LNG Fueled Offshore Support Vessels in the Americas

Abstract

Abstract This paper details the strong incentives to use gas as a marine propulsionfuel. The gas fuel ship is a very attractive option considering theenvironmental and economic drivers even though the gas fuel support systemsinitially cost more and are a challenge to arrange within the ship. The scopeof the paper covers the pros and cons of the use of:–LNG fuel for marine applications,–Diesel scrubber technology versus utilising natural gas–Classification and regulatory hurdles–Some offshore support vessel arrangement considerations. There has been a significant amount of interest and discussion in recent monthsin the US regarding the application and benefits of using natural gas as asource of fuel for marine vessels. There are many examples of vessels (LNGcarriers, passenger, patrol, ferries, etc.) currently in operation usingnatural gas in Europe; however, it has been slow to progress in North Americaas a fuel for operating vessels. International class societies have been overseeing the design and operation ofnatural gas fuelled vessels for over a decade now; however, most classsocieties have only recently created or put into force gas propulsionguidelines and rules. Luckily, most of the guidelines and rules are similar innature because they have been developed from roadmap International MaritimeOrganization guidelines. Although the American Bureau of Shipping has draftrules that follow the intent of the international rules, the US Coast Guard hasadditional domestic interpretations of the international rules that areconsidered more stringent. In order to suit the particular regulations in theUS, the configuration of the vessel plays a large part in the ability to fit anLNG propulsion system without sacrificing cargo capacity, especially foroffshore supply vessels. The capital investment for gas fuelled propulsion and the associated gasdistribution equipment is large but the return on investment is achieved in arelatively short amount of time if the costs of the gas fuel are compared withultra-low sulphur diesel and the cost of urea for the selective catalyticreactor (SCR), and the SCR itself. A conservative annual estimate for thesavings in fuel costs are 2 to 2.5 million USD when compared to conventionaldiesel fuel. Long term maintenance costs for the gas engines is also purportedto be less and still more cost effective to maintain compared to an SCRsystem.