Performance Research Of The Cooling, Heating And Power Cogeneration System Based On SOFC/GT

This paper introduced that low temperature waste heat recovery system was applied in SOFC/GT hybrid power generation system, in order to realize the energy cascade utilization and provide combined cooling heating and power and greatly improve the efficiency of energy utilization. It can further make the system energy conservation and emissions reduction realized to improve the SOFC/GT hybrid power generation system and the low temperature waste heat recovery system. The new system was simulated by using the EES software based on the developed mathematical models, and the system performance consisted of energy analysis and exegy analysis was evaluated by the first and second laws of thermodynamics.A new SOFC/GT/KCS combined power generation system was built by referencing Kalina cycle to collect mixed flue gas waste heat from traditional SOFC/GT power generation system. The results indicate that the SOFC electrical, the system overall electrical and the exergy efficiencies reach about 49.2%,67.6% and 68.16%, respectively, under the rated conditions. It is also found that the largest exergy loss occurs in the waste heat boiler followed by the SOFC, the gas turbine, the HR3, and the after-burner in the system. In addition, there is an optimal fuel utilization factor (0.85) to reach the maximum overall electrical, exergy and the SOFC electrical efficiencies. And the overall electrical and exergy efficiencies can be improved by decreasing the air flow rate, fuel flow rate, and the steam-to-carbon ratio within the range of parameters studied.A novel combined power generation system driven by dual SOFCs was proposed by using a Kalina cycle to recover the waste heat of exhaust from the dual SOFC/GT. Compared with the traditional SOFC/GT hybrid power generation system, the modified SOFC/GT hybrid power generation system sent H2 separated by the membrane separation device from SOFC1 anode exhaust into SOFC2 anode to take part in electrochemical reaction after the condensing, inflating and preheating, in order to improve the overall energy efficiency of SOFC/GT systems. The results indicated that the SOFC electrical efficiency, the overall electrical and exergy efficiencies of the proposed system is 58.88%,72.75%and 72.6%, being increased by 9.78%,2.75% and 5.12% in comparison with the reference system’s, respectively. The largest exergy loss occurs in SOFC1 followed by the gas turbine and the waste heat boiler. It is also found that the SOFC electrical efficiency, overall electrical efficiency and exergy efficiency can be improved by increasing the fuel utilization factor of the SOFC2 and the steam-to-carbon ratio, and by decreasing the fuel utilization factor of the SOFC1 within the range of parameters studied.To improve the power generation efficiency of SOFC, oxygen-enriched air was sent into the SOFC cathode in this article. After electrochemical reaction, SOFC cathode exhaust still has high oxygen concentration. The new SOFC/GT hybrid power generation system was built in order to collect oxygen-enriched air in cathode outlet and increase the outlet temperature of the combustion chamber at the same time. Meanwhile, the high and low temperatures double heat sources Kalina cycle is designed to recover the high and low temperatures waste heat from the new SOFC/GT hybrid power generation system. The results indicate that the SOFC electrical efficiency of the proposed system is 51.07%,1.42% higher than the reference system. The overall electrical and exergy efficiency of the proposed system are 73.24% and 67.82%, increased by 3.37% and 3.42% in comparison with the reference system, respectively, under the rated conditions. The exergy analysis results show that the largest exergy loss occurs in the waste heat boiler 1 followed by the gas turbine 1, SOFC, the waste heat boiler2 and combustion chamber. It is also found that SOFC electrical efficiency, overall electrical efficiency and exergy efficiency can be improved by increasing the O2 purity of oxygen-enriched air and the fuel utilization factor within the range of parameters studied. Moreover, an increasing in SOFC cathode exhaust diversion ratio to combustion chamber has negative effect on overall electrical efficiency and exergy efficiency. And there is the optimal steam-to-carbon ratio (2.053) to reach the maximum overall electrical efficiency and exergy efficiency of the proposed system. There is the optimal fuel flow rate (4.421mol/s) to reach the maximum overall electrical efficiency and exergy efficiency of the proposed system. There is the optimal air flow rate (81.05mol/s) to reach the maximum overall electrical efficiency and exergy efficiency of the proposed system within the range of parameters studied.Generation and refrigerating capacity can be achieved by using the ammonia-water power/refrigeration cogeneration cycle to recover the mixed flue gas waste heat from SOFC/GT power generation system. A new SOFC/GT/ST combined system was proposed by using the cogeneration to generate heat and power. The results indicate that the SOFC electrical, the system thermal and the exergy efficiencies reach about 49.7%,68.96% and 73.4%, respectively. It is also found that the largest exergy loss occurs in the gas turbine followed by the the waste heat boiler, the after-burner, SOFC, and the preheater3 in the system.