A new scheme for large marine vessels LNG cold energy utilization from thermodynamic and thermoeconomic viewpoints

Abstract

With the implementation of International Maritime Organization's new emission regulations in 2020, it has a huge impact on shipping industry. To meet the strict emission regulations and policies, liquefied natural gas, as a promising fuel, can replace the traditional heavy oil, and effectively and practically act as the main power source of marine engine. When liquefied natural gas is vaporized from −162 °C to room temperature, a large amount of cold energy is released to the outside world. To reuse the cold energy efficiently and economically, a new scheme integrated with organic Rankine cycle, seawater desalination, subzero storage and air-conditioning is proposed through comparison of six solutions. With a series of analysis and comparison, R290, NH3, R32 and R152a are determined as the best working fluids for organic Rankine cycle, subzero storage, seawater desalination and air-conditioning modules, respectively. After optimizing the parameters of the scheme by genetic algorithm, the exergy efficiency, net work and payback period reach 55.91%, 210.3 kW and 4.27 years, respectively, showing excellent thermoeconomic performance. Therefore, the proposed method provides a new idea for cold energy recovery of natural gas engine on ships.