Abstract:

The need for seaborne transport of natural gas has increased significantly in recent years. This has resulted in the contracting of a large number of new Liquefied Natural Gas (LNG) ships. The size of these ships is increasing from the 130,000 m3 capacity developed in the 1970's to ships designed for up to 240,000 m3 capacity.

While a number of new LNG export trains are built in the Middle East and South East Asia, the development of new receiving terminals in particular in the US and Western Europe is slow because of extensive environmental and safety approval processes. New technology for floating receiving terminals is therefore developed, as well as a concept for re-gasification onboard. For both these concepts gas transport to shore takes place through conventional pipelines.

The seaborne LNG transport chain is rather energy intensive because of the need for liquefaction and later re-gasification. It is estimated that around 15% of the energy content is lost due to these processes. More efficient liquefaction technology is therefore being developed, but new ideas to avoid liquefaction and instead transport natural gas under high pressure are also on the drawing board. Such Compressed Natural Gas (CNG) concepts have the potential to provide a cost advantage compared to LNG concepts for distances between 500 and 3000 nautical miles and for annual production volumes of 1-3 tcf. The focus on reducing ships emissions to air of CO2, SOX and NOX have led to development of new propulsion systems using Liquefied petroleum Gas (LPG) and LNG as a fuel replacing the traditional crude oil bunker fuel. Ships with such propulsion systems are already in operation. Some coastal ferries in Norway operate with LNG as fuel, and several supply ships operating in the North Sea have a propulsion system using LPG.

INTRODUCTION

LNG shipping has evolved over the past four to five decades and the number of LNG carriers in service is at present around 180 (May 2005). The core of this shipping business is a limited number of ship owners, mostly with fully integrated operations. Their business has been developed in close co-operation with charterers and cargo owners and is characterized by attractive long-term contracts and fixed trading patterns. These operating conditions have secured stable employment and a regular cash-flow for maintenance and new investments. This specialized shipping segment has therefore been spared the roller-coaster ride other ship-owners so frequently experience.

The development of new technical solutions has however been limited, both as regards hull and containment system solutions and choice of propulsion units. It is fair to say that the LNG transport segment has been among the most conservative. On the other hand very good technical and operational standards have been typical for this type of shipping .The skills of people involved, both onboard and ashore, have been undisputable and the safety record for LNG carriers is among the best in the whole shipping industry. No major accidents or release of cargo have occurred.

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