Viability of electric only propulsion in 2018 - is there a good option after all?

[Jim Cate]

Originally Posted by OldMan

Day and night? Solar doesn't generate anything at night.


Do you have experience with 500W push a 30' boat @ 2-3kts?

Hmm.... let's see:

500 W installed solar under good conditions of solar input will produce full power for <8 hours a day... let's be generous and say it averages 250 watts for all the 24 hours. That's on the order of 1/3 of a horsepower.

Must be a pretty slippery 30 foot design!

Jim

[StuM]

Originally Posted by Jim Cate

Hmm.... let's see:

500 W installed solar under good conditions of solar input will produce full power for <8 hours a day... let's be generous and say it averages 250 watts for all the 24 hours. That's on the order of 1/3 of a horsepower.

Must be a pretty slippery 30 foot design!

Jim

That's very generous. A common rule of thumb is about 5 hours of full sun equivalent per day which woud yield about 2500 Watt hours. So you are looking at more like 105W or 0.2HP.

[KTP]

In becalmed flat water 500 watts would easily push a boat at 2 to 3 knots.

Probably 100 to 200 watts would push it at 2 knots.

Think about a sculling oar. People are able to get .5 to 1 knot from that and the very maximum a human can sustain is around 100 watts (Lance Armstrong could do 200 watts fully doped up).

[OldMan]

Originally Posted by KTP

In becalmed flat water 500 watts would easily push a boat at 2 to 3 knots.

Probably 100 to 200 watts would push it at 2 knots.

Think about a sculling oar. People are able to get .5 to 1 knot from that and the very maximum a human can sustain is around 100 watts (Lance Armstrong could do 200 watts fully doped up).

maybe a kayak, but not a 30' sailboat

[Jim Cate]

Originally Posted by KTP

In becalmed flat water 500 watts would easily push a boat at 2 to 3 knots.

Probably 100 to 200 watts would push it at 2 knots.

Think about a sculling oar. People are able to get .5 to 1 knot from that and the very maximum a human can sustain is around 100 watts (Lance Armstrong could do 200 watts fully doped up).

I seriously doubt your first statement, and he doesn't have 500 watts continuous to play with... only a small fraction of that, and that's not even considering system losses. Remember, he reckons that it would do the speed day and night, forever. Don't think si

Now, as to your human equivalent thoughts... I think your numbers are quite wrong:

"The average human, at rest, produces around 100 watts of power. ... Over periods of a few minutes (or a few hours in the case of trained athletes), we can comfortably sustain 300-400 watts — and in the case of very short bursts of energy, such as sprinting, some humans can output up to 2,000 watts.Sep 5, 2012 "

So, your sculling oar comparison becomes a bit less telling, doesn't it?

I've moved medium sized cruising boats around in calm conditions with a dinghy using a 3.5 hp outboard. Could get up to a couple of knots eventually, but that's over 2000 watts, a far cry from the postulated small fraction of 500.

So, I remain quite skeptical!

Jim

[KTP]

Originally Posted by Jim Cate

I seriously doubt your first statement, and he doesn't have 500 watts continuous to play with... only a small fraction of that, and that's not even considering system losses. Remember, he reckons that it would do the speed day and night, forever. Don't think si

Now, as to your human equivalent thoughts... I think your numbers are quite wrong:

"The average human, at rest, produces around 100 watts of power. ... Over periods of a few minutes (or a few hours in the case of trained athletes), we can comfortably sustain 300-400 watts — and in the case of very short bursts of energy, such as sprinting, some humans can output up to 2,000 watts.Sep 5, 2012 "

So, your sculling oar comparison becomes a bit less telling, doesn't it?

I've moved medium sized cruising boats around in calm conditions with a dinghy using a 3.5 hp outboard. Could get up to a couple of knots eventually, but that's over 2000 watts, a far cry from the postulated small fraction of 500.

So, I remain quite skeptical!

Jim

No, there are people who scull for hours and claim to maintain 0.5 to 1 knot, which means unless they are super buff, they are not putting out 300 to 400 watts. 100 or *maybe* 150 watts.

A 3.5hp outboard with a tiny prop is much more inefficient than a electric inboard brushless motor turning a very large prop slowly. I bet the inboard electric turning a big prop slowly is 3x more efficient, so you would see a couple of knots from 2000/3 or ~750 watts. I have driven a 4000 pound sailboat at 2 knots with a Torqeedo 1003 at 80 watts in very flat water. I think 500 watts turning a big prop would move a 5 ton 30 to 32 foot sailboat at 2 knots easy. Actually when we get back to our boat and I finish up our system, I will be able to let you know exactly how many watts will push a 14,000 pound 34 foot Pacific Seacraft. I have shunts and meters to log power, rpm, speed. Just waiting on the gale force winds to die down.

[KTP]

Here is a chart of power needed to push a 36 foot Pearson from Sailing Uma. I think it was something like 250 watts were needed to push it at 2.3 knots.

