Kirby Christens Nation’s First Hybrid-Electric Towboat

A single barge has the carrying capacity of 16 rail cars or 70 tractor trailers, which makes moving cargoes on the inland waterways by far the most efficient and environmentally friendly mode of transportation.

Now, Houston-based Kirby Inland Marine is leading the way to take barge transport in the United States to a new level of sustainability with the christening of the nation’s first plug-in hybrid-electric inland towing vessel, the mv. Green Diamond.

Kirby christened the Green Diamond on August 25 at the company’s Old River Fleet in Channelview, Texas.

“We are excited to be the first to market with a plug-in hybrid inland towing vessel,” Kirby Inland Marine President Christian O’Neil said in a statement following the christening. “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.”

Speaking to the huge crowd gathered for the event, O’Neil said the journey to the christening of the mv. Green Diamond began three years ago, when leadership at Kirby set out to “redefine what a towboat is capable of.”

“That was the goal,” O’Neil said.

Achieving that goal was made possible through the collaboration of Kirby-owned companies, namely Stewart & Stevenson Manufacturing Technologies, which Kirby acquired in 2017, and San Jac Marine, Kirby’s affiliated shipyard. Stewart & Stevenson and San Jac Marine teamed up on the design of the vessel, and San Jac also built it.

“It’s a Kirby boat, through and through,” said Mitch Jones, vice president of San Jac Marine.

As a plug-in hybrid vessel, the 74- by 30-foot mv. Green Diamond features two battery rooms that each house an Orca energy storage system from Corvus Energy. Those Corvus batteries, when fully charged, offer a total of 1,243 kW-hours of power, which according to Jones is enough to power a typical house for an entire month or to drive a Tesla for 6,000 miles.

Those battery arrays drive the vessel’s two 575 kW electric motors from Danfoss, which combine for the equivalent of 1,542 hp. The electric motors aboard the Green Diamond, paired to Reintjes marine gears from Karl Senner, turn 72- by 51-inch stainless steel Sound propellers from Texas Wheel Works. Besides its battery power, the Green Diamond is equipped with a pair of Caterpillar C18 generators from Mustang Cat.

Rio Controls & Hydraulics supplied the Green Diamond’s steering system and controls, while Rio Marine provided the electronics.

“There’s almost four miles of wires, and they pulled every bit of it,” Jones said of Rio Marine.

The Green Diamond has tankage for 6,500 gallons of fuel, 1,400 gallons of potable water and 3,200 gallons of wash water. Hiller supplied the vessel’s fire protection system, while Nance International provided the air conditioning and ventilation systems. RC Schmidt & Sons did the machine work aboard the Green Diamond, and C&M Contractors did the blasting and painting.

The Green Diamond will primarily work in the Houston harbor and be time-chartered by Shell Trading Company. Shell New Energies US LLC installed the Zinus charging system at Kirby’s dock, while Shell Energy Solutions, which provides retail energy in deregulated markets, will supply electricity to the charging station. Power to charge the Green Diamond’s battery system will be purchased through certified renewable energy certificates.

Karrie Trauth, Shell’s senior vice president for shipping and maritime, traveled from the United Kingdom to Channelview and spoke at the christening on behalf of Shell.

Based on the operational profile of the harbor boat the Green Diamond is replacing, Kirby officials expect it to run on battery power, whether underway or plugged in at the dock, about 80 percent of the time. Kirby estimates that will result in an 88-95 percent reduction in emissions, compared to a conventional diesel-powered towing vessel. With the generators running, the Green Diamond will offer an estimated 27 percent reduction in emissions, compared to a conventional towboat, according to Kirby.

When underway for extended periods and the batteries become depleted, the vessel will automatically switch from battery power to the generators, which will be able to both power the electric motors and recharge the batteries.

“I like to say that our boat is a battery-powered boat that can recharge itself either through plug-in power or generator power,” Jones said. “What makes it efficient is that the vessel will primarily run on battery power and only run the generators when necessary, due to a low state of charge in the battery banks. This is all done and controlled automatically through the vessel’s onboard power and battery management [and] charging systems.”

Vessel Design

The Green Diamond’s hull is basically the same as a conventional towing vessel, Jones said. On deck, the boat even features a pair of petite stacks, which actually vent heat from the battery rooms. Making the boat a plug-in hybrid did require some mostly unseen design changes.

“We did reduce the amount of fuel on the boat, and we had to adjust the size and configuration of the ballast and potable water tanks on the vessel to compensate for the weight of the batteries and associated control cabinets to maintain proper stability and trim,” Jones said.

Chad Joost, executive vice president of Stewart & Stevenson, said the firm already had extensive experience with electric power in the oilfield.

“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,” Joost said.

With its huge fleet of towboats and barges, Kirby is already a constant presence in Houston’s harbor. O’Neil said he anticipates the same to be true of the Green Diamond.

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

Following prayers of blessing offered by representatives from the Seamen’s Church Institute, Taylor Dickerson, vice president of Kirby’s project management office and the company’s ESG leader, broke a bottle of champagne over the Green Diamond’s rail, officially christening it into the Kirby fleet.

Caption for top photo: The mv. Green Diamond, built by San Jac Marine and designed by Stewart & Stevenson and San Jac, is the nation’s first plug-in hybrid-electric towing vessel. It will operate in the Houston Harbor and be time-chartered by Shell Trading Company. (Photo courtesy of Kirby Inland Marine)