Tug of War - Electric vs Diesel

[Jim Cate]

Originally Posted by BigBeakie

Rustic,

Are you considering only the initial costing? How much motoring are you expecting to do over the next 5 years, therefore fuel costs?


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So, Beakie, does not the required gen set consume fuel? And is it not true that burning diesel to run a gen set to make electricity, and then converting the electrical energy back into mechanical energy to drive the boat is inherently less efficient than a conventional drive? And if you wish to reduce fuel costs does not the massive solar array, associated controllers, massive battery bank and cabling cost quite a lot of money? And over your stipulated five year period, is it not likely that the battery bank would need replacement? And if you want to utilize regeneration, are you willing to give up the sailing performance this entails?

Glossing over these points sure helps legitimize the advantages of electrical propulsion...

Jim

[Rustic Charm]

Originally Posted by BigBeakie

Rustic,

Are you considering only the initial costing? How much motoring are you expecting to do over the next 5 years, therefore fuel costs?

Sent from my iPad using Cruisers Sailing Forum

If I had a motor cruiser, or had to motor a lot, then I'd certainly take that into consideration. But, I'd be lucky to fill my 170 liters a year. The most I need to motor in a run would be when I go up and down our river to get to the slip. Now that that's about 18litres each way, max once a year. Other than that my engine is used for entering ports, anchoring etc. it's just not worth taking it into consideration at all.

[44'cruisingcat]

Originally Posted by BigBeakie

Rustic,

Are you considering only the initial costing? How much motoring are you expecting to do over the next 5 years, therefore fuel costs?


Sent from my iPad using Cruisers Sailing Forum

On a sailboat, it's almost certainly going to take more than 5 years to recover the extra cost.

To fit a diesel electric propulsion system to my boat would have cost roughly (it's been several years since I looked it this) an extra $25,000.

In nearly 6 years full time liveaboard cruising we would have barely spent $6,000 on fuel.

Even if the diesel electric system used NO fuel, we'd still be waiting another 15 years or so to break even.

[44'cruisingcat]

Originally Posted by Rustic Charm

If I had a motor cruiser, or had to motor a lot, then I'd certainly take that into consideration. But, I'd be lucky to fill my 170 liters a year. The most I need to motor in a run would be when I go up and down our river to get to the slip. Now that that's about 18litres each way, max once a year. Other than that my engine is used for entering ports, anchoring etc. it's just not worth taking it into consideration at all.

Funnily enough, if you could find one at a comparable price, electric might work well for you. If you only motor short distances, and can plug in at a marina to recharge batteries, you won't need the genset, or a huge battery bank.

There's plenty of appeal: silence, very good response, no diesel exhaust, no diesel smell in the boat, almost maintenance free...

It's once you start needing the motor for longer periods, and thus require a genset that the advantages start to become questionable.

[Rustic Charm]

Originally Posted by 44'cruisingcat

Funnily enough, if you could find one at a comparable price, electric might work well for you. If you only motor short distances, and can plug in at a marina to recharge batteries, you won't need the genset, or a huge battery bank.

There's plenty of appeal: silence, very good response, no diesel exhaust, no diesel smell in the boat, almost maintenance free...

It's once you start needing the motor for longer periods, and thus require a genset that the advantages start to become questionable.

yep. I can definitely see the advantages. It's just not sensible given the outlay. If it was a couple extra thousand I'd seriously consider it. But not when electric is so rediculously over priced I'd have to want to do it for nothing more than the environmental ideology.

[Kalinowski]

My conversion will cost around $13k. Total. My son works at West, so we got about $2k discount on batteries & chargers.

[four winds]

Originally Posted by Kalinowski

My conversion will cost around $13k. Total. My son works at West, so we got about $2k discount on batteries & chargers.

Converting the Pearson 424? That's a big cruiser, and I think many here would be interested in a thread on your efforts. Please consider doing that.

Have you started the conversion?

Best of luck to you.

[Rustic Charm]

Originally Posted by Kalinowski

My conversion will cost around $13k. Total. My son works at West, so we got about $2k discount on batteries & chargers.

How

A 42 footer can you share the information on where this conversion is coming from so the rest of us can gain from the huge savings? At that price I'd be very interested but it's very clearly not from either site suggested earlier.

[med]

Originally Posted by Rustic Charm

If I had a motor cruiser, or had to motor a lot, then I'd certainly take that into consideration. But, I'd be lucky to fill my 170 liters a year. The most I need to motor in a run would be when I go up and down our river to get to the slip. Now that that's about 18litres each way, max once a year. Other than that my engine is used for entering ports, anchoring etc. it's just not worth taking it into consideration at all.

Those 18 litres are equivalent to about 80KWH. That is more than the 65KWH of your average Tesla car's battery.

