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Old 28-08-2010, 13:01   #91
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Originally Posted by gosstyla View Post
My experience contradicts that statement.

My experience was that if the diesel motor from the generator was used to drive props directly it could do so at least as effectively as using it in a generator to make electricity with which to run an electric motor to drive props.
What was you experiment like? Did you swap engines and eMotors to find out? I do agree I was skeptical when I first read about it ; I guess the proof of the pudding is in the eating (thanks Gideon).

I was on a 45 ft cat with twin retractable 10 KW (each) motogens. With (total) 20 KW (27 eHP) the boat was easily driven at well over 8 knots. To do the same with diesel power you would need at least twin 30 -40 HP rated engines if not more. A lot is to gain when optimizing the props; since they are retractable focus can be on regeneration en propulsion efficiency rather than a low drag when sailing. I noted the props were very 'full' (DAR about 70% I believe); this vastly improves propeller efficiency.

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Old 28-08-2010, 20:34   #92
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The point is the electric motor needs electricity to run - the power required to make that electricity can used as effectively, or more so, to drive the props directly.
The point that the power can be used effectively to drive the props directly is not nor never has been an issue. You were making a very specific claim about a performance comparison. That was the point of my question.

It is generally agreed that comparing just direct drive diesel vs diesel electric the direct drive will be more efficient, unless the system is optimized to take advantage of other aspects of electric system. This could be better use of the power curve of the electric system to drive a more efficient prop, regenerative systems that put power back into the system while under sail, flexibility in the installation of the motor since it does not have to be linked to the shaft directly, multiple power sources, using efficient HV DC systems, easier shaft alignment, etc.

In my case I would be willing to accept a loss in efficiency from converting diesel to electric to drive for the advantage of flexibility in the installation and better access to the drive system. Not however if it costs double the price of a new diesel.
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Old 29-08-2010, 11:48   #93
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What was you experiment like? Did you swap engines and eMotors to find out? Eric
I had a 47' Crowther custom built by Alwoplast in Valdivia, Chile specifically to be powered by the Glacier Bay diesel/electric system. The 33 hp electric motors were high efficient DC designed an built by Glacier Bay. They were powered by 2 25Kw HV DC gensets built by Glacier Bay using the small Mercedes common rail diesels used in the Smart Car. All electrical systems on the boat were designed to make best use of the power available.

Alwoplast had built 5 or 6 similar 47' Crowthers prior to mine with various size direct drive diesels so they were very familiar with the performance of that Crowther design.

Starting in September, 2007 I sailed the boat from Valdivia, thru the Panama Canal up to Ft. Lauderdale - approximately 4,600 nm. I let Glacier Bay show the boat during the 2008 Miami Boat Show.
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Old 29-08-2010, 12:22   #94
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..It is generally agreed that comparing just direct drive diesel vs diesel electric the direct drive will be more efficient, unless the system is optimized to take advantage of other aspects of electric system. ...
I agree, unfortunately for my objectives and type sailing, e.g. a couple living aboard doing long passages to remote locations the available advantages of an electric system were less than the disadvantages when compared to a direct drive diesel system.

But yes, there are many situations where electric propulsion works, for example:

1. When non-propulsion electric needs are great - equal or exceed the propulsion energy requirement. Examples:
a. Large passenger vessels. My first experience with these was in the early 50s when my mother and I traveled from Seattle to Tokyo on diesel/electric naval vessel to join my dad then stationed in Japan. A couple of years later my parents, new baby sister and I did a similar return trip from Tokyo to San Francisco.
b. War ships

2. When high torque is needed at low rpms. Examples:
a. Ice breakers
b. Large tugs

3. When batteries can store sufficient energy for most outings and shore side power is available for charging. Examples:
a. Duffy type electric boats for harbor and lake use.
b. Harbor 20 type sailboats just using the motor to get away from the dock.
c. Trolling on small fishing boats
d. Hobi now offers a Torqeedo for some of their kayaks

4. Special situations. Examples:
a. Submarines
b. Special Ops where low noise and low heat signature is needed, e.g navy seals.
c. Lakes and other areas where "petro" motors are prohibited.

However, for objectives such as mine I don't believe electric motors will be competitive with other alternative propulsion systems until a way of generating electricity more efficiently than with a diesel motor become readily available. Maybe fuel cells will someday become practical.

