Crowley Maritime Corp. has announced plans to build the first zero-emissions tugboat in the United States.
The 82-by-40-foot eWolf will perform ship assist work in San Diego using a fully electric propulsion system. It will be powered by twin 2,100-kW (2,816-hp) motors drawing electricity from battery banks installed below deck. Bollard pull is estimated at 70 tons.
Two 400-hp diesel-powered generators on the main deck will be available to charge the batteries during long voyages, although Crowley does not expect to need them during typical operations.
“It is designed with enough battery power to do its work totally on electric,” said Ray Martus, vice president for Crowley Engineering Services.
ABB designed the propulsion package for the new tugboat, which will be built in Alabama by Master Boat Builders. Crowley Engineering Services provided the tug’s design, which is available to other operators considering electric propulsion.
The machinery space on an electric tugboat has little resemblance to one on a conventional diesel-powered vessel. The main engines, of course, are absent. Forward, the tug will have six racks of Corvus batteries that store energy.
Moving aft, the tug will have switchboards and other components supplied by ABB that manage the electrical supply and deliver it to twin 2,100-kW Ramme motors. Those will be installed atop Schottel L-drives that propel it like a traditional azimuthing tugboat. Markey Machinery will supply the electrically-driven winch.
Cochran Marine will develop a shoreside charging station using renewable energy to replenish the tug’s batteries between jobs as needed. Crowley intends to do most of the recharging during off-peak hours.
Despite the new propulsion system, eWolf should perform similarly to a conventionally-driven tugboat — but with some notable enhancements. The tugboat has no exhaust stacks, improving visibility aft, Martus said. Electric motors can turn the propeller as slowly as 1 rpm, offering captains far more control in close-quarter situations, or while operating in areas sensitive to prop wash.
“For its intended purpose I don’t think we are making any tradeoffs,” said Porter Sesnon, Crowley’s director of business development. “We have two 60-plus-ton (bollard pull) vessels in San Diego now, so it will be more powerful.”
Much like an electric car, eWolf will generate zero emissions when underway. Crowley estimates the tugboat will save 30,000 gallons of diesel fuel each year. Over a decade, the company estimates it will generate 178 fewer tons of nitrogen oxide (NOx), 2.5 fewer tons of diesel particulate matter, and 3,100 fewer metric tons of carbon dioxide (CO2) versus a conventional tug.
“Crowley’s first-of-its-kind electric tugboat is a game changer. It checks all the boxes by providing environmental, economic, and operational benefits for our communities and maritime industry,” Michael Zucchet, chairman of the Port of San Diego Board of Port Commissioners, said in a prepared statement.
Crowley has partnered with multiple federal, state and local organizations on the project, including the EPA, the U.S. Maritime Administration, the San Diego County Air Pollution Control District and California Air Resources Board (CARB). These agencies provided millions of dollars in grant funding toward the eWolf project.