Electrical Propulsion vs Diesel Propulsion

[El_Guero]

4134,

Yes, no, maybe so.

If everything is set up properly. Yes, it is more efficient to run directly. Most of your fancy, expensive, and GREEN cars are not set up properly - because of cost.

Remember, all you are doing is what the Germans perfected back in the 40's. We have only improved on this recently.

And usually, you just throw more money at it to fix it.

Wayne

[websailr]

I spent a week in BVI on Waypoint, Lagoon's 1st hybrid cat. It had 2 LA banks & 2 Emotors (20 ft apart), with 15kW genset. They delivered it from France to Chesapeake motorsailing, using hot water showers, refr/freezer, video/audio, heat, etc. Never had to run genset due to sailing & spinning the screws/dc motors. Owners moved it to BVI to charter & had to double fuel tankage as folks just motored from Pusser's to Pusser's & ran the AC. No battery saver circuit, so dummies ran batteries flat & killed them. When I got to it batteries were weak, but it was still a dream to maneuver - want 1 rpm at the screws? No idle creep. Just turn switches on & motors are ready all day. If someone falls overboard, just pull the sticks back & stop in less than a boat length. No noise or stink. Flexible battery placement & very small motors. Backup genset has tons of power beyond batteries. I would like it for general sailing, but it it would really shine on passages.

[deckofficer]

Originally Posted by websailr

I spent a week in BVI on Waypoint, Lagoon's 1st hybrid cat. It had 2 LA banks & 2 Emotors (20 ft apart), with 15kW genset. They delivered it from France to Chesapeake motorsailing, using hot water showers, refr/freezer, video/audio, heat, etc. Never had to run genset due to sailing & spinning the screws/dc motors. Owners moved it to BVI to charter & had to double fuel tankage as folks just motored from Pusser's to Pusser's & ran the AC. No battery saver circuit, so dummies ran batteries flat & killed them. When I got to it batteries were weak, but it was still a dream to maneuver - want 1 rpm at the screws? No idle creep. Just turn switches on & motors are ready all day. If someone falls overboard, just pull the sticks back & stop in less than a boat length. No noise or stink. Flexible battery placement & very small motors. Backup genset has tons of power beyond batteries. I would like it for general sailing, but it it would really shine on passages.

I know just what your saying on maneuverability at 1 rpm instead of clunking in and out of gear at 600 rpm. It is so sweet. My last rig was diesel-electric but on a larger scale to the tune of 32,000 tons with (6) 5,000 electric motors just to hold a static position over a wellhead.

[Hyprdrv]

Websailr,
I own boat #3 of the 3 410 Lagoons that where built. Waypoint was boat #1. I wouldn't trade my boat for anything. I've been around since the topic first came up here at CF and had to take the heat from all the nay sayers. "It will never work". "A waste of money". Over the last 4 years I've burned 60 gals of fuel and probably 2/3rds of that was because I was getting worried the fuel was going to go bad.
After hearing all the complaints about saildrives I am happy to have a straight shaft off the Electric motors. I will NEVER own a sail drive.
As for the Genset the way to do it is to rectify the Genset output to match your Motors and Battery bank. In my case I have 144V bank and motors. Once the batteries are run down to (in my case) 50% I start the genset up to charge the batteries based on the Amperage output. I can run the motors at the same time as charging with no battery charger in the mix. I monitor the battery state with several gauges and shut down once the batteries are full. My genset has variable output so I can match the output to the needs of the motors and batteries. Boat #2 has a new 21KW DC generator with 144V direct output so the motor starts and stops automatically. Mine is the original 16KW.
As for the Batteries the new Lithium batteries are the way to go. Period!

Steve in Solomons MD

[bryguy67]

