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Old 08-12-2015, 11:45   #31
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Re: Tug of War - Electric vs Diesel

As others have stated, the test means nothing. The electrics would be at max torque immediately and the diesels would need to reach peak revs to hit their max torque. This means that if both throttles were set to wide open at the same instant, the electric motors would get the jump on the diesels and begin moving the diesel boat backwards. At this point, the diesels would not only have to fight the thrust of opposing boat, but also the momentum of both boats. If you could hold both boats stable until they were both at max thrust, then the result would probably fall in favor of the diesel boat. Either way, the limiting factor of electric motors is not the motors. We have been making super efficient electric motors for a while now. Batteries are the real issue. Way more potential energy is stored in a tank of diesel than in a fully charged battery bank. When they find a way to generate unlimited energy via the sun, fuel cell, cold fusion or whatever then electric will kill the internal combustion engine.

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Old 08-12-2015, 12:27   #32
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Re: Tug of War - Electric vs Diesel

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I am an electrical engineer and would LOVE to go electric for many reasons, some very specific to my boat and the current engine installation. But it doesn't make sense, due to cruising range and cost.

To get a cruising range of 200-400 nm is impossible with batteries. Even 100 nm range is impossible with the typical cruising boat. That leaves the only option to install a diesel generator to power the electric motor. BUT, now you have put an engine back into the boat and at a much higher cost than just using a diesel for power directly. I've checked the costs and it is roughly triple the cost to go with electric drive with a generator than it is to just install a diesel to drive the boat. Also, until recently there were no commercially available electric drives that had the power to replace my 58 HP diesel.

So tell us the solution to these issues and I will be the very first to jump on the electric band wagon and as soon as I have the spare change, will install the system in my boat.
Maybe with some sails?

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Old 08-12-2015, 15:35   #33
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Re: Tug of War - Electric vs Diesel

IMHO Elco is the gold standard in marine electric propulsion. Unfortunately they're also priced like that. An Elco costs as much as an equivalent diesel. Depending on the batteries you choose they can be very expensive. I priced LI batteries at the St Pete Boat Show last weekend & they were $1,100. The 20 hp Elco would need 6 of these to get the required 72 volts. In addition, to be able to actually cruise with this motor you would need to get a generator so after installation of the whole system you are looking at 2 to 3 times the cost of a simple diesel set up. If you already have a generator then the price would be more reasonable assuming the generator has enough capacity. On top of that a large solar system would make a lot of sense but add even more to the cost. According to Elco you can cruise for about 6 hours on the 6 batteries before the generator would need to kick in which is pretty reasonable.

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Old 08-12-2015, 18:42   #34
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Re: Tug of War - Electric vs Diesel

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Maybe with some sails?

goat (always helpful)
Well goat, obviously you haven't seen the current photo of my boat.
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Old 08-12-2015, 18:50   #35
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Re: Tug of War - Electric vs Diesel

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Well goat, obviously you haven't seen the current photo of my boat.
I did actually, I was following Don's thread too. I just didn't want to rub salt in a wound, and that was very nice of me.

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Old 08-12-2015, 18:57   #36
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Re: Tug of War - Electric vs Diesel

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IMHO Elco is the gold standard in marine electric propulsion. Unfortunately they're also priced like that. An Elco costs as much as an equivalent diesel. Depending on the batteries you choose they can be very expensive. I priced LI batteries at the St Pete Boat Show last weekend & they were $1,100. The 20 hp Elco would need 6 of these to get the required 72 volts. In addition, to be able to actually cruise with this motor you would need to get a generator so after installation of the whole system you are looking at 2 to 3 times the cost of a simple diesel set up. If you already have a generator then the price would be more reasonable assuming the generator has enough capacity. On top of that a large solar system would make a lot of sense but add even more to the cost. According to Elco you can cruise for about 6 hours on the 6 batteries before the generator would need to kick in which is pretty reasonable.

Electric Boats, Motor Yachts, Launches, Electric Powered Boats
Have done the math several times and always came up with the same answer; electric with an appropriate generator will be 2-3 times more expensive that a new diesel engine and transmission.

One thing I can't understand. I priced other electric motors and they are way, way cheaper than these "marine" units. A heavy, continuous duty 40-45 kW industrial motor which is equivalent power to my 58 HP diesel can be purchased for under $2000. A new 60 HP electric motor for my wife's Prius is under $1000. So how come a "marine" electric motor is $5-$10,000? I know they aren't that much different from an industrial motor. Even so, I could buy 2 or 3 industrial motors for spares and still have money left over.
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Old 08-12-2015, 18:59   #37
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Re: Tug of War - Electric vs Diesel

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I did actually, I was following Don's thread too. I just didn't want to rub salt in a wound, and that was very nice of me.

