Harbor Tug Electrification – Experiment or a New Era?

Last year was a landmark with regard to electric harbor tugboats. The all-electric, 82’ eWolf was christened by owner Crowley for service out of the Port of San Diego in June, making it the first all-electric ship assist tugboat in the United States. North of the border, SAAM Towage Canada announced that the company’s first all-electric harbor tugboats Dynamo and Dynamo II (both ElectrRA 2300-SX models) were ready in April for service to the Port of Vancouver, BC, Canada. The launchings were marked by a flurry of positive reception from both public and private partners. 

“Electric vessels have already been used in several marine applications for decades and the technology is now proliferating into the commercial space to a greater degree,” said Michael LaFleur, Vice President of Maritime at Port of San Diego. The first Chinese-built all-electric tugboat the Yungang Electric Tug No 1 went into operation at the Port of Lianyugang in 2021. “We have no doubt that we will see greater innovation in this space.” 

“In all the world, there are only a handful of electric tugboats in operation. We’ll now see two of them hard at work in Vancouver’s magnificent harbor,” said Premier David Eby at a ceremony for the Dynamo sisters that included a First Nations blessing. “The reduction in pollution from these electric tugs is the equivalent of taking 600 vehicles off the road. The future is happening right now in British Columbia.” 

What are we really dealing with here beyond the positive press? Are electric harbor tugs a game changing new standard that will save the world, or are they an experiment that could go either way? Let’s take a closer look.

Harbor Tug Design Features

The plucky harbor tug serves as the miniaturized workhorse of any given working waterfront, tasked with the duty to help maneuver far larger vessels in and out of port. Unlike her bigger sisters that are built to tow massive loads across oceans, a harbor tug is often crewed by two and operations are limited to the immediate demands of the homeport. Sizing up the design features of these new tugboats is just as important as navigating the electrification angle. Electric or no, a harbor tug needs to be prepared for a rigorous working life.

A Jones Act vessel, eWolf was designed by Crowley Engineering Service based in Seattle and constructed by Master Boat Builders in Coden, Alabama. The ABB Marine electrical propulsion system works with German Schottel hardware. Two SRP 430 LE 2,050kW rudder propellers and a MariHub data IoT Gateway and monitoring solution are integrated aboard. eWolf’s reported bollard pull is around 70 short tons with a top speed of 12 knots powered by a Corvus Energy 6.2-megawatt-hour main propulsion battery array. Seattle-based Markey Machinery supplied eWolf’s DEPC-48 hawser winches that spool about 500’ of 9” circumference line rated to 430 tons.

The Dynamo sisters, both ElectRA 2300-SXs, were designed by Vancouver-based naval architect firm Robert Allan Ltd., built by Turkish Sanmar Shipyards, and (like the eWolf) use electric power systems built by the Norwegian company Corvus Energy. The nearly 77’ ElectRA 2300-SX has 3,616 kWh battery capacity that according to the designer should lead to hours of normal operations or a full hour of 70-tonne (77 ton) bollard pull capabilities. The customized skeg resulted from a survey of SAAM’s local crews for their preferences and sea trials on tugboats. The skeg has been optimized for tight quarters maneuverability.

All things told, both vessel models appear very similar to each other and their peers in terms of capabilities. One layout perk is that the electric boats do not require a large smokestack for exhaust, providing skippers an unencumbered 360-degrees of visibility.

Non-Climate Pros and Cons of Electric Harbor Tugs

The limited scope of practice, continuous access to infrastructure, and relatively low investment have likely contributed to harbor tugs being targeted for potential electrification by British Columbia and West Coast governments, corporations, and advocates seeking to reduce carbon emissions. But there are also less idealistic reasons to explore all-electric harbor tugboats. Many of the same performance perks of electric cars apply to electric tugboats. Accelerating to full throttle can be achieved more quickly with an electric propulsion system, a real perk for a harbor tug that needs to push and pull massive loads quickly in tight spaces. Leaping up a few thousand horsepower in seconds is a hard performance perk worth considering.

Like electric cars, electric harbor tugs are also far quieter to operate, but this feature is not merely for comfort. Writing as someone who worked a week on a tugboat from Kodiak to Seattle (story for another time), the ambient decibel level of all that roaring horsepower on tugboats is high. Anecdotally, my ears were ringing for days after working aboard despite following ear protection practices. The studies on the matter are elusive, but I wouldn’t be surprised if working on tugboats had quantifiable negative effects on crew hearing. This makes a strong case for the electric tug from a worker health perspective.

One con of the electric harbor tugs of today are that they have less range to make transits. This isn’t a problem if the harbor tugs are truly devoted to a single port, but in many places harbor tugs split their time between ports that are dozens if not hundreds of miles apart from each other. This is one of the factors that have given ports in Puget Sound pause, as their harbor tugs may occasionally be required to make lengthier transits outside the immediate waters of a single port. Even if the electric tug has the range to reach other ports they must have the land-based infrastructure including available charging outlets that allows the tug to be charged.

