Examination and optimization of a novel auxiliary trigeneration system for a ship through waste-to-energy from its engine

Abstract

Considering the thermal processes with the help of smart heat recovery, this study proposes a novel auxiliary trigeneration system for a ship based on the waste heat of its engine to produce electricity, cooling, and freshwater. The system consists of a regenerative organic Rankine cycle (RORC) with R600 working fluid, a lithium-bromide/water single-effect absorption chiller, and a humidification dehumidification (HDH) desalination unit. A multi-heat recovery technique is implemented in the design framework, having a well-organized waste-to-energy system. Technical 3E (energy, exergy, and exergoeconomic) analysis together with a multi-criteria optimization using a genetic algorithm is conducted. Furthermore, a parametric study is employed regarding the impact of changing design parameters, namely, pinch point temperature difference of the high recovery vapor generator (HRVG), turbine inlet pressure, and top temperature of the HDH on the thermodynamic and exergoeconomic criteria. The results indicated the high sensitivity of the outputs from varying the turbine inlet pressure. Besides, the optimum net output power, cooling, and generated freshwater are calculated to be 783.9 kW, 959.8 kW, and 98.1 m3/day, respectively. Also, the optimum energy and exergy efficiencies and total cost per unit exergy are computed to be 58.4%, 43.0%, and 0.1494 $/kWh, respectively.