Multi-objective optimization and life cycle assessment of an integrated system combining LiBr/H₂O absorption chiller and Kalina cycle

Abstract

Multi-objective optimization of an integrated waste heat recovery system combining absorption refrigeration cycle and Kalina cycle is investigated in present research. Life cycle assessment (LCA) is inserted into the multi-objective optimization model to evaluate the environmental performance. Eco-indicator 99 (EI99) method is used to translate eleven environmental impacts into a single criterion EI99. The proposed multi-objective optimization model includes three objective functions: thermal efficiency, annualized total cost (ATC) and EI99, from the energetic, economic and environmental (3E) aspects. Non-dominated sorting genetic algorithm II is employed to solve the conflicts among three objectives of this optimization model. Pareto optimal solutions are obtained, presenting the optimal trade-off among objectives. Technique for Order Preference by Similarity to an Ideal Solution and Shannon entropy approach are combined for decision making. Results show that the presented multi-objective optimization model properly handles the contradictions in this optimization problem. By using the combined decision-making technique, the final optimal solution is determined. This optimal scheme achieves around 9.34% and 9.53% higher thermal efficiency and EI99 at the cost of 3.03% higher ATC. Therefore, with sufficient consideration, this final optimal solution is superior to other solutions. LCA of this proposed system is then comprehensively conducted and compared with the individual KC. Comparison results indicate that this integrated system is obviously better than the individual KC from the environmental point of view. This research provides in-depth knowledge of the 3E performance analysis and multi-objective optimization of a cascade waste heat recovery process.