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Old 23-08-2010, 03:02   #16
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The real solution for electric drive is to add an air cooled dedicated generator with capacity to charge the batteries or drive the engines directly. They are far better balanced than a marine engine with props etc, don't need to be run except when you really need them, and will run for a few days in spite of the really dark weather that makes motoring worthwhile.
They also provide domestic voltages for microwaves, washing machines, clothes dryers, and those strange gadgets only women seem to need. Food Mixers?
Diesel can be stored away from living spaces, preferably in tanks, but not constrained by conventional fuel to engine to prop layout.
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Old 23-08-2010, 03:43   #17
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In short, I agree with anjou. I have played with both in the past.
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Old 23-08-2010, 04:10   #18
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A serious question here If converting diesel into power via an engine is x percent efficient, then some of that available power is lost in the drive train due to friction etcetera, how can you not have a further loss when you turn that power into electricity and then apply the electricity to turn your drive chain?
I can clearly see the benefits of having a silent electric engine charged at the dock or via solar/wind systems but diesel electric doesn't make sense to me.

P.
There are a couple of places you can improve efficiency and therefore fuel consumption.

First of all, an electric motor can be directly coupled to the propeller shaft, eliminating drive train friction.

A generator can run the engine at the speed that represents the best fuel economy for power generated. By contrast a normal marine engine has to run over a wide range of RPMs and will not always be used at the most fuel efficiency speed.

You can run a much much more efficient propeller. I have read that up to 50% of your engine power is actually turned to thrust. The rest is lost.
Generally a larger, slower spinning propeller is more efficient. A normal engine only develops usable power over a certain range of RPMs.
An electric motor runs at a lower RPM and can use a more efficent prop. It can also provide full and efficient power over the full RPM range of the motor.

Each improvement is not huge, but it adds up.
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Old 23-08-2010, 05:23   #19
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Thankyou Handmer, you saved me alot of typing.
The other advantages in terms of location, maintenance (lift it off the boat and take by car to a service garage), breakdown (ditto), and the dual voltage option on many gennies to allow domestic voltage kit, including his and hers power tools, air compressors for diving, direct air supply for deeper snorkelling, inflating bouyance bags, etc etc etc.
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Old 23-08-2010, 07:55   #20
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No one said it wasn't possible, but you're not going to cross the Panama or Suez Canals, or get through the European canals armed with an electric. The Pardey's have no engine of any type and do more sailing than I do (with a Yanmar) so it's obviously do-able, but the guy asked why more people don't do it and yeah, there ya go.
Rebel Heart:

Why can't you do a canal trip under electric propulsion? I've got a picture of me trying to clear the raw water engine intake in muddy Erie Canal water on trip up to Canada I made in the ole Diesel Days. I had to do that at least twice during the trip. I'd do that same trip today in a heartbeat with electric propulsion and would not have the same problem (since there is no raw water intake) and it would be a lot quieter and less fatiguing even with the Honda generator running instead of the diesel vibrating the whole boat for hours on end. IMO electric propusion really shines in sheltered waters like a canal.
Why don't more people do it? I think it is fairly new for recreational boats and for most people it is fear of the unkown. Now I would not pull out a perfectly good diesel engine to put in electric but, that diesel will die or rust out at some point. That's what happened to me. I won't preach but, I am glad I made the switch.

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Old 23-08-2010, 08:21   #21
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Has anyone looked at a diesel-electric system? I don't think running engines from batteries is realistic, but using a genset to power multiple electric drives seems completely workable. This setup has been used by ocean liners and trains for decades.
Muskoka:

Certainly can be done. Like you said the Queen Mary 2 does it and also a lot of ferries. I did not go that route when I repowered because I spent way too much of my life crunched down praying/cursing to the iron pig of a diesel over the years or paying someone else to scratch their heads at $$$ an hour. I was sick of wiping up oil and antifreeze spills in that cramped space and changing water impellers etc... The Honda 2000 along with the solar panels and windgenerator fulfills all my needs for charging and propulsion and I can maintain it above deck in a comfortable position. Plus I use it to operate hand tools on board. If it should ever fail I could take it to a shop for repair or just pick up and new one and I'm off again. Electric propulsion may not work for all boats (at this point) but, for those 35 foot and under I'd say it's very doable.

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Old 23-08-2010, 08:38   #22
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When you think about it, its much the same reason we do no have battery powered passenger aircraft crossing the oceans.

Jet fuels and diesel fuels propulsive force-hours per unit of weight is far greater than that of batteries. Sure, batteries have regenerative energy. But the energy that can be regenerated back to a battery is small in comparison to the amount of propulsive energy that can be stored in the same weight unit of diesel.

For most, the first factor has more relative importance than the second factor.
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Old 23-08-2010, 20:55   #23
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I must confess that I too have jumped off the deep end into electric territory. My Atomic 4 seized my first time that I left the marina, and I decided that at this point it would probably be more economical to simply replace the engine.

I'm nervous as heck about this decision, as obviously it's not the popular one and I'm clearly new around here. However, there is but a single drawback to the electric, and I think we all know what it is: range.

