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Kirby Christens Nation’s First Plug-In Hybrid Electric Towing Vessel

The Green Diamond is the first plug-in hybrid electrical inland towing vessel in the United States.

Posted on August 30, 2023

Kirby Inland Marine, part of Houston-based Kirby Corporation (NYSE: KEX), has christened the first plug-in hybrid electric inland towing vessel in the U.S.

A christening ceremony for the Green Diamond was held for the vessel on Friday in Houston, Texas.

The vessel will be time chartered by Shell Trading (US) Company, which will use the boat to push barges throughout the port of Houston area.

The Green Diamond was constructed by San Jac Marine, LLC, Kirby’s shipyard in Texas, with power management, control, and propulsion systems designed and installed by Stewart & Stevenson Manufacturing Technologies, another Kirby company.

Shell Energy Solutions will provide renewable energy certificates to match the electrical power used to charge the battery system.

“We are excited to be the first to market with a plug-in hybrid inland towing vessel,” said Christian O’Neil, President of Kirby Inland Marine. “Barge transportation is already the cleanest and greenest way to move a wide variety of cargoes in America, and we are working to make it cleaner and greener. Our customers who are focused on reducing their emissions want more efficient options. This solution is available today.”

The Green Diamond is powered by two 575 KW Danfoss electric motors that can be run by Corvus’ Orca-series battery system or onboard Caterpillar generators. A Shell New Energies US-owned charging system will be used for dockside charging, allowing the vessel to operate on trips within the Houston area without ever needing to start the generators.

“We expect the Green Diamond, with its unique ‘Eco-Tug’ logo, to be a fixture in the Port of Houston for years to come,” O’Neil added.

Chad Joost, Executive Vice President at Stewart and Stevenson, said the company drew upon their experience of providing high horsepower electrical oilfield fracturing equipment for the project.

“We were able to adapt that patented technology to the marine environment and enable this vessel to operate on shore power and charge the batteries while on dock, then get underway on battery power. On extended trips, the generators will be used to supply power to the motors and charge the batteries. All of this happens seamlessly through Stewart and Stevenson’s power management system,” said Joost.

According to Kirby, the Green Diamond can reduce fuel use by almost 80%, leading to an estimated 88-95% decrease in emissions of nitrous oxides, carbon monoxide, and hydrocarbons. Compared to a conventional inland towing vessel, engine run time can be reduced by 93-98%. When running in hybrid mode with the generators on, the vessel is expected to have a 27% reduction in emissions compared to a conventional towing vessel.

“The plug-in hybrid design offers numerous advantages for towboats in certain trades,” added Mitch Jones, Vice President of San Jac Marine. “We are already looking at building follow-on vessels.”


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