Exergoeconomic analysis and optimization of a transcritical CO2 power cycle driven by solar energy based on nanofluid with liquefied natural gas as its heat sink

Abstract

The thermodynamic and economic analysis of a transcritical carbon dioxide power cycle is coupled with solar thermal subsystem and LNG subsystem. Solar thermal subsystem consists of parabolic trough collectors and a thermal storage tank, and the Copper-Therminol VP1 nanofluid is used in this subsystem. In most hours of the day, the solar subsystem based on Copper-Therminol VP1 nanofluid has a better thermal performance, which includes the output temperature of the collector and temperature of the storage tank, compared to the solar subsystem based on Therminol VP1. LNG subsystem is employed as a heat sink of the transcritical CO2 power subsystem, as well as the power generation by LNG turbine. The exergoeconomic analysis is performed to evaluate the effects of the key parameters, including turbine inlet temperatures and pressures, condensate pressure, CO2 mass flow rate and LNG pressure, on the exergy efficiency and product cost rate. In addition, parameter optimization is conducted via genetic algorithm. TOPSIS decision making technique is employed to select optimum point. System is capable of producing power with exergy efficiency of 8.53%, and product cost rate is equal to 2.09 million dollars per year, under optimum conditions. The values of exergoeconomic variables for each component of the system are calculated. The results represent that solar collector, evaporator, condenser, CO2 turbine and LNG turbine have the highest total cost rate of exergy destruction and investment $$ (\dot{C}_{\text{d}} + \dot{Z}) $$, respectively. The highest amount of investment cost rate $$ \dot{Z} $$ occurs in solar collector. The condenser has the lowest value of exergoeconomic factor which indicates that the costs associated with condenser come from exergy destruction rate.