Optimisation of operational modes of short-route ferry: a life cycle assessment case study

Owing to high operation cost of traditional power systems and serious environmental situation, the usage of hybrid power system on board is increasingly attracting attentions. Applying life cycle assessment (LCA) approach, the key objective of this paper is to evaluate and optimise the operational modes of hybrid power system for a short-route ferry in Scotland. The applied hybrid system is mainly comprised of generators and lithium ion batteries and there are four operational modes based on the power requirements during voyages. To carry out this study, a top-bottom design strategy is applied to build up the short route ferry with hybrid power system in GaBi. The cradle to grave of the ferry is modelled referring to a practical ship life: con-struction, operation, maintenance and dismantling. In order to determine the optimal power distribution and minimal emissions, a series of operation profile cases with different power distributions were investigated for a certain route with following operational phases: transiting, manoeuvring and at slip. The comparison results from different voyage phases indicated the optimal power distribution between gen-sets and batteries with minimised operation costs. The environmental assessments for each case were carried out in order to identify the relationship between power distributions and emissions. The study concluded that there are sig-nificant impacts on the energy consumption and environment during the life cycle of a hybrid power system and therefore it is essential to apply appropriate operation optimisation on the system.