Ahhh, Eric is starting to see the picture as far as larger boats go. Distance also is a factor. When I first thought of my 41ft Lagoon as a distance cruiser under electric I didn't think it was practical and even posted it as such. But then I was just thinking of it in Electric mode. A big concern was just parts in far away locations. Then I became more familiar with my system and figured out that there was only a few parts that would be an issue (controllers) then to at the higher speeds I would be regenerating power under for longer periods than in the Chesapeake Bay I normally sail. With 80A from the genset I can run that "all day" plan if I needed to get out of the way of a storm at say 5 knots and still have enough juice in the batteries to run another couple of hours if the Genset crashes. O ya that's if there is no wind. Then I have a house bank to handle any loads if the 144v system goes down. Then I have a few handhelds if I get struck by lighting (in the microwave of course). And then again I could actually put up the sails and SAIL the thing!!!...:o)
At this time I don't have any solar panels but once I get a few other things taken care of there are some 230+watt panels that might be interesting to install above the dingy. (I wonder how fast the 2.2HP dingy motor could push an 18 ton cat??) Anyway I'm just excited that Eric may be getting on the Big Boat thing. Some day I'll get him out on EG and maybe we can figure out how to get the tiger out of the tank (as they use to say in the olden days). :o)
Steve in Solomons MD
Lagoon 410 SE
Hi Micah,
Keep in mind that this power demand is only for conditions where you can't sail. Cuttng the panels in half, you should still collect 7.5kWh per day, in normal cruising conditions that should handle all of your house loads and collect enough excess power to motor about 6nm at 3kts. Running a big battery bank like the one's suggested means that you would almost never need to run the diesel unless you had a long day of motoring. Pulling away from port, you would have almost 20 miles of low speed motoring on tap and three days of sunshine under sail would top your batteries off completely, even with a 2.5kWh daily house consumption. On the hook or while sailing, you would probably never need to run your generator/diesel, the big bank could cover the house loads for more than a week without solar before needing a recharge.
The appeal to me would be the ability to slowly motor out of the doldrums on solar alone. Even a few miles of progress in the right direction could really improve your outlook. Since most crossings are done with little motoring to save the fuel for recharging the house batteries or making water, a solar electric hybrid like you suggest would be a big improvement in the day to day experience on board. The owner might find that they would have to mark the calendar every couple of weeks to remember to run the diesel for an hour or so, just to keep it in running shape. Plus you would have the safety net of being able to motor for days on diesel to get out of harm's way.
Since you're only talking about a small electric boost, perhaps something like a Torqeedo Cruise 4.0 would suffice. It could be stashed in a locker when not in use. The experiment would be to jury rig a borrowed 10hp outboard on the intended boat and see how it works. If it has enough power, then developing a permanent well for the Torqeedo should be fairly reasonable. With no fuel or fumes, the well could be under a berth with a lock down hatch to prevent ingress in stormy conditions. The electric would be a fair weather drive only, but that's why you're keeping the diesel.
I'm just tossing out ideas. I'm slowly warming to the idea of hybrids, but mostly in larger boats 40'+. For 30 footers, I don't think that the weight/volume/expense/complexity is justified.
Keep thowing out questions and ideas, maybe somebody will bite...
Fair winds,
Eric
Marina del Rey, CA
--- In electricboats@yahoogroups.com, Micah Broussard <micahbroussard@...> wrote:
>
> thanks for going through the detail on this it is most helpful. At least it
> seems in theory it would work out ok but until it has been tried it will be
> a bit of an unknown. I suppose the question at the end of the day is the
> investment in the EP system worth it as it stands now it seems the added
> expense would be nearly enough to fuel the boat for nearly a full
> circumnavigation. To each his own on that one.
>
> Maybe if I am lucky someone will try it out before I have to roll the dice
> on that decision
>
> On Sun, Aug 7, 2011 at 04:38, Eric <ewdysar@...> wrote:
>
> > **
> >
> >
> > Hi Micah,
> >
> > The first thing that I'll say is that I've got no real life data about
> > electric sailboats that are this large, so anything that I say here will be
> > theoretical speculation. That said, let me take a stab at it.
> >
> > First, I looked up data on a few 55' steel yachts. It looks like you would
> > be dealing with a LWL of about 45' and a displacement between 30 and 40
> > tons. Based on a number of different rules of thumb, I'll peg your 3kt power
> > demand to be around 2.5kW. If that is the case, then a 5kW drive system
> > (about $4000-$5000) should suffice for low speed cruising (max speed around
> > 4kts).
> >
> > Let's call "all day" 12 hours. At 2.5kW, you'll need 30kWh to run at that
> > load for 12 hours. If you want half of your power to come from solar, you
> > shoud have at least 3kW of total solar panel capacity. That works out to be
> > fifteen 200W panels, each panel is roughly 3' x 5', so the array would be
> > 225 sq ft. (15' x 15'). Finding that much space for solar panels might be
> > problematic. The panels would cost about $12,000 US and weigh about 500 lbs.
> >
> > You'll also need at least 15kW of usable battery capacity. Let's examine
> > some options:
> >
> > In flooded golf cart batteries you would need almost 30kWh of rated
> > capacity to supply 15kWh to a 60% depth of discharge. these batteries would
> > weigh about 1300 lbs and cost about $3200 US.
> > In AGM batteries, you would need 24kWh of rated capacity to supply 15kWh to
> > a 70% depth of discharge. These batteries would weigh about 1200 lbs and
> > cost nearly $5900.
> > In Lithium (LiFePO4) batteries, you would need 20kWh of rated capacity to
> > supply 15kWh to 80% depth of discharge. These batteries would weigh about
> > 500 lbs and cost about $8500.
> >
> > To recharge the 15kWh from a regular diesel engine with a 1800W (150A x
> > 12V) alternator dedicated to recharging, it would take almost 12 hours to
> > replace the energy that was missing from the batteries. Of course, the
> > alternator should be matched in voltage to the drive system.
> >
> > All of this data is centered on cruising at 3kts under power alone, no
> > sails. You could decrease the size of the panels by increasing the size of
> > the bank, however, you should be getting an idea of what this project might
> > cost.
> >
> > So, could this work? Perhaps. Is it complex, heavy and expensive? Yes.
> > Could it be worth it? That is up to you.
> >
> > These figures are all guesses, but if you did the conversion, you may find
> > that they are fairly close.
> >
> > Fair winds,
> > Eric
> > Marina del Rey, CA
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