Electric Propulsion

[fastcat435]

Originally Posted by David M

The primary problem is that the energy density (Stored energy per amount of weight) of Diesel is still much greater by many factors than the most efficient batteries. Were this not the case then we would have battery powered commercial aircraft.


Since boats are sensitive to weight and there is no way around this fact, then batteries will have to become much lighter per amount of energy stored, and not physically larger either, if it is ever going to compete equally with Diesel.

Hallo David , you are right off course , energy density for fossil fuel is much greater than the most efficient batteries. it is however possible to cruise with out Fossil fuel, with an electric sailboat with regenerative possibility's like solar, wind and renegerating electric motogen it is possible and it is proven to work. The only problem arises if the sailor is in a hurry to go somewhere and there is no wind and or the batteries are empty.
We are presently building catamaran that will be with out a generator,
this boat will have 1700 Wp solar power , a masthead mounted wind generator (max output 400 watt) and the electric motors can generate up to 3 Kw each per hour, ( speed depending )
We will build in Fuel tanks and the space for a generator in case the future owner wants to install one later.

The weight saved by going this route is around 600 kilo or 1300 Lbs. about 7 % of the total weight of this cat making the boat a bit faster.
Energy densities of batteries are slowly going up, at this moment commercially available types reach 180 wh per kilo but in laboratory test over double this wattage has been reached.
If the sailor can motor at a slow speed of 5 to 6 knots 4 to 6 hours of motoring is presently possible, in our setup we can also use the house batteries as a spare tank for 2 hours of extra motoring. this gives a total motoring range of about 50 nm. with the newer improved batteries this will double in a few years.

The case for going electric is the possibility to regenerate, that is impossible with fossil fuel.
The initial cost is still high. I expect these cost to go down as the produced numbers go up as I also expect that fossil fuel will become much more expensive so at some stage there will be a break even point.
I find the advantage of being autonomous fantastic and the added bonus of not having noise, smoke, vibration and keeping a cleaner environment helps.
I read somewhere in this thread that electric motors give less speed at full power,
In case of the exchange of 2 x 30 Hp diesel for 2 x 10 Kw electric motors that is not the case. On the contrary the electric version that has a slightly higher weight ( + 5 % )
has a top speed of 8.2 knots compared with 8.0 for the diesel version .

[mbianka]

Originally Posted by DeepFrz

You can't call it green with the battery bank that is required. Cpt. Mike uses a generator to recharge, so it is a hybrid solution, not a purely electrical solution. His solution uses a gasoline powered generator, larger boats I'm sure would use diesel powered generators and therein lies the rub. A diesel electric solution has so far proven to be less efficient in a "small" (I mean a cruising type sail/power boat, not a super yacht, although I haven't heard of any mega yachts successfully using diesel electric). So, where is the magic?
.

Deep Frz:

I actually use a three legged stool approach to recharging. Solar, wind turbine and generator. Yes, I do use the Honda for recharging (primarily through the bulk cycle) but, not always. For example one night when I was in the middle of cooking dinner I ran out of propane. I dropped off the mooring motored the boat over to the dock (under battery only) and went to find a store a get a propane cannister. When I left it was dead calm when I got back it was blowing 20 to 25 knts. I powered off the dock (under battery power) and spent about twenty minutes trying to get back on the mooring. Everytime I'd get up to the mooring the wind would make the bow fall off and I'd have to get back to the helm and throttle up to make another pass. I always had plenty of power to maneouver even in those conditions. Finally I was able to get back on the mooring. I had used about 8% of the battery bank that night. I finished cooking dinner and went to bed. By the time I got up the next morning the battery bank had been charged back up to 100% by the wind generator alone. Having the ability to make your own fuel (energy) is a nice side benefit of going to electric propulsion. Like many cruisers I'll stop and anchor some place for a few days and often the generator is never turned on with the solar and wind generator keeping things charged very nicely.

[daddle]

Originally Posted by mbianka

...spent about twenty minutes trying to get back on the mooring. Everytime I'd get up to the mooring the wind would make the bow fall off and I'd have to get back to the helm and throttle up to make another pass

Consider backing up to the mooring. The bow won't misbehave. You'll save kWh. However, can be nasty if the seas are big.

