RECENT TRENDS IN SHIP TECHNOLOGY
Brief Introduction
Technological developments in shipping and shipbuilding have, heretofore, been focused primarily in the areas of energy conservation and labor saving. Recently, however, the industry has begun to challenge to more broad and diverse technology themes. These include： "Protection of the Global and Marine Environment," "The Pursuit of Safety and Reliability," "The Application of Advanced Information Technology and Productivity Improvement," and "The Sophistication of Shipbuilding Technology and the Creation of New Demand."
This article summarizes and introduces these new tasks.
1. Protection of the Global and Marine Environment
The United Nations Environmental Program (UNEP) has been playing a leadership role with regard to conservation of the global environment. The themes that will be taken up here and which directly concern the shipping and shipbuilding industries are： "The Prevention of Marine Pollution," "The Prevention of Air Pollution," and "The Prevention of Global Warming."
1-1 The Prevention of Marine Pollution
1) The history of the prevention of marine pollution with oil dates back to the 1954 MARPOL Protocol. A significant topic in this context in recent years is the requirement of double-hulls on tankers. The policy of requiring double-hulls on tankers has its roots in the oil spill by the EXXON VALDEZ accident. The revised MARPOL including the compulsory double-hull provision for tankers was adopted in March 1992, and it has been applied to all tankers construction contracts for which were signed on or after July 6, 1993.
At the meeting of IMO, Japan made several proposals regarding technical content and implementation timeframe. Japanese proposal of the Mid-deck design as an equivalent alternative to the double hull, was approved and adopted.
2) With regard to other marine pollution prevention efforts, the Shipbuilders' Association of Japan led the world with its decision to limit the use, beginning in 1991, of anti-fouling paints for ship bottoms that contain tributyl tin (TBT) compounds. In January 1993, paint manufacturers discontinued sales of these products. In November 1998, a resolution prohibiting the use of anti-fouling paints containing the TBT compound was adopted by the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO). A total ban on the use of these coatings effective January 1, 2008 was incorporated in the resolution, and substantive movement toward the worldwide elimination of harmful coating substances is gaining momentum.
1-2 The Prevention of Air Pollution
Currently world attention is being focused on SOx and NOx as particularly serious air pollutants. At the 1990 MEPC meeting of the IMO, the goal of reducing current levels of SOx by 50% and NOx by 30% not later than 2000 was debated. Since then debate has continued regarding the regulation of ship emissions of, in addition to SOx and NOx, halon, chlorofluorocarbons and VOC, and at the 40th MEPC of the IMO held in September 1998, a new Annex VI to the MARPOL 73/78 Convention was adopted.
1) The cause of SOx is sulfur contained in fuel. Although some hold the opinion that fuel containing large amounts of sulfur should be driven from the market, huge investment in refineries would be necessary in order to remove sulfur from the currently used type of marine fuel, which is a very heavy fraction of petroleum, and this would inevitably cause the price of this fuel to rise. There is, of course, methane which is the cleanest of all natural gases. In order to use this gas as a fuel for general ships, it would be necessary to equip the ships with proper storage facilities; this would not be a simple undertaking. Similarly, while fuel cells are another extremely desirable device for the conversion of energy, the road leading to its general use is long.
The removal of SOx from exhaust gas would require expensive infrastructure investment in all vessels. In particular, the method of neutralization and removal through scrubbing with the calcium carbonate in sea water presents the problem of the permissible consumption limits of the calcium carbonate in sea water.
2) In the case of NOx, the nitrogen contained in air accounts for most of the generation. The currently employed marine diesel engines achieve combustion through high heat and high pressure, resulting in very high thermal efficiency. However, in order to control the generation of NOx, the combustion heat has to be lowered; lowering the heat leads to an increase in fuel consumption. Research is currently underway on methods of lowering combustion heat without adversely impacting fuel consumption. These methods include： spraying fuel oil and water, combustion of premixed fuel, and two-stage combustion.
Further research and development has been planned recently on an alternative anti-NOx method. This is the exhaust gas recirculation (EGR) method which has the advantages of being very economical, safe and free from the pitfall of increased CO2 emission.
1-3 The Prevention of Global Warming
1) At the COP3 held in Kyoto in December 1997, a goal of reducing atmospheric warming gases such as CO2 produced by advanced industrial nations was established, and Japan also publicly pledged to reduce its overall emissions (based on their 1990 level) by 6% as early as the year 2010. Hereafter it is expected that demands will be made for the reduction of CO2 produced in the fields of marine traffic and other modes of transportation.
As a result, such issues as energy conservation in ships as well as responding to the social demand for a modal shift away from overland to maritime transportation (within the sphere of long distance cargo transport) have posed challenges in need of address.
