Economics of cell design and thermal management in solid oxide fuel cells under SOFC-GT hybrid operating conditions

Abstract

Typical operating parameters of a SOFC-GT hybrid system have been established to study the influence of SOFC-cell design variables such as cell length, rib width, interconnect thickness, and operating variables such as degree of pre-reforming and air utilization, upon thermal cell management and economics. Various SOFC production scales are being considered. Fuel utilization, air utilization and operating voltage were held constant while the number of cells was adjusted to meet the utilization specifications. Based upon the particular cell design and number of cells, the cost of the stacks has been established which is then converted to specific cost in $(2019)/kWDC. Findings show that in co-flow SOFCs specific costs can be effectively reduced by maximizing the cell width/number of parallel channels without impacting current density and thermal cell management. The cost optimum for the cell length was found to be in the range of 15–20 cm. While overall temperature differences were reduced in shorter cells, local gradients were reduced in longer cells. Increasing the rib width offers a cost-effective solution for reducing thermal gradients in the cell. Air utilization reaches a cost optimum around 45% and the operating voltage shows that lower cell voltages increase overall temperature differences and local thermal gradients while reducing specific SOFC cost.