Switched to Electric

[Mark Morwood]

Is there some advantage to that over a diesel ICE? I can't think of anything compelling, though I can think of many compelling disadvantages.

Operationally - not really, other than a clean exhaust. Environmentally - yes.

No CO2 footprint in the fuel, assuming you use green hydrogen generated using renewables rather than blue hydrogen produced from natural gas.

Probably more likely to use hydrogen to power a fuel cell connected to an electric motor than in an ICE. Even then, storage for small forms of transport like cars and boats is likely to favour batteries over hydrogen.

[Edit: Sorry, replied to this without checking how far behind I was in the thread. All of what I said has been covered before]

 

[floater]

Some client packs are well past 10 years in use now and still going.

that's more or less my understanding. the modern Li battery is likely to outlast the rest of the system.

 

[hoektron]

So, all we need to do..... invent an AC or 3-phase batter

Thats basically what BLDC motors are, and you can get power tools with that now. Lithium is here to stay for a while. 

 

[floater]

Turbocharged right?  I was trying to stay as close to apples to apples as I could, so went with simple gas powered, naturally asperated engines.  

But your right if you bring in Turbo's the difference is even greater...

and supercharged. ICE up front. electric in the rear. so, in sport mode, the engine runs the front wheels and a generator (I assume) which powers the rear wheels. or, in all electric mode, it's just rear wheel drive. or, in gas mode, it's just front wheel drive.

which leads me to wonder how Kolibri plans to charge the batteries. He has said solar - which seems quite practical as a boat is outdoors all day. except for the shady parts. But there are other options: hydro and wind generators.

as well as a hybrid system. (pack a generator on board). I mean, my hybrid vehicle is an amazing bit of technology (but I wouldn't want to go to sea with it. lol). 

 

[hoektron]

Yes. But even with unlimited time, there are situations where an engine can help keep you safe and where time is not on your side. If your anchor should drag late at night in an anchorage during a squall or some such, the motor will be very helpful and waiting will not.

I agree with the first part, but dragging anchor at night is a crappy example. Even at 10% battery you will have enough juice to reposition and re-anchor.

A better one would be punching against an adverse current and/or wind for multiple hours, or motoring for days in a lull to avoid bad weather. 

 

[mckenzie.keith]

I agree with the first part, but dragging anchor at night is a crappy example. Even at 10% battery you will have enough juice to reposition and re-anchor.

A better one would be punching against an adverse current and/or wind for multiple hours, or motoring for days in a lull to avoid bad weather. 

I meant dragging anchor at night in heavy wind. You have to punch through the heavy wind to drive up on the anchor to raise it and then maneuver through heavy wind to re-set it. This has happened to me. We were maneuvering close to other boats at anchor. The point is not range but short term power. Again I may be wrong, but it seems like a lot of the installations are low on power and low on range.

 

[DDW]

A very small BLDC motor can put out a very large amount of power for a very short time. Then the thermal time constant catches up to you. This is why a Tesla S can do 0-60 mph in 3 seconds, but can't tow a trailer. That is a problem that can be solved with a large seawater cooling system - which ICEs have had for a century. 

 

[mckenzie.keith]

A very small BLDC motor can put out a very large amount of power for a very short time. Then the thermal time constant catches up to you. This is why a Tesla S can do 0-60 mph in 3 seconds, but can't tow a trailer. That is a problem that can be solved with a large seawater cooling system - which ICEs have had for a century. 

I agree. However, the drive electronics also need to be up to the job. And usually their thermal time constant is shorter than the motor's. Also, power loss in motors goes as the square of motor current. But torque is proportional to current. So efficiency inexorably goes down as the torque goes up over most of the usable RPM range. Motors don't operate efficiently if you over-torque them (at any speed).

Also, the model S uses an induction motor (or at least the first years of production did, according to many reports on the internet). What you say holds just as true for induction motors as it does for BLDC's and PMSM's. People think of induction motors as giant cast iron things, but they can be made quite a bit lighter if the cooling is attended to. And they can be made very efficient if they are designed to be run by a motor controller exclusively (do not need to start up at line frequency of 50 Hz or 60 Hz).

 

[DDW]

I think the Tesla still uses an induction motor, but as you say the same holds true. Tesla claims something like 400 hp from each motor. In consumer vacuums and air compressors the manufactures claim "develops 5 hp" for a motor that is at best 1 hp based on an instantaneous value. Same deal - I've not seen a claim from Tesla as to what the maximum continuous power is but I'd be very surprised if it was even 100 hp. A 100 hp induction motor intended for continuous output weighs more than that whole car. 

A Tesla is fast as shit - just don't try to use that power more than a few seconds. That is a great thing for a car, but not so great for a boat. 

