This schematic illustrates the physical nature of the Modelica modeling process. As can be seen, there are external connections for the thermal (thermal_port), reactant input and output (caPort_a, caPort_b, anPort_a, and anPort_b), and electrical ("p" and "n") processes and variables. These connectors can be used to interface the one-dimensional (1D) Fuel Cell model into an external system or can be used to connect the 1D Fuel Cell model into a quasi-2D model.