Study on thermodynamic performance of SOFC-CCHP system integrating ORC and double-effect ARC

Abstract

A combined cooling, heating and power system (CCHP) based on solid oxide fuel cell (SOFC) is studied in this paper. The top cycle consists of the SOFC subsystem and the gas turbine (GT) subsystem. The bottom cycle consists of an organic Rankine cycle (ORC) subsystem, a double-effect absorption refrigeration cycle (ARC) subsystem, and a heating subsystem. The system can operate in series mode or parallel mode through the control of the throttle valve. The proposed system is modeled and simulated in Aspen Plus and Fortran. This article carries out an overall exergy analysis and compares the difference of exergy destruction rate between series mode and parallel mode, which provides a direction for the system optimization. The effects of the following key parameters on system performance are studied separately: flow rate of fuel, fuel utilization rate and steam-to-carbon ratio. Finally, the output area diagram of the system under constant input parameters is drawn, and the possible output range of the system is analyzed to meet the user demand. The results show that the electrical efficiency of SOFC and comprehensive energy utilization rate of the system can achieve 48.42% and 87.16% under the design conditions. The electrical efficiency and the exergy efficiency of the system are 63.21% and 62.67% respectively. Whether in series mode or parallel mode, the exergy destruction rate of SOFC subsystem is the highest. Compared with the series mode, the exergy destruction rate of the ORC subsystem decreases from 10.36% to 8.34% in the parallel mode, and the exergy destruction rate of the heating subsystem increases from 2.48% to 3.69%. The proposed system is highly efficient and flexible, which provides a new direction for SOFC-CCHP system.