You can see that as you approach something like 7 knots you need a boatload of power, but for slow speeds you don't need much at all.

[Jim Cate]

I think 500 watts turning a big prop would move a 5 ton 30 to 32 foot sailboat at 2 knots easy.

But, once again, the poster will not have 500 watts 24/7... not even close. So I still maintain that his claim of driving the boat at 2-3 knots forever are bogus.

If you don't agree, that's ok with me, but it doesn't make him right.

And now I think we've beaten this horse enough. He's unlikely to build the boat to those specs and so we'll likely never have proof one way or the other.

Jim

[KTP]

No you are right about that. 500 watts of panels would probably be lucky to produce 3kW-h per day.

We are aiming to have a lot more than that, something around 1200 watts. We would be lucky though to get 4kW-h per day with shading and such. I guess if the sails are down because there is zero wind, we might a bit more.

So maybe you could motor at 2 to 3 knots for about 6 hours every 24 hours using just solar. 12 to 18 nm per day at that rate. I guess it would be better than nothing.

[Matt Johnson]

KTP- Have you ever cruised on a sailboat full time? Like Uma, it's very hard to understand what you are giving up with the conversion without diesel experience. Maybe ignorance is bliss (not the bad kind of ignorance). But I'd hate to think of all the experiences I would have missed over the years had I not been able to travel to some spots that required motoring.

I don't think I've seen an experienced monohull cruiser convert from a diesel to electric... or even one that think it's a good idea with current technology.

There are very few flat calm conditions when cruising. Even windless days have swells large enough to prevent most boats from obtaining 2-3 knots with so little power spent. Again, I'm sure you'll be happy with your conversion, but I really think you'd be happier with a diesel.

[CatNewBee]

That's ridiculous.

Do you have an idea how many watts is nessecary to overcome windage of a 30ft boat at let's say 6kn on the bow? A tiny inefficient wind generator is able to collect this out of the wind, a boat has a larger surface exposed, then there is current, what is much stronger.

You may be able to go 1-2kn downwind with 500W, but no way to push against the wind and current.

[KTP]

I thought we were discussing days with no wind and flat water. I agree that with swells and such on the open ocean that even with no wind you might find it hard to get 2 knots with only 500 watts but on flat water it is easy enough with no wind.

So those of you who full time and do a major crossing of 3000+ miles, do you run the diesel the whole trip??? That is a large amount of fuel, right? What do you do if there are weeks of no wind?

[KTP]

Originally Posted by funjohnson

I don't think I've seen an experienced monohull cruiser convert from a diesel to electric... or even one that think it's a good idea with current technology.

I do not really see the difference between cruising with electric and cruising with no engine at all, and I know there are experienced monohull cruisers who do without an engine. As long as you realize the electric propulsion is just there to get you in and out of moorings and *maybe* help you point a bit closer to the wind (and maybe up to a kilowatt of regen according to some accounts if you have strong favorable winds).

I think I could be really happy with a 65 foot trawler with twin diesels and a 5000 gallon tank though. I would just get some noise cancelling headphones and be able to go anywhere without a care for wind and current.

[Augi]

Originally Posted by CaptainIglo

This https://youtu.be/-uTy5owBsUE is a pretty good analysis of what it would mean to dispense with Diesel engines and go fully electric for propulsion.

The tldr is electric range 20nm with 4 Tesla power walls (which aren’t marine certified but are used for thought experiments sake) versus 800nm with the 700 liter diesel tank of the leopard 45. (Its 800nm at 5 knots or 400nm at close to 8 knots, more on that later)

OUCH!

Double ouch because 4 Tesla power walls provide enough power to supply 3 single family homes with enough power for 24 hours.

That really is a shame, it seems to me that not only is electric a more elegant solution (more quiet, no smelly exhaust) but has so many benefits. Feel free to correct me if I’m wrong or missing something

- maintenance on a electric drive train is less complicated because they are mechanically much simpler, engines last longer
- engines like the oceanvolt servoprop can double as hydrogenerators when not in use without clumsy mechanisms to lower them into the water (I’m looking at you watt&more)
- having a large battery bank for engines provides a big comfort bonus and gives you a lifestyle close to onshore living

But... Is there another option that would give a similar range than Diesel engines?

I did some quick napkin math.

The above mentioned oceanvolt Servoprop has a 15kw engine. According to some online resources a 20kw generator (so we have some spare capacity) uses about 1.6 gallons/ 6.4 liters per hour at full load. That means you could run it for about 109 hours on above mentioned 700 liter tank.

Ocean volt specs say the max Speed of a servo prop on a 45 foot multihull is about 8.5 knots.

Let’s assume 8 knots sustained is realistic. This would give you a range of 872 nm - which is not only a superior range to diesel but at almost twice the speed on top of it. And the 872nm are not the hard limit of the range but only what you could do in “one go”. You would still be able to do 20nm indefinitely per recharge cycle if you have wind to hydro generate or solar.

