Improving the efficiency of a gas-fueled ship power plant using a Waste Heat Recovery metal hydride system

Abstract

Due to environmental, energy, and operating cost constraints, the number of liquefied natural gas (LNG)-powered ships is increasing. To avoid decreasing the thermal efficiency of two-stroke, low-speed diesel engines, high-pressure gas injection is used. The specific energy consumption of a gas fuel compressor is around 0.35 kWh/kg, which has a negative impact on the efficiency of ship power plants. To reduce the primary energy consumption of a gas fuel supply system, waste heat recovery (WHR) technologies may be used. This study investigated whether WHR metal hydride technology was suitable for improving the efficiency of low-grade heat waste in marine diesel engines. The key factors of this technology were revealed, and the design scheme was described. Working fluids were also analyzed, and a mathematical model of a WHR metal hydride plant was developed, and the results were represented. The calculations showed that the above technology could increase the operating power of a propulsion plant by 5.7-6.2%. The results demonstrate the possibility of applying WHR metal hydride equipment for gas fuel compressor drives in LNG-powered ships. The novelty of this study lies in the investigation of metal hydride technology for application in the waste heat recovery systems of LNG-powered ships.