A new energy saving tanker with non ballast-water is proposed. The round and streamlined hull of the ship drastically reduces the viscous resistance, and multi-podded-propulsors moving up and down keep enough depth of the propellers from water surface.Resistance tests of model ships of the proposed tanker with different stern shapes are carried out in the towing tank of Osaka Prefecture University to reveal that the form factor of the model in full load condition can be reduced to be 0.08, which is almost 1/3 of a conventional tanker with full shape of hull. This means that the viscous pressure resistance of the new ship is about 30% of that of a conventional tanker. The round cross section of the mid-ship parallel part of the ship reduces the wetted surface by 6.1%, and it reduces the friction resistance by the same percentage. The resistance of the proposed tanker in light weight condition is much smaller than that of a conventional tanker in ballast condition because of the very small draft. The experimental results also show that the form factor of the ship is 0.1 in light weight condition. These experimental results demonstrate that the total energy consumption in shuttle service of the tanker between production place and consumption place is reduced by 36% by introducing the new proposed concepts.
One of the authors proposed a concept design of a new non-ballast-water tanker by introducing podded-propulsions moving ups and down to keep enough depth for the propellers. The targets of developing the ship are as follows; the ship can reduce the frictional resistance due to a round hull shape by 10%, the viscous pressure resistance due to a stream-lined stern-shape by 20-30%, and the frictional resistance in light weight condition due to eliminate ballast water by more than 40%.