Electric propulsion in the future

[Lindsaymcm]

Kia Ora (greetings) from New Zealand, where I own a replica classic 33-foot launch powered by a 39hp Lombardini diesel which drives her at 8 knots burning 3.5 lph for a range of approx 600 nm.

Looking ahead 20-30years to the time when the engine may need to be replaced I’m wondering if electric propulsion may be feasible by then.

It seems to me that if electric cars are already capable of 300-400km range, and buses can already run all day on batteries, and both ferries and heavy vehicles are all in development, then the rapid pace of change suggests that by 2040 a small diesel could be replaced by sparky.

Thoughts?

[Sandy Frank]

It all comes down to recharge rate (sources) and storage density. It looks like you have 75 hours of run time on a 40hp?

Convert the hp to KWh and you have 30 KWh (x) 75 running hours for 2250 KW of energy storage in that diesel tank. The equivalent in 280ah lifepo4 batteries is about 700 batteries. That is just storage, not even considering charging rates.

In 2040? Sure. Whatever starts during American big rig trucks will likely become the powerplant for pleasure craft. I would bet hydrogen, but who knows.

But I had a drink or several and could be hilariously wrong.

[Mike Burch]

Originally Posted by Sandy Frank

It all comes down to recharge rate (sources) and storage density. It looks like you have 75 hours of run time on a 40hp?

Convert the hp to KWh and you have 30 KWh (x) 75 running hours for 2250 KW of energy storage in that diesel tank. The equivalent in 280ah lifepo4 batteries is about 700 batteries. That is just storage, not even considering charging rates.

In 2040? Sure. Whatever starts during American big rig trucks will likely become the powerplant for pleasure craft. I would bet hydrogen, but who knows.

But I had a drink or several and could be hilariously wrong.

700 batteries @ 0.28KwH each equals 196KwH. I don't under stand how you get 700? I make it 8,036 LiFePo4 batteries, which you would need to round up to perhaps 10,000 to avoid completely discharging them. And then the weight would mean that you would be powering a submarine...



It's still to early in the day for me to have had a drink (at least, of the spirituous or fermented persuasion), but I guess I too could be hilariously wrong.


I am impressed by Lindsay's claim of burning only 3.5 litres an hour at 8 knots in something with a waterline length in the vicinity of only 30 feet. That's a speed/length ratio of 1.46, which is very high, and a fuel burn of less than half a litre per knot-hour at that ratio implies a remarkably efficient hull design.

[Lindsaymcm]

I am impressed by Lindsay's claim of burning only 3.5 litres an hour at 8 knots in something with a waterline length in the vicinity of only 30 feet. That's a speed/length ratio of 1.46, which is very high, and a fuel burn of less than half a litre per knot-hour at that ratio implies a remarkably efficient hull design.[/QUOTE]

Yeah it’s a 1912 design of a type known here as a “settler’s launch”, originally powered with a c.20hp petrol engine. Very narrow beam (2.4m) and very economical.

[Bill Seal]

KW is like HP
KWH is like gallons of fuel.
You don't say "how far can you go on 140 horsepower, or "how fast can you go on a gallon of gas"

[sailingchiro]

Not yet. But, super lithium batteries are offering some options in the future. But, those batteries need to be charged. Solar or wind will not be able to keep these batteries charged and a generator will be needed. In the future (5-7 years) it is promising to run genset for 3-4 hours and run electric motors for 24 hours but the wires and genset would be massive but doable.

Currently, it is easier to pump energy into a tank than charge batteries. They are designing cars that will drive 600 miles on one charge. I would imagine the technology will get to marine industry in 5 years or longer. The question: are the progressives going to win the war against oil or is the electric propulsion be cost effective. Either way, it will cost us much more in the future in the current climate. Of course the climate can change.

[CFS Klopas]

This is a production yacht that claims to run 100 mi/d indefinitely on solar. It has an optional inflatable kite to extend that.
https://yachtharbour.com/news/silent...128?src=_pos_4

[StuM]

Originally Posted by CFS Klopas

This is a production yacht that claims to run 100 mi/d indefinitely on solar. It has an optional inflatable kite to extend that.
https://yachtharbour.com/news/silent...128?src=_pos_4

It has 17kW of solar. (42 x 400W panels? ) That's about 85 square meters of panels (900 square feet for those who don't grok metric ) !

[valhalla360]

Originally Posted by Lindsaymcm

It seems to me that if electric cars are already capable of 300-400km range, and buses can already run all day on batteries, and both ferries and heavy vehicles are all in development, then the rapid pace of change suggests that by 2040 a small diesel could be replaced by sparky.

Thoughts?

What you have to keep in mind is propulsion of cars and even more so city busses, is a wildly different use case. The rated ranges assume significant low speed city driving with lots of stops and starts.

If you can feed an electric motor, it easily beats out ICE but feeding it is the problem.

With cars and city busses, they take advantage of the operating regime:
- When braking, they recover power that would otherwise be lost.
- Average speeds are low and thus wind resistance is minimal. When you take those cars up to 75mph freeway driving, the range drops substantially.
- Even at highway speeds a small aerodynamic car only takes around 30kw to maintain speed, so 3hr range with 90kwh battery pack, gets you 210miles.

A displacement cruising boat simply gets up to speed and stays there using constant HP to fight the drag from the wind and water.
- If it takes 20kw to maintain cruising speed of say 7kts, even 180kwh battery bank will only get you 56miles. Fight a headwind or current and that can easily drop by half or more.

If you look at the Silent Yacht website, they don't put speed and range together. To maintain 100miles per day, you have to drop back to something like 4kts speed. Take it up to a more expected 7-8kt cruise speed and you will be lucky to get 1/4 of that range...and this is on a fairly extreme design.

