The future is now for hybrid propulsion at Great Lakes Towing


The Great Lakes Towing Co. operates some of the oldest harbor tugboats in the country, thanks largely to its presence in freshwater ports. Its newest tugs will be some of the most environmentally friendly.

Great Lakes Shipyard, a division of the towing company, is building four tugboats at its yard west of downtown Cleveland. Ohio was scheduled to enter service in the Port of Toledo around June 1. Sister tugs Michigan and Pennsylvania will be finished in July and October, respectively. The fifth vessel, expected by mid-2020, has not been named yet.

The new tugs are based on the same 65-foot Damen 1907 ICE-class platform as Cleveland, built two years ago. But Ohio features a hybrid generator system, eliminating the need for a second diesel genset. Michigan and the two others under construction will have diesel-electric hybrid propulsion capable of driving the propellers from the main engine or electrically from a genset.

Logan Clutch Corp. of Cleveland supplied the hybrid system components. Its genset solution is called FlexaGen, while its hybrid propulsion package is called FlexaDrive. Michigan will be the first tugboat equipped with the FlexaDrive hybrid system, said Joe Starck, president of Great Lakes Towing.

“What I really like about this hybrid system, as compared to many others on the market, is that it uses strictly electric motors powered by a diesel generator, and no batteries,” Starck said during a recent interview in his Cleveland office.

Ohio features softer bow fendering than Cleveland, built two years ago.

Courtesy Great Lakes Towing Co.

Cleveland is the lead boat in the 10-vessel project. The towing company plans to keep the first five or six and possibly sell the rest. The tugs they keep will update a fleet of single-screw tugs, many dating back a century or more. Damen’s 1907 ICE model aims to replicate the simplicity and function of those existing tugs while adding power, maneuverability and reliability. They also were designed to reduce manning needs from three to two.

Great Lakes Towing operates about 30 tugboats in 11 ports between Duluth, Minn., and Buffalo, N.Y. Ship-assist services for U.S- and Canadian-flagged Great Lakes freighters, foreign-flagged “salties” and the occasional barge or ATB is the primary mission. The tug design utilizes three-blade, 71-inch props in nozzles to accommodate shallower waterways. Harsh winters on the Great Lakes require heavily reinforced hulls to provide icebreaking services.

Capt. Scott Baker is one of Great Lakes’ primary captains in the Port of Cleveland. He said Cleveland performs admirably in the narrow, winding Cuyahoga River. “She’s fantastic for what we are doing here in the Great Lakes,” he said in a recent interview aboard the tug Mississippi, built in 1916. “You can trust her to get where she needs to be, and do what she needs to do.”

Starck also had high praise for the new tug class. He considers it a modern version of tugs that the firm has operated for more than 100 years — albeit with 50 percent more horsepower and double the bollard pull. For each new tug the company adds to its fleet, two older tugs will be retired. Six tugs were decommissioned within the last year, he said.

Cleveland operated for nearly a year before construction started on Ohio, giving the company a chance to add creature comforts requested by the captains and crews, and incorporate lessons learned during construction on the lead tug. While the hull itself is unchanged, channel coolers installed on Cleveland were replaced with Duramax Marine keel coolers on subsequent boats, reducing labor costs. Softer, more forgiving Schuyler Cos. loop-style fendering protects Ohio’s bow, in place of thinner, firmer extruded rubber fenders used on Cleveland.

The aft deck on Ohio features a sturdy H-bitt and a 15-hp capstan. Future tugs in the series could be fitted with a towing winch.

Courtesy Great Lakes Towing Co.

The biggest changes between the lead boat and its sister tugs can be found in the engine room. Twin MTU 8V 4000 Tier 3 mains generating 1,000 hp each at 1,600 rpm will be installed across the class. But in Ohio, a single 65-kW John Deere/Marathon diesel genset provides standby power, while ship service power underway comes from the Logan FlexaGen system.

The installation runs on a gearbox-driven electric motor installed aft of the port main engine. Electrical power output varies depending on main engine speed but is always more than sufficient, especially while underway, according to Jonathan Leivo, Great Lakes Shipyard’s director of engineering.

“The FlexaGen is always rotating when the port main engine is in operation. It is driven by a power take-off on the back of the gear,” he said. “The only question is when to send electricity to the switchboard. We foresee that happening shortly after starting the mains … more than likely without ever starting the diesel genset.”

