Boat U.S. - March 2009 - (Page 59)

be done electrically. They’re smaller than diesels and easier to mount low in the hull, providing a horizontal shaft orientation. It’s easier to soundproof an engine-driven generator, or genset, in its compartment than to isolate an engine that’s attached to a drive shaft. But the main reason for using the hybrid drive in large vessels is that it permits multiple propulsion engines that can be more accurately sized to the specific load. One engine/generator will put out enough power to move the ship slowly. To reach higher speeds, the crew starts up additional generators until the total power sent to the electric motors matches the need. Matching engine to load increases efficiency, which translates into greater range and lower fuel consumption. As a bonus, the same generators produce electricity to run all the onboard comfort and safety systems, including pumps, air conditioning, watermakers, and electronics. You’re not likely to want a half-dozen little gensets all over your 30-footer in order to do exactly what the big ships do, but the hybrid idea easily scales down to small craft with a single generator and electric drive, anyway. Freeing a naval architect from having to put a diesel, shaft, and drive in a specific spot lets him or her use interior space more efficiently and better balance the boat. The lower sound level and plentiful electricity for boat systems are all positive factors. Pushing a boat with an electric motor requires a significantly larger than average battery bank. Big Concepts Can Work On Little Systems A Serial Hybrid doesn’t have a transmission and can turn a big prop with relatively little energy consumption, so its total efficiency can be higher than a direct-drive diesel, although it has proven hard to achieve in practice. The hybrid must overcome the losses that come from generating and transmitting electricity. That depends on getting the right combination of valve timing, fuel injection, and generator rpm for each load condition; it takes a well-programmed computer to do that. It’s a complex problem, but well worth solving. The European Union sure thinks so. They’re funding a study group with an impressive 2.5 million euros to see if hybrid power is worthwhile for small craft. The key person in this operation is the American-based boating writer Nigel Calder, the world’s foremost authority on small-craft propulsion systems. If you’ve been in boating very long, you undoubtedly have a copy of Calder’s invaluable book Boatowner’s Mechanical and Electrical Manual and probably a couple of his other references, as well. Nigel Calder has rigged his new boat, a Malo 46, to be driven by either direct diesel or by the electric motor for test purposes. The Island Pilot DSe can run at six knots all day using solar power, or the diesel engines can boost that speed to 13 knots.

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Boat U.S. - March 2009 Contents Reader Forum Boat U.S. Reports What’s New In The Brew? The Perfect Paint Job Launch Into Spring Boats Gear Wheels One Mom, Two Teens, No Exit So, Nigel Had This Idea Ice Devices It Was A Club Of Their Own Expanding The Boating Universe Tech Connection A Case Study In Getting Results Let’s All Do This Together Classifieds Member Benefits/At Your Service

Boat U.S. - March 2009

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