Thursday, June 11, 2009

[Electric Boats] Re: 29' CAL Looking to switch to EV



on almost any mono hull regardless of prop design your not going to get much regeneration from the prop. This is due to speed through the water. Think about it. You put 40 amps through the motor to turn the prop what, 1200 rpm. so.. lets just arbitrarily call that 4000 watts. In regeneration you only get the water speed to turn the prop.. so at 4 or 5 knots you get what 50 rpm? your going to get about 100 watts back. so you have to drag the prop 40 minutes to get one minutes motoring in the end.

Now if you designed a huge prop of some kind that turned real slow with lots of torque you could generate a lot of power on just 2 to 4 knots of speed or current. The prop would look more like a wind generator though, and be feet in diameter rather than inches.

If the prop slowed the boat down from 6 knots sailing speed to 0 knots of sailing speed then it would be able to pass the same energy back to the motor that you used to drive the vessel at 6 knots with the motor.

There is no free lunch.

The only people that have gotten any usable regen on props that I can tell is some of the catamarans that can go 10 to 15 knots. at that speed your energy transfer is magnitudes greater. It is still not a supper significant number though.. maybe you get back 300 or 400 watts with a supper optimized system. I'm just guessing here.

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