Fuel cell cogeneration system, method of operating

A method of operating a fuel cell cogeneration system, the method comprising the steps of:

• (A) cooling a fuel cell by circulating an internal heat transfer medium through the fuel cell while the fuel cell is generating electric power;
• (B) storing an external heat transfer medium in a heat utilization portion, the external heat transfer medium having recovered heat from the internal heat transfer medium via a heat exchanger provided at an internal passage through which the internal heat transfer medium circulates;
• (C) detecting remaining calories of the heat utilization portion by a first detector provided at the heat utilization portion;
• (D) increasing a temperature of the fuel cell to an operating temperature by carrying out a first temperature increasing operation comprised of increasing the temperature of the fuel cell by circulating, when the remaining calories are at a threshold or more at the time of start-up, the internal heat transfer medium to which the heat is transferred from the external heat transfer medium via the heat exchanger;
• and
• (E) increasing the temperature of the fuel cell to the operating temperature by carrying out a second temperature increasing operation comprised of increasing the temperature of the fuel cell by circulating, when the remaining calories are less than the threshold, the internal heat transfer medium heated by a heater provided at the internal passage.