VESSEL REVIEW | Shimokita Maru – Japan’s NS United places hybrid LNG-electric limestone carrier into service

Japan's Tsuneishi Shipbuilding recently handed over a new bulk carrier to local shipowner NS United Kaiun Kaisha. Shimokita Maru replaces an older, similarly named vessel in the NS United fleet.

The newer Shimokita Maru has an LOA of 93.8 metres (308 feet), a moulded beam of 18.2 metres (59.7 feet), a moulded depth of 9.9 metres (32 feet), and a deadweight tonnage of 5,646.

It will be operated mainly on the route between the ports of Shiriyazaki in Aomori and Muroran, transporting limestone under a charter contract with Nippon Steel Corporation and Nippon Steel Cement.

Hybrid propulsion for a range of operating modes

The vessel is powered by a hybrid propulsion system consisting of an 8L30KG 3,560kW (4,770hp) LNG-fuelled engine and a 2,847kWh lithium-ion battery pack manufactured by Kawasaki Heavy Industries.

The batteries will be used mainly for entering and leaving port, as these will help the vessel in achieving zero local emissions. LNG supplied by Japan Petroleum Exploration will meanwhile be used for high-power, long-distance, and long-duration navigation.

The hybrid propulsion system does not affect the vessel's loading and unloading operations, similar to conventional vessels. This is due to the design of the cargo holds.

When in normal operating mode, the ship exclusively consumes LNG for propulsion and to meet onboard power demand. The LNG fuel will reduce CO2 emissions by approximately 24 per cent compared with conventional heavy fuel oil, and the vessel's exhaust gas does not contain SOx.

The NOx emissions will also be far below the maximum limit according to IMO Tier III regulations.

A load fluctuation control system enables the ship to maintain load on its main engine at fixed levels. Even when greater propulsive force is required under severe hydrographical conditions, the batteries will cover it.

Low emissions combined with enhanced crew comfort

The LNG tanks use seven per cent nickel steel plate developed by Nippon Steel Corporation, which the company claims delivers the same performance as conventional nine per cent nickel steel plate.

Measures to control limestone dust, vibrations, and unit lavatory adoption in all cabins will improve safety and the onboard living environment.

This accommodation block is laid out with a bright and open space that is designed to provide the crew with a relaxing and stress-free environment. The multifunctional furniture pieces can also be rearranged within the compact space depending on crew preferences.

The combination of fabrics and furnishings was also the responsibility of the yard.