Tug of War - Electric vs Diesel

[skipmac]

Originally Posted by Kalinowski

Electric seems to makes sense for powering in and out of marinas. With motor regeneration, wind, and flexible solar panels installed on sails (UK sails presently doing this), recharging doesn't seem to be a problem. Of course long distances under power are not viable, but that's what sails are for. Fast motoring is for stink pots anyway. Check out the Systems section of December's Sail magazine, page 33.

In general I much prefer sailing to motoring, to the extent of sailing on and off anchor without starting the engine. But cruising the east coast if you do any of the Intra Coastal Waterway you have to motor. It is also against the rules/regulations/law? to pass through an opening bridge under sail.

I guess I have to confess, as much as I like to sail, the 1000 nm upwind trip from FL to the VI I am sorely tempted to motor sail and get there in half the time.

[valhalla360]

Originally Posted by Kalinowski

Seems as though those that would prefer to power rather than sail have a valid argument. WWSS (what would Slocum say?).

I bet he would say, this awesome. Just turn the key and the engine wisks you away at a brisk pace.

Like most of these silly historical comparisons, most would love to have the modern amenities but they simply couldn't get them. Do you really think capt cook wouldn't have loved a diesel backup on his voyages?

[a64pilot]

Originally Posted by StuM

???????

Care to explain what you really mean by that?

No, I'm not getting into a discussion on semantics


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[valhalla360]

Originally Posted by goat

Quite correct, and as I said, I'm sticking with diesel. However, becalmed, without fuel, 2000 miles from land, which will fill up faster; your fuel tank or your battery bank? As far as I can tell that's the only advantage to electric power until battery and/or solar charging technology catches up. Oh, and the noise...

goat

If you really try, you can always come up with a scenario (there was a lot of paranoia about 2 engine jets crossing oceans but now it's common place). Given the range of a typical modern cruising boat, if you find yourself in that position, you messed up and there are enough ways that you can mess up that you are likely to find anther that gets you in trouble.

We are on the low side of fuel storage and at 60 gal we have close to 3 days motoring at normal cruise speed. If we slow down to say 4kts, that jumps to 5-6 days motoring. A lot of cruising boats have double or triple that range. Being able to add 2-3 miles per day from solar panels just doesn't move the needle.

[EWOL Props]

Don't want to start any new polemic here, so please take it softly, but look at where these guys have arrived with an 1978 boat transformed all electric. They started 1 year ago and are completing the World tour in coming months.
Isn't this the proof that it works ?

Notre position | Eco Sailing Project

For more infos on this specific project:

Eco Sailing Project | Le tour du monde écologique à la voile

We have other working examples...if you have an interest

[K_V_B]

Originally Posted by charliehows

okayyyy...let me get this right; in order to get the same or somewhat less utility as my existing 35 year old diesel, I would replace the diesel engine with a similiar sized or preferably larger diesel generator and add an electric engine as the drive source, complete with all its highly complicated and questionably reliable control systems?

Well, if your engine is still working perfecty you should indeed keep it.
But a few points:

In a diesel-electric system the generator can be way smaller than the engine it replaces.

So for example,
boat a): 40 HP engine, is usually run at cruise at an RPM where it produces only 20 HP.
boat b): 20 kW electric motor and a 15kW genset. (about 20 HP).

Boat b has a much smaller engine, but has indeed some more complexity. However, on boat b) you can now take advantage of the fact that it has ample electriciy available by for example doing away with gas and cooking electric as well.

[StuM]

Originally Posted by K_V_B

Well, if your engine is still working perfecty you should indeed keep it.
But a few points:

In a diesel-electric system the generator can be way smaller than the engine it replaces.

So for example,
boat a): 40 HP engine, is usually run at cruise at an RPM where it produces only 20 HP.
boat b): 20 kW electric motor and a 15kW genset. (about 20 HP).

Boat b has a much smaller engine, but has indeed some more complexity. However, on boat b) you can now take advantage of the fact that it has ample electriciy available by for example doing away with gas and cooking electric as well.

And when you need 40HP to buck wind and current or power off a lee shore where does the power come from?


Motors should be spec'ed to meet peak demand, not " as usually run at cruise".

[valhalla360]

Originally Posted by K_V_B

Well, if your engine is still working perfecty you should indeed keep it.
But a few points:

In a diesel-electric system the generator can be way smaller than the engine it replaces.

So for example,
boat a): 40 HP engine, is usually run at cruise at an RPM where it produces only 20 HP.
boat b): 20 kW electric motor and a 15kW genset. (about 20 HP).

