Oshima Shipbuilding Co., Japan and DNV announced at last week’s Norshipping exhibition, the first results of their ECO-Ship 2020 joint programme to develop a concept design for an open hatch bulk carrier (OHBC). The term “open hatch” means that the hatches are almost the full width of the ship allowing rapid charging and discharging of the cargo. The integrity of the hull with the large hatches must be compensated for by increasing the deck strength.
Caption: The Oshima Shipbuilding Co., Japan and DNV design concept open hatch bulk carrier (OHBC) ECO-Ship 2020
Image credit: Oshima Shipbuilding / DNV
The aims of the design are to significantly lower fuel costs yet comply with present and future emission regulations and at the same time improving the commercial operational efficiency of the ship.
The design marks a radical change from present bulk carriers in several respects. Considerable input was provided by Rolls-Royce Marine concerning propulsion. The propulsion is by LNG powered diesel mechanical drive with diesel electric boost via a shaft generator/motor (PTO/PTI). Four C-type LNG tanks each of capacity 3,000m3 are located aft in the ship.
A twin-skeg twin-engine configuration is used with a wide air lubrication hull form. The engines themselves are medium speed four stroke gas engines running purely on LNG and would utilise waste heat recovery equipment. For example the Bergen B32:40L8P rated at 4 MW at 750 rpm. An auxiliary gas engine generator could be around 1,400 kW
Caption: Two medium speed four stroke gas engines of 4 MW each provide the main propulsion.
An auxiliary gas engine generator could be around 1,400 kW.
Image credit: Oshima Shipbuilding / DNV
The Promas propeller and rudder combination comprises a full-spade rudder fitted with bulb that smoothly connects to the propeller hub via a hubcap. This gives a more efficient rudder with lower drag and better recovery of rotational energy from the propeller slipstream A well-designed twist adapts the rudder to the rotation of the propeller slipstream and reduces the local angle of attack on the rudders leading edge.
Flipper fins sometimes called bilge fins are used to deflect bilge vortices to get wake gain and accelerate the flow near the top of propeller to reduce propeller-hull interaction. The aft-end fin is added for rectifying the flow around the centre of propeller to reduce resistance.
The Promas propeller and rudder combination comprises a full-spade rudder fitted with bulb that smoothly connects to the propeller hub via a hubcap. This gives a more efficient rudder with lower drag and better recovery of rotational energy from the propeller slipstream A well-designed twist adapts the rudder to the rotation of the propeller slipstream and reduces the local angle of attack on the rudders leading edge.
Flipper fins sometimes called bilge fins are used to deflect bilge vortices to get wake gain and accelerate the flow near the top of propeller to reduce propeller-hull interaction. The aft-end fin is added for rectifying the flow around the centre of propeller to reduce resistance.
The vessel has Oshima's patented 'Seaworthy Bow' which is designed to be efficient at a range of drafts rather than the traditional bulbous bow. It has excellent seaworthiness and is adopted for improving speed performance in rough weather conditions.
To enable a rapid turnaround in port there are four large capacity electric jib cranes and to reduce weight, the hatch covers made of a composite material that weighs about 50% less than traditional steel covers.
In conclusion, the design offers low fuel consumption, high energy efficiency, flexible propulsion and power generation and excellent maneuverability. No emissions of SOx or particulates
and a 90 per cent NOx reduction with CO2 reductions of at least 50 per cent compared to base case
On the commercial side, the ECO-ship requires an additional investment of about $23M compared to a conventional Oshima OHBC. This extra investment is expected to be earned back within 10 years. The ECO-ship improves the expected net present value before tax by $38M over a lifetime of 25 years.