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Your kindness and forbearance is noted and appreciated.
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Old 08-12-2015, 19:27   #38
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Re: Tug of War - Electric vs Diesel

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Originally Posted by Scout 30 View Post
IMHO Elco is the gold standard in marine electric propulsion. Unfortunately they're also priced like that. An Elco costs as much as an equivalent diesel. Depending on the batteries you choose they can be very expensive. I priced LI batteries at the St Pete Boat Show last weekend & they were $1,100. The 20 hp Elco would need 6 of these to get the required 72 volts. In addition, to be able to actually cruise with this motor you would need to get a generator so after installation of the whole system you are looking at 2 to 3 times the cost of a simple diesel set up. If you already have a generator then the price would be more reasonable assuming the generator has enough capacity. On top of that a large solar system would make a lot of sense but add even more to the cost. According to Elco you can cruise for about 6 hours on the 6 batteries before the generator would need to kick in which is pretty reasonable.

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I think you will find that Kamewa is the RR of marine electric propulsion.


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Old 08-12-2015, 21:10   #39
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Re: Tug of War - Electric vs Diesel

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Have done the math several times and always came up with the same answer; electric with an appropriate generator will be 2-3 times more expensive that a new diesel engine and transmission.

One thing I can't understand. I priced other electric motors and they are way, way cheaper than these "marine" units. A heavy, continuous duty 40-45 kW industrial motor which is equivalent power to my 58 HP diesel can be purchased for under $2000. A new 60 HP electric motor for my wife's Prius is under $1000. So how come a "marine" electric motor is $5-$10,000? I know they aren't that much different from an industrial motor. Even so, I could buy 2 or 3 industrial motors for spares and still have money left over.
I agree. How can a simple electric motor cost as much as a diesel? The diesel is much more complex & must cost much more to manufacture. Just the transmission alone probably costs as much to build as the electric motor. I know I'd be much more inclined to buy one if they were more reasonable.
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Old 09-12-2015, 00:08   #40
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Re: Tug of War - Electric vs Diesel

tag catamarans has several youtube videos about the electric hybrid. Also see the Genie Green electric cat vids. I will make mine carbonfiber, solar, carbonfoam batteries, and regeneration electric motors, no more fossil fuel for me. See the men Dave Tether and Greg Young
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Old 09-12-2015, 00:16   #41
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Re: Tug of War - Electric vs Diesel

It seems obvious to me that electric motors are simply not yet ready, or compatible enough to fulfill a crushing role.

But, what about something completely different. thinking out of the box. How about a wind up boat like, with rubber bands? Just wind it up and let it go.. Using a gear box of course
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Old 09-12-2015, 04:51   #42
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Re: Tug of War - Electric vs Diesel

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I agree. How can a simple electric motor cost as much as a diesel? The diesel is much more complex & must cost much more to manufacture. Just the transmission alone probably costs as much to build as the electric motor. I know I'd be much more inclined to buy one if they were more reasonable.
Elco EP7000, rated for 29.75 KW continuous output (38 HP) $17,375.00. I can certainly buy a new diesel and transmission for that. Totally insane.

How can a "marine" electric motor cost ten times more than an equivalent power industrial motor or twenty times an equivalent automotive like the one in my Prius? Yes I know economy of scale and such but still.
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Old 09-12-2015, 07:20   #43
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Re: Tug of War - Electric vs Diesel

I think you would be better served with a boat built specifically for electric than trying to convert from an ICE. A few thousand pounds of batteries in lieu of ballast, thin film solar panels double as sails.

One thing I would like about the idea of electrical propulsion is the ability to refill the 'tanks' when in the middle of an ocean.

For now, I'll put up with my 2gm to push me when needed, and wait for the technology to advance just a little more.

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Old 09-12-2015, 11:19   #44
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Re: Tug of War - Electric vs Diesel

I've found an application where electric power may make sense. They are advertising electric power canal boats in England. They apparently have to move every so often and usually have shore power available. I would stick with diesel myself ...
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Old 10-12-2015, 18:53   #45
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Re: Tug of War - Electric vs Diesel

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Torque and HP have nothing to do with this. What counts is just the propeller's parameters and the rpms. Of course, the engine has to be able to supply enough torque so as to keep the propeller turning at the given rpms while overcoming the hydrodynamic resistance, for which in turn the engine must have enough power.
Actually I just looked at my bollard pull calculator and the pull is proportional to (HP x prop diameter)^2/3. It assumes that the props are pitched to allow maximum HP
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