2024 Tugboat of the Year: eWolf

eWolf dockside in San Diego this spring.
eWolf dockside in San Diego this spring.
eWolf dockside in San Diego this spring.

Crowley’s electric tugboat signals cleaner future for U.S. towing fleet
eWolf will begin assisting ships in San Diego this spring

Crowley Capt. Joshua Ferguson eased eWolf off the dock in the Port of San Diego, spun the vessel 180 degrees and glided toward San Diego Bay.

The first electric-powered tugboat in the United States remained eerily quiet as it accelerated toward 10 knots. There was no engine noise. No vibration. No exhaust sounds or smells. When asked about eWolf’s best attributes, Ferguson didn’t hesitate.

“Honestly, it’s the noise, or the lack of noise,” he said in mid-March after docking back at the Port of San Diego. “That is one of the coolest things about this tug.”

Crowley took delivery of the 82-by-40-foot eWolf in early 2024 from Master Boat Builders in Coden, Ala., after two years of construction and outfitting. Crowley’s engineering services group designed it from the keel up for zero-emission operations. The 4,200-kW (5,632-hp) tugboat generates 73 tons of bollard pull ahead and 70 tons astern.

A 2,100-kW Ramme electric motor installed atop a Schottel drive.
A 2,100-kW Ramme electric motor installed atop a Schottel drive.

EWolf’s 6.2-megawatt-hour powerplant relies on nearly 1,100 Corvus Energy lithium-ion batteries for power while underway. Those batteries supply electricity to twin 2,100-kW Ramme electric motors installed atop Schottel L-drives. ABB provided key electrical components and integration know-how.

Two 400-hp generators installed in the deckhouse provide electrical power during emergencies or to extend its range for offshore vessel rescues. Crowley expects eWolf will remain in California, with its longest voyage being to Los Angeles or San Francisco Bay for dry dockings if San Diego facilities aren’t available.

As of early spring 2024, eWolf had not yet entered service. That is expected later this spring once the dockside charging station is finished, according to Paul Manzi, a Crowley Shipping vice president. It will feature two 1.5-megawatt-hour Corvus Energy power storage systems. Crowley designed the tug to operate all day without replenishing the batteries. Recharging will happen at night when demands on the power grid are lower.

Engineer Peter DeMaria stands alongside Corvus lithium-ion battery banks below deck in eWolf’s mechanical space.
Engineer Peter DeMaria stands alongside Corvus lithium-ion battery banks below deck in eWolf’s mechanical space.

Crowley partnered on the project with multiple federal, state and local agencies, including the U.S. Maritime Administration, California Air Resources Board and San Diego Air Pollution Control District. Taken together, these agencies provided $13.67 million in grants that offset construction costs. 

Crowley has not said how much eWolf cost to design, build and outfit. But officials indicated the charging station and vessel together cost roughly twice that of a similarly sized diesel-powered azimuthing stern drive (ASD) tugboat.

EWolf replaces an existing tug with engines that meet EPA Tier 2 emissions standards. During normal operations over the next decade-plus, that Tier 2 tug would generate about 178 tons of nitrogen oxide, 2.5 tons of fine particulate matter and 3,100 tons of carbon dioxide, according to Crowley. It also would burn about 30,000 gallons of fuel per year. Meanwhile, eWolf will generate zero emissions during typical operations.

“The tugboat to be replaced under this project operates full-time at the Port of San Diego, where nearby communities face significant air quality challenges,” the U.S. EPA’s West Coast Collaborative said in a 2020 newsletter describing the project.

Frank Urtasun, chairman of the Port of San Diego Board of Port Commissioners, described eWolf as “a game changer” for the port and the broader towing industry.

“Not only is this a zero-emission tugboat, but it’s got a 70-ton bollard pull, which is more powerful than the diesel-powered tugboats we already have in the port,” Urtasun said in March during a vessel tour at the port.

The lack of exhaust stacks on eWolf is perhaps the most obvious design difference compared to a conventional ASD tugboat. It is far from the only one. Instead of an engine room, the tugboat has a mechanical space below deck that houses an immense electrical system that governs vessel operations.

The mechanical space has no main engines and no gensets. Instead, it is anchored by a row of electrical cabinets on the port and starboard sides along with a handful of standalone electrical cabinets that together disperse electrical power throughout the vessel as it’s needed. Miles of electrical cables running beneath the floor grating connect these critical systems.

Twin watertight, air-conditioned battery rooms are located forward on eWolf’s port and starboard sides. Each battery room contains three banks of Corvus lithium-ion batteries weighing roughly 70,000 pounds. A robust cooling system maintains 68 degrees within each room, and water fog systems are installed for fire suppression.  

Coulston Van Gundy, vice president of Crowley Engineering Services, said stability was a huge factor in the overall design. On a conventional tugboat, fluid management is integral in maintaining an even keel as fuel in the tanks burns off. That’s much less of a factor on eWolf, which carries at most 10,000 gallons of fuel for the backup generators.

“When a battery is depleted, the weights do not change at all,” Van Gundy explained. “They weigh the same as they do fully charged. So, we really had to nail our stability right at the outset.”

