With increasing pressure to reduce emissions from ships and yachts, particularly in US waters, many commercial ships and work boats are starting to be built capable of operating on LNG (liquid natural gas) as a fuel. In the US, the first offshore support vessel to operate on LNG has just entered service and now the builders of this vessel, Gulf Coast Shipbuilders, have developed a superyacht design based on the same hull and using the same engines and fuel technology.
US yacht builder Trinity Yachts is part of the Gulf Coast Group, so this LNG-fuelled yacht will be marked under their name. The concept drawings transform the LNG concept from a functional workboat into a stylish explorer-style luxury yacht. It is conceived as an ocean going expedition yacht with five decks above the main deck and a large, open aft deck. Space has been included on the open deck space for the stowage of a large tender, a helicopter pad and aft on the main working deck an A-frame launching system for a submersible.
This yacht has a length of 94.5 metres and a bean of 19.5 metres, creating generous interior and exterior space for accommodations. But it is the machinery that is of special interest. This will be based around a diesel-electric propulsion system with the electric power being generated by three generating sets supplied by Wartsila. Each of these is powered by a Wartsila 6L 34DF diesel that develops 2610 kW and is capable of operating on dual fuel, diesel and LNG.
Wartsila delivered the complete package for the LNG installation including the LNG tank and the fuel handling system as part of their integrated supply system. Diesel fuel and fresh water tanks are all built into the hull structure but the LNG tank, which can hold a total 76,604 US gallons, is a separate tank located on the centre line amidships. Here it is located above the double bottom tanks and between the side tanks so that in the event of a grounding or a collision the LNG tank is fully protected. The space in which the LNG tank is located also forms the link between the forward engine room and the aft propulsion units so it is in effect a tunnel running much of the length of the hull. The yacht can operate for seven days on LNG as a fuel and a lot more using diesel fuel.
For propulsion, there is a pair of Lips azimuthing thrusters, which are driven by Alconza electric motors of 2700 kW each. The Harvey Energy, the workboat version was fitted with two very powerful two bow thrusters rated at 1,280 kW each. The output from both the bow and the stern thrusters can be combined in a Konsberg dynamic positions system. This is the installation for the vessel's role in the offshore oil arena and can of course be modified to meet the requirements of a super yacht.
In addition to being able to operate on LNG, the offshore versions building also meet the stringent criteria enabling her to qualify for the ABS Enviro+ Green Passport notation. When operating on only LNG, this vessel meets the new Tier IV sulphur and nitrogen oxide emissions regulations that will come into force in a few years time for parts of the North American Emission Control Area and in many European waters.