There is a whole other way to look at this. They type of system that has been talked about here is a serial system (vs. Parellel). Serial hybrids, when compared to automotive are like the Chevy Volt ($40,000+). The main propulsion is the electric motor backed up by a large generator. It's a very expensive way to go about it. A parallel system is comparable to most other hybrids on the road (Prius, Fusion etc. for $25,000+) in which the engine is the main source of propulsion and a smaller electric motor can operate the vehicle alone under lighter loads. YANMAR has a parallel hybrid system available for boats which is warranted by Yanmar and can be run via a sail drive or shaft drive. Isara Catamarans are offering this system as an option and I'm sure others will follow. No generator is needed and an all electric galley is a shoe-in by product if you choose, as are other charging methods (solar, wind). All electric motoring is available for light duty such as docking, no-wake speeds and motor sailing. Full diesel power (55 HP each on their Isara 45) is available for tough conditions and/or charging while motoring. And yes, they act as hydro-generators when sailing. Cost? Within 20% of a non-hybrid system since no generator is needed. Weight of the hybrid system is off set by the lack of generator. Pull in to your authorized Yanmar repair center for warranted, off the shelf parts. Here's a link: http://www.bayacht.com/aaa/Isara/Yan...d+brochure.pdf

[mbianka]

Originally Posted by 4134me

Thanks guys

Mbianka, I was always under the impression that running through batteries with yet another change in energy form was less efficient than running the motors directly from a generator? and that finding a charger able to make use of all the available current was difficult? If this is not the case then DC could be the way to go!

Well yes it helps to avoid voltage conversions if you can. Not only because of the losses but, also the increased complexity. If you are running a 48 volt generator that happens to be connected to the 48 volt battery bank you do not have any conversion losses. The batteries will just act as a backup power source if the generator should suddenly stop. But, you need to make sure the generator will not overcharge the batteries too. As an example I have 48 volt solar panels and 48 volt wind generator connected to my propulsion battery bank but, they do not provide that much power for motoring but, they do help. BTW my 12 volt house bank has it's own separate charging systems. The 48 volt Zivan NG-1 battery charger that I also use as a "power supply" when motoring when just using electric propulsion does have to convert the Honda's 120 volts to 48 volts. So there is a little loss there but, not a lot. While it's output is only 900 watts it can move my boat about 3 knots with it without drawing any additional amps from my battery bank. My Honda 2000i generator can put out 1600 watts continuous so I am operating well below it's capacity when using the charger as a power supply. I could also if I wanted add an additional 48 volt power supply of say 500 watts and still not be red lining the Honda generators output. Yeah, it would be nice if there was a 48 volt generator that was as light, quiet and reliable as my Honda 2000i but, I have yet to find one. I don't really worry about the small conversion losses. Also you really want to have a smart charger when charging up the battery banks to avoid over charging and the NG-1 does that too when I use it for only for charging. Besides the Honda also is useful for many other things on board such as powering the laptop and power tools as well as for charging the 12 volt house bank. It also takes the place of an alternator on a diesel engine when for example using the electric windlass to raise the anchor. Lots of power in a 47 pound package that has a lot of diverse uses on board even if some do involve some conversion losses sometimes.

[Hyprdrv]

I will add to Mike's points here.
Mike has a smaller boat than my 41ft Cat so our needs and capabilities are different. However the principles are the same.
Bryguy67 you didn't mention how you got power when on the hook. I see you have to start the motor to charge the batteries. That system is fine for a standard sailboat. In my case the 144V bank charges the house bank or I can start the genset up and run off of it and charge the Propulsion bank at the same time. Regen is also possible while sailing and most of my needs are handled under Regen when boat speed is in the 6 knot range. One day when the installed Genset goes south I will by a DC 144V output Genset. They are now available.
The good news, as you pointed out was that more and more companies are offering alternative propulsion options to the standard ICE machines. Sailboats are one of the best uses of these systems and in 20 years when my motors bearings need replacing (about $100 to replace) I'll look back and figure out how much I saved buying an Electric 2004 boat. The good news was I bought it at the cost of a standard system, I was offered a whole lot more last year when people started to realize I wasn't crazy for buying an Electric Cat. Don't even talk about the Power boats that sat at the docks because they couldn't afford the fuel to go for a day trip. They went sailing with me. )

Steve in Solomons MD

[bryguy67]

Originally Posted by Hyprdrv

Bryguy67 you didn't mention how you got power when on the hook.

Steve in Solomons MD

Steve,

When at anchor with this system we could either charge via solar (planning on 1000-1200 watts) or simply start either of the drive engines as the 10kw electric motors attached to either engine will act as a 5kw generator (whether sitting in port or while powering the vessel). In essense, this would be equivelent to having 2 generators and 4 seperate ways to power the boat (not including the sails). Redundant systems in case of break down of any of them.

