Exergy and Thermoeconomic Analysis for an Underground Train Station Air-Conditioning Cooling System

The necessity of air-conditioning causes the enormous energy use of underground train stations. Exergy and thermoeconomic analysis is applied to the annual operation of the air-conditioning system of a large underground train station in Taiwan. The current installation and the monitored data are taken to be the base case, which is then compared to three different optimized designs. The total revenue requirement levelized cost rate and the total exergy destruction rate are used to evaluate the merits. The results show that the cost optimization objective would obtain a lower total revenue requirement levelized cost rate, but at the expense of a higher total exergy destruction rate. Optimization of thermodynamic efficiency, however, leads to a lower total exergy destruction rate, but would increase the total revenue requirement levelized cost rate significantly. It has been shown that multi-objective optimization would result in a small marginal increase in total revenue requirement levelized cost rate, but achieve a significantly lower total exergy destruction rate. Results in terms of the normalized total revenue requirement levelized cost rate and the normalized total exergy destruction rate are also presented. It has been shown by second law analysis when applied to underground train stations that lower annual energy use and lower CO2 emissions can be achieved.