[mbianka]

Originally Posted by daddle

Consider backing up to the mooring. The bow won't misbehave. You'll save kWh. However, can be nasty if the seas are big.

Hmmm good idea. I think what I finally did was point the boat into the wind near the mooring and adjusted the throttle so I was making no headway then as the boat drifted by the mooring line I was able to pick it up. Worked well but, it took a few passes to figure it out. Would have been easier if I had crew on board but, then I would have had to feed them.

[virginia boy]

I have read through this entire thread, whew! I also have searched the Thoosa website but could not find specific pricing and have yet to receive a price quote from them. I currently have an 18 hp Yanmar and would like to know how much a Thoosa package comparable to the one on Bianka would cost (sans batteries). West marine's prices were ridiculously high. 15K if I remember correctly! Has anyone gotten a price quote?

[Adamante]

Originally Posted by daddle

Prove it.

If you are willing to accept the notion of "the proof is in the pudding", there are numerous examples of boats with electric propulsion whose performance can be readily compared to their diesel engine powered versions:

1. Lagoon 420 Hybrid - this boat is/was offered in both a standard version with twin 40 HP diesels, or with twin 8-10 KW motors, which is around 11-14 HP.

Enigma, a Lagoon 420 Hybrid, successfully participated in the 2010 ARC and crossed the Atlantic while motoring a good portion of the way. They weren't one the faster boats, but kept pace with the other boats in their class. That suggests that the equivalence of a 40 HP diesel with a 14 HP electric motor is appropriate for this purpose.

2. A CF poster named Hyperdrv with a Lagoon 410 Hybrid has noted speeds of 6 knots with throttles set at one third. That would suggest his 12 HP motors (9 KW) are appropriately sized for his boat which would be normally powered with 30-40 HP diesels.

3. Green Motion, a 44 ft catamaran, made a passage from South Africa to Holland powered with twin 12 HP submersible motors. The non-hybrid version of this catamaran is offered with 30 HP diesels. Green Motion's passage speeds were extensively covered in another CF thread and appear to be comparable to speeds achieved by similarly-sized catamarans equipped with 30 HP diesel drives.

4. Tang, a 60 ft. hybrid catamaran recently made a passage from South Africa to the Caribbean. It is equipped with twin 18 KW motors, or 24 HP each . I would estimate that a boat of this size would normally be powered by twin 50 HP diesel engines.

Now, some of these boats have experienced various problems during normal operations, but lack of speed due to undersized electric motors was not one of them. That suggests to me that the electric motor to diesel engine HP relationship of 40% to 50% most likely represents an accurate estimate.

[Adamante]

Originally Posted by virginia boy

I have read through this entire thread, whew! I also have searched the Thoosa website but could not find specific pricing and have yet to receive a price quote from them. I currently have an 18 hp Yanmar and would like to know how much a Thoosa package comparable to the one on Bianka would cost (sans batteries). West marine's prices were ridiculously high. 15K if I remember correctly! Has anyone gotten a price quote?

I looked at the Thoosa pricing last year, and from memory the 9000 system was around $9K. This would be for the controller and motor. If you are replacing an 18 HP diesel, you might get by with one the smaller Thoosa systems.

[allanpeda]

I would like to see someone adapt (err Marinize?) the drivetrain of the Chevy Volt to create a hybrid propulsion system for a boat. Long range of an engine, flexibility and quiet of electric with total inability to repair away from a GMC dealer.

I had to throw that in. Solar might offset that, but for KISS effect a diesel seems the way to go.

[Adamante]

Originally Posted by Zonker

Does this setup make sense ?

Originally Posted by Zonker

10KW Genset
2 KW Solar Panels
40KWh Li Batteries (what voltage ?)
2x20KW El. motors

Batteries
- 30 min full power
- 1h half power
if 50% discharge allowed

Solar panels don't provide enough power to support genset or batteries

So if batteries are empty the genset could provide at least 2x5KW

Bottom line - is a larger genset required for long term motoring ?

The voltage of a battery bank for this size motors is typically 144 volts.

A 40 KWh LiFePO bank should provide about 32 KWh of useful energy (20% discharge), so around 45 minutes at full power, 90 minutes at half power (nominally).

