RECENT TRENDS OF TECHNOLOGY ON SHIPS AND OFFSHORE STRUCTURES
Technological development initiatives in the shipping and shipbuilding industries are increasingly concerned with "conservation of the global environment," and this theme is taking over the dominant position of cost reductions, the most favorite subject until some time ago. Also, a large proportion of recently built ships and offshore structures embodies awareness of the need for "conservation of the global environment."
Recent trends in Japan's new maritime technology will be described below with reference to specific examples.
1. Unique Ships
The size of the largest container ships has already surpassed the previous Panamax class, and Over Panamax vessels have been increasingly built over the last 10 years. At present, the biggest per-vessel capacity is 7,000 TEU, but 10,000 TEU or even bigger container ships are likely to emerge in the not too distant future. Actually, trial designs have already been made, and builders are readying themselves for the construction of giant container ships. Huge container ships cannot serve their purpose unless port facilities can accommodate them, but ports adequately equipped for loading and unloading of Over Panamax container ships are being developed one after another across the world, and in this respect, too, economies of scale can be expected.
One hundred or even more bulk carriers are built every year, and especially handy bulkers embody their owners' and builders' ingenuity. They range in size from 32,000 tons to 52,000 tons, each characterized by greater energy conservation, higher cargo handling efficiency and larger deadweight capacity for a vessel of the same size. More bulk carriers unique in one way or another, will continue to emerge because they are the ship type which is needed everywhere in the world.
The double-hull structure for tankers has established itself over the last 10 years, and double-hull technology is steadily practiced particularly for VLCCs mainly of the 300,000 dead weight tons class. Altogether 5 million tons oftankers are built every year, of which about 10 units are VLCCs totaling some 1.7 million gross tons. Tankers will continue to be one of the pillars of shipbuilding in Japan.
Unique vessels are also found among LPG carriers, LNG carriers, naval vessels, patrol craft and work vessels among others.
2. Newly Developed Designs
Double-Acting Tanker (DAT)
The Double-Acting Tanker (DAT) jointly developed by a Japanese shipyard and Kvaerner Masa-Yards uses a pod-type electrical propeller, which enables the vessel to turn 360 degrees. The type of tanker, which sails ahead while normally at sea and astern when navigating icy waters, has its bow and stern optimized for normal sailing and frozen sea navigation, respectively. The vessel excels in maneuverability and its electrical propulsion ensures environmental friendliness. It represents a developmental initiative in making a technological difference in the Nordic market.
Contra-Rotating Pod Propulsion System
A contra-rotating propulsion system combining a control-lable-pitch propeller with a pod-type propeller has been developed. This system is expected to reduce fuel consumption by 10 to 15%. The mounting of two propellers helps reduce vibration, and the propellers capable of swiveling 360 degrees, when combined with bow thrusters, allow the vessel to berth and unberth itself without relying on a tugboat. The new system has been developed for use on ferries and passenger ships.
Large Container ship with Contra-Rotating Propeller
A trial design of a hull form, which can realize a speed of 20 knots (with 20% sea margin) with a single main engine and a single propeller, has been developed for application to 10,000-TEU container ships, and is expected to emerge in the not too distant future. It will prove to be much more energyefficient than the conventional twin-engine twin-propeller arrangement.
Bulkhead Fuel Oil Tanks
A Panamax class 4,500-TEU container ship whose transverse bulkheads are used as fuel tanks has been designed, and will be completed in the near future. This arrangement serves to prevent environmental contamination by oil leaks in the event of damage to shell plating. The use of the double-bottom and side tanks for ballasting would contribute to greater stability and an increased number of loadable containers.
3. Advancement in Design Techniques
Handing-Down of Design Knowledge
In the shipbuilding industry today, system structure is being pursued with a view to handing down design know-how to future generations and substantially enhancing design efficiency by integrating accumulated design know-how into a database and incorporating it into the computer-aided design (CAD) system. Further attempts are being made to keep faults identified at the design stage and in production shops under unified management on an in-house network and to visualize how these faults are addressed. The system is intended for accumulation and re-utilization of design know-how based on actions to improve the design process and on the faults experienced in the course of design work.
ZoHaku Web represents collaboration by shipbuilders and ship machinery manufacturers to switch the way of exchanging technical information from the traditional delivery of "paper" to digitized "data transmission", and is already being applied to construction of actual ships since 2001. If and when the operation of ZoHaku Web becomes routine, both shipbuilders and ship machinery manufacturers can benefit from improved business efficiency and faster transmission of information. The use of electronic data has also enabled shipyards to extensively rely on three-dimensional CAD systems.