Short of a major leap in battery technology, electric comes with major downsides. You can do it but it's expensive and less capable.

[danstanford]

Originally Posted by Lindsaymcm

Kia Ora (greetings) from New Zealand, where I own a replica classic 33-foot launch powered by a 39hp Lombardini diesel which drives her at 8 knots burning 3.5 lph for a range of approx 600 nm.

Looking ahead 20-30years to the time when the engine may need to be replaced I’m wondering if electric propulsion may be feasible by then.

It seems to me that if electric cars are already capable of 300-400km range, and buses can already run all day on batteries, and both ferries and heavy vehicles are all in development, then the rapid pace of change suggests that by 2040 a small diesel could be replaced by sparky.

Thoughts?

Based on the commercial opportunity and resultant effort, energy storage will continue to increase in density and decrease in cost and recharge time.

The real question is your use case. I have an electric sailboat and my use case is generally motoring from my slip out to open water whereupon I can sail to my heart's content then motor back in and connect to power to re-charge. I have about a 20 nm range and it has been perfect for every day of use in the 3 years I have owned her.

If I had to go places more than 15 nm away with a strict weather independent schedule my use case would not be suitable. Adding generation to the package would solve almost all the use cases possible and that is what I have done with a suitcase generator I take only on long trips.

One of the things I find aggravating is the electric haters decrying the suitability of electric motors for any solution in a boat. I am not sure if it is defensiveness or lack of curiosity but it isn't helping the discussion. Frequently some of these people dismiss the auxiliary generator option as proof the concept is flawed but I would see these same people with fuel cans tied to their boats as a range extender!

[GordMay]

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and under 3.4 atmospheres of pressure.

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[Pete7]

Originally Posted by danstanford

One of the things I find aggravating is the electric haters decrying the suitability of electric motors for any solution in a boat. I am not sure if it is defensiveness or lack of curiosity but it isn't helping the discussion. Frequently some of these people dismiss the auxiliary generator option as proof the concept is flawed but I would see these same people with fuel cans tied to their boats as a range extender!

I am quite interested in swopping to electric propulsion as the Volvo 2003 is now 34 years old and takes some nursing. Electric Yacht did a forecast for me recently which fits in with what I thought we could achieve. 150w of regen possible above 5 knots a bonus, but means a fixed prop constantly turning. The alternative is a feathering prop which is more attractive.

So if you have 10 - 14Kw of battery capacity and don't use it for propulsion because you have been sailing, then it could be used for something else, like cooking perhaps? However, the one problem I can't really solve is heating. At 50'N we have run the heater in August before now, never mind early Spring or winter time. Looks like diesel heating will have to stay a while.

Pete

[valhalla360]

Originally Posted by danstanford

One of the things I find aggravating is the electric haters decrying the suitability of electric motors for any solution in a boat. I am not sure if it is defensiveness or lack of curiosity but it isn't helping the discussion. Frequently some of these people dismiss the auxiliary generator option as proof the concept is flawed but I would see these same people with fuel cans tied to their boats as a range extender!

I would love a viable electric propulsion system. Electric motors are simply better.

What aggravates me is the unicorn fart proponents who refuse to run the actual numbers.

Sure you can use a generator to charge the batteries but it's more efficient to just connect the ICE directly to the prop shaft.

Electric if viable now if you only need power to get in and out of port and are willing to sail regardless of conditions otherwise. The problem is 90% of cruisers don't do that when coastal cruising and the rare cruiser who does sail in all conditions, doesn't use much diesel anyway, so they aren't gaining much and killing the resale of the boat.

I think for a low speed dingy (vs having a 2hp outboard), electric propulsion is viable.

I also think for canal cruisers it could be viable. Often there is a speed limit well below hull speed and you spend a lot of time not moving as you go thru locks, so it takes less power and significant periods of time, the motors are drawing nothing...plus depending on the waterway, there is often access to power outlets, so you aren't entirely dependent on solar which has significant limitations.

[misfits]

Originally Posted by Pete7

So if you have 10 - 14Kw of battery capacity and don't use it for propulsion because you have been sailing, then it could be used for something else, like cooking perhaps?
Pete

I use my 48v propulsion bank to power up a 1000 watt 48v dc water heater element. I use my electric motor very little, prefer to sail. I also have a separate 12v house bank. I'm on a mooring or hanging out on the hook so I rely on the solar system to keep everything powered. It's worked out very well for the way I presently use my boat. I pretty much liveaboard her for 10-12 weeks during the summer.
I also have a suitcase generator, ran it once last season.

I am a seasonal boater up in Maine & have considered what implications I'd face if I decided to head south for a winter. As the sun gets lower in the sky with less daylight hours, if I had to rely on my auxiliary motor, (ICW) I suspect my solar system would not be capable of sustaining the propulsion bank & I'd be forced to use the generator.

[wholybee]

Originally Posted by Sandy Frank

It all comes down to recharge rate (sources) and storage density. It looks like you have 75 hours of run time on a 40hp?

Convert the hp to KWh and you have 30 KWh (x) 75 running hours for 2250 KW of energy storage in that diesel tank. The equivalent in 280ah lifepo4 batteries is about 700 batteries. That is just storage, not even considering charging rates.

In 2040? Sure. Whatever starts during American big rig trucks will likely become the powerplant for pleasure craft. I would bet hydrogen, but who knows.

But I had a drink or several and could be hilariously wrong.

Even with a 40hp motor, at cruising speeds he is probably only using about 15HP, or about 10kW. 750kWh for 75 hours. Each 280Ah cell is .896kWh, for a total of 837cells.

For a more realistic system, most people will not run for more than 12 hours at a time. That would be 120kWh, or 143 cells. That would give you a good day on the water (maybe a weekend if you anchor someplace) starting and ending at the dock to recharge from shore power.