Integrated design of propulsion, re-liquefaction and cargo handling system for large-scaled liquefied hydrogen tanker considering energy efficiency and GHG emissions

Abstract

This study presents an integrated design methodology for the energy system, the boil-off hydrogen re-liquefaction system, and the cargo handling system for a liquefied hydrogen tanker for long-range bulk liquefied hydrogen transport. First, this study proposes an optimal energy system for a liquid hydrogen tanker using LNG as fuel which is the most realistic alternative fuel in terms of technology and economy. The three main propulsion systems (high pressure ME-GI engine, low pressure X-DF engine, combined cycle gas turbine) and two power generation engines (dual fuel generation engine and fuel cell) are combined to form candidate machinery configurations. The study predicts the amount of electricity used from ship operations, quantifies the annual CO2 emissions and the amount of evaporative hydrogen emissions from an economic perspective, and proposes an optimal energy system through cost-benefit analysis. Second, the study develops a re-liquefaction system cycle for boil-off hydrogen treatment based on the proposed energy system, and proposes it by optimizing in terms of efficiency and operation cost. Third, for economical hydrogen import or supply, we present a cargo handling system and cargo tank operation plan for optimizing the processing of evaporative hydrogen gas generated during loading operation and unloading operation.