So is hybrid the way to go? Even if running a single generator still means relying on diesel, it is easier, quieter, requires less maintenance than running 2 large Diesel engines

Certainly, the initial purchasing cost is higher but you would likely find the 20nm range provided by hydro generated power sufficient in most cases for things like getting back to the Marina or get into the wind so this would amortize against reduced diesel cost.

Am I missing something?

Shouldn’t this be the holy grail of sailing propulsion?

Below is the text of an email update sent to people on Dick Vermeulen's of Maine Cat Catamaran's email list. Dick will likely build you a boat with whatever auxiliary propulsion system you want. For a hybrid system he is advocating a system built by E-Tech Electric Drives. Until recently he was suggesting Torqueedo for an electric system. Attached is E-Tech's Catalog.

No, I am not Dick Vermeulen's shill.

""METS 2018 EXHIBTION HALL 2 OF 12 - INCREDIBLE
Very successful trip in November to Amsterdam and METS trade show, the world’s largest marine trade show. Lynn and I spent most of our time at the show in hall 7 at the E-nnovation Lab showcasing the newest electric and hybrid marine propulsion systems. In the main hall (photo above) we had the opportunity to talk at length with representatives from Victron, Whisper Power and E-Tech. We had met the owner of E-Tech, Grigorij Shenkman, at the Annapolis Sailboat in October. We had continued our interest in their unique electric drives and asked for a test ride while in Amsterdam during the show.

With the wind up and the temperature in the low 50’s we hopped aboard a 12,000 lb. displacement canal tour boat for a test ride out into the Zuider Zee. If you are familiar with the hull shape of Amsterdam canal boats you know these are not high performance boats. Running at 5 knots - creating a substantial bow wave - we were using 25 amps from the 48 volt Li-ion battery bank. That is only 1200 watts. Virtually silent, no vibration and carrying on conversation normally.

During our tour of the E-Tech factory near Warsaw they had two E-Tech motors connected shaft to shaft with measuring equipment for rpms and electrical power output. Spinning our 4.3 kW motor at 400 rpms we saw 250 watts produced. With twin motors down on the new MC 38 LS-E - sailing at 9 knots - we calculated we can hydro-generate over 1,000 watts per hour to add back into our 10,240 Wh Li-ion battery bank. We are making our own fuel.

We have found a better solution for the auxiliary powering and charging systems on all future Maine Cat performance sailing cats.


E-TECH ELECTRIC DRIVES - MAKING EVERY BOAT BETTER


Why Electric Motors are better than internal combustion


Counter rotating props - no prop walk
No exhaust bubbles at prop - eliminating engine cavitation and poor powering in reverse
Instant high torque - better maneuvering in close quarters
Better propeller efficiency, larger diameter, more blade area, smaller hub
Operates at very low RPM for more precise handling in docking situations
No maintenance - no oil changes, no impeller, no carburetor fouling and cleaning
No smell - no pollution - no vibration - virtually silent running
Hydro- generate huge amount of electric while sailing to use for ship systems
Air conditioning all night long without running a generator
Longer life - no circulating sea water through engine cooling which eventually clog
Same zero drag when lifted clear of the water on power trim and tilt bracket
No reason to stop on a long distance cruise for fuel
In hybrid mode longer range under power than outboards, 500 nm
No engine control cables to corrode or mechanical level shifter to maintain
Lighter weight


Maine Cat now E-Tech Representative for North America

Maine Cat is proud to announce we are the North American representative for the E-Tech rugged electric drive systems. We can custom design an electric propulsion system for your boat whether you are looking retractable outboard motors like we are using on the new MC 38 LS-E or shaft drive inboards, pods or steerable outboards. E-Tech can custom build an electric drive to fit your boat and your cruising agenda. Maine Cat can engineer the system and supply highly efficient solar panels, chargers, Li-ion batteries, and a light-weight diesel genset. For boaters looking for powerful hydro-generators we can also supply a very affordable efficient system. ""

[Dockhead]

Originally Posted by KTP

I thought we were discussing days with no wind and flat water. I agree that with swells and such on the open ocean that even with no wind you might find it hard to get 2 knots with only 500 watts but on flat water it is easy enough with no wind.

So those of you who full time and do a major crossing of 3000+ miles, do you run the diesel the whole trip??? That is a large amount of fuel, right? What do you do if there are weeks of no wind?

Days of no wind and flat water almost do not exist in the ocean.


I did a trip of 4000 miles this summer, part of it in the Arctic Ocean. Here is how I used the diesel:


1. Light wind from behind, motorsailing.


2. Light wind on the nose, motoring.


3. No wind, motoring.


I did not use the diesel most of the trip -- we had plenty of good wind, and several days over 200 miles.



I ran the diesel once 4 days and nights straight -- a calm counts as a weather window in the Arctic, and a very precious one in latitudes where it can blow F9 for weeks.


Running the diesel in the calm, and maintaining about 7 knots, so roughly 160 miles a day. You wouldn't want to do less, or you're hanging about waiting for the next storm.