Manzi, the Crowley Shipping vice president, said the vessel is intended to perform as good or better than a diesel-powered counterpart. Beyond that, Crowley expects to see a sharp reduction in maintenance and lifecycle costs from eWolf. Diesel fuel, engine overhauls, lube oil, filters and other routine maintenance intervals add up with diesel engines. Many of those costs are eliminated with electric propulsion.

And while eWolf performs job after job in San Diego, Crowley expects to gain crucial insights into the electric propulsion system. “What we are trying to understand is, what are the total cost of operations?” Manzi said.

In doing that, he added, the company wants to identify how overall life cycle costs change and how quickly the higher construction costs can be recouped through reduced operations costs. He expects overall maintenance costs to fall by up to 60 percent.

“These are the long-term goals. We’ll be exploring the full cost of ownership,” he said. “There are very few operating (electric tugboats) to go by.”

Engineer Peter DeMaria was still acclimating to the propulsion system in mid-March. After 35 years working on diesel engines, he admitted the electric propulsion system was intimidating at first. He and other engineering personnel learned the system together and helped each other along the way.

“I am very comfortable with it, but again I am still at a point where things are happening that I have no way to remedy the problem,” DeMaria said.

The propulsion system is equipped with a suite of sensors and monitoring software that analyze and identify performance metrics. It also can track potential issues in real time. ABB technicians can remotely log into the system to address problems. DeMaria and his colleagues also can talk it through with offsite techs using video calls.

“That engineering mentality will get you through it to where you can figure it out,” he said. “But you get to a point sometimes where you need help. You have to be able to ask for it.”

Capt. Joshua Ferguson and engineer Peter DeMaria stand alongside one of two Markey winches.
Capt. Joshua Ferguson and engineer Peter DeMaria stand alongside one of two Markey winches.

Before eWolf arrived, Capt. Ferguson primarily operated Crowley’s 4,500-hp Tioga and 4,800-hp Scout, which has Voith Schneider cycloidal drives. But eWolf is another animal altogether.

The electric motors, for instance, are more responsive than traditional diesels. They can provide immediate thrust, with no need to clutch into gear. As such, the system gives the operator greater control, particularly when the job calls for a light touch. Operators can feather the controls for as little as 1 rpm during precision maneuvers.

“It operates just like the Tioga does in a sense,” Ferguson said. “The main difference is you can literally take (eWolf) down to zero (rpm). If you are not doing anything, you can literally go to zero and you are not using much power.”

Operating an electric tugboat as quiet as eWolf also took some getting used to. “You don’t really realize how many audio cues you have available on board a traditional vessel,” Ferguson said. “But now that you have none, and couple that with the power of the electric motors that spool up very fast like a Tesla does, you have to change the way you operate the vessel.

“There is a little bit of a learning curve,” he continued, “but we are really excited about it.”

Capt. Joshua Ferguson steers eWolf into berth at the Port of San Diego in March. eWolf’s wheehouse is equipped with a JRC/Alphatron integrated bridge with displays that can retract into the dash.
Capt. Joshua Ferguson steers eWolf into berth at the Port of San Diego in March. eWolf’s wheehouse is equipped with a JRC/Alphatron integrated bridge with displays that can retract into the dash.

The wheelhouse on eWolf is equipped with a JRC/Alphatron Marine integrated bridge with retractable touchscreen displays that can disappear into the dash when not needed. Each screen is customizable based on operator preference to show radar, electronic charts, closed-circuit TV cameras or other information.

On the operator’s left, a rectangular touchscreen display built into the dash monitors critical electrical system performance in real time, including battery settings and remaining charge.

“Any information that is available in the engine room is also available up here,” Ferguson said, “which makes it very, very handy. There are three stations where this is available: Here, the engine space, and in the galley.”

“Each battery cell is monitored with different set parameters for things like voltage and temperature,” he added. “If the system detects any issue for any one of those cells, it takes that one offline.”

Other features include an ABB joystick steering system and ABB Ability Marine Pilot Vision and Marine Pilot Control, which use numerous sensors to enhance the operator’s situational awareness. Starlink Marine provides satellite connectivity. 

EWolf will return to the same berth each night to recharge its batteries. As such, it is equipped as a day boat. Its main deck is equipped with a well-appointed galley with stainless-steel appliances and a full head. The single cabin has two double bunks to accommodate four crewmembers on rare overnight voyages.

Crowley’s interior design solutions team outfitted the interior with sustainable, durable materials, including recycled products where possible. That includes a Formica countertop and LEED-certified Lonseal marine flooring. A mural on the galley wall uses a welcoming blue-green color palette for an “eco coastal vibe,” according to Jayne Russell of the Crowley interior design team.

Back in the wheelhouse, where the temperature was set to a comfortable 68 degrees, Ferguson praised Crowley for seeking crew feedback when designing eWolf. That input, he suggested, ensured a user-friendly and highly capable platform.

“Ultimately, it is still a tugboat, and it just has a different way of operating, which requires a different way of thinking things through,” he said. “But I am excited to see where it goes.”