Multi- objective optimization and life cycle assessment of a cascade system integrating LiBr/H2O absorption refrigeration with transcritical CO2 power cycle

Abstract

Energy, economic and environmental (3E) analysis of a cascade system combining absorption refrigeration (AR) and transcritical CO2 power cycle (TCPC) for low-grade waste heat recovery (WHR) is conducted. Life cycle assessment (LCA) is applied to evaluate environmental performance. A novel comprehensive index Eco-indicator 16 (EI16) integrating seventeen environmental impacts was proposed which involves human health, ecosystem and resource. A multi-objection optimization model with thermal efficiency, annual total cost and EI16 as three objection functions is established and solved by Non-dominated sorting genetic algorithm II (NSGA-II). The final optimal solution is obtained after decision making with Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) and Shannon entropy method. The results show that payback time can be less than 7 years and there is a synergistic relationship between energy efficiency and environmental performance, while energy efficiency and economic performance are mutually contradictory. The final optimal solution achieves an increase by 13.17% in thermal efficiency and a decrease by 13.49% in Eco-indicator 16 at cost of an 8.94% increase in annual total cost. In all environmental impact categories, the contribution to the climate change is the largest, which is beneficial to the human health and ecosystem protection.