Application of classification rules to hybrid marine electrical propulsion plants

With the advent of advanced power electronics converters, energy storage devices, and alternative fuel technologies on marine vessels, hybrid electric propulsion plants are becoming a more common alternative for vessel owners seeking ways to improve electric plant efficiency, reduce emissions (both noise and pollution), and improve safety in emergency egress and blackout recovery situations. Hybrid marine electric propulsion plants offer flexible usage alternatives to traditional electrical plant configurations to allow vessel operators more options for optimizing the electrical plant configuration to best service the required load profile during different modes of plant operation. Additionally, just as they have in other transportation industries, the efficiency of marine electrical plants can be dramatically improved to save on fuel costs, and air pollution emissions can be significantly reduced to comply with the new stringent MARPOL Annex VI pollution regulations required in environmentally sensitive areas. Lastly, hybrid electric plants using stored energy as a backup for the main power sources allow vessel operators to enhance safety in response to emergency scenarios where all main power is lost, or in situations such as explosive natural gas buildups where internal combustion engines/other rotating machinery may not be able to be operated safely. Applying traditional rules and regulations for sizing of these types of electrical plants requires some special considerations with regard to the interpretation of the sizing criteria for main power sources as they apply to stored energy devices. Traditional methods of determining the minimum size and quantity of main electrical power sources must be tailored to include the non-spinning reserve provided by hybrid electrical plants in the form of energy storage. This paper will provide background information on the development of hybrid electric plant designs, discuss the advantages of this emerging technology, explain the different types of hybrid plants currently available, describe typical applications where hybrid electric plants are used, provide examples of how the current ABS Rules are applied to hybrid electrical plants, and suggest future possible rule changes to better, more directly address these types of power plants.