By the way the diesel/electric propulsion system in my boat cost me about $150,000.
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Old 29-08-2010, 16:29   #95
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So, gosstyla, given that you used a hybrid system where range was a non-issue (I'm assuming?) what were the biggest drawbacks of your system that make you feel conventional diesel is superior for the cruising sailor?

Inadequate Power to drive the boat? Cost?
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Old 29-08-2010, 16:56   #96
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By the way the diesel/electric propulsion system in my boat cost me about $150,000.
Do you have a price break down on that? That seems like a huge amount of money...

But yeah, I would be unenthusiastic about electric propulsion too if it cost $150k!!
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Old 30-08-2010, 08:43   #97
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"I think that diesel and electrically propelled boats are equally screwed by a lightning strike.... "

Yep I agree all bets are off in a lightning strike. Diesel or Electric propusion. It all depends on what type of a mood Thor woke up in that morning. I feel my industrial quality controller is pretty robust. But, whether it will survive a lightning strike well I hope to never find out. But, does anyone really believe that the half dollar semi conductor component that powers the electric fuel pump on most diesels would survive too?
My boat has had a number of thunderstorms pass over it on the mooring and so far has not been damaged. In 2008 on the maiden voyage with electric propulsion I ran into a line of thunderstorms. I dropped sail and ran under electric propulsion for 45 minutes and had a number of instantanous lightning and cracks of thunder nearby. As my crew huddled down below I stood in the companionway keeping watch. But, we were still able to have casual conversation because of the quiet operation of the motor and listen as the sounds of the thunder moved away from us before we raise sail again. BTW I'm currently cruising and yes my batteries are fully charged even though I have not touched a dock since Thursday and probably will not for the next two weeks.
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Old 30-08-2010, 11:52   #98
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I can settle the horsepower question. Check any engineering website regarding horsepower equivalent. The measure used is the Braking HP or the torque required to stall the engine. All internal combustion engines develope peak torque at peak RPM. Series DC motors develope peak torque at zero RPM. A direct measurement of "work",(mass * Velocity moved), clearly shows a 1HP electric motor will move twice the mass at a given RPM than a 1HP diesel. It is merely an engineering guideline and has nothing to do with the drive efficiency or the prop, although additional gains are possible there with the wide flat torque curve of an electric when compared to the curve of a diesel. In a boat since it will spend most of its time at the optimum speed anyway the biggest advantage is the small size of the electric motor of the same "equivalent" power. for mine 100lbs in a 8" by 14" cylinder compared to a 800lb 24" by 18" by 26" approximatly V shaped cube. the small light electric allows as has been pointed previously unconventional mounting I.E. pod or movable drives. Right now both systems are a wash for performance and an off the shelf electric system in unquestionally more expensive. The big advantage is the next battery pack will likely have 2, 3, or 4 times the range and power with little additional cost of upgraded components. right now the tank of fuel will carry way more energy even with efficiency gains. With electric you can go far or fast, but not both. With diesel you can go both.
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Old 30-08-2010, 12:23   #99
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Has anyone looked at a diesel-electric system?
That's how the big ships do it. Makes sense to me, but what do I know.
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Old 30-08-2010, 12:26   #100
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By the way the diesel/electric propulsion system in my boat cost me about $150,000.
Yow. That's what has pretty much vetoed the diesel electric for me. The advantages I was looking for:

1. Eliminate v-drive
2. Improve access to prop shaft and stuffing box
3. ease prop shaft alignment
4. move/modify main engine installation.
5. drive boat with genset that could be sound insulated, isolated from boat structure, etc. ie. very quiet.

However, even with only one hull and one engine (see there's another advantage to monohulls ) I'm looking at $30-$60,000 to end up with equivalent power and speed to my existing engine. For that much money I can hire a full time mechanic and never again get grease under my fingernails.
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Old 30-08-2010, 13:04   #101
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There's no way it would cost $150k just for the Electrics, that must have been for the whole boat!. My setup is around $40k from Solomons for a Cat (dual everything). As Mike said there are a lot of options out there from other manufactures a lot cheaper but you get what you paid for. It's amazing to me how a guy will preach redundancy, the sky is falling if you do it such a way then scrimp on a part that could sink a boat like a hose clamp. People will complain about the cost of fuel but won't give up a knot or 2 to go electric. My motors are capable of eating up 120amps each. I've never pushed them that hard because I know the batteries would last about 1 hour but I could get EG up to about 11 knots in theory. I've done 8 but prefer the 6 knot range at around 55A total. Ya it's more expensive up front but I'm an old gear head and frankly I didn't want the hassles of a couple more ICE's in a cramped engine room. I'm so happy with my setup. I've had issues and am still trying to make it better, it's my nature, but I've learned an incredible lot over the last year and a 1/2 about a technology we all are going to be using a lot more of in the future.
Cost 2009 to maintain the system = $1500 (had a controller go bad. Fuel tanks were filled with 120 gal for genset on purchase)
Cost to date (2010) = $112 (oil change on the Genset and filling the tanks with 31 gal. of diesel last week).
Top that...

