Many propulsion aspects were not covered in our previous Quantum report, therefore we call this one Quantum 2. Container ship designs go for maximum hull speed requiring highest practicable engine power. The slump of the last two years has meant that ships often steam well below their designed maximum speed. Many propulsion arrangements were investigated for the Quantum, however a diesel electric solution was most favored using a twin propeller arrangement for full redundancy. It was decided the best option was two steerable Azipods. Adding further flexibility, all the gen set engines are dual MDO/LNG fuel and the two on board LNG tanks allow engine operation in emission sensitive areas.
Conventional container ship designs usually go for maximum hull speed requiring highest practicable engine power. The slump of the last two years has meant that ships often steam well below their designed maximum speed resulting in higher specific fuel consumption and possible engine damage running at prolonged low speeds and combustion temperatures for which the engine was not designed.
Many propulsion arrangements were investigated including a single screw direct driven two-stroke engine, twin four-strokes in a TISO configuration and diesel electric. Different twin screw permutations were looked at even including a triple screw arrangement however in the end, taking everything into account including the wish for a redundant, flexible, propulsion system for the Quantum, a diesel electric solution was most favored. Rather than one large single propeller, a twin propeller arrangement was preferred giving full redundancy.
Although there are high efficiency configurations of contra-rotating propellers using fixed and /or steerable thruster(s) it was decided the best option was two steerable Azipods. Thus this vessel has two thrusters each of which is powered by two generator sets: the main bus allows switching of power from any one gen set. The gen sets envisaged, all are four-stroke medium-speed engines such as the Wartsila 50 DF or the MAN 51/60DF series. There are two engine rooms: port side with twin nine cylinder engines and starboard side one nine and one six cylinder.
Adding further flexibility is the ability to operate on LNG and two large gas tanks are included in the design. As all the gen set engines are dual MDO/LNG fuel: in emission sensitive areas, the ship can run exclusively on LNG, in harbor, cold ironing is not required as the gen set(s) remain on LNG. Two azimuth pods ensure excellent maneuverability and increased harbor efficiency.
A through life cost analysis prepared by ABB of this diesel electric propulsion configuration against a single screw two-stroke engine with 12MW gen set is: investment M€ 29.2:11.9, maintenance M€ 1.067:1.268, fuel 25,208:23,357 tons/year with a cumulative cost after 30 years of M€ 212:187 – equivalent to 11 per cent higher cost. Like all things there are advantages and disadvantages and this is no exception. Whether the many additional features justifies the higher cost is for the owner to decide.