With a 10 KW genset, the motors would be limited to 25% throttle. Based on other examples, I would estimate that this 60+ ft catamaran (?) would cruise at 4-6 knots at 25% throttle in relatively calm waters.

Is that enough? I guess that would depend on the circumstances, but I would probably plan to put two 10KW generators on a boat this size. They need not be run together, but two sets would provide redundancy. And even with a dead battery bank, with both generators running, the boat should be able to move at 7-8 knots, which would be enough to make the passage of the PanamaCanal within the required time limit.
I would go heavier on the solar, maybe 3 KW or more, a 60 ft catamaran has the acreage even at today's solar panel densities. My time horizon is around two years, and I am hoping to install upwards of 7 KW solar without sinking the boat.

[LauderBoy]

Originally Posted by virginia boy

I have read through this entire thread, whew! I also have searched the Thoosa website but could not find specific pricing and have yet to receive a price quote from them. I currently have an 18 hp Yanmar and would like to know how much a Thoosa package comparable to the one on Bianka would cost (sans batteries). West marine's prices were ridiculously high. 15K if I remember correctly! Has anyone gotten a price quote?

Don't know if this is current or not: https://ssl12.chi.us.securedata.net/...facturers_id=1

[skipmac]

Originally Posted by Adamante

If you are willing to accept the notion of "the proof is in the pudding", there are numerous examples of boats with electric propulsion whose performance can be readily compared to their diesel engine powered versions:

1. Lagoon 420 Hybrid - this boat is/was offered in both a standard version with twin 40 HP diesels, or with twin 8-10 KW motors, which is around 11-14 HP.

Enigma, a Lagoon 420 Hybrid, successfully participated in the 2010 ARC and crossed the Atlantic while motoring a good portion of the way. They weren't one the faster boats, but kept pace with the other boats in their class. That suggests that the equivalence of a 40 HP diesel with a 14 HP electric motor is appropriate for this purpose.

2. A CF poster named Hyperdrv with a Lagoon 410 Hybrid has noted speeds of 6 knots with throttles set at one third. That would suggest his 12 HP motors (9 KW) are appropriately sized for his boat which would be normally powered with 30-40 HP diesels.

3. Green Motion, a 44 ft catamaran, made a passage from South Africa to Holland powered with twin 12 HP submersible motors. The non-hybrid version of this catamaran is offered with 30 HP diesels. Green Motion's passage speeds were extensively covered in another CF thread and appear to be comparable to speeds achieved by similarly-sized catamarans equipped with 30 HP diesel drives.

4. Tang, a 60 ft. hybrid catamaran recently made a passage from South Africa to the Caribbean. It is equipped with twin 18 KW motors, or 24 HP each . I would estimate that a boat of this size would normally be powered by twin 50 HP diesel engines.

Now, some of these boats have experienced various problems during normal operations, but lack of speed due to undersized electric motors was not one of them. That suggests to me that the electric motor to diesel engine HP relationship of 40% to 50% most likely represents an accurate estimate.

In the examples cited I am guessing that the electric motors were used primarily to motor during calm conditions when the boats could not sail. In that case, a small electric or even a small diesel will easily give you close to hull speed.

My concern is motoring in conditions other than calm. In my dozen or so crossings of the Gulf Stream from FL to the Bahamas I have usually motored. So how will an electric motor that is half the power of my diesel engine (in HP, KW or however you want to rate it) going to do when punching into 3-4' seas and a 10-15 kt headwind? Or similar conditions motoring down the ICW although usually with the wind and not the seas.

Also I can see an issue with how the electric motors are rated. From posts on this thread it appears that an electric motor can short term put out much more than it's continuous power rating. So maneuvering around the docks if you need a quick burst of power you can do it. But I see a lot of potential for a less than reputable supplier to rate their motors at a level that would not be conducive to long term reliability of the motor.

[mbianka]

Originally Posted by virginia boy

I have read through this entire thread, whew! I also have searched the Thoosa website but could not find specific pricing and have yet to receive a price quote from them. I currently have an 18 hp Yanmar and would like to know how much a Thoosa package comparable to the one on Bianka would cost (sans batteries). West marine's prices were ridiculously high. 15K if I remember correctly! Has anyone gotten a price quote?

