Fuel cell system with partial heating of each individual fuel cell

A fuel cell system comprising

• a fuel cell including a plurality of individual fuel cells stacked in a stack direction to construct an integrated fuel cell stack, for generating electric power by an electrochemical reaction of hydrogen and oxygen;
• wherein a first portion of each individual fuel cell is collectively heated when the fuel cell is warmed up in a warm-up operation;
• a thermal medium circulation path through which a thermal medium is circulated into each individual fuel cell;
• a first thermal medium circulation device for controlling an amount of the thermal medium circulated through the thermal medium circulation path;
• a bypass path through which the thermal medium is circulated into the first portion of each individual fuel cell while bypassing a second portion of each individual fuel cell, the bypass path being part of the thermal medium circulation path;
• a cooling device provided in the thermal medium circulation path, for cooling the thermal medium;
• a heating path provided in the thermal medium circulation path;
• a heating device provided in the heating path, for heating the thermal medium;
• and
• a flow switching device for switching a flow of the thermal medium to one of the cooing device and the heating device, wherein:
• the flow switching device is operated such that the thermal medium is circulated to the heating device in the warm-up operation of each individual fuel cell, and the thermal medium is circulated to the cooling device in a normal operation of each individual fuel cell, where each individual fuel cell normally performs power generation.