In collaboration with its hybrid technology partner, XeroPoint Energy, Aspin Kemp & Associates (AKA) has developed an innovative and efficient means of generating, storing and distributing power on vessels. The hybrid system is now deployed in several tugboats including two on the west coast of the United States.

One evening around the dinner table, a group of AKA employees discussed the desirability of a flexible power and propulsion system that would allow a vessel operator to choose the most efficient mode of operation at any given moment.  By the end of the conversation, the framework for the XeroPoint hybrid system had been conceptualized. “The concept was driven by the realization that we were consuming way too much fuel by idling our engines and we definitely weren’t doing the environment any favours either,” says John Eldridge, Hybrid Project Manager with AKA and owner-operator of a whale watching vessel in St. Andrews, New Brunswick. “The motivation for the hybrid system was originally for my eco-tourism vessel but after discussion with my colleagues at AKA, we realized that the market for the system was much larger and more diverse than just my specific application” indicates Eldridge.

In fact, AKA has identified the tugboat market as the “sweet spot” for its hybrid technology.  “The hybrid system takes advantage of duty cycle variability, which means, vessels that have an operational profile with several unique power and propulsion requirements are most likely running their diesel engines inefficiently” explains Eldridge. “Typically, tugboats require a considerable amount of power for a relatively small percentage of their duty cycle and spend large portions of their operational day at low power” adds Eldridge.

In 2006, AKA began discussing the concept with Foss Maritime and the developments that followed would revolutionise marine propulsion system design. “When we met Foss, they were well into the construction of a series of new ‘Dolphin Class’ tugs. Foss had already undertaken a number of initiatives that had demonstrated the company’s commitment to reducing its environmental impact. Ultimately, Foss’s goal was to build one of its new vessels with a fuel-efficient hybrid propulsion system” explains Paul Jamer, VP Corporate Development with AKA.

A review of the operational data from Foss’s existing harbour-assist vessels indicated, as anticipated, that full power was very rarely used (less than 5 per cent of the time). Conversely, the vessels were spending in excess of 85 per cent of their operating time at less than 15 per cent of their rated power. The result was that the diesel engines were operating at their worst fuel efficiency for the majority of the time.

The design of the propulsion system for Carolyn Dorothy – the world’s first hybrid tugboat, addressed this problem. The XeroPoint hybrid system provided the flexibility in the configuration required to enable the propulsion system to be optimised for those points of its duty cycle where the vessel spends the majority of its time. “The results were dramatic,” said Jamer. “Third party analysis of Carolyn Dorothy’s hybrid system, as compared to a sister vessel working in the same harbour, indicated a 27 per cent reduction in fuel consumption, a 73 per cent reduction in particulate matter, and a 51 per cent reduction in NOX.”

Foss and AKA have now received joint patent protection for the hybrid system and have recently completed the hybrid conversion of a second Dolphin class vessel, Campbell Foss.

“The best part about the hybrid system” says Jamer “is that everyone involved benefits from the technology. Foss has reduced their fuel consumption in the hybrid vessels by over a quarter and they continue to lead the industry as environmental stewards. At AKA, we believe that this is the way of the future and we look forward to playing our part, as owners and operators strive for a healthier environment and bottom line.”