Quite the thread we have here. Who would have thought that a topic could cause more angry than anchor choice.
I've been interested in electric propultion for quite some time, but as Cam and others have pointed out several times in this thread it is not more efficient pound for pound, dollar for dollar, or by most other measures. I won't argue with the disadvantages, as they've been well explored on this thread and are quite valid. What I feel is lacking from the particular discussion is the other aspects that electric and electric/hybrid have over conventional diesel.
What attracts ME to electric/hybrid systems is similar to what has attracted me to hydraulic systems in the past. Here is what I like:
1: Silent motoring (or nearly with a very well insulated genset)
2: Easier to mount a dual prop setup (still only one diesel generator) for better maneuvering and redundancy.
3: Lots of options for motorsailing.
4: Instant availability of power from the electrics in case of sail failure or diesel genset failure.
5: The possibility of sitting at anchor and slowly augmenting your fuel supply by generating power.
6: The possibility of creeping home (albet slowly) after diesel failure on a windless day.
Allow me to flesh out each of these advantages a little:
1: For starters I LOVE the idea of silent motoring. Yes I know sails are silent and that's why I use them when I can but the fact is that in the PNW with the type of cruising I do I motor about 50% of the time. I have seen many a small genset so well insulated that you can't even tell it's on dockside. Literally a whisper. I guess you "could" sound insulate your main motor this well, but I've never seen it done. It also appears that you can use a much smaller diesel for your genset (than you would for your main engine) and insulate it more easily with off the shelf technologies. If my motor were quiet I'd hate motoring less.
2: I'm getting better at docking, and less stressed as I practice, but I own a heavy full-keeled boat with a unidirectional wind powered bow thruster (large bowsprit). My maneuverability in harbor SUCKS. A dual prop setup of high torque electric motors would be a HUGE advantage in close quarters maneuvering. I would go out more often having confidence in a setup like this. I also recently had a large rug wrap itself around my prop on a windless day. If I had two props, it wouldn't have been an issue. Mounting one genset and two pods is possible, mounting two engines, transmissions, etc is just not possible for me.
3: The owner with the E-pod gemini (that Chuckles mentioned) talks at length about the options he has for motorsailing. I'm one of those sailors that doesn't mind using the nylon sails and drifting along all day. Problem is that drifting at 2 knots sometimes means having to use the engine at the end of the day to beat darkness or make a slack tide appointment. I would much prefer to SAIL all day with a couple amp hour push from the silent motors helping me along. Apparently they don't use much power in this role. I am much more likely to use this setup instead of fire up, warm up, and engage the rattlebanger. Once again, another advantage that would allow me to sail more.
4: Instant availability of power would help keep the stomach ulcers away. I try and maintain my diesel so that it won't suddenly die, but they all do sometimes. With my big heavy ketch I can't set my sails quick enough and short tack in a marina to keep off the breakwater. I keep my anchor at the ready, but an electric system that will continue to run if the diesel genset dies would eliminate this problem. Also if sailing and lines foul and suddenly I'm headed for a lee shore I have electric backup again in case the diesel doesn't want to start. It's a safety and stress-relieving feature. A safety feature I do without today, as when my motor dies I have exactly zero engine motoring time in reserve, but it would be "nice to have" even that 1 or 2 hours of motoring time in your batteries for after your diesel engine (genset in this case) fails.
5. Sitting at anchor topping up your tanks. This is more of a sate of mind really than a real savings. I compare it to the smirk of superiority that I see on trucks with biodiesel bumper stickers. It would take far too much to fill up an empty tank, even with a week at anchor in a windy sunny spot. But you could add some, especially with a nice windy night, and the though of it is nice.
6. We all know that mechanical things like diesel engines have two states of being: 1. Broken. 2. waiting to break. I've had my diesel die while out cruising and I've usually managed to creatively fix it at anchor. It would be nice though to have the option of crawling home at 2 or 3 knots using your battery bank if your diesel genset dies. Can the electric setup fail? Of course, but it's another tier of redundancy, much like an outboard to back up your main inboard. Recently when the rug wrapped itself around my prop and we had EXACTLY 0 wind I had to call buddies at my marina to come fetch us in outboard powered tenders. Had we even 1 knot of wind I could have sailed most of the way home. I still would have been screwed trying to dock with nylon sails in a close marina in 1 knot. With the electric setup I could have limped home at 2 knots using low amps from the remaining motor and even docked myself. I've also had the engine die in wind. We sailed into anchor but sailing into anchor would be easier with a little electric backup even if only for the final maneuvering in the (hopefully) wind-protected anchorage. I love redundancy and self sufficiency and this would add another step.
The technologies are not mature right now. I thought E-pods were a good bet until I saw the photos of the rusted out ones and the stories of poor service. Other companies have hot-headed CEOs.
So for now they're not good enough for me to fork over more than the cost of a regular repower but hopefully soon they'll get more reliable, cheaper and hopefully batteries will get better as well.
Here is a link to the gentleman with the dual E-pod gemini. He has some really good real world data (including real amperage usage vs speed graphs) on his setup as well as a good explanation of some of the advantages that aren't normally listed when people compare the technologies side by side.
Epods in Use
speed vs. amperage
From the link to this page:"(update: the epods actually take half the power indicated on the chart to reach the speed),"
Medsailor (not affiliated with anything electric or diesel)