Conventional and advanced exergy and exergo-economic analyses of a CCHP system considering methanol-fueled solid oxide fuel cell and energy cascade utilization: A comprehensive parametric and optimization study

Combined cooling, heating, and power (CCHP) systems driven by fuel cells have been recommended as one promising energy technology to alleviate fossil energy crisis and environmental pollution problem. These kinds of tri-generation systems are commonly evaluated by traditional exergy analysis methods, while the true irreversibility within system components cannot be revealed due to method limitations. This study conducts performance evaluation of an innovative CCHP system combined with a methanol-fueled solid oxide fuel cell (SOFC) and an internal combustion engine (ICE) for sufficient energy cascade utilization. Parametric study and performance optimization are performed by using exergy, economic, and exergo-economic analysis methods. Analysis results illustrate that the system exergy destruction varies in opposite trend versus the system investment cost rate when core system parameters are changed. The application of R600 in organic Rankine cycle (ORC) achieves the greatest reduction in system investment cost rate, while R1234ze(E) and R600a present the most potential for optimizing system performance. Advanced exergy and exergo-economic analyses of the whole system are further presented to reveal the true thermodynamic and economic irreversibility at component-level in energy conversion processes. Results indicate that most of system components exhibit significantly higher unavoidable endogenous parts of exergy destruction compared to unavoidable exogenous parts, and the most significant avoidable endogenous parts of exergy destruction appear in the SOFC, ICE, and Preheater 1. SOFC and Inverter are dominated by unavoidable endogenous parts of investment cost, accounting for 91.8 % and 93.0 % of their investment cost rates, respectively. At last, proper optimization strategies for reducing avoidable exergy destruction cost rates are developed.