9. Conclusions

Like all natural gases, LNG is cleaner than coal or oil and offers an opportunity to diversify energy supplies. LNG will be the most viable option for automobile for long range use in comparison to CNG as LNG offers special advantages over CNG, that it can be transported and stored easily and with better density than gaseous methane. LNG also offers additional flexibility as liquefied-to-compressed natural gas (L-CNG) Therefore, it has been considered as a safe and clean fuel for future. Main factors that contribute to the global growth of LNG include climate change, escalating oil price, the decreasing LNG costs, increasing overall energy needs, fuel switching, the availability of natural gas from various offshore/onshore sites, the scope of utilization of low grade coal for LNG production, recovery of coal bed methane and the availability of natural gas from biogas resources. The existing cryogenic gas industries can suitably diversify in the LNG field because of their historical depth of knowledge and width of expertise in handling and storage of cryogenic liquids. Moreover the implementation of new safety measurements, increasing demand of LNG and expending LNG technology will drive LNG to become a globally promising fuel alternative.

Acknowledgements

This research was supported by a grant from the GAS Plant R&D Center funded by the Ministry of Land, Transportation and Maritime Affairs (MLTM) of the Korean government and also respectfully supported by BK 21 Program funded by the Ministry of Education (MOE) of Korea.

Natural gas is becoming a more popular energy source worldwide and its use is expected to increase dramatically over the next 2 decades. Natural gas has been gaining wider significance as a result of sustained high oil prices, a need for energy diversification and security, the growing global awareness of environmental issues, and the development of new gas-related technologies. Traditionally natural gas has been delivered to markets using two main commercially proven methods--pipelines and liquefied natural gas (LNG). Each of these alternatives is highly capital intensive and requires considerable working terms regarding the quantities and distances to market. In other words, these two methods are economical only over a specified range of quantities and distances and not over the whole range, which opens the door to a number of alternative technologies that have the potential to make the development for smaller quantities to be transported to specific distances. The most advanced among these alternative technologies include onshore gas-to-liquid (GTL), floating LNG and GTL, natural-gas hydrates (NGH), adsorbed natural gas (ANG), and compressed natural gas (CNG). However, none of these has been developed yet and been proved on a commercial scale, although they have proved themselves viable on the basis of technical parameters. This paper will be concerned mainly with (1) marine CNG alternatives, which are currently in their final stages of commercialization, indicating the various available marine CNG technologies used worldwide; (2) the operating differences between LNG and CNG transportation; (3) technical and economic evaluation of both the obstacles facing the commercialization of marine CNG transportation and its advantages.