However, here's what you get in return for accepting that limitation:
1. trivial maintenance (my initial installation was out of alignment, so I pulled out the engine while at the dock and fixed it)
2. extreme quiet
3. built in power generation (for regenerative systems)
4. no diesel or gas smell
5. fine docking control. I'm a complete newbie at maneuvering under power (have done it maybe 6 times total), and yet have received compliments on my single-handed docking abilities.
6. enormous battery bank for house systems
7. turn key departure - no warm up or cool down or opening seacocks and fuel valves

I think there are a few factors that can make the difference in whether electric is sensible or not.
1. Where on the cruising spectrum does on fall? i.e. camping vs. comfort. If you're not running any high power electrical systems like refrigeration or a watermaker, electric may make sense
2. What is the local geography? If it involves long narrow channels, then the limited range of electric is going to be a dealbreaker. If, however, the distances involved between open water and anchorages/docks are typically only of order a mile, electric can be a perfectly reasonable alternative, especially with regenerative charging.
3. How big is the boat? Electric scales poorly with boat size. Smaller boats can get by with a modest bank. With 4 105Ah batteries, I easily have a range of 12 miles at 3 knots, which is more than adequate for weekending. For longer cruising, solar, wind, or a generator is a must for use at anchor. However, for passagemaking, the regenerative capabilities* of the motor should be more than adequate by themselves to recharge between ports of call.

The Panama Canal question has bothered me. However, there are several options: 1.) use a generator. 2.) use the dingy outboard. 3.) Get a tow. (although I suspect buying the generator may be cheaper than this option!)

*i'm just going by the spec sheet on regeneration. Haven't gotten it working yet myself, which may be due to some combination of my inefficient propeller and the fact I haven't had winds of more than the single digits when I was at the boat since I finally got my boat into a vaguely operational state.
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Old 23-08-2010, 22:20   #24
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ad astra:

It took me several months to make the decision to go electric in 2008. I went through all the pro and cons before I decided to go with it. It was either going to be a very expensive mistake or the best choice for repowering. I'm happy to say it was the best decision I could make. My shake down cruise was a hundred mile trip to Newport. No problems at all. While my harbor is a quick run into LI Sound I find I often sail in and out. Something I never did when I had the diesel. I'd always warm up the diesel before I left the mooring and make sure that everything was working: oil pressure, temp, water pumps etc... and then motor out before raising sail. Now I just get off the mooring with a little thrust of electric propulsion raise sail and sail out. I know if I get into trouble in the channel the electric propulsion system will be availble to get me out of it.
If I'm under sail and the wind dies I'll operate under electric propulsion for an hour or until the battery bank has dropped down to 90 to 80% capacity. If the wind has not picked up by then I'll crank up the generator and power the boat that way. I can do about three knots without discharging the battery bank. Even then I am using less than half of the generators output. The limitation being the current output of the battery charger I am using. I've personally operated over four hours at times using the generator and electric propulsion. Though I know of a sailor who ran for twelve hours under electric propulsion after losing his mast in very sloppy seas. I've gradually added solar and a wind generator into the charging mix too. I too have not gotten regen to work but, then again I did not change props after conversion either and have not often seen the five plus knots of boat speed to try it. I think it may be better to electro sail and just turn the prop enough so it negates the prop drag and get an nice bump in boat speed and unlike motor sailing with a diesel it is extremely quiet. Anyway I hope you come to like the electric propulsion system as much as I do. I don't miss anything about the diesel at all.
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Old 23-08-2010, 23:40   #25
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Diesel Electric power for vessels has been around since WW1 in various forms. The most notable system was the drive on USN fleet submarines where the diesels were nothing more than diesel gen sets providing current to the electric motors when running on the surface. Submerged, the motors ran on current from the huge banks of storage batteries. A fairly large number of merchant ships built in Germany in the 1930s also used diesel gen sets providing power to electric motors.

The economy of the systems were the diesels could turn at higher rpms, since they did not work through gear boxes, and thus their rpms were optimum for fuel efficiency while the electric motors benefited from shorter shaft runs and no transmissions--reversing was merely a matter of reversing polarity. Additionally, the diesel gen sets could be placed wherever convenient and did not need to be in close proximity to the motors they were supplying.

Currently a number of designs are being used on some yachts:

Whisperprop - Electric Drive Systems and Hybrid Drive Systems | Fischer Panda
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Old 23-08-2010, 23:59   #26
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This article on the 88m Triton superyacht discusses the realistic pros and cons of diesel electric by the supplier Imtech Marine

I have worked with Imtech before and they do not sugar coat the facts

M/Y Triton - 88m superyacht by Platinum Yachts - Design News - SuperyachtTimes.com
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Old 24-08-2010, 07:14   #27
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A diesel with plenty of tankage is not just a convenience issue, it's a safety issue.
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Old 24-08-2010, 07:38   #28
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A diesel with plenty of tankage is not just a convenience issue, it's a safety issue.
How is a generator with an motor that can be on instantly with more torque less safe than diesel?
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Old 24-08-2010, 07:42   #29
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Because the electric motors available today do not have nearly the range of a diesel.
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Old 24-08-2010, 08:19   #30
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Just a few quick points...

Doing the French canals would be non problematic as your range is increased quite a bit as there are no real currents on the canal...Might also add that the new generation of canal boats being built for bare boats are in fact diesel/electric hybrids and there are already plans to add charging stations at various halt nautiques.

The Panama canal is two partial days of motoring and doable easily on our boat (a CAL 34) using our Honda 2000 as a poor mans hybrid system when needful or just under battery power is still possible though that would be shaving it a little close for my tastes.

One nice thing not mentioned that in poor mans hybrid mode our Honda only uses a kiss more than a liter per hour so a couple of jerry cans goes a LONG way..

Off hand I don't buy the extreme range as a safety factor argument as in a lifetime of sailing have I ever encountered a problem that would be solved by being able to motor more than a couple of hundred miles which is the maximum distance that most people would find themselves from a port of refuges... Since ocean crossings are beyond doable under power for most sailboats I just dont see the advantage of diesel over electric where long passages are concerned...
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