Electric Propulsion

[DeepFrz]

But a efficient genset/ hybrid system is still more efficient and will return better consumption then a straight diesel.

Has not proven to do so yet. Do you have any published scientific papers that you can reference? Nordhavn tried it and spent a lot of money trying to make it work and will not try it again for a long time, in my estimation. There have been many failed attempts to produce a hybrid system on a cruiser. I would really be interested in reading 3rd party scientific study that says I am wrong.

[EAS]

I love our electric sailboat too. The new Sevcon Gen 4 is amazing. We reach hull speed easily. The system is 48V 170A max power (capable of 250A max!). Regen charges the batteries at 4-5A in at 6-7knot sailing with good wind. We should be able to increase the re-gen capability through motor programming and by adding a dripless stuffing box. Estimated speed/power numbers. The boat will motor at 2-3Knots (10Amp draw) 3-4Knots (20amp draw) 4-5knots (35A) 5-6 knots (50A) 7knot hull speed (75A). I will have some exact figures after the next sail. We have 8x100AH AGM cells and A Tetrapod 12V lithium house battery system. AGM's will soon to be upgraded to LiFePo4. Range from the AGM's has been better than expected. with the 200AH 48V pack 10.5 hours cruising at 3-4knot (48V@15A/720W) would use 80% of the battery pack. Real world will likely be more like 7-8 hours at 3-4 knots.

[donradcliffe]

I was very impressed the solar/electric propulsion used on the pacific voyagers canoes. The boats are 73 ft long, with a panel array in the stern which is maybe 10x15 ft. They can motor up to 5 knots for 2 hours before they need a recharge, which is plenty for maneuvering around harbors. Propulsion units are pods between the hulls, and swing up for drag-free sailing.

The canoes have made it from New Zealand so far, and are about halfway from Hawaii to San Francisco today.

[goboatingnow]

Originally Posted by 44'cruisingcat

The electric torque talk is nonsense - how can you have maximum torque at zero rpm? Or 1 rpm or 5 rpm? You're supposedly applying the MAXIMUM torque the motor is capable of producing to the propellor, yet it's only turning at 0 or 1 or 5 rpm? Nonsense. Either that or it's a very weak motor.

That stuff applies to cars, but not boats.

Fact is a diesel (or petrol) engine can turn the prop when it's idling. Put it in gear, and it doesn't stall.

No it's more complicated. For exAmple for maximum acceleration max torque should be available low down in the rev range something a diesel is poor at. Yes stall torque is never an issue but that doesn't mean that it isn't available or useful.

Dave

[daddle]

Originally Posted by fastcat435

You are right of course 0 rpm is also 0 torque however from 1 rpm up to the max rpm setting the torque level is almost the same. With a sailing vessel we already have the way to convert wind energy in to electric energy and in a very efficient way with out burning fossil fuel or raising Co2 levels. We fill our electric tanks ( batteries ) with wind and solar power.

No, you don't understand electric motors. They have maximum torque at low RPMs, yes. But the torque decreases linearly with increasing RPM. Torque reaches zero at whatever RPM they freewheel at. You might counteract that by increasing the voltage but the motor will probably melt. That's how they work. What the have is nearly constant power.

Second, no boat can carry enough solar or wind generation capacity to effectively cruise. Not yet.

[daddle]

[QUOTE=goboatingnow;733876]What nonsense. Torque is a measure of angular force. Max torque at zero rpm is not zero HP that's only a function of the internal combustion engine./QUOTE]

Ummm. No. Power is the product of force and distance. Fact not opinion. If the motor isn't spinning something it's producing zero power. It's all heat in the motor.

You are correct the an electric motor is a great way to spin a propeller. With a variable pitch propeller it would be even better. But the problem is not with the electric motor, it's with generating the electricity. Posters here a writing about maneuvering in a marina. That is about 1% of the use of a cruising boat's motor. What a cruiser needs is some large part of an engine's power for many hours, perhaps days on end. You are not going to beat a properly sized and properly propped diesel at this task. You are not. You would see diesel electric engines in long haul trucks if that were the case. You don't.

My old boat had a $8000 20hp diesel. She was 16,000 pounds displacement. To do the Baja Bash, a 750nm windward chore, I would set 75% power at Cabo San Lucas and 8 days later, set idle at San Diego. One quick fuel stop at halfway. Your electric system is not going to do that. That's an energy expenditure at the propeller of over 2 megawatt-hours or 45,000 Amp-hours on your 48V battery bank.

Cruiser's who arrive here in Palau from south of the equator do comparable amounts of motoring because the ITCZ makes sailing nearly impossible.

Explain how I might even accomplish even a fraction of that with an electric system. What would it cost?

A lithium ion battery, as wonderful as it is, has only 2% the energy content of the same weight of diesel fuel. So my 500 pounds of diesel fuel might be replaced with 14 tons of batteries? That I then must charge up?

My opinion: Shameless promotion. Salesmanship. Self-delusion. That's what we've got going on in this thread.

