Comprehensive sustainability assessment and emergy analysis of a combined cooling, heating and power system integrated with high-temperature solar thermochemical complementation and low-temperature solar thermal collection processes

Combined cooling, heating, and power (CCHP) systems integrated with solar energy have garnered widespread attention because of their superior efficiency, cleanliness, economy, and reliability, making them a hotspot of current research. However, few studies have involved sustainability assessment and emergy analysis. This research constructs a novel solar-assisted CCHP (SACCHP) system that integrates a high-temperature solar thermochemical process and a low-temperature solar heat collection process. Taking a solid oxide fuel cell-micro gas turbine as the core prime mover, both a double-effect lithium bromide chiller and a heat exchanger are used to recover the waste heat of flue gas exhausted from micro gas turbine, thus realizing the comprehensive complementarity of renewable energy and fossil energy and the cascade utilization of energy. A quantitative sustainability evaluation model is established to comprehensively assess the system's overall sustainability index from thermodynamic, economic, environmental, and reliability perspectives by using the information entropy method. The results indicate that the SACCHP system achieves the highest comprehensive sustainability index of 0.646 when the high-temperature solar collector area accounts for 75 % of the total. An emergy analysis is conducted for the SACCHP system under this scenario and compared with a traditional CCHP (TCCHP) system without solar integration. The results indicate that the SACCHP system significantly outperforms the TCCHP system in all emergy indicators. Specifically, the environmental sustainability index of the SACCHP system is 0.72, greater than that of TCCHP system, demonstrating the great sustainability of the SACCHP system.