Thermo-economic analysis of SOFC-CLC cogeneration system based on CO2 separation with natural cooling

An advanced cogeneration system combining CLC (Chemical Looping Combustion) and SOFC (Solid Oxide Fuel Cell) is proposed to reduce CO2 separation energy consumption in this paper. The method can separate CO2 without energy consumption to achieve minimum carbon dioxide emissions through natural cooling and improve energy conversion efficiency. SOFC is used to efficiently transform chemical energy of fuel into electrical energy, and the CO2 separation is achieved without energy consumption by CLC technology to significantly reduce CO2 emission during the energy conversion process. Besides, absorption heat pump is utilized for the recovery of lowgrade cold-end waste heat to achieve dual goals of minimum CO2 emissions and zero waste heat emissions. The performances are evaluated from an energy, economic and exergy perspective. The study demonstrates that the efficiencies of power generation, exergy and thermal are 66.22 %, 74.01 % and 91.04 % under the design parameters. Compared to the reference system, the efficiencies of power generation, exergy and thermal are enhanced by 3.05 %, 4.36 %, and 3.53 %. The three components with the highest exergy losses are the SOFC, CLC and direct current-accommodation converter (DC-AC), and accounts for 28.07 %, 27.16 % and 17.63 %. The levelized cost of exergy (LCOE) is 0.1026 $/kWh. The dynamic payback period is 7.03 years, which is reduced by 2.35 years compared to the reference system. Additionally, a sensitivity analysis is conducted. As fuel utilization rate, SOFC operating pressure and SOFC operating temperature increase, the thermal efficiency remains around 91 %, and exergy efficiency rises from 68.26 %, 61.84 % and 69.57 % to 74.00 %, 73.51 % and 73.01 %, and power generation efficiency improves from 60.18 %, 54.62 % and 62.76 % to 66.22 %, 66.89 % and 66.48 %, while the heating load decreases from 75.88 kW, 88.80 kW and 69.38 kW to 61.40 kW, 59.67 kW and 61.09 kW. With an increase in current density, exergy efficiency and power generation efficiency decrease from 73.34 % and 66.71 % to 71.84 % and 65.14 %, and the heating load increases from 60.42 kW to 63.65 kW. As the split ratio increases, the thermal efficiency, exergy efficiency and heating load increase from 77.77 %, 72.57 % and 25 kW to 91.04 %, 72.88 % and 61.40 kW, while the power generation efficiency decreases from 67.66 % to 66.22 %.