Nigel Ingram of Marine Construction Management talks to David Glenn about a pioneering power system for large sailing yachts. They are both currently aboard Adele, the build of which Nigel also project managed, in the south Atlantic. See David Glenn’s blogs here. 

A diesel electric power system is to be installed aboard a new 44m Dubois-designed sloop about to start building at Vitters in the Netherlands. The use of diesel electric aboard private yachts has been mooted for some time but this application is thought to be the first aboard a sailing yacht.

Nigel Ingram, of Newport-based Marine Construction Management (MCM), who is project managing the new vessel, explained that Siemens have developed the system in conjunction with Vitters using four separate Steyr engines driving generators. Power is then transferred via converters, through a single bus, or channeling system, to all the onboard users, be it for main propulsion, hotel services like air conditioning or refrigeration, driving the hydraulics for thrusters or rig control.

The Steyr engine has a particularly advantageous power to weight ratio and at 4,500rpm is relatively high revving which means a gearbox doesn’t have to be used to reach the generator speeds needed to supply adequately the electric motors used for main propulsion.

The four separate generating units, two at 180kW and two at 90kW can be placed almost anywhere. In this 44m yacht, which has a lift keel system and an internal casing taking up a fair amount of space, the freedom to place the motors to suit the interior arrangement and engine room layout is important. The engines can automatically cut in and out depending on the power demand.

As far is cost is concerned there isn’t a great deal of saving in the hardware itself, said Nigel Ingram, but the ability to bring a variable number of generators on line and direct power through a single bus to any application makes it simpler and more efficient than conventional systems.

There is also built-in redundancy because if one engine fails the three remaining units will still be able to deliver motive power. In this yacht’s case there are three electric motors driving the shaft and because they are able to develop sufficient torque across the full rpm range the need for a variable pitch propeller is minimised.

Nigel said they might go for a folding or feathering prop but the final decision hasn’t been made. VP systems are used so that the main engine can remain at a high rpm to retain torque while the blade pitch is altered, a comparatively complex and uneconomical arrangement.

Reduced noise and vibration is also an attraction. Submarines used to be fitted with similar systems so that they could reduce their acoustic footprint and the effect should be the same in this yacht. Siemens are using a range of equipment called Elfa, designed for well-proven commercial applications including buses.

The 44m yacht should be launched in the Spring of 2009.