Operational guidelines for a residential solid oxide fuel cell-combined heat and power system with an optimal system layout design

Abstract

Operational guidelines for safe and optimal load following operation of a residential solid oxide fuel cell-combined heat and power system are suggested. System layout design optimization via feasibility test and performance analysis is preceded. Then, the effect of system parameters on system performance is analyzed in a parametric study to draw an operating window and to derive optimal operating conditions. Owing to complete analytical expressions equipped in an in-house one-dimensional solid oxide fuel cell stack model, reliable estimation of the stack performance under various operating conditions is accomplished. The operating window is drawn from the feasibility criteria, which consider system thermal integration and durability. It is found that the operating range of low current density, low fuel utilization, and low air utilization values leads to unfeasible thermal integration. Moreover, the operating range of high current density, low fuel utilization, and high air utilization leads to defect in system durability. Finally, the optimal operating conditions are suggested to supply heat and power for extreme seasonal energy demands. The optimal operating condition for summer is suggested by the air utilization of 17.5%, the current density of 0.4 A/cm2, and the fuel utilization of 80%, providing the net electrical power of 18.5 kW, the electrical efficiency of 44.1%, and the heat to power ratio of 0.95. The optimal operating condition for winter is suggested by the air utilization of 17.5%, the current density of 0.3 A/cm2, and the fuel utilization of 60%, providing the net electrical power of 15.5 kW, the electrical efficiency of 37.0%, and the heat to power ratio of 1.23.