Energy, exergy and thermoeconomic analysis of a novel combined cooling and power system using low-temperature heat source and LNG cold energy recovery

Abstract

This paper deals with the energy, exergy, and economic analysis of a novel ammonia-water combined cooling and power cycle using waste heat as low-temperature heat source and LNG cold energy as thermal sink. For this purpose, thermodynamic modeling of the proposed system is presented and the performance of the cycle is investigated based on the following performance criteria: net power output, cooling output, first-law efficiency, second-law efficiency, and sum unit cost of the products (SUCPs) of the system. In this respect, the simulation revealed that the net power output, cooling output, first-law efficiency, second-law efficiency, and total SUCP of the system can be calculated 1379kW, 1736kW, 43.25%, 22.51%, and 133.7 $/GJ, respectively, showing a considerable enhancement through this integration. In addition, the irreversibility of each component and overall system are presented showing that heat exchanger 2 accounts for the highest exergy destruction among all components which is followed by the throttling valve 1. Moreover, a comprehensive parametric study is conducted to investigate the effects of considered key parameters, namely, vapor generator pressure, LNG turbine inlet pressure, evaporator temperature, condenser temperature, heat source temperature, and ammonia concentration on the performance criteria. It is observed that one can obtain a higher first-law efficiency at higher ammonia concentrations, heat source temperatures and LNG turbine inlet pressures or at lower condenser temperatures and vapor generator pressures, while a higher second-law efficiency can be obtained at lower ammonia concentrations, heat source temperatures and condenser temperatures or at higher vapor generator pressures, evaporator temperatures as well as LNG turbine inlet pressures.