Arc, a marine technology company, has begun engineering the battery-electric conversion of Harbor Sentinel, a 50-foot harbor tug owned and operated by Pacific Maritime Group (PMG). Supported by funding from the Port of Long Beach through its Technology Advancement Program (TAP) and SWIFT Program, along with a Volkswagen Environmental Mitigation Trust grant administered by the Bay Area Air Quality Management District, the project will replace the tug’s twin diesel engines with an Arc electric powertrain.
Naval architecture firm Glosten is leading vessel engineering. Following commissioning, Harbor Sentinel will return to work from PMG’s Long Beach terminal for a 12-month demonstration.
The Harbor Sentinel joined PMG’s harbor fleet in 2023. The tug currently runs on two Cummins KT19 diesel engines producing 950 horsepower and carries 8,900 gallons of fuel. Its work includes moving barges and supporting construction and shipyard operations. In converting to electric power, the tug joins other efforts by the California Air Resources Board (CARB) to improve the air quality in California.
Glosten completed a feasibility study and hull scan before engineering began. The firm is now adapting the vessel and designing onboard systems to meet applicable U.S. Coast Guard Subchapter M requirements.
PMG will remove both diesel engines and install an integrated electric powertrain tailored to the existing vessel. The system includes a battery bank targeting 2 MWh of usable energy, electric motors and drivetrain, power electronics for the vessel’s existing AC equipment, updated helm controls and captain displays, and onboard charging with a DC fast-charge inlet. Telematics will support 24/7 remote monitoring. To accommodate the system, PMG in-house will widen the Sentinel 3.5’ and build a new deck, midbody, and pilothouse.
Arc will integrate, commission and test the system, then support PMG’s crew on site and remotely after the tug returns to service. Arc will also prepare the technical documentation required for Coast Guard review of its systems and components.
The Port of Long Beach’s Technology Advancement Program supports demonstrations of emerging technologies on working port equipment as part of the San Pedro Bay Ports Clean Air Action Plan. During the 12-month demonstration, Arc will collect data on performance, operations and charging, report results to the Port quarterly, and deliver a final report evaluating the technology and its potential for broader commercial adoption.
This project compliments other conversion projects in the Port of Los Angeles. Through the Harbor Sentinel conversion, Arc and Pacific Maritime Group aim to demonstrate the technical and economic feasibility of repowering existing commercial vessels with electric propulsion systems.