4. Environmental Challenges
Prevention of Air Pollution
Air pollutants which are attracting worldwide concern today include SOx and NOx. The 1990 session of the MEPC (Marine Environment Protection Committee) of IMO discussed setting the reduction targets of SOx and NOx to 50% and 30% of their respective current levels by 2000. The discussions continued eventually to propose possible addition of halons and chlorofluorocarbons (CFCs) and volatile organic compounds (VOCs) to SOx and NOx as objects of control of emission from ships. At the 40th IMO/MEPC session held in September 1997, it was decided that, in order for the new Annex Vl "Regulations for the Prevention of Air Pollution from Ships" of the MARPOL 73/78 Convention to take effect, at least 15 countries representing not less than 50% of the gross tonnage of world's merchant shipping should become contracting parties to (ratify) the instrument. By October 2002, six countries including such flag-of-convenience countries as Panama, Liberia, Greece and Cyprus, had expressed their positions in favor of the protocol, which is expected to be ratified by around June 2003.
The Japanese industries involved in this issue carried out a project of "research on NOx prevention systems, including exhaust gas recirculation (EGR)" for two years from 1999 through 2000 with the support of the Shipbuilding Research Association of Japan and the Nippon Foundation. Taking up marine main diesel engines as its object, the project covered both technical and economic implications of the regulations for the control of NOx emissions when they were implemented.
The research project included the possibility of marine application of the EGR system, which is much less susceptible to the penalty of an increase in CO2 emissions than other anti-NOx measures and excels in economy and safety. It also revealed that the feared adverse effects on the reliability of cylinder liners and piston rings could be eliminated by incorporating a seawater-utilizing exhaust gas cleaning apparatus into marine diesel engines running on low-graded heavy fuels, thereby affirming the practicability of the EGR system. This means that the EGR system could prove a promising option for realizing an NOx reduction by 30% or more, which is foreseen in a second stage of tightened control by the IMO.
Prevention of Global Warming
In 1993, the Transport Technology Council gave a recommendation regarding the "Desirable Orientation of the Development of Ship Technology for the New Era," and stressed the need for active attempts to develop a marine gas turbine system which would impose less load on the environment. Meanwhile in 1997, the IMO adopted a protocol providing for control on nitrogen oxide (NOx) emissions from marine engines. Thus environmental issues are addressed as common international challenges. Under such circumstances, five companies well experienced in gas turbines organized the Technological Research Association of Super Marine Gas Turbine (SMGT) with the support of the Association for the Structural Improvement of Shipbuilding (the Corporation for Advance Transport & Technology from fiscal 2002 onward) and The Nippon Foundation. The association is engaged in a six-year (fiscal 1997-2002) R&D project on a low-NOx and high-efficiency marine gas turbine of the next generation (Super Marine Gas Turbine, abbreviated to SMGT) far surpassing any traditional concept with a view to realizing a low environmental load marine propulsion plant. SMGT is a regenerative twin-shaft gas turbine of 2,500kW, whose performance targets are: 1) an NOx emission level below 1 g/kWh, 2) a thermal efficiency of 38 to 40%, and 3) compatibility with heavy fuel oil. The NOx emission level is about 1/10 of that of existing diesel engines, and the thermal efficiency is comparable to that of high-speed diesel engines. The basic plan was formulated in fiscal 1997, and from fiscal 1998 through 2000, energetic efforts were made to develop such elements of the gas turbine as a liquid fuel-fired dry low-NOx combustor, a high-efficiency compressor combining the axial-flow type and the centrifugal type, and a plate fin-type regenerative heat exchanger, resulting in successful achievement of each individual research target. From fiscal 2001 onward, a 2,500-kW class experimental engine will be produced capitalizing on these achievements, and it will be put to land trials by the end of fiscal 2002 to assess its performance.
The National Maritime Research Institute, an independent administrative institution, in fiscal 2001 launched a five-year project to develop the Super-Eco Ship using a high-efficiency gas turbine-powered electrical propulsion system and a contra-rotating pod propeller for coastal shipping in the 21st century. Successful accomplishment of the project will contribute to directly reducing the emission of greenhouse effect gases, one of the major environmental challenges of today.