Performance and design optimization of different numbers and bolt torque for air-cooled open-cathode proton exchange membrane fuel cells

Air-cooled open-cathode polymer electrolyte fuel cells have attracted increasing attention in the field of portable energy equipment. This study explores the influence of the number of single cells, and bolt torque on stack performance based on the measurements of polarization curves, the single-cell voltage, and temperature distribution. The stack bolt torque and the number of single cells present a linear relationship and should be reasonably matched to improve the stack performance. Remarkably, the more cells, the greater bolt torque is required to achieve better stack performance. The results show that the optimal range of the number of single cells for the air-cooled open-cathode polymer electrolyte fuel cells is 20-25. When the cell number increases to 32-40, stack operating temperature exceeds the optimal range, thus reducing the output power and mass power density. A novel modularized design for the stack with the optimal number of single cells is firstly proposed which effectively improves the thermal management and power performance index of the stack. The work conducted could provide the reference and guidance for the stack design and accelerate the application of aircooled open-cathode fuel cells.