I don't think so. That boat weights twice as much as my Hunter 376 with twice as much water friction and that's why it's equliviant diesel is a yanmar 100 hp to my yanmar 40 (came with yanmar 36).
electric engine in sailboat
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Electric motor on sailboat
Couple of thoughts then I will quit beating the dead horse-power!
Motor sailing in a pretty severe seaway is an effective way of maintaining momentum and steerage under reduced sail when the waves crash you to an almost shuddering stop..
Diesel electric does not transfer power as efficiently as a gearbox does. The losses in the wiring and motor controllers and the inefficiencies in the generator and electric motor do that. (not counting superconductivity here) It is used on locomotives because it provides the equivalent of an infinitely variable gear ratio, and a great set of brakes. It is used on big tugboats because it lets the azimuth drive swivel.. Think huge trolling motor that can swivel to give the tug excellent maneuverability. It is used on conventional tugs and push boats to replace the separate gearboxes which get really expensive above some number in the 1000 HP range. (full capacity reverse gearset instead of a switch)
That said, Diesel Electric is an excellent choice for catamarans because it ends up being more efficient to only run one engine to power both electric motors.. I don’t have the numbers handy, but a diesel is somewhere around 30-35% efficient at turning fuel into horsepower. The generators and motors are in the 90-96% range.. so it makes sense to only suffer the big inefficiency one time instead of two .. This is a generalization and there can be instances that will go against this one.. but like I said it looks like it really makes sense to power catamarans this way.. with or without battery back-up power. Diesel Hydraulics have been used for things like this too but the fluid power losses are higher than diesel electric..
Couple of thoughts then I will quit beating the dead horse-power!
Motor sailing in a pretty severe seaway is an effective way of maintaining momentum and steerage under reduced sail when the waves crash you to an almost shuddering stop..Diesel electric does not transfer power as efficiently as a gearbox does. The losses in the wiring and motor controllers and the inefficiencies in the generator and electric motor do that. (not counting superconductivity here) It is used on locomotives because it provides the equivalent of an infinitely variable gear ratio, and a great set of brakes. It is used on big tugboats because it lets the azimuth drive swivel.. Think huge trolling motor that can swivel to give the tug excellent maneuverability. It is used on conventional tugs and push boats to replace the separate gearboxes which get really expensive above some number in the 1000 HP range. (full capacity reverse gearset instead of a switch)
That said, Diesel Electric is an excellent choice for catamarans because it ends up being more efficient to only run one engine to power both electric motors.. I don’t have the numbers handy, but a diesel is somewhere around 30-35% efficient at turning fuel into horsepower. The generators and motors are in the 90-96% range.. so it makes sense to only suffer the big inefficiency one time instead of two .. This is a generalization and there can be instances that will go against this one.. but like I said it looks like it really makes sense to power catamarans this way.. with or without battery back-up power. Diesel Hydraulics have been used for things like this too but the fluid power losses are higher than diesel electric..
In the typical diesel/electric set-up, (again, tugs and locomotives) there is no huge battery bank. The small diesel runs all the time, and no locomotion forces are provided by a battery. The battery bank is used only for house loads and for the feel-good green crowd, but let's be real; I've motored for days on end (the Baja Bash) and was glad I had a 50hp diesel. The only issue was fuel capacity. I had to carry bladders and jerry jugs. A smaller, more fuel-stingy diesel, turning a generator that powered an electric motor would have been more efficient and less noisy. If you give up the notion of battery-powered locomotion and stick with a modest size house bank, I think the idea has merit.
When I worked for an electric utility vehicle company we discussed replacing the outboard on my H260 with an electric motor. We first searched for available motors and found Minn Kota's 2HP motor. It uses a 48V battery bank, but didn't have near the horsepower a 26' boat needed.
http://www.minnkotamotors.com/products/motors/detail.asp?pg=edrive
Then we found the Ray Electric outboards that are used on some pontoon boats, but they only went up to 5 Hp and they recommended a bank of 10 batteries to give over an hour of running time. The total cost was approaching a new engine, but the weight and low Hp still didn't sell me.
http://www.rayeo.com/pricing.htm
In the end we couldn't find an electric outboard that had the Hp the boat needed, and I wasn't willing to put enough battery weight on the boat to get adequate range. Maybe if battery technology makes a giant leap forward we'll be able to put two smaller motors on the stern without as much weight penalty.
http://www.minnkotamotors.com/products/motors/detail.asp?pg=edrive
Then we found the Ray Electric outboards that are used on some pontoon boats, but they only went up to 5 Hp and they recommended a bank of 10 batteries to give over an hour of running time. The total cost was approaching a new engine, but the weight and low Hp still didn't sell me.
http://www.rayeo.com/pricing.htm
In the end we couldn't find an electric outboard that had the Hp the boat needed, and I wasn't willing to put enough battery weight on the boat to get adequate range. Maybe if battery technology makes a giant leap forward we'll be able to put two smaller motors on the stern without as much weight penalty.
MikeH—
My understanding is that HP for an electric motor isn't quite the same as for a diesel, since the torque curves are very different. You can generally get away will a smaller electric motor than you could with a diesel.
My understanding is that HP for an electric motor isn't quite the same as for a diesel, since the torque curves are very different. You can generally get away will a smaller electric motor than you could with a diesel.