~Bryan

[jostalli]

I love hearing positive reviews from the Lagoon 410 hybrid guys. What is confusing is why did almost all of the hybrid Lagoon 420's convert to diesel? I have been searching for the last remaining hybrid 420's but cannot find any left. Apparently there was still the option of purchasing the latest hybrid system in the 420 (maybe even the 421) but I have not heard of anyone going that route.

The new Yanmar hybrid saildrives seem to be a great option to offer new boats but Lagoon isn't offering them (maybe because they were burned before by hybrid).

[bryguy67]

On that yanmar hybrid system, the nice thing is that it can either be installed from the boat builder as new...OR...can be added on to most any used boat. This is good news for buyers like us who are still undecided (due to price) as to whether we will be ordering a new Isara 45 or a new/used Lagoon 450. The hybrid system can be economically installed either way.

[DITB]

I have this crazy idea of fitting a paddle (!) between the hulls of a cat, with an electric engine in each side. It would be a serial hybrid setup in the sense that when batteries are low, a generator would supply the power (but not propulsion directly).

The paddle would be retractable so it does not incur resistance when going for sails.

With one single paddle, one would need bow/stern thrusters, and there are a few other issues to be solved. But I really like the idea. Lot's of solar cells topside, and maybe one or two wind turbines, to top up batteries. The weigh of batteries should match that of saved diesel engine weight.

The paddle can double as a generator, so while moored with any kind of current, the paddle would double as a generator. Also while sailing, needing to charge the batteries could be done this way (at the cost of speed, obviously).

Before you shoot me down, this is just a thought I had. I didn't say it's a superior design, nor that I am going to build one - I just liked the concept.

[deckofficer]

Props are a science in shape, hard to beat them. For electric propulsion the key would be as large a diameter that fits, coupled to a higher number pitch for slower turning. Most the ships I was on were direct drive and 118 rpm max speed for engine and prop.

[mcarling]

Originally Posted by 4134me

I was always under the impression that running through batteries with yet another change in energy form was less efficient than running the motors directly from a generator? and that finding a charger able to make use of all the available current was difficult? If this is not the case then DC could be the way to go!

As others have mentioned, using DC generators, batteries, and DC motors all at the same voltage improves efficiency, but DC-DC converters should only be taking roughly about 1%. I would choose 144V DC because that is the most efficient voltage for an inverter producing 110V AC. Wiring is also lighter. The disadvantage of 144V versus 48V DC is that more solar panels need to be connected in series (managed by an MPPT, of course, ideally managing each panel independently because of partial shading) to produce 160V DC charging current.

Anyway, whether the propulsion battery bank is 48V or 144V, a DC-DC converter (designed for battery charging, not just power supply) will probably be the best option for keeping a 12V or 24V house bank charged.

If I were specifying a system today, I would choose 144V for the propulsion bank and 12V for the house bank, with 110V AC -- if I could install enough solar panels to produce 160V. If the space for solar panels was more limited, then I would probably choose 48V unless I could find a suitable DC-DC converter that could take a wide range of lower input voltages from the solar panels and produce steady 160V output.

An alternative would be to stay with 144V for the propulsion bank and have the solar panels charge the 12V or 24V house bank rather than the propulsion bank and use the DC-DC converter as a back-up. Then the propulsion bank would be charged by regeneration while under sail, the diesel genset, or shore power. However, I would prefer to have the solar panels charging the propulsion bank.

[4134me]

Thanks for the input guys, didn't realise It was as simple as matching all the voltages to remove the need for a charger. Would it be possible to stop charge going to the batteries during a long period of motoring to avoid the generator stopping and starting?

[mcarling]

Originally Posted by 4134me

Thanks for the input guys, didn't realise It was as simple as matching all the voltages to remove the need for a charger.

It's not that simple. Matching the nominal voltages improves efficiency, but power electronics to regulate the voltage delivered to the batteries is still required.

Originally Posted by 4134me

Would it be possible to stop charge going to the batteries during a long period of motoring to avoid the generator stopping and starting?

During motoring, the batteries will be powering the motor. You might have some solar power contributing to the batteries during this time, but probably just a fraction of what the motor is taking. For long periods of motoring, the genset will have to kick in to keep the batteries charged. The duty cycle will depend on how the various components are sized relative to each other. I don't see a good reason for the genset to be sized much bigger than the propulsion motor, so I would expect the duty cycle of the genset to be about 75-90% during long periods of motoring.