Boat b has a much smaller engine, but has indeed some more complexity. However, on boat b) you can now take advantage of the fact that it has ample electriciy available by for example doing away with gas and cooking electric as well.

If you want an under powered boat, save yourself the complication and just put a 20hp diesel in. Unless you get into towing contests, it will perform just as well.

The reality is around the dock, it's rare to use more than 5-10hp. When power boats use more, it typically has bad results.

[a64pilot]

Extra power would come from the battery bank, just like a hybrid car.
There are hybrid tugs that have worked very well, seems a tug just motors around most of the time and only really pulls hard for short intervals, for this a hybrid seems to work well.
A lot of big ships are of course Diesel electric, largely I believe as you can put the engine where you please. There are advantages and of course disadvantages. But if you don't in the design phase use the advantages, then of course it's not so attractive. Reason
I believe the conversions aren't more popular


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[K_V_B]

Originally Posted by valhalla360

If you want an under powered boat, save yourself the complication and just put a 20hp diesel in. Unless you get into towing contests, it will perform just as well.

The reality is around the dock, it's rare to use more than 5-10hp. When power boats use more, it typically has bad results.

I don't want an underpowered boat. But I don't want an overpowered, smelly boat either... In fact, one of the advantages of doing the maths on electric propulsion is that it really gets you to think on how much (or how little) power you really need.

I've been doing the maths, re costs, weight etc.. And I think that for a new build diesel electric drive can be quite attractive. Basically it would mean that in stead of having a diesel engine, and a generator you would have a electric motor and a generator.

[skipmac]

Originally Posted by valhalla360

The reality is around the dock, it's rare to use more than 5-10hp. When power boats use more, it typically has bad results.

Rare but over the years I have had a few occasions when I needed all the power I had to avoid a problem docking.

The most recent, I came into a marina for fuel where I had never been before. Approaching into the fuel dock I discovered a current almost 3 kts pushing me into an 80' sailboat with a beautiful, perfect, Awlgrip paint job. If I had been equipped with an underpowered engine I would certainly have ended up crunching the side of that boat.

[Terra Nova]

Originally Posted by K_V_B

I don't want an underpowered boat. But I don't want an overpowered, smelly boat...

There have been a couple references to this.

In the hundreds of boats I've been on, the "smelly" ones had waited too long to replace their sanitation hoses, or used seawater to flush. A couple of them had cats aboard. The few that had diesel smell had badly neglected engine maintenance and fuel leaks on very old installations.

[charliehows]

basically, my disagreement with this type of argument is the 'money where your mouth is' aspect. In theory there is no filter for stupid, in practice stupid costs lots of money and tends to leave you on a howling windy lee shore with no effective survival tools.
If I've learned one thing from my many years of mucking around in boats its that experience at sea drives boat designs which one may arrogantly assume one can radically improve at ones peril. Its a slow, steady, considered process and so far, electric engines for small boats are not anywhere near being more efficient than diesel. It may come or it may turn out that small diesels are inherently better for the purpose.

[valhalla360]

Originally Posted by a64pilot

Extra power would come from the battery bank, just like a hybrid car.
There are hybrid tugs that have worked very well, seems a tug just motors around most of the time and only really pulls hard for short intervals, for this a hybrid seems to work well.
A lot of big ships are of course Diesel electric, largely I believe as you can put the engine where you please. There are advantages and of course disadvantages. But if you don't in the design phase use the advantages, then of course it's not so attractive. Reason
I believe the conversions aren't more popular


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If you are outfitting a tug, your argument works. Just cruising about the harbor, they need drastically less HP but for short bursts of 5-10min as they push a big ship around, they need several times as much HP. With a cruising sailboat, peak HP would generally be when fighting a strong current or headwind while bashing into waves. The problem is you typically need that power for an extended period of time at least a 1/2 hr and quite likely multiple hours. Hybrid cars only need peak power for 10-30seconds to accelerate up to speed.

Big ships or trains using diesel electric because building a mechanical transmission to transfer that much power is complicated and expensive. On the small scale of a cruising boat, it's simpler and more efficient to use a mechanical transmission.

[Muckle Flugga]

Originally Posted by Jim Cate

There are so many ways that this sort of comparison can be skewed, either deliberately or through ignorance or chance, that it is meaningless. And as others have already said, even if totally correct, the static bollard pull is not relevant to our sailing/motoring practices.

Waste of bandwidth!

Jim

And yet the tug of war between Alecto and Rattler sealed the fate of the paddle steamers…