Thermodynamic Optimization of a Composition-Tunable ZeotropicORC Using LNG Cold Energy as a Heat Sink

The organic Rankine cycle (ORC) is a promising power generation cycle to fullyutilize the cold energy of liquid natural gas (LNG). ORC is usually operated under variableworking conditions, and the operation performance is significantly worse than under designconditions. In this paper, a novel composition-tunable zeotropic ORC using LNG cold energy-based liquid-separation condenser is proposed and a thermodynamic optimization model isformulated. A case study is then conducted to validate the superiority of the proposed ORCand analyze the important operation parameters to explore the reasons for the performanceadvantages of the novel system. The results show that the novel ORC has a higher evaporationtemperature, lower condensation temperature, lower condensation pressure, and lower pinchpoint temperature difference than the basic ORC. The exergy loss of the condenser is reduced,and the exergy efficiency is improved. The novel ORC features 2.86% higher annual average netpower output, 2.47% higher annual average thermal efficiency, 2.85% higher annual utilizationefficiency of cold energy, and 2.76% higher annual exergy efficiency of cold energy recoverythan the basic ORC.

Automated summary

This paper proposes a novel composition-tunable zeotropic ORC using LNG cold energy-based liquid-separation condenser and formulates a thermodynamic optimization model. The results show that the novel ORC outperforms the basic ORC in terms of energy efficiency, net power output, and cold energy utilization efficiency.