Energy-exergy-economic-environmental (4E) analysis and multi-objective optimization of a cascade LiBr/H2O refrigeration and Organic Rankine cycle integrated system for power generation

This study aims to propose a comprehensive evaluation index which comprises energy, exergy, economy, and environment (4E) for analyzing the novel cascade LiBr/H2O refrigeration and Organic Rankle cycle integrated system for low-grade residual heat recovery. Life cycle assessment (LCA) is used to evaluate the multi-dimensional environmental performances, and a new index, namely Eco-indicator 16 (EI16) is utilized for aggregating multiple environmental impacts in Recipe 2016 method into a quantitative score. Besides, A multi-objective optimization model using net energy generation (NEG), exergy efficiency (ɛ), annual total cost (ATC), and EI16 as the objectives has been developed for sustainability-oriented optimization of the integrated system. NSGA-II is applied for multi-objective optimization, and multiple decision-making methods are used to select the Pareto solution set and obtain the optimal solution. The results show that the payback time is about 5 years under the world average electricity price and interest rate. The optimal working condition increases NEG by 3.27 times, exergy efficiency by 3.26 times, and the ecological index EI16 decreases by 3.23 times at the expense of increasing the ATC by 26.17 %. The system contributes the most to improving the climate and has significant benefits to human health. This study offers guidance for the 4E analysis of a coupled system operating in low-grade residual heat in a cascade.