Cogeneration system for controlling fuel cell devices based on operation mode

A control method of a control device in a cogeneration system, the cogeneration system comprising a plurality of fuel cell devices supplying heat and power to a heat load and a power load, the control device connected to the fuel cell devices, the method comprising:

• calculating, by the control device, a heat demand value of the heat load;
• determining, by the control device, an operation mode of the fuel cell devices on the basis of at least one of the calculated heat demand value of the heat load and a power demand value of the power load, wherein the heat load receives the heat from the plurality of fuel cell devices and the power load receives the power from the plurality of fuel cell devices;
• calculating the heat demand value and the power demand value on the basis of at least one of weather, gas rate, power selling or purchasing rate, break-even point of a consumer facility, day of week, degradation degree of the fuel cell devices, time of day, or gas consumption,
• controlling, by the control device, a power generation efficiency and a heat recovery efficiency by controlling the plurality of fuel cell devices on the basis of the operation mode determined, wherein said controlling comprises:
• in response to the calculated heat demand value being smaller than a first predetermined value, determining a power generation efficiency priority mode as the operation mode,
• under the power generation efficiency priority mode, controlling the fuel cell devices to maximize power generation efficiency by controlling power generation amounts of the fuel cell devices to be the same,
• in response to the calculated heat demand value being equal to or greater than a second predetermined value that is greater than the first predetermined value, determining a heat recovery priority mode as the operation mode, and
• under the heat recovery priority mode, controlling the fuel cell devices to maximize heat recovery efficiency by controlling a power generation amount of at least one of the plurality of fuel cell devices to become zero,
• wherein
• the power generation efficiency is a ratio of a total electrical power generation amount to a gas consumption amount of the fuel cell devices,
• the heat recovery efficiency is a ratio of a total heat recovery amount to the gas consumption amount of the fuel cell devices, and
• when a power load factor increases, the power generation efficiency increases while the heat recovery efficiency decreases, the power load factor indicating a maximum power generation amount of the fuel cell devices.