Electric propulsion thumbs up or down?

FourPoints · Apr 28, 2011

caguy said:
After researching the idea of regenerating power with the prop is not practical. However using electric propulsion is not off the table.

it's not efficient, but it does work. the hunter they were showing with the elco drive was setup for prop regeneration. I guess it takes an hour or more of sailing to regenerate about 10 minutes of use, so by it's self it won't keep the batteries charged, but it will still contribute to the overall charge.

Old Skool Neil · Apr 28, 2011

Has anybody heard of the compass being affected by the inevitable Gauss fields?

kenn · Apr 28, 2011

Roger Long said:
The physics would support that, in fact make it inevitable. There are losses anytime you convert from one form of energy to another and significant losses charging batteries. The engine driving a prop is going to be way more efficient than driving a generator, charging batteries, and then running an electric motor.

Absent huge solar panels or frequent plug ins, a "hybrid" has to burn a lot more diesel for the distance covered than a conventional drive.

Even diesel electric where the generator directly drives the electric motor has a significant fuel consumption penalty.

I agree that currently there's an inefficiency over direct drive, but I don't agree that it's inevitable that hybrid will always be substantially more inefficient, especially if you consider the intermittent way that aux propulsion is often used.

Also, if you're able to recharge the boat batteries via shorepower or solar (a reasonable assumption for the casual or weekend sailor) then you're hardly running the diesel at all. That's a savings in both fuel and wear.

Finally, the 'piggyback' hybrids originally linked, which have the electric motor/generator connected at the coupling of a conventional shaft, do have direct IC drive, giving you both direct-drive efficiency and drive redundancy. I'd be quite interested to hear feedback from anyone who's got experience with this approach.

kloudie1 · Apr 28, 2011

Don't neglect to include that in generating the electricity which appears at your dock hook-up, the plant is about (a little less than) 30% efficient in converting fuel to power.. Then ya lose another 7% or so getting it from the plant to your dock outlet.. then another 10-15% loss in the charger.. and some more % crarging and then storing then re-converting to power.. It works well in hybrid cars because they have a firm connection to the ground and can recover braking power.. and they are underpowered (not all, but the ones that really do well on fuel use) compared to regular cars.. and the air drag is much less than water drag .. I am a proponent of electric power, but only where it makes sense.. When electric storage capacity matches what I can do with 25 gallons of diesel (250 mile range and recharges in 10 minutes), and comes close to matching that in price, I will consider converting. For folks who never use their boat that way and won't sell it to someone who does, it probably is close to making sense today albeit at a price premium.. Now.. back to the cool glass of Sailor Jerry!

Steve Dion · Apr 28, 2011

What about the cost of battery replacement and weight?

I doubt that there will be a economical replacement for the internal combusion engine unless something VERY dynamic happens with battery technology. These current system require 48 volts or more to operate.

kenn · Apr 28, 2011

kloudie1 said:
Don't neglect to include that in generating the electricity which appears at your dock hook-up, the plant is about (a little less than) 30% efficient in converting fuel to power.. Then ya lose another 7% or so getting it from the plant to your dock outlet.. then another 10-15% loss in the charger.. and some more % crarging and then storing then re-converting to power..

That's very green of you to consider it in those terms

Still, in terms of cost to the end-user it's more efficient to produce electricity in bulk, and there are many non-petrochemicals sources of electricity (hydro, nuclear, windfarm, etc). It's also my understanding that due to plant/grid design and demand patterns, using electricity just at night (eg charging) is pretty low-impact overall.

When electric storage capacity matches what I can do with 25 gallons of diesel (250 mile range and recharges in 10 minutes), and comes close to matching that in price, I will consider converting.

Diesel and gasoline are downright magical in terms of their energy density. We've all been spoiled, basically. Seems a shame, then, that we're blowing through the stuff so fast, when we could be meeting alot of our everyday transportation needs in more efficient ways. Not the discussion for here...

kloudie1 · Apr 28, 2011

Current non-fossil power production in the USA is about 15%..
Power loss is power loss no matter what time of the day it happens..Inefficiency all generally comes out as heat.. Global warming has a bunch of other causes beside co2.. Yes there is "Off Peak" pricing and the plants have to be kept warm for the morning surge in demand, but that doesn't change the inefficiencies..
I do consider myself to be a green thinker.. I drive sensible vehicles .. I recycle I compost, I sail.. I use LED's where I can.. I don't drive to work (ok I am retired

) .. I am co-owner of two patents to increase heat recovery (energy efficiency) in processing plants.. In my opinion, being green is about considering macro effects and not micro effects to our life support system (Earth) ..
OK I am off the soapbox now..