About 6000 AH with 12V batteries. Or about 100 decent sized lead acid batteries. Assuming you only use 60% of capacity and don't discharge too far.

[Rustic Charm]

Originally Posted by med

Those 18 litres are equivalent to about 80KWH. That is more than the 65KWH of your average Tesla car's battery.

About 6000 AH with 12V batteries. Or about 100 decent sized lead acid batteries. Assuming you only use 60% of capacity and don't discharge too far.

Would you mind putting that I to the queens English for me? Actually, any English will do.

[med]

Originally Posted by Rustic Charm

Would you mind putting that I to the queens English for me? Actually, any English will do.

You need a lot of batteries to get the same range as 18 litres of diesel.

[Rustic Charm]

Originally Posted by med

You need a lot of batteries to get the same range as 18 litres of diesel.

ah, yes. Way too many. I'd need a Jenny if I ever go that way.

[BigBeakie]

Originally Posted by Jim Cate

So, Beakie, does not the required gen set consume fuel? And is it not true that burning diesel to run a gen set to make electricity, and then converting the electrical energy back into mechanical energy to drive the boat is inherently less efficient than a conventional drive? And if you wish to reduce fuel costs does not the massive solar array, associated controllers, massive battery bank and cabling cost quite a lot of money? And over your stipulated five year period, is it not likely that the battery bank would need replacement? And if you want to utilize regeneration, are you willing to give up the sailing performance this entails?

Glossing over these points sure helps legitimize the advantages of electrical propulsion...

Jim

Jim,

To take your questions one by one:
1. The genset for battery charging does consume diesel. It is required only when the range of the propulsion LFP bank is exceeded. How often that happens depends mainly on where you cruise as you well know, as well as how well your boat sails in light winds ie whether you have an efficient performance cat or a condomaran. If it is not used very often, then the genset can be considered like an insurance policy, hardly ever needed but good to have if circumstances arise.
However the Island Cruising Association out of NZ has surveyed their members ( over a long period of time) and found a surprisingly ( to me anyway) high number of engine hours per year reported by their members that actively cruise the South Pacific. They report an average of 700 engine hours/year. Say average diesel burns 4 liters /hour and at $2/liter thats $5,600 per year fuel.
Obviously this is not the cruising profile of either Rustic Charm or 44' Cruising Cat, so diesel hybrid electric is not a cost justifiable solution for them. It sounds to me Rustic Charm has very modest motoring requirements, so maybe EP could work for him where he can plug in at the end of the day.

But as I reported, one electric cat uses 1 liter /hour to recharge enough to keep going non-stop at cruising speed. Smaller electric motors, smaller generator required, system in balance. To ask one of your rhetorical type questions, is 1 liter per hour less than 4 liters per hour? Which system is more efficient?

2. But EP does not rely ALONE on the genset. For the vast majority of the time EP is used, it uses free fuel. So which is more efficient, a system that you pay at the pump every single time you fill up, or one where the fuel dock attendant says "Never mind, it's on the house?"

3. No, over 5 years the LFP bank would not need to be replaced. An LA system undoubtedly would , due to the lower capacity of charge cycle life.

4. Users of these EP systems that use feathering props for regen report a loss of a quarter to half a knot boat speed during regen. I'll take that hit any day of the week for the amount of charge that is achieved back into the LFP bank. Don't forget, when the charge is topped up, then you pop the props back into feathering mode. So you've been on the hook in some nice lagoon for a week and it's been really cloudy so not enough solar to keep house bank up, just go sailing for a few hours under regen and you just got a free fill,.... again.

Sounds pretty efficient to me. And do it again and again over a 5 to 10 year cruising plan.

[Terra Nova]

Originally Posted by BigBeakie

...one electric cat uses 1 liter /hour to recharge enough to keep going non-stop at cruising speed...
For the vast majority of the time EP is used, it uses free fuel...
Users of these EP systems that use feathering props for regen report a loss of a quarter to half a knot boat speed during regen...

Oh come on!

[med]

Originally Posted by BigBeakie

Jim,


But as I reported, one electric cat uses 1 liter /hour to recharge enough to keep going non-stop at cruising speed. Smaller electric motors, smaller generator required, system in balance. To ask one of your rhetorical type questions, is 1 liter per hour less than 4 liters per hour? Which system is more efficient?

The system with the direct drive diesel is more efficient. The gain in efficiency running a the engine at optimum speed and load in a generator is not enough to compensate for the losses in generating electricity and then using it in an electric motor.

The fact that the diesel engine is using 4 liters per hour means that it is generating 4 x the power the generator is generating and the electric motor is using. The net output will be less than 1/4 of that of the diesel engine at 4 litres per hour.

There is no free lunch unless you have a few solar panels like this electric powered boat:-