The conversation about maritime electrification tends to hyper fixate on carbon emissions. But diesel and gas emit many compounds, including heavy metals, volatile organic compounds (VOCs), and more. A busy port tends to contribute to a smoggy sky and gas sheen waters with all associated health issues, but electric harbor tugboats do not. However, the electricity comes from somewhere and that somewhere is where the differed emissions from the electric harbor tug truly lie.

Looking Under the Hood of Carbon Emissions Claims

It would be wonderfully simple to live in a world where we could just log a boat’s diesel gallons burned and proclaim whether or not the vessel is exacerbating climate change. With regards to electrification, one must roll up the sleeves to look a little deeper for the full truth. When looking at the eWolf and Dynamo sisters it’s vital to examine their energy source within their ports of operation: San Diego and Vancouver respectively. 

Firstly, the claims. According to Crowley, eWolf will generate 3,100 metric tons less carbon dioxide, 178 tons less nitrogen oxide, and 2.5 tons less of diesel particulate matter during the first decade of operations. According to EPA estimates, Crowley states this is equal to sparing 350,000 gallons of gas from combustion and ABB states that eWolf’s reduced emissions are roughly equivalent to 100 cars annually. 

But now we look to the San Diego power grid from which eWolf draws power. San Diego General Electric reports that 41.4% of the electricity the company delivers to homes and businesses comes from solar, wind, and other renewable energy while fossil fuels make up the rest. The City of San Diego has instituted a Climate Action Plan to pursue zero emissions targets for the city’s energy grid, but the success or practicality of the vision remains to been seen. For now, roughly half the electricity eWolf expends will be from non “green” sources. Figuring out the true emissions of this half of eWolf’s electricity diet would be complex. 

With the Dynamo sisters in the Port of Vancouver, SAAM reports 2,4000 metric tons of reduced carbon emissions annually. Vancouver’s energy mix is largely hydroelectric, a blessing of the city’s geography.

“At BC Hydro, 98% of the electricity we generate comes from clean and renewable resources,” said Chris O’Riley, president and CEO of BC Hydro. “We are committed to helping organizations like SAAM Towage take vital steps to electrify their fleet and reduce their carbon emissions.” This sounds like an ideal realization of the electrification goal. 

But what kind of operations will these new harbor tugs be supporting in British Columbia? While the two Dynamo boats will be assets for the Neptune Terminal of the Port of Vancouver, a major development for BC’s maritime infrastructure is Canada’s rapidly growing liquified natural gas (LNG) export industry. The nation’s first massive-scale LNG export facility is schedule to begin operations up the coast from Vancouver this year. LNG Canada reports that the facility’s initial capacity will produce 12.7 million tonnes (14 million tons) of LNG for the global marketplace. In fact, three hulls of another model of ElectRA, the electric-LNG hybrid 2800, are already in service for the facility. 

If one uses the Center on Global Energy Policy of Columbia University standard of one metric ton of LNG resulting in 2.76 tonnes (3 tons) of carbon dioxide when combusted, the new LNG Canada export facility will be adding about 35 million tonnes (38.6 tons) of carbon dioxide into the atmosphere annually. If we take the manufacturer claims that the Dynamo sisters are indeed saving 2,400 tonnes of emissions per year, then they are offsetting about .000007% of the new facility’s output. It’s nice to point to the little harbor tug in the harbor as green, but if it’s only there as part of an apparatus to export massive abouts of LNG… can we really pat ourselves on the back as climate heroes?

The Takeaway

In summary, reducing the pros and cons of electric harbor tugs to good versus bad is probably too simplistic. The many perks include rapid acceleration, no smokestack in the skipper’s line of sight, quiet operation for crew health, and none of those nasty particulate pollutants from exhaust. One can interpret the carbon emissions case as you will, but it’s clearly more complicated than advertised. Notably, fully electric harbor tugs of today can’t make long commutes to assist ports further afield of homebase. 

All in all, the timeless saying “there is no perfect boat, only a series of compromises” rings as true as ever. These boats are probably great for the specific uses they are designed for. Whether they are signifiers of great change is a question the maritime industry—and civilization at-large—will determine in the years ahead.

eWolf Specs:

Owner/Designer: Crowley Maritime Corporation/Crowley Engineering Services
Builder: Master Boat Builders

Dynamo I and Dynamo II (ElectRA 2300-SX) Specs:

Owner/Designer: SAAM Towage Canada/Robert Allan Ltd.

Norris Comer Editorial Director

Ahoy! I'm thrilled to lead the Best4Boats editorial. From Alaska greenhorn to oceanographer and R2AK racer to award-winning writer, I'm passionate about aquatic experiences and marine journalism. Follow along to stay informed and afloat.

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