Virginia Boy:

When I installed my system four years ago the price for the motor, controller was around 8k add another 2k+ for batteries. A few tools like a heavy duty crimper, connectors, wiring and a 48 volt wind generator and mount and I think my conversion came in around 12K. This compared favorably with my intial plan to repower with a Beta Marine diesel. My Thoosa 9000 replaced my 1986 Westerbeke 27. I agree with Ademante you probably don't need a 9000 system for your boat but, might be able to go with a smaller lower priced system. I don't know what the current prices might be though.

[Alberto]

Originally Posted by skipmac

In the examples cited I am guessing that the electric motors were used primarily to motor during calm conditions when the boats could not sail. In that case, a small electric or even a small diesel will easily give you close to hull speed.

My concern is motoring in conditions other than calm. In my dozen or so crossings of the Gulf Stream from FL to the Bahamas I have usually motored. So how will an electric motor that is half the power of my diesel engine (in HP, KW or however you want to rate it) going to do when punching into 3-4' seas and a 10-15 kt headwind? Or similar conditions motoring down the ICW although usually with the wind and not the seas.

Also I can see an issue with how the electric motors are rated. From posts on this thread it appears that an electric motor can short term put out much more than it's continuous power rating. So maneuvering around the docks if you need a quick burst of power you can do it. But I see a lot of potential for a less than reputable supplier to rate their motors at a level that would not be conducive to long term reliability of the motor.

My experience: we usually motor between 3 and 4 knots. My boat is affected by choppy waters and by the wake of large powerboats. With the diesel, speed would drop, and large wakes would eventually stall progress. With electric the difference is significant, half a knot at the most and immediate recovery. In terms of short bursts, docking maneuvers have improved dramatically, in particular in reverse; the initial high torque makes a huge difference.

I've motored against 18 knot winds at 4.6 knots without problem, but only for one hour, and the batteries had enough capacity left for at least another hour when we arrived at the marina (my battery bank is smaller than most).

As per reliable information, some motors (ETEK, Lynch) have been around for a long time and I have not seen any complaints regarding performance. I would be more concerned with the information regarding controllers… but again, the “usual suspects” have a very good track record.

[four winds]

I'd like to offer a couple of statements to consider in relation to the relative power of engines and motors.

Of course, neither actually produce (create) energy. They simply convert energy from one form to another. Fuel from the tank in the case of engines and electrical potential in the battery in the case of motors.

I think it's important to consider the efficiency of process of each.

In a motor electrons stream through the system, from the battery through the motor and to ground. Or from ground through the motor to the battery if you were taught electron flow theory like me. Either way the energy is already in its usable form. And also important, is that all motion in the system, the energy conversion stage, is rotational. Everything is spinning, and the electrons are ubiquitous in the system. This is a relatively efficient process compared to engines.

In engines the liquid fuel is mixed with air and ignited. The resulting combustion is used to "push" a piston down a bore in a linear fashion. Depending on the engine this is done hundreds of times a minute in multiple cylindrical bores. This linear motion is then converted to rotational motion through the use of connecting rods and crankshaft. The rotation is then at a speed to great for use on a prop so gearing is utilized to adjust the rotation to a usable speed.

This later process is much less efficient than the former. Combustion pressure forces the rings with great force against the cylinder walls, to contain the energy released and keep the oil in the block and not the combustion chamber. There is considerable friction here, and the results can be seen during a rebuild. Also, converting the linear motion to circular motion results in energy loss in the process, as does using gearing to change the speed of rotation.

Most old gear heads like me are aware of the difference when rating an old hot rod or Harley engine straight off the flywheel or at the rear wheel. It is significant and that's the loss in the drive train only, not the internal inefficiencies of converting from a liquid to an explosion, from a linear to a rotational motion, and the friction producing heat.



My belief would be that an all electric system could be rated less than an internal combustion system and perform the same work, for the reasons stated above. And I think the anecdotal evidence from systems on boats discussed above bear this out.

[skipmac]

Did some further reading and research on the Thoosa electric systems and came across this comment on the spec sheet for their 12 KW system.

"12 KW continuous power. Replaces a 25 - 40 HP combustion engine"

So based on the manufacturers own statement I would need an 18 - 28 KW electric motor to replace a 58 HP diesel.