LNG as marine fuel takes another step forward as Eidsvaag AS took delivery of the first vessel of the Rolls-Royce prize winning Environship range this week, featuring a combination of Rolls-Royce design and technologies which reduce CO2 emissions by up to 40 percent compared to similar diesel powered vessels.
Once in operation the vessel will operate a demanding schedule with a weekly round voyage along the Norwegian coast delivering feed pellets to fish farms regardless of weather conditions. On arrival at the storage location at a fish farm the ship will hold its position using its DP system and the pellets will be delivered by means of a crane operated transfer system over the bow. Up to 1,450 tons of feed can be carried in the 62 specially designed tanks on board which are connected to the unloading system, and the speed needed to meet the weekly schedule is 15 knots.
The ship is designed with focus on the actual sea conditions experienced in the area in which it will operate. Extensive model testing was carried out in the towing tank and the ocean basin at Marintek. Testing has confirmed that the hull is extremely efficient in both calm waters and heavy seas. A patented bow form reduces hull resistance in waves by up to 10 percent compared with an optimised conventional bow. This is confirmed by careful benchmarking comparisons in head seas in the towing tank.
On an overall length of 74.7 metres the NVC 401 LNG has a beam of 13.6 metres and a loaded draught of about 5 metres. The superstructure is located forward, with accommodation for eight people, and the machinery and LNG tank aft, the cargo tanks occupying the main part of the hull.
A Bergen C26:33L9PG gas engine, developing 2,430kW at 1,000rpm turns a CP propeller in a Promas solution integrating the propeller, a nozzle and the rudder in an efficient propulsion system.
The reduction gearbox handles power take-off and take-in for the 1,100kW shaft generator in a variable speed HSG (Hybrid Shaft Generator) configuration linked to the two 469kW auxiliary gensets. The HSG makes the vessel energy optimal in operation. This generator continues to supply electricity of correct voltage and frequency even at reduced revolutions of the engine and propeller. This means that the propulsion system can run on combinatory control, varying propeller rpm as well as pitch instead of the fixed revolutions required by other shaft generators. The propeller speed can therefore be that needed for best efficiency at the chosen ship speed. By this means the energy usually wasted by turning the propeller faster than is actually needed can be saved.
The high lift rudder is complemented by a 540kW tunnel bow thruster and a similar unit in the stern skeg.
The LNG system supplied by Rolls-Royce has a capacity of about 110 cubic meters which gives a range of around 1750 nautical miles. Developed in cooperation with Linde Cryo, the result is a system that controls the supply of gas to the engine optimally despite rapid changes in load. Furthermore Rolls-Royce has delivered the engine and thruster controls, an integrated automation system with gas control and monitoring, the DP1 system with joystick, and the electrical system.
All together the propulsion solution will reduce CO2 emissions by 22 percent, NOx emissons by 92 percent and SOx emissions by 99 percent, while emission of particulates are negligible.
Built at the Vard Aukra yard in Norway and owned by Eidsvaag AS, the NVC 401 LNG forage carrier will work for Skretting AS.
Several Environship vessels under construction
The Environship concept can be adapted for different ship types and a number of Environship vessels already in build will take to the seas during 2013. In the last quarter of the year the first of two cargo ships for the Norwegian Company Nor Lines will be delivered by the Tsuji Heavy Industries (Jiangsu) Co. Ltd yard in China. Passenger ship designs are also under development. Last year Rolls-Royce signed a teaming agreement with Italian company Lauro Shipping to design innovative new gas powered ferries based on the Environship concept.
Earlier this year, Rolls-Royce received the Green Ship Technology Award for its Environship concept, and in 2011 it received the Next Generation Ship Award at the Nor-Shipping exhibition. It is also nominated to this year’s “Ship of The Year” award at Nor-Shipping.