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Electric or Diesel-Electric Hybrid propulsion conversion viability


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In my search for a yacht, I've come across a few out there that are in need of a re-power due to a dead engine or having extremely high operating hours and my thoughts have turned to the viability of an electric or diesel-electric hybrid propulsion conversion. It definitely won't suit everyone's needs but I would think that there are situations where it would be a viable option like those that do longer passages, just use the motor around marinas and moorings or anchoring, etc. I think the load would also be a factor so electrical needs, yacht size and weight will have a bearing.

 

The biggest downside to the pure electric option would be reduced range and a slightly reduced cruising speed under power to help maximise the available range. Not ideal for those that must somewhere at a certain time but for those with more flexibility with their schedules and destinations and a desire to sail it's probably not a major issue. On the plus side, you could run it just enough to remove the impact of prop drag thus gaining a little extra sailing speed or alternatively use it in the regeneration mode to put a charge back into the batteries. This wouldn't be a huge amount and is dependent upon sailing speed but it might be helpful. Obviously, there are other charging options available such as solar, wind and hydro generators. You also get an opportunity to reduce noise, vibration and smell from the diesel and reduce the number of holes in your hull. 

 

Another potential downside is for those that run desalinators that aren't 12V so a generator would be required. My thought was a small diesel generator that could power the desalinator and/or recharge the battery bank when required but doesn't always have to run when you use the motor. Also, I'd think using a generator to run a desalinator or charge batteries etc. would make more sense than running an engine used for propulsion. Yes, it would mean a diesel engine back on the boat but the usage and requirements would be different and the diesel could also be used for heating.

 

Generally, the biggest hurdle seems to be the cost of batteries, particularly Lithium Ion which means you're effectively paying for your fuel up front. The electric motors, controllers, etc. aren't that expensive, heavy or bulky and spares could be carried. 

 

Are my thoughts on the right track and what am I missing?

 

 

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I enquired about the Oceanvolt system and it cost $45,000 to have a full system, including a Genset to allow for sustained cruising as well as powering the boat electrics. The space taken doesn't seem that large as the batteries are smaller and the engine is very small. It featured a Lithium Ion battery bank that could be recharged while sailing, the drag was something like 0.5 knot at 6 knots. I really like that idea, and substantial costs could be made by having a smaller cheaper genset for emergency use.

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BP, the generator was a possible solution to powering the desalinator as from what I understand the 12V versions aren't that efficient. Of course, if you don't need it then so much the better and cheaper.

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It's not as simple as it sounds.
Basically, the issue is in replacing the power you use in a time frame that makes an electrical system worth while. It's easy if you can plug into the grid with a dirty great cable and download a huge hunk of power quickly. But if out cruising, that's not really possible. For the weekender or day sailor, it could be worth it, but then I doubt many of those types of Boaties would want to spend that kind of money. For the Cruiser, the issue is how to fill up the Battery bank after depleting it and getting it back to a usable charge level in an acceptable time. Even a small system to get you in and out of a Marina will suck up a huge amount of Power. For those of you with Bow Thrusters, you will know how much those little motors suck. So you are kind of forced to have a Genset and to me, if you are going to have a genset to charge the batteries to power the Electric motor, you may as well just have an engine.

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That decision as to what is acceptable becomes a personal decision. I think it would work for a long time cruiser with the right mind set. You are always going to arrive after a passage fully charged. All you then need is net positive charging at anchor and you are there.

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From my continuing searching, it appears that for most users dropping the speed under motor to around 4 knots generates considerable savings in power consumption and a good increase in potential range and at around 2 knots their solar systems seem to be able to keep up with the draw rate if the batteries are drained which is fine when it's calm but against a strong tide/wind would be an issue if the motor is needed. Also, it seems regeneration under sail starts around the 4-5 knot mark. Obviously, a purpose made hydro generator will be much more efficient but apparently a feathering prop is not too bad by all accounts. 

 

The other thing that seems to be a common thread is the realisation that it is a different technology to internal combustion and so requires a different approach to its use. It is not a direct replacement. Those expecting the same will likely be disappointed but those willing to adapt seem quite happy with the trade-offs. 

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That decision as to what is acceptable becomes a personal decision. I think it would work for a long time cruiser with the right mind set. You are always going to arrive after a passage fully charged. All you then need is net positive charging at anchor and you are there.

Sure, I get what you mean, but do understand that power consumption for an electric motor capable of propelling a mid size boat for say just an hr, is huge. Where as the recharge ability of Solar, Wind and Water towed Gen are comparatively very small. It could take many days to replenish. And if you are also trying to run Fridge/Freezer, Watermaker, lights and so on, then you have to factor that into the equation as well.

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Battery will get better as time goes buy , but for now they are still developing with lipo etc , with every plus electric motor there is two minuses. Fire , explosion , all thoes are highly related to these type of battery's for marine electric motors , solar panels take up to much room , boats get left sitting to long , battery's don't like salt water , connector don't like salt water , electric motors internals do t like salt water , and these lips cell battery from my usage get very hot , when one gives up it usually explodes Masses amounts of smoke , then fire , the amount of smoke would fill the average bedroom sollid with smoke then fire , and that's only 3 inches long buy an inch either way , energy cell is the only way , but what energy to put in it ,

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Urs but i would be happy with zay 5 to 1 ratio.

 

It's far far away from that BP. Lets say a 10Kw (that's not large) motor for 1hr. That's 12000 Amps you have to get back into the bank for just one hr of motor use. Even with a 120A ALT, that's 100hrs plus of charge time. Try doing that with Solar, wind and Tow Gen. You probably aren't even going to have that bank topped up by the time you sailed to the Islands.

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Do these systems have enough grunt ie battery power, to haul a large anchor and chain off a deep bottom? Its a big 12 volt drain on my boat, or would you need to go to a manual winch for this?

 

I don't hit the button on my windlass without the engine running as it draws some big amperage especially in deep water.

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I have some figures for a 20kV 48V motor pushing a 36' 8,000kg yacht with a 19.2kW/h battery pack. Speed has a big impact.

You wouldn't want to run flooded or AGM batteries to 80% DOD or they would be expensive paperweights in no time.

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Remember it is 48V, so 400Ahr at 48V is a heck of a lot of batteries, hence the weight. Which as I said earlier, that's a heck of a lot of panels and you won't get a Towable Gen at 48V, and i know no Marine wind genny at 48V. So you would be stuck with a large Solar panel set up, or a Genset and charger.

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I don't know about standalone 48V hydro generators but there are 48V marine wind generators available such as the D400 and the Silent Wind. You can also get some regeneration from the prop under sail, normally starting around 4 knots from what I understand.  

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Lets say a 10Kw (that's not large) motor for 1hr. That's 12000 Amps you have to get back into the bank for just one hr of motor use. Even with a 120A ALT, that's 100hrs plus of charge time. Try doing that with Solar, wind and Tow Gen. You probably aren't even going to have that bank topped up by the time you sailed to the Islands.

You may want to do the amps calculation again.

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