The bulk carrier of the future

30 Nov 2011
Image of the ‘ECO-ship 2020’ open hatch bulk carrier developed by Oshima and DNV

Image of the ‘ECO-ship 2020’ open hatch bulk carrier developed by Oshima and DNV

Oshima Shipbuilding and DNV recently completed the first milestone of the joint programme to develop the ‘ECO-Ship of the future’ project, first described in The Motorship, July-August 2011.

ECO-Ship is described as a natural response to the increasing environmental focus both from a regulatory and commercial point of view as well as the increasing cost of fuel. The resulting concept design has a number of innovative, yet feasible features, which have been evaluated for cost-benefit. Oshima ECO-Ship 2020 is an open hatch bulk carrie’ (OHBC) for the future and features a number of design solutions to be researched and developed for reduced fuel consumption and efficient operations.

The design has been executed as a joint project between Oshima and DNV. Rolls-Royce Marine has contributed solutions for LNG, engines and propulsion while Kockums of Sweden and FiReCo from Norway have contributed to the development of GRP solutions.

A market and logistics study performed by DNV ProNavis targeted the expected characteristics of the ECO-Ship. The study identified that the backbone of the OHBC segment is the pulp trades and that a ship size of about 62,000dwt meets the needs of this market, as well as identifying a number of potential trading routes. For the purpose of simulating fuel consumption, three typical routes were created. On these routes the average load level for an OHBC is about 77% of the total cargo capacity and, because of the typical multi-port operational profile, these vessels very seldom sail in pure ballast condition.

The design speed of 14.5 knots is somewhat lower than a typical for existing OHBC and results in a significant fuel saving. Reduced design speed allows for a wider hull form, while a twin-screw propulsion system offers high propulsive efficiency. Other features include an air lubrication system that supplies air to the wide flat bottom, and Oshima’s ‘seaworthy bow’, both lowering frictional resistance, and flipper fins to improve the hydrodynamic flow to the propeller.

To meet post-2020 emissions limits as well as ECA and European port regulations, and future restrictions, lean-burn natural gas engines are thought to offer a suitable solution. The ECO-Ship has a single-fuel system where all engines run on LNG. LNG contains no sulphur and the combustion process emits 90% less NOx and will eliminate almost all particulate emission. Also CO2 emission is reduced by 20%, including methane slip. Furthermore, the risk of accidental oil pollution is minimised through LNG being the only fuel onboard.

Space for LNG fuel tanks in an OHBC presents some challenges due to lack of deck space. The ECO-Ship arrangement uses two cylindrical, vacuum-insulated C-type pressurized LNG tanks in the lower part of cargo hold no. 8, and another two tanks above the machinery room. This arrangement is feasible since four-stroke engines require less height in the machinery room compared to two-stroke engines. Around 2,700 m3 of LNG can be carried, giving an operational range of about 17,000 naut miles.

Two Rolls-Royce Marine engines, each of 4,000kW, with a 1,400kW auxiliary and a 1,500kW Rolls-Royce hybrid shaft generator (HSG) PTO/PTI system allow for flexible power use. Frequency converters provide stable electric power from variable propeller rpm and generator load. The ship has two CP propellers which form an integral part of the Promas system adapted to twisted full-spade rudders with a rudder bulb connected to the propeller hub. The twin screw CP system with CP propellers with bow thruster allows berthing without tug assistance.

The high temperature clean exhaust gas associated with LNG fuel lends itself to waste heat recovery (WHR) to generate electric power, which can be fed into the  PTI and to supplement the propulsion power, saving about 5% fuel at normal speed. Power from WHR and the auxiliary engine together could raise ship speed by about 0.5 knots.

All deck machinery is electrically driven, with four large 75-tonnes jib cranes which consume less energy and reduce operational time compared with conventional hydraulic equipment. The hatch covers are made of a glass-reinforced plastic (GRP) sandwich construction, which is about half the weight of a steel hatch cover. As a result, the cranes can be used to move the hatch covers, which eliminates the normal hydraulic hatch cover deck mechanism.

Single, rather than dual, fuel operation means simplified operation and lower maintenance. Because the ECO-Ship has some 20% less ballast water capacity than a conventional ship more cargo space is freed-up and there are fewer ballast tanks to coat and maintain. The ECO-Ship is expected to require an additional investment of around $23 million. Despite this, Oshima and DNV claim the ECO-Ship is expected to be more profitable than a conventional OHBC. The economical performance was estimated using a detailed financial analysis on a stochastic model. The ECO-Ship was compared to a reference ship selected to represent a typical existing OHBC modified to meet the regulations in force at delivery in 2020. The investment decision is assumed to be taken in 2018. Taking into account crude oil price forecasts and expected LNG prices, including possibility of CO2 taxation, the model showed that the ECO-ship’s expected pay back time is 9.5 years. These results do not take into account the fact that the ECO-ship has a higher cargo carrying capacity and could potentially achieve higher earnings than the reference ship. And with the expected drop in the relative cost of LNG storage tanks, as the LNG fuel ship market grows and more suppliers and solutions enter the market, the expected pay-back time could fall to 7.7 years.

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