 

[mckenzie.keith]

I think the Tesla still uses an induction motor, but as you say the same holds true. Tesla claims something like 400 hp from each motor. In consumer vacuums and air compressors the manufactures claim "develops 5 hp" for a motor that is at best 1 hp based on an instantaneous value. Same deal - I've not seen a claim from Tesla as to what the maximum continuous power is but I'd be very surprised if it was even 100 hp. A 100 hp induction motor intended for continuous output weighs more than that whole car. 

A Tesla is fast as shit - just don't try to use that power more than a few seconds. That is a great thing for a car, but not so great for a boat. 

Well, I don't think it is absolutely necessary for induction motors to be that heavy if they are liquid cooled and designed for very high efficiency. The big heavy motors we are accustomed to are designed to operate with air cooling only at ambient temps up to 40 C with long service life. Also, they are efficiency challenged because they need to start on line frequency. So that ups the dissipation which means the case, which is also a heatsink, needs to be big. I am not a motor designer but this is what I have gleaned from reading technical literature about motors.

Also, it is torque that heats up a motor, not power. High power at high speed does not require high torque. So putting out 100 HP at freeway speeds may not be a stretch. But putting out high torque at low speed for an extended time will likely overtax the Tesla motor, even at power levels less than 100 HP. For example towing a trailer up a hill.

Electric vehicles can actually benefit from multi-speed transmissions, but Tesla has created the expectation that electric vehicles don't need them. I would expect that as time goes on we will see lower cost electric vehicles with multi-speed transmissions.

 

[DDW]

As I said before, cooling the motor on a boat isn't a problem if that is what is required. I noticed that the efficiency of BLDC motors drops off fairly steeply once out of the sweet spot. I wonder if the solution for a boat is a variable pitch prop? The motor could be run at it max efficiency rpm all the time, and the power needed adjusted with pitch. It might also greatly improve the efficiency of regen when sailing, too.

 

[mckenzie.keith]

As I said before, cooling the motor on a boat isn't a problem if that is what is required. I noticed that the efficiency of BLDC motors drops off fairly steeply once out of the sweet spot. I wonder if the solution for a boat is a variable pitch prop? The motor could be run at it max efficiency rpm all the time, and the power needed adjusted with pitch. It might also greatly improve the efficiency of regen when sailing, too.

Where are you seeing the efficiency drop? I think if the motor is controlled properly it will be efficient at a variety of speeds as long as the torque is not too high. You may be looking at the wrong graph or something. The principal cause of power loss is motor phase current which is proportional to torque over a wide speed range. Luckily for boats, most of the time high torque is not required at low speed. Unless you run over a cargo net or something.

 

[floater]

idk the details - but the marketing is as follows: "The software controlled variable pitch sail drive adjusts the pitch of the propeller blades automatically so that the power generation and power output are optimal." https://oceanvolt.com/oceanvolt-blog/introducing-oceanvolt-servoprop-variable-pitch-saildrive/

 

[hoektron]

idk the details - but the marketing is as follows: "The software controlled variable pitch sail drive adjusts the pitch of the propeller blades automatically so that the power generation and power output are optimal." https://oceanvolt.com/oceanvolt-blog/introducing-oceanvolt-servoprop-variable-pitch-saildrive/

Ive looked through their website a few times.  Seems like a nice product. If I ever decide to go electric, I would be looking for something like this. No idea if they are any good though.

The regen would be a big priority since I would want to put them on a fast cat and actually get some juice out.

 

[floater]

it says that "ServoProp is capable of generating more than 1 kW at 6-8 knots". iiuc, that is a shitload of power. but it's also my understanding that yes. you do need some boatspeed to get hydro to work.

so a fast cat seems like the thing. your typical 5ksb, perhaps not so much.

 

[Rasputin22]

     Your 'Fast Car' will no longer be so fast under sail once it is regenerating any appreciable amount of current back into the massive battery bank. I designed a 50' fast expedition sailing catamaran and supervised most of the build and did a lot of the actual hands on work on an installation of the Electric Wheel motors. Solomon Technologies was marketing those motors (which we fine motors as they had been developed as hub motors for the original Moon Buggy) but the rest of their system (or lack thereof) and it didn't take long into sea trials to come to the conclusion that most of their sales spiel was total snake oil salesmanship.

