4. Global system

The fuel cell can be thought of as a black box, with a fuel inlet (a connection to the natural gas network, for example), an exhaust outlet, a connection to the heat network (in the case of a stack operating in cogeneration) and a connection to the electrical network (figure 19 ). Between these connections and the electrochemical stack lies the system that will enable the stack to be powered, cooled... and to transform the direct current produced into constant-voltage alternating current compatible with a connection to the electrical grid.