Holistic modelling of LNG carrier systems

Abstract

As the human population increases in parallel with an increase in the standard of living, the world energy demand also continually grows every year. Fossil fuels are the major components contributing to this energy supply. Natural gas, one of the fossil fuels, has shown promising growth due to it price and lower pollutant emissions compared to other fossil fuels. One option for transporting natural gas is the use of Liquefied Natural Gas (LNG) carriers. The LNG carrier is one of the most expensive, complex and potentially hazardous cargo carriers that are operating across the world’s oceans due to its cargo, thus proven components are required to build this type of ship. There are seven main components involved in constructing an LNG carrier and they are manufactured by a range of different companies. This situation has created a competitive environment for this industry; however it has also introduced a new challenge to the shipbuilder, engineer and ship-owner in terms of selecting the right components. For a new ship design, there would typically be an incremental change in one or more technology elements from a base design and over time this may result in a less than optimum design. This thesis therefore aims to develop a holistic methodology that can be employed in order to help the ship-owner in particular to select the right combination components for an LNG carrier to rationalise the fleet size, minimise overall costs of construction and operation, and control the total mass of pollutant emission products in preliminary design stage. This methodology is based on the mutual symbiosis between the tools used: namely a comprehensive ship system simulation method, an artificial neural network (ANN) evaluation process and an integrated ANN based multi-objective optimisation process. It is a comprehensive methodology that can be applied to all types of ships, although in this study, it focuses on LNG carriers