either tack.
> > >
> > > Hope I described that adequately.
> > > Am I nuts?
> > >
> > >
> >
>
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