“We can go from shore power to the FlexaGen or from our diesel generator to the FlexaGen without experiencing any momentary blackout whatsoever, which is a drastic improvement from the older systems we’re all used to,” Leivo continued.

Western Towboat of Seattle operates a FlexaGen on its 15-year-old oceangoing tugboat Ocean Titan, and is considering installations on other vessels in the fleet. Vice President and Capt. Russ Shrewsbury said crews run the system on round-trip voyages to Alaska, sharply reducing run time on the generator.

Ohio runs a single John Deere genset thanks to the FlexaGen hybrid system.

Courtesy Great Lakes Towing Co.

“This has equated to about 2,000 to 2,500 gallons of saved fuel on our 10-day trips, as well as delayed and less frequent oil changes and maintenance that would have to routinely be done on the main generator,” he said in an email. “The system not only has performed great, it has also created a noticeable difference in the decibel levels on the boat, which the crews have also enjoyed.”

The Logan FlexaDrive diesel-electric hybrid propulsion package on Michigan and its follow-on sister tugs incorporates the use of two 99-kW John Deere/Marathon diesel gensets to produce electrical power. That current runs 75-hp electric motors installed on each Twin Disc reduction gear. The electric motors turn the gears, thereby turning the shafts to propel the boat.

Three primary propulsion modes are available to the operator. Hybrid mode utilizes the gensets and electric motors for propulsion, while the main engines remain off. The towing company envisions crews using this mode when transiting to a job or idling alongside a ship before work begins. The second mode uses just the main engines for propulsion and power, with the electric motors operating “in reverse,” sending electric power to the main switchboard while the diesel gensets remain off.

Finally, in “boost” mode, the main engines and the diesel-electric generators operate simultaneously. The hybrid motors add propulsion power, boosting thrust output by 10 percent. This mode will be reserved for groundings and other extreme situations when every pound of bollard pull is critical, Starck said.

The various modes of operation are unique, especially considering the tug’s conventional propulsion system. “Twin Disc really stepped up to work with Logan to engineer this gearbox with a double-clutch system that allows us to operate in all these different modes,” Starck said. “I think they saw a niche here that I don’t think anybody else offers.”

The contemporary wheelhouse aboard Ohio and its sister tugs features modern Furuno and Simrad electronics. It also has a helm chair, unlike some existing tugs in the Great Lakes fleet.

Courtesy Great Lakes Towing Co.

Great Lakes Towing received grant funding from the Ohio EPA to support the hybrid project. Money from a diesel emissions reduction program will cover 40 percent of the hybrid machinery and equipment. “The tug Ohio was already too far along in construction when the final package was ready for manufacture, and timing restraints only allowed for the installation of the FlexaGen system, but Hulls 3, 4, and 5 will sport the full FlexaDrive hybrid package,” Starck said.

As he sees it, both hybrid systems offer several benefits. They are quieter and will reduce vibration. The propulsion system should burn substantially less fuel, reducing costs and cutting emissions. It will also allow reduced operating hours and wear on the main engines, lowering maintenance needs and extending time between expensive overhauls.

“Maintenance is expensive, especially engine maintenance,” Starck said, noting that less fuel consumption by the main engines and generators will extend the maintenance cycle accordingly. “If we are using (the hybrid system) as much as I think we’ll be using it, we could stretch it out 10 years.”

The basic layout of the tugboat has not changed between Cleveland, Ohio and subsequent boats in the series. From the main deck entrance, stairs lead up to the wheelhouse — equipped with Furuno and Simrad navigation electronics — or down into the crew spaces. The forecastle deck below includes a small mess and lounge, as well as cabinets for the hybrid controls. Forward is a berthing space with storage, while the head and access to the engine room is aft.

On deck, the tug has towing bitts fore and aft, where crews will attach tow lines in most applications. The 15-hp capstan on the aft deck assists with line handling. The tugs are large enough to handle towing winches, and Starck said future tugs might have one for added flexibility and earning potential.

Ohio will be christened June 21 at the National Museum of the Great Lakes in Toledo. Organizers will memorialize one of the region’s oldest surviving tugboats, the 116-year-old former Great Lakes Towing tug Ohio, while commemorating its thoroughly modern successor.    

Highlights: Hybrid system saves fuel, engine wear • Design optimized for Great Lakes harbors • Replaces tugs built more than 100 years ago
By Professional Mariner Staff