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Old 30-08-2010, 13:57   #102
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There's no way it would cost $150k just for the Electrics, that must have been for the whole boat!. My setup is around $40k from Solomons for a Cat (dual everything).

Steve in Solomons MD
I just rechecked Solomon and was redirected to Technipower? I assume that is their new name or new owner. Anyway, the largest motor they list is 12 HP. I would be willing to give up a little performance but for a single engine, 42', 25,000 lb boat 12 HP is not going to cut it.

What size electrics do you have in your Lagoon?

Did the $40K price include the cost of the genset?

Thanks
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Old 30-08-2010, 14:08   #103
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I just rechecked Solomon and was redirected to Technipower? I assume that is their new name or new owner. Anyway, the largest motor they list is 12 HP. I would be willing to give up a little performance but for a single engine, 42', 25,000 lb boat 12 HP is not going to cut it.

Thanks
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You might like to check here: Solomon or here Green Motion.

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Old 30-08-2010, 16:59   #104
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You might like to check here: Solomon or here Green Motion.

Eric
Thanks Eric,

Went to the link you sent for Solomon and got the same motors and spec sheets that I found via Google. Max motor 12 HP.

Had been following the Green Motion threads. They mention systems to 25KW which is about 34 HP but their web site doesn't list any systems for sale. Would be very interested in what they have to offer.

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Old 31-08-2010, 16:04   #105
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I can settle the horsepower question. Check any engineering website regarding horsepower equivalent. The measure used is the Braking HP or the torque required to stall the engine. All internal combustion engines develope peak torque at peak RPM.

I believe if you check the specs on most marine diesel you will find the max rated torque occurs before the max rated rpms.

Series DC motors develope peak torque at zero RPM. A direct measurement of "work",(mass * Velocity moved), clearly shows a 1HP electric motor will move twice the mass at a given RPM than a 1HP diesel. It is merely an engineering guideline and has nothing to do with the drive efficiency or the prop, although additional gains are possible there with the wide flat torque curve of an electric when compared to the curve of a diesel.


With the appropriate DC motor and controller the torque and rpms can be about any combination desired as long as the torque x rpms does not exceed the hp or watts or whatever minus inefficiencies being fed the motor. Glacier Bay told me my system was programmed so that torque was level throughout the rpm range. I don't know if that was true but it is not obvious to me that that would be the most efficient torque rpm combination.

Early on the difference in the prop power curve and the diesel torque curve was used as a potential item the diesel/electric system could exploit for efficiencies. With the electronic controlled common rail diesels whatever possible advantages diesel/electric had are now gone.

In a boat since it will spend most of its time at the optimum speed anyway the biggest advantage is the small size of the electric motor of the same "equivalent" power. for mine 100lbs in a 8" by 14" cylinder compared to a 800lb 24" by 18" by 26" approximatly V shaped cube. the small light electric allows as has been pointed previously unconventional mounting I.E. pod or movable drives.

At least to meet my objectives electricity still has to be generated onboard, so when you add the diesel and other equipment needed to generate the electricity the volume and weight of the diesel/electric is greater than an equivalent direct drive diesel.

Right now both systems are a wash for performance and an off the shelf electric system in unquestionally more expensive.

I agree with that.

The big advantage is the next battery pack will likely have 2, 3, or 4 times the range and power with little additional cost of upgraded components. right now the tank of fuel will carry way more energy even with efficiency gains. With electric you can go far or fast, but not both. With diesel you can go both.

I expect it will be a long time before an economical battery pack will be available that will be able to power a cruising boat the minimum 2,500nm needed to cross oceans.

"With electric you can go far or fast, but not both."

I disagree - you can go fast.
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