||02-02-2009 06:56 PM
I chartered Waypoint (Lagoon's 1st electric 41 cat with 15kW genset) in Tortola a few years ago. They motorsailed it across the Atlantic (using AC/heat, hot showers, freezer/refr, TV/stereo) & arrived with more power than they left with.
The concept is great, though that boat needed automatic start on the genset since non-tech users ran the batteries flat too many time$$$. In addition they had to add fuel tankage since nobody used it for passages (BVI islands are minutes apart) & users wanted to sit at anchor with AC going. It still was a fine experience to have instant torque - forward or reverse without having to wait for RPM to spool up. You want 2 shaft RPM - no problem, (vs diesel idling at 800 RPM so anytime you are in gear you are moving). Sailing at 8 knots & somebody falls overboard - just pull back on throttles (motors are not in use but ready) & boat stops in 1 boatlength.
Electric motors have double the torque of similar Hp diesel so Emotors can be rated half as big. Fewer moving parts means very high efficiency & more miles for the fuel $.
Yes there is drag during generator mode, but with a double-digit-speed cat, you have the power to do it. Not as good for heavy keelboat. DC motors let you store the energy you make, but with the added weight of batteries. AC is an option & 3 phase is ideal - all the big ships & locomotives use it. I saw a 3 Hp 240V AC 1 phase industrial motor, powered by 5kW Honda portable generator in aft lazarette of a 30' keelboat. He could select any shaft RPM & he had lots of kW to run appliances when not full-speed motoring, plus lots of extra storage in what used to be a crowded engine compartment.
Fuel cells may be economical someday. Hybrid diesel or gasoline over electric is here now, competitively priced, off-the-shelf & greener by 50% or more.