Alternative fuels for enhanced ship energy efficiency: A conceptual design study of a handymax bulk carrier

Alternative fuels stand out as the key solutions for increasing concerns about low-carbon and energy-efficient maritime transportation. This paper investigates the energy efficiency and design features of a concept bulk carrier powered by alternative fuels of LNG, methanol and hydrogen. Firstly, a benchmark study is conducted to obtain the main characteristics and propulsion trends of handymax class bulk carriers. Then the bulk carrier with an overall length of 178 m and a capacity of 35000 DWT is conceptually designed. The Energy Efficiency Design Index is calculated and the environmental impacts of the concept design with conventional diesel prime mover, LNG and methanol-powered dual-fuel engine systems integrated with the shaft generator are discussed. Finally, the design properties of the concept bulk carrier with alternative fuels are analyzed and compared. According to the results, the attained EEDI of the LNG-powered concept design, excluding the methane slip phenomenon, is approximately 17.1% lower than that of the MDO-powered design and 13.7% lower than the MeOH-powered design. Besides, the primary fuel choice significantly impacts fuel storage, supply, safety, and the vessel's effective range. The propulsion systems using alternative fuels require approximately 2-4 times more space and additional safety measures than conventional systems powered by MDO.