Emergy analysis and comprehensive sustainability investigation of a solar-aided liquid air energy storage system based on life cycle assessment

Recently, the solar-aided liquid air energy storage (LAES) system is attracting growing attention due to its eco-friendliness and enormous energy storage capacity. Although researchers have proposed numerous innovative hybrid LAES systems and conducted analyses around thermodynamics, economics, and dynamic characteristics, very few studies have involved emergy analysis and sustainability assessment. In fact, even conventional LAES (C-LAES) systems lack emergy analysis and sustainability evaluation in the literature. To fill this gap, based on C-LAES system, an innovative multi-generation solar-aided LAES (M-S-LAES) system is put forward, adequately utilizing air compression heat and solar heat to provide power, cooling, heating, and hot water. Emergy analysis and sustainability assessment are conducted to evaluate and compare the sustainability performances of these two systems. The results show that the innovative system significantly outperforms the conventional system from the perspective of emergy analysis. For the innovative system, among the five regions mentioned, Dunhuang stands out in several aspects. It boasts the largest share of renewable resources of 56.62%, the lowest emergy investment ratio of 0.766, and the highest environmental sustainability index of 3.01, indicating that Dunhuang exhibits promising prospects for achieving long-term environmental and economic sustainability. In addition, based on nine indicators spanning energy, economic, environmental, and society dimensions, the comprehensive sustainability assessment result of the innovative system shows that the composite sustainability index of Dunhuang is the highest (0.9642), with an energy efficiency of 70.15%, net present value of 365.44 million$, levelized cost of energy of 0.088 $/kWh, and dynamic payback period of 5.46 years. The annual emission reduction of CO2, SO2, NOx and PM2.5 are 9.55E+07 kg, 7.90E+05 kg, 6.83E+05 kg and 3.33E+05 kg, respectively. Furthermore, enhancing energy storage capacity can significantly improve the overall sustainability performance of the innovative system.