    I won't bore you here with the travails we experienced but on a short (35 mile) hop with the building crew to Tortola to pick up the proper battens for the mainsail I had the owner along for the first real evaluation of the regen. The boat had been on shore power battery charging for days as final fitout was done and the 12 AGM 4D batteries were as fresh and topped up as could be. The 1 mile exit from our marina to the seabouy at Salt River where we raised sail was as quiet as promised and I was logging motoring speed and draw. Just raising the main dropped the current draw dramatically as we went into motorsailing assist mode. Even with conventional three blade Michigan props with some careful tweaking of the tiny joystick throttles we were excited to see in real time the regeneration start up as we raised the jib and trimmed to the 15-20 knot Tradewinds on a beam reach. The owner was ecstatic with the output and I kept logging speed vs regen and it was soon apparent that those amps and watts didn't come without a surprising cost in terms of speed. You don't get something for nothing...

    We got off to a late start and should have been able to make Roadtown before customs closed if we had just shut down the electric drive system and sailed but the owner was more concerned with sticking his head into the reefer box to watch the holding plates frost up and he was anxiously awaiting his first 'regen cooled beer'. He finally came up with a couple of luke cool beers to toast the wonders of regen under sail and asked how soon we would be in Roadtown. I told his our average and distance to goal and said it would be just before dark. He was shocked and then it dawned on him that all the dicking around with the wonders of the regen miracle had cost us a lot of time. I then put the drive system into what the Solomon tech called 'null out the props' mode (sort of a virtual neutral) and the boat immediately accelerated a couple of knots and the ETA moved up to where we might just be able to clear customs. Most of the young Cruzan kids who had been part of the build had never been off their home island especially on a sailboat and were really excited too. I was dreading having to deny them getting off the boat to kick up their heels if we didn't get cleared in and there was really no food on board for dinner. 

    I finally told the owner that his home cooled cold beer was going to result in all sorts of downstream problems and he told me to start the diesel genset to keep from having to use battery capacity just to offset the propellor drag. Once we did that and trimmed for best VMG the generator started losing seawater cooling prime due to our speed and the fumes soon made some of the young fellows get seasick. The noise and heat in the cockpit from the generator was really messing with the owners head and I finally suggested that we shut down the generator and trim for speed and get to our destination and clear in, anchor up, let the kids go wilding, and start the gen back up while we sit at the waterfront bar and drink really cold 'grid cooled' beer and rum drinks and listen to the purr of the genset from a distance! 

     And that was just the beginning of a rude awakening on the pros and cons being debated here. No debate for me. Been there and done that!

    I skippered that boat for another year and weeded out some of the system goofs but electric refrigerators and induction cooktops and convention electric oven were always going to be a wet dream... 

    Best improvement I made was borrowing a three blade AutoProp which the engineers said would never regenerate but they were wrong in so many ways. A pair of AutoProps would have made the boat almost sustainable on a cruising or liveaboard situation but the 15 KW genset was no match for the pair of 9KW Electric Wheel motors. I guess we just needed the proverbial 'infinite length extension cord'!

 

[weightless]

you do need some boatspeed to get hydro to work

Speed and / or a bigger prop. I think the upper bound is the Betz limit which is more or less a function of v2 and area.

Some kind of closed loop control system with a variable pitch prop might be set to optimize power or efficiency or something but, just to state the obvious, ultimately there'll always be a limit and a cost.

 

[floater]

..conventional three blade Michigan props ..    And that was just the beginning of a rude awakening on the pros and cons being debated here..

    Best improvement I made was borrowing a three blade AutoProp which the engineers said would never regenerate but they were wrong in so many ways. A pair of AutoProps would have made the boat almost sustainable on a cruising or liveaboard situation..

but didn't you point to a solution here?

which mirrors the copy from oceanvolt: "A normal fixed propeller (that by nature does not have the blades ideally shaped for regeneration) generates less than half the power of ServoProp at a given boat speed."

 

[Rasputin22]

Go take a look at a AutoProp, its blades are optimised with twist, cup and a foil shape and when you go for regeneration it flips over so works as well in reverse as forward. Brilliant design and way more simple that the servo actuated OceanVolt. Actually I like the idea of the OceanVolt but haven't used one myself. (Although I did see one in action in a tank at the Newport Boat Show 3 years ago and stayed in a Holiday Inn...)

 

[Fah Kiew Tu]

As I said before, cooling the motor on a boat isn't a problem if that is what is required. I noticed that the efficiency of BLDC motors drops off fairly steeply once out of the sweet spot. I wonder if the solution for a boat is a variable pitch prop? The motor could be run at it max efficiency rpm all the time, and the power needed adjusted with pitch. It might also greatly improve the efficiency of regen when sailing, too.

Something I've been saying for ages now WRT diesels.

But AFAIK, nobody currently makes one in small (less than 50HP) sizes.

Sometimes I think of doing it myself but the market isn't there as nobody will pay what they would cost I expect. And I've already sufficient projects to keep me fully occupied until I reach 150 years old, at least.

FKT