The generator inside

Tirelessly obeying Newton’s first law of motion, the flywheel in your boat’s diesel engine is destined to spin its life away in obscurity. Now, however, the lowly flywheel is on the cusp of newfound status; Steyr Motors North America in Franksville, Wis., is offering marine diesels with an integrated flywheel-based generator unit that can reportedly produce up to 300 amps of DC power.

Dubbed the “Integrated Flywheel Generator” (IFG), the unit consists of a rotor and stator windings located inside the engine’s flywheel housing. The rotor is attached to the engine’s flywheel. As the flywheel does its inertial duty of keeping the crankshaft turning, it also spins the rotor through the windings and induces a flow of electrical current. The IFG is a three-phase, brushless unit that incorporates permanent magnets in its rotor. This design reduces maintenance, as there are no brushes to wear out and replace.

Steyr, which manufactures its engines in Austria, has built diesels for such automakers as BMW, and they have also built marine versions for recreational vessels. “We build small, lightweight diesels for smaller boats,” said Russ Polansky, President of Steyr Motors North America. “There’s always a space availability issue.” By incorporating a generator inside the housing of the engine, Steyr aimed to reduce the need for a separate AC generator, the space for which is often at a premium on smaller boats.

One of the ideas for offering the IFG came from Steyr in Europe, which has offered regenerative systems on a variety of land vehicles in co-operation with vehicle-electric/electronic specialist Iskra in Slovenia. “We are in the off-highway and military equipment markets,” Polansky said, “where regenerative energy is used in braking systems. A lot of buses in Europe use flywheel systems as a brake.”

Output from the IFG is controlled with an external charge control unit that monitors the load on the flywheel generator and makes adjustments as needed. The IFG can produce either 14V or 28V DC.

Using an IFG system to produce electricity does come with a price. Just as it takes horsepower to spin an external alternator via a drive belt, the IFG soaks up some power. Another aspect of the IFG is dissipating the heat it produces. According to Polansky, that problem is handled by the engine’s existing water jacket. Coolant is directed from the engine’s main cooling system to water channels cast into the flywheel housing.

Steyr offers the IFG marine diesels from 85 hp to 250 hp. The IFG option adds $4,675 to the cost of the engine.

By Ocean Navigator