Assessing the potential of hybrid energy technology to reduce exhaust emissions from global shipping

The combination of a prime mover and an energy storage device for reduction of fuel consumption has successfully been used in automotive industry. The shipping industry has utilised this for conventional submarines. The potential of a load levelling strategy through use of a hybrid battery–diesel–electric propulsion system is investigated. The goal is to reduce exhaust gas emissions by reducing fuel oil consumption through consideration of a re-engineered ship propulsion system. This work is based on operational data for a shipping fleet containing all types of bulk carriers. The engine loading and the energy requirements are calculated, and sizing of suitable propulsion and the battery storage system are proposed. The changes in overall emissions are estimated and the potential for fuel savings identified. The efficiency of the system depends on the storage medium type, the availability of energy and the displacement characteristics of the examined vessels. These results for the global fleet indicate that savings depending on storage system, vessel condition and vessel type could be up to 0.32 million tonnes in NOx, 0.07 million tonnes in SOx and 4.1 million tonnes in CO2. These represent a maximum 14% of reduction in dry bulk sector and 1.8% of world's fleet emissions.

► Global shipping makes a significant contribution to CO2, SOx and NOx emissions.
► We examine noon reports from a fleet of bulk carriers to identify the amount engine is operating off design.
► A hybrid propulsion system is proposed that uses multiple diesel–electric generators and battery storage.
► Analysis indicates hybrid may give an attractive rate of return as well as emissions savings in emissions.
► Implementation will require review of class society regulations.