[44'cruisingcat]

You're right of course Daddle. But electric motors can reach maximum (rated) power at zero rpm - that's because the power of an electric motor is not measured by the power it produces, like internal combustion engines are, but electrics are rated by how much power they CONSUME. So a stalled electric motor could be consuming maximum power (for a short time) while actually producing none.

[LauderBoy]

Originally Posted by daddle

A lithium ion battery, as wonderful as it is, has only 2% the energy content of the same weight of diesel fuel. So my 500 pounds of diesel fuel might be replaced with 14 tons of batteries? That I then must charge up?

My opinion: Shameless promotion. Salesmanship. Self-delusion. That's what we've got going on in this thread.

I don't hear anyone saying energy storage isn't an issue. But not everyone cruises in a way that requires motoring. For some people if there's no wind they'll just wait til there is.

And for long voyages it can still work. 500 watt solar would give around 60 AH @ 48v per day? Prop regen might see 20-40 amps on a good wind day. That "budget" could then be spent on no wind days for 3 knots of motoring all day. Though if you have several days without wind, you won't be making much headway unless you have a gen.

It's a pick your poison issue. Can you deal with a lack of multi-day motoring? If so, electric sounds very nice. No maintenance, fuel independence, far fewer things to go wrong, no mess or noise.

If you need multi-day motoring and the ability to recharge fuel in minutes instead of days, forget it. You're stuck with fossils and all the support systems needed to maintain your engine: cooling, fuel filtering, lubrication, electric starting system.

[fastcat435]

Originally Posted by LauderBoy

I don't hear anyone saying energy storage isn't an issue. But not everyone cruises in a way that requires motoring. For some people if there's no wind they'll just wait til there is.

And for long voyages it can still work. 500 watt solar would give around 60 AH @ 48v per day? Prop regen might see 20-40 amps on a good wind day. That "budget" could then be spent on no wind days for 3 knots of motoring all day. Though if you have several days without wind, you won't be making much headway unless you have a gen.

It's a pick your poison issue. Can you deal with a lack of multi-day motoring? If so, electric sounds very nice. No maintenance, fuel independence, far fewer things to go wrong, no mess or noise.

If you need multi-day motoring and the ability to recharge fuel in minutes instead of days, forget it. You're stuck with fossils and all the support systems needed to maintain your engine: cooling, fuel filtering, lubrication, electric starting system.

Storing electric energy is always an issue however with a sailboat that can regenerate while sailing it is not as big an issue.

What range is needed for a sailboat under engine or electric motor power is what it boils down to.
Depending on the type and size of battery power on board the all electric range can be as much as 50 NM.
Not much off course but we are sailors, with a back up generator ( range extender ) this range can be extended.

there are many advantages and disadvantages in going electric with regenerating capability.
first the disadvantages.

1. Cost, more expensive to purchase and install.
2. all electric range (limited)
3. weight if AGM or gell batteries are chosen. ( much higher )
4. complexity, more complex than the standard diesel installation.
5. depending on the type of installation it can take up more space.

advantages

1. No or very limited fuel consumption depending on having a backup generator on board ( recommended )
2. even with the generator running lower fuel consumption.
3. capable of filling the batteries while sailing or with sun or wind or shore power
4. almost no noise, no smoke or sooth
5. Lots of electric power on board to do all needed

off course there are more advantages or disadvantages but above are the major ones

having a electric propulsion system with out being able to regenerate while sailing is only useful for day trips where at night the batteries are charged true shore power.

[capn_billl]

Right now electric propulsion is a technology in transition. I am saying that as a technology insider with personal experience. The arguements about the RPM or torque of an electric motor is specious. The Motor does not produce energy like an I.C.E does it merely converts one form of energy to another. what you put in is what you get out.

The torque curve of ICE is small at low RPM because most of the energy produce by the engine is used to power it's own functions, (move the pistons, alternator, cooling, etc...). at higher RPM it has more power left over to drive a load up to max RPM at which it will suffer a mechanical failure.

Fact is ICE will some day go the way of the steam engine and for the same reason.

The electric motor which comes in several forms now ranges from series wound, shunt wound, compound wound, to DC brushless, servo motors. Up to now the main limitations of electric motors is the cost and complexity of controlling them.

recent breakthroughs in semiconductor power controllers, (digital signal processors, IGBT's, and high power analog IC's), have overcome these limitations. Now it is possible to control either an AC or DC motor from micromotors used in robotics to a main drive capable of moving a container ship.

These motors convert electrical energy to mechanical so efficiently they actually overcome the losses from converting fuel to electricity in the first place. (most modern freighters use diesel electric drives, the US navy is converting it's warships), they gain a 2%-18% in efficiency with corresponding gains in top speed, and acceleration.

These gains do not come without a cost. 1 added complexity of two systems 1 to produce the electricity, (power generation gains come from running diesels at most efficient RPM. We often talk of Horsepower, and torque curves on ICE engines, but seldon talk about efficiency curves, (the HP produced vs fuel burn at that RPM).

fact is ICE engines have a very narrow band that they operate at peak efficiency. Unfortunately in real world you seldom want to travel at that specific speed, (to maximize time in that band cars use transmissions with many gears, a few years ago a 3 speed was common, now 5 is more common with a corresponding increase in rated MPG caused by more time at that RPM).

