Auxiliary Engine

An Auxiliary Engine is a smaller engine aboard a ship that drives a generator to produce the vessel's electrical power, as opposed to the main engine that provides propulsion. Together an auxiliary engine and its generator form a “genset” (diesel generator), and ships carry several so that power is always available and maintenance can be done without a blackout.

The auxiliaries supply the electricity for everything on board except propulsion: lighting, pumps, cargo and deck machinery, the engine-room systems, navigation and communication equipment, accommodation, and — crucially on reefer ships — refrigerated container power. Their combined output must meet the ship's varying electrical load in different conditions (at sea, in port, during cargo operations). Auxiliary engines are typically medium-speed diesels, run and maintained by the engine department under the Chief Engineer as part of the planned maintenance system, and consume fuel that counts toward the ship's costs and emissions. Some ships reduce auxiliary running in port by using shore power. Auxiliary engines are essential to keeping a ship functioning, complementing the main engine. They are fundamental to shipboard power.