We may like innovations but we will put our money on cost an efficiency. I don't think we would put our money behind noise reduction as we mostly sail with our engines off. If the difference in weight and size of the engines is offset by the weight and size of the required battery bank I don't think it will get our moneys either. Diesel/elctric does not solve the noise-pollution and fuel dependance issues. I agree that electric is the future but until it becomes on a cost basis more efficient than a diesel you will not see many applications.
For this we have to look at duty cycle. Some electric motors are rated for a 50 percent duty cycle others of the same physical size can be rated as continous duty but won't carry the same hp ratings. The same thing applies to our pleasure boat engines. Somewhere I have a discription of the ratings for pleasure, military and law enforcement and commercial service.
As an example the exact same engine can be rated 375 hp pleasure boat service and 300 hours per year, 325 hp for law enforcement/military service 1500 hours per year and 250 hp commercial service unlimited hours. The maximum rpm and propeller size are the determining factors.
Its just not practical
1 gallon of diesel is about 140,000 btu.
That converts to about 41,000 Watts.
Lets say you burn 1/2 gallon every hour mucking about in your sailboat.
That converts to 20Kw/Hour.
Your Group 31 battery will give you at best 1.2Kw/Hour.
You can derate for engine efficiency and bla bla.... but, you cant beat the energy storage of good old fossil fuels.
1 gallon of diesel is about 140,000 btu.
That converts to about 41,000 Watts.
Lets say you burn 1/2 gallon every hour mucking about in your sailboat.
That converts to 20Kw/Hour.
Your Group 31 battery will give you at best 1.2Kw/Hour.
You can derate for engine efficiency and bla bla.... but, you cant beat the energy storage of good old fossil fuels.
oh yes you can...it's called nuculear...
but putting that aside, diesel electric is not about replacing diesel storage of energy, it's about using it most efficiently.
The great thing about Diesel electric is that you don't have to buy a generator because you already have one.
Electric engines are used on locomotives and ice breaker boats because the torque curve is flat. Unlike a combustion engine that has to have rpm before it produces torque. Electric engines produce the same torque at any speed, so I hear.
Not about efficiency either...
With a car you can make the efficiency argument cause of traffic and different speed paterns but a boat .... I dont think so.
And I do disagree about energy storage - its ALL about energy storage IMHO.
You have to make two conversions - from diesel to electric with a generator and then you have to use a motor to go from electric to propeller.
With a car you can make the efficiency argument cause of traffic and different speed paterns but a boat .... I dont think so.
And I do disagree about energy storage - its ALL about energy storage IMHO.
Because you have the same HP at all speeds with an electric engein, you don't need as much hp, so you don't need as big a diesel engine to run the generator which give you better fuel economy. And, you can use that same generator to run the AC while you are anchored.
I say diesel electric isn't about replacing energy storage because the storage is still the diesel fuel...that was never replaced.
Franklin, if you are running at a constant speed, you are using a constant amount of power without regard for the source of that power. If you drag a turbine to suppliment the other sources of power you will either slow down or have to increase power input to maintain your speed. The manner with which you move energy from the source to the point of consumption is for the most part determined by the efficiency of the method of transmission.
Seperate components
By separating the components (genset and electric motor) you can have the genset be powered by a ideally sized engine and run it at its' best efficiency. While you can have an electric motor that spins a large high pitch prop at low RPM.
Now figuring out if all that additional efficiency actually overcomes the inefficiencies of changing chemical to mechanical to electrical transmitting it a distance and converting it back to mechanical and finally thrust vs chemical to mechanical and then thrust is pretty hard to figure with out building one and testing.
By separating the components (genset and electric motor) you can have the genset be powered by a ideally sized engine and run it at its' best efficiency. While you can have an electric motor that spins a large high pitch prop at low RPM.
Now figuring out if all that additional efficiency actually overcomes the inefficiencies of changing chemical to mechanical to electrical transmitting it a distance and converting it back to mechanical and finally thrust vs chemical to mechanical and then thrust is pretty hard to figure with out building one and testing.
Ahhhhh.. another way to store energy is in a capacitor.. A box that holds electricity as electricity instead of holding chemicals that produce electricity on demand.. Google “Eestor” and get some info. The patent is here: http://gristmill.grist.org/story/2008/8/11/155522/905
Apparently, a storage unit of about the capacity of the Tesla battery would only weigh less than 300 pounds instead of the 950 for a chemical battery.. Neat idea if it works.. The neat thing about capacitors is that they can release or take in electricity at very high rates because there is no chemical conversion going on.. Looks like Lockheed and some other gov contractors are looking at these seriously. The problem in the past with capacitor storage was that the self discharge rate was pretty high.. These guys claim to have worked that pretty hard. Energy storage density is still a tenth of diesel, but almost twice that of the lithium ion batts.. Interesting
Right now, this is a MAJOR undertaking with very little gains. In other words diesel is better for a sailboat. It is cheaper and easier to take care of. Image changing $5000 worth of batteries every 5 to 10 years. How much do you use it? What would be the gain in dollars of switching. It is a pipe dream!
Diesel are great engines, the best Jerry, the best!
I am an electrical engineer and can tell from an engineering point it doesn't not make sense. Maybe in new construction, where the batteries are part of the bailiest system, BUT I wouldn't buy one!
Diesel are great engines, the best Jerry, the best!
I am an electrical engineer and can tell from an engineering point it doesn't not make sense. Maybe in new construction, where the batteries are part of the bailiest system, BUT I wouldn't buy one!
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