How to identify trade-off of thermodynamic and economic performance of the S-CO2 cycle caused by the cycle structures?

Abstract

Generally, the improvement of thermodynamic performance of supercritical CO2 Brayton cycles is realized by more complex cycle structures at the expense of expensive system cost. How to identify trade-off of the thermodynamic and economic performance of the S-CO2 cycle is a challenging issue because system structure is hard to be optimized with its nature of discrete variable. Therefore, taking the net power output and cost of electricity as the objective functions, this study tries to solve this issue by multi-objective optimization of superstructure of supercritical CO2 Brayton cycle for gas turbine waste heat recovery. Besides discussing the effect of heat source temperature and cooling temperature, the optimization results of the superstructure are compared with the traditional structures. The results show that at different heat source temperatures, the distribution regularities of the cycle structures on the Pareto-front are the same, and the structure of the trade-off solution tends to be the same. With the increase of heat source temperature, the costs of trade-off solutions are reduced by 8.86%, 11.16% and 16.51%, respectively. The change of cooling temperature has a great effect on the structure of the trade-off solution. In addition, superstructures have obvious advantages over the traditional structures in terms of trade-off solution performance and structure selection.