The big advantage of hybrid power is the ICE can spend all of its time, at it's most efficient RPM generating electric power and shut off when it's not needed, (no longer wasting fuel at idle). Then when the batteries are full the electric can run with a sophisticated electronic controller to give the motor that precise voltage and current it needs to operate at any RPM with ANY load. As long as you have electricity you have as much or as little power as you need.

The big downside Battery technology has no where near caught up with the rest of the technology, lead acid is the lowest energy reaction there is, Lithium is still too new, (and expensive). Other technologies have been bought up by companies that either have gone out of business, or have no interest in developing it, (see chevron/cobasys).

SO that leaves you either running a genset, (it still gives you more flexibility), solar, (you would need an array bigger than your boat), wind, (see solar), or some combination.

Electric drive still has a long way to go to perfection, but the ease of driving your boat with the same convenience of flipping on a light, ....is priceless.

[DeepFrz]

They work very well in large ships, not so well in cruising boats. They are very nice for local boating in small boats as well. Its getting that magic to work for a cruiser that, so far, has been impossible to achieve.

[fastcat435]

All I can say is come and join for a sail ( and motor experience )
So far 3 independent sailing magazine's have tested our system and found it to work well.
Yachting monthly September issue 2010
Yacht magazine January issue 2011
Waterkampioen May issue 2011

[capn_billl]

Originally Posted by DeepFrz

They work very well in large ships, not so well in cruising boats. They are very nice for local boating in small boats as well. Its getting that magic to work for a cruiser that, so far, has been impossible to achieve.

Not impossible, the magic of scaling has worked to move freight train sized systems into auto's, it will soon work to scale freighter sized systems into cruisers.

The systems are out there, they are still a little expensive. Time and volume will bring the cost down.

For the DIY it is now possible to adapt a motor from another purpose, (fork lift or other), or buy a purpose built marine electric drive, and build a small system that will propel your boat at least as well as a gas outboard, (with a simular range as an outboard tank).

Or build something slightly bigger, (speed, range, or low cost/weight) pick two out of the three.


The big advantage is flexibility, anything can be turned into electricity. I saw in a third world country a stream that had been diverted down a well to turn a propeller running a small perm magnet generator that powered all of the lights in the area.

Electric motors can be extremely small for the HP, the big limitation is cooling, (waste heat from eddy currents, and base resistance). The rated HP from a motor, (IE forklift), assumes it is buried in the guts of the forklift with no cooling and operated 24 hours per day under full load, the motor is oversized to dissipate this heat through cunduction. Add external cooling, (fans, water jacket, etc...), and the rated HP can be multiplied by the amount of cooling, 5X or even 10X. Add an optimized waveform to decrease eddy currents, and wasted electricity, and it can be multiplied again.

I have seen a 2 HP motor used in aircraft the size of your fist. Compare to the 1 HP under your washing machine.

[jkleins]

Thanks Capn_bill for some perspective.

I will disagree that it has been impossible to achieve. We have posters on this very forum that are doing it successfully showing that it is not "impossible".

I do agree that we don't have a good commercial alternative to going out and buying a Yanmar and putting it in a boat that is already built for a Yanmar, but that is more about the size of the market and the ease of penetration then it is about the technology. I have no doubt that if Yanmar wanted to spend the money to get into this market they could and would be successful. They probably couldn't be profitable though and that is the crux of the problem. It is not the torque or the energy density or any of the other things we are arguing about.

The market for this technology is small and not so likely to get bigger that a company can do what Toyota did in cars. If Yanmar took the losses that Toyota had on the Prius before they started selling enough to turn a profit they would be out of business.

If one was to design a sailboat from the ground up with places in the full keel for large traction batteries (like Steve Dashew has been using successfully on his boats for years) instead of lead ballast and a nice space for the electric motor and a separate space for a nice sized generator you could put together a system that would be effective and economical. You couldn't put that together cheaply or try to fit it in the same space as we already put our diesel propulsion engines. This will come with time but I think it will be a long time simply because there are not enough new boats being built that even a significant percentage of those opting for hybrids would hardly make a noticeable dent in the market.

Threads like this will continue almost unchanged until then because we will always be comparing commercial systems versus somebody's one-off build that no one else can reproduce. When these systems are touted by a vendor we won't believe them because they are "just trying to sell something" and when by a user they will give up after being attacked by the naysayers because they don't care enough about convincing people to get into it. They will just be enjoying their electric/hybrid boat and using the blender whenever they want to.

Jim

[Billy Higgins]

LauderBoy is on the right track - it all depends on the type of cruising you do. My first ocean boat had no engine at all and with her I sailed 7,000 miles and crossed the Atlantic. When there was no wind, I waited. It's not like life stops. So I think this forum is divided into those who prefer all the mod-cons, and really have not yet learned to live slowly even while out sailing - which is surely the worlds second slowest sport (curling is first). The other group is those who are probably more in tune with the wind and the sea and live a slower, possibly more aware life.

It won't supprise you to know I am planning for a limited range 48v electric motor. Charging to be solar and wind. I cheerfully accept those limitations.

Thanks to all in this forum who continue to provide technical info.