VESSEL REVIEW | Green Diamond – Hybrid electric pusher for Kirby Corporation’s inland shipping division

US-based Kirby Corporation, via its Kirby Inland Marine division, recently took delivery of a new plug-in hybrid electric inland pusher tug.

Green Diamond was designed and built by Kirby-owned San Jac Marine based in Channelview, Texas. Stewart and Stevenson Manufacturing Technologies, another Kirby company, designed and installed the power management, control, and propulsion systems.

The tug has a length of 73.6 feet (22.4 metres), a beam of 30 feet (9.1 metres), and an electric propulsion system consisting of a Corvus Orca Energy 1,243kWh battery pack, two Danfoss 575kW motors, and Caterpillar 565kW backup generators. A Shell New Energies US-owned charging system purchased from Zinus will be used for quayside charging of the battery system, allowing the vessel to operate on trips within the Houston area without ever needing to start the generators.

According to Kirby's modeling, when operating on shore supplied power, the fuel use can be reduced by almost 80 per cent, resulting in an estimated 88 to 95 per cent reduction in emissions of NOx, carbon monoxide, and hydrocarbons. Engine run time can also be reduced by as much as 98 per cent compared to a conventional inland tug. When in hybrid mode with the generators running, the tug can yield an estimated 27 per cent reduction in emissions compared to a conventional towing vessel.

Green Diamond will be time-chartered by Shell Trading (US) Company, which will use the vessel to push barges throughout the Houston port region.

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