How do you all feel about electric boats? Are they a viable or possible option?
Not until battery technology makes some quantum leaps!
Or nuclear marine propulsion becomes available to the public.
Seriously, we are so far away from practical electric boating we may as well think of its progress as being in the stone age. Aside from a handful of electric tour boats that you may see around some parts of the country that putz around at 5mph for less than an hour, it'll never be mainstream - especially in performance applications - for a very long time.
The practical limitations:
I'll use my boat as an example because I know the numbers off the top of my head.
2x500hp = 1000hp
180 gallons fuel capacity.
1 gal of gasoline has a potential energy capacity of 125,000 BTU's, which = about 36,600 watt-hours.
So, I can carry 6,048,000 watt-hours of energy.
It weighs about 1080 lbs.
So this is about 5600 watt-hours/LB energy density.
The average stock modern reciprocating 4-stroke internal combustion engine has an efficiency of approximately 20%.
1HP = 745.7 watts
Therefore, at WOT making 1,000HP at 20% efficiency, I'm consuming about 3,725,000 watts per hour and with 180 gallons aboard I can keep it up for about 1.62 hours.
Let's compare that to electro-mechanical physics.
The best Lithium-Ion batteries have an energy density of about 120 watt-hours per LB. Compare that to gasoline's 5600 watt-hours per pound.
I would need 50,400 pounds of batteries to do what I do now. Unfortunately my boat would have sunk and my bravos would have blown up carrying that much weight.
Lead-Acid batteries are far worse. They have an average energy density of 40 watt-hours per pound.
To make the same 1,000 HP for 1.6hours, I would need 151,000 pounds of lead acid batteries.
This is the same reason why Locomotives and cruise ships that are propelled by electric motors carry with them a diesel engine, not batteries.
The advantage is that electric motors are 90% efficient and they can make 100% torque virtually throughout their entire rpm range, thus it makes more sense to use them for the actual locomotion. The diesel engine does nothing other than turn a generator which can be tuned so that the diesel is running at it's peak torque and efficiency at all times versus varying its rpms which yields a more efficient use of its fuel.
Applying the same to a boat in our size range would still be far too heavy for the vast majority of boats and you can forget about performance.
A fully dressed 502 BBC weights what? 1,000#. So 1HP per Pound.
A 500HP electric motor would weight 3,500Lbs. I need two of them. In addition I'd need a 1,250 HP diesel engine (power in * efficiency = power out) and an equivalent generator. We're looking at a 20,000 LB powertrane plus fuel.
Last edited by CigDaze; 07-20-2011 at 03:10 PM.
But if more boat builders started putting out models with those options, would you adopt?
And if someone does develop in my lifetime some unobtainium-ion battery that's up to the task and a 1,000 HP electric motor that weighs less than 2,000 LB, It would still be a resounding no.
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