Energy and Exergy Analysis of an Integrated SOFC–LiBr/H₂O Absorption Trigeneration System: Parametric Effects on Power, Heat, and Cooling Performance

This paper presents a comprehensive thermodynamic assessment of a trigeneration system integrating a solid oxide fuel cell (SOFC) with a lithium bromide-water (LiBr-H2O) single-effect absorption chiller. A systematic parametric analysis is conducted to investigate the influence of key SOFC operating parameters including current density, fuel utilization, operating temperature, and pressure on electrical output, thermal recovery, and overall system efficiency. In parallel, the effects of generator and absorber temperatures on the cooling performance are evaluated to clarify the coupling between SOFC waste heat and absorption refrigeration. In addition to the energy analysis, a second-law evaluation is performed to assess the exergy efficiency of the integrated trigeneration system. The results reveal pronounced trade-offs between electrical and thermal performance. Increasing current density from 2000 to 15 000 A/m2 enhances heat production by approximately 34%, while electrical output decreases by nearly 28% due to intensified polarization losses. Similarly, raising the SOFC operating temperature from 600 to 1100 K increases recoverable heat by about 34%, but reduces electrical work by 28%. Pressurizing the SOFC up to 500 kPa improves electrical efficiency by approximately 9%, while an optimal fuel utilization range of 0.82-0.86 maximizes electrical efficiency without anode starvation. The exergy analysis indicates that system performance strongly depends on operating conditions, with exergy efficiency reaching values of approximately 42% under optimal conditions and decreasing significantly at high current densities and temperatures due to increased thermodynamic irreversibility. For the absorption subsystem, the highest coefficient of performance (COP approximate to 0.78) is achieved at low absorber temperatures around 298 K, which also enhances both energy and exergy utilization of the recovered heat. Overall, the system performs best with moderate current densities (2000-6000 A/m2), operating temperatures of 600-750 K, higher pressures up to 500 kPa, optimal fuel utilization, and low absorber temperatures, ensuring a balanced combination of electrical output, heat recovery, and thermodynamic efficiency. These findings provide useful design guidelines for improving the performance of SOFC-based trigeneration systems for building energy systems, industrial applications, and decentralized power generation.