Hybrid Tugboats are Cleaner and Quieter: Energy Products Articles: Eco20/20

Hybrid Tugboats are Cleaner and Quieter

Tugboats don't just consume power; they torment it first. Leaning hard into a full-open throttle, a tug will bind the howl of fuel and air funneling into its diesel engines to the staggering roar of its exhaust, and raise a thrum in the air so potent passing ducks will flinch. So how does anyone devise emissions controls for such extraordinary brutes?

The San Pedro Bay Ports Clean Air Action Plan

* When a major reduction of emissions was mandated for the San Pedro Bay area ports, to help combat air pollution, Foss Maritime stepped up to the challenge. They designed a hybrid tugboat able to use less fuel and yield far fewer emissions while retaining that vital measure of savage horsepower required to discharge a brutally hammering duty. Noise-reduction tagged along as a bonus.

Foss' Green Assist™ Hybrid Tug

* The Foss hybrid has as much power as the Dolphin-class tugs it was based on. But, for handling the challenges tugs encounter, the hybrid relies on a computerized energy management system to oversee adjustable operating parameters to put forth the best mixture of power from its batteries, generators and main engines. The configurations have been classified into four levels: a stop/idle setting for minimum emissions, a slow-cruising transit, a mid-range setting, and a full power assist.

* Power-Train

The hybrid's two 1,700hp main engines are supplemented by 126 storage batteries, weighing in at 18,000lbs total, together with two 310kw Cummins generators, and two Seimens motor generators. At full power, this merging delivers a total clout to the two stern drives that, for critical applications, exceeds 5,000hp in applied power and can offer about 60 tons of bollard pull.

o Bollard pull is a term used when comparing the pulling force of watercraft, particularly tugboats. A mooring bollard is used as an attachment point for measuring the pull of the craft.

* Control Systems

Relying on insights gained from well over a hundred years of doing business, Foss Maritime picked an existing hybrid technology, created by Jason Aspin of Aspin Kemp & Associates and John Eldridge of XeroPoint Energy, and modified it for use in their new tug design. The selected control system is more than flexible enough to handle the duty requirements.

o When the tug is idling or docked, the diesel-powered engines shut down, emissions are minimized, and there is no engine sound. When the tug is manipulating a ship, or running open-throttle across the bay, the diesels are engaged.

The success of Foss Maritime's Green Assist™ Hybrid Tug has far exceeded expectations. The modifications cut nitrogen oxide and particulate emissions nearly in half, fuel use has been estimated at 30 percent less than the standard Dolphin tugs the hybrid resembles, and the noise reduction is a truly splendid bonus.