Abstract: In the SOFC system, the fuel gas flow rate at the time of the start of start-up is set to the maximum fuel gas flow rate that is less than or equal to 1.3 times the maximum fuel gas flow rate FgMAX at the time of the rated power generation, the fuel gas flow rate F2 until the temperature T of the fuel cell stack reaches T1, at which the reduction of the oxidized Ni in the fuel cell stack is performed, is set to be less than or equal to F1, and thereafter, until the start of the power generation, fuel gas flow rate F3 is further reduced from F2, and the average fuel gas flow rate FAVE is set to be equal to or greater than 0.6 times the average fuel gas flow rate FgAVE at the time of the rated power generation.

Abstract: An object of the invention is to improve durability of a SOFC system and secure favorable power generation performance during the actual useful service period of the system. In the SOFC system, a fuel gas flow rate to a fuel cell stack is set at F1 at the time of start-up. At a time point when a temperature T of the fuel cell stack reaches a first temperature T1 or higher after the temperature is started to increase, when it is determined that the stack temperature T at the time of the previous system stop is lower than or equal to a predetermined value Tb, the fuel gas flow rate is decreased to F2a (which is less than F1), and when it is determined that the stack temperature T is higher than the predetermined value Tb, the fuel gas flow rate is decreased to F2b (which is less than F2a) to slow the temperature increase rate. Furthermore, when the stack temperature T reaches T2, the fuel gas flow rate is returned to F1 so as to increase the fuel gas flow rate and then the process proceeds to the next process.

Abstract: During system start-up in S11, an ATR process begins, and the hydrogen-enriched fuel gas is generated by the autothermal reaction. In S12, a cell temperature T is compared to a minimum reduction start temperature T1 of the cell support and, in the case of T?T1, the process proceeds to S13. In S13 a hydrogen concentration of the fuel gas is set to 50% or less. In S14, the cell temperature T is compared to a maximum reduction start temperature T2 of the cell support, and in the case of T>T2, the process proceeds to step S15. In S15, the temperatures of the reformer and the fuel cell stack are continuously raised, while gradually increasing the hydrogen concentration.

Abstract: A SOFC system houses a reformer and a fuel cell stack in a module case. Each cell forming the fuel cell stack is made of a porous material having a composition containing at least nickel metal, includes a cell support having a gas passage through which the fuel gas from the reformer flows from an lower end to an upper end on the inside thereof, and the excessive fuel gas is combusted at the upper end of the gas passage. Here, after the power generation stops, until the temperature of the upper end of the fuel cell stack falls below the minimum oxidation temperature of the nickel metal, the supply amount of the fuel gas to the fuel cell stack is controlled in terms of a heat flow rate within a range of 0.1 to 0.5 times that during the system rated power generation.

Abstract: In a fuel cell system, when an electric current drawn from fuel cells is controlled based on a target power generation value, an upper limit of the electric current is optimally set to make suspensions of operation caused by voltage drops to be as infrequent as possible. The upper limit of the electric current is set by adding a predetermined offset value (e.g., 2 A) to an average value of the electric current before a predetermined delay time (e.g., 10 seconds). Moreover, when the electric current drawn from the fuel cells is controlled based on a target power generation value, the value of the electric current is compared with the upper limit of the electric current, to control the electric current.

Abstract: This fuel cell system monitors the temperature of an off-gas combusting unit detected by a combustor temperature detecting unit in a constant output operation state such as a rated operation state where a sweeping current of a cell stack becomes constant, rather than directly measuring the fuel property, and controls the flow rate of the cathode gas so that the temperature of the off-gas combusting unit reaches a target temperature. Moreover, the fuel cell system determines the fuel property based on the variation of the flow rate of the cathode gas changed until the temperature of the off-gas combusting unit reaches the target temperature and the temperature of the cathode gas. Thus, it is possible to simplify the configuration required for determining whether the fuel property has changed or not as compared to a conventional method of measuring a plurality of factors of the fuel property.

Abstract: The present invention provides a fuel cell system including a reformer that reforms a raw fuel using a reforming catalyst to generate reformed gas, a fuel cell that generates electric power using the reformed gas generated by the reformer, a heat exchanger that exchanges heat between heat of combustion exhaust gas discharged from the fuel cell and water introduced thereinto, a condenser that condenses steam contained in the combustion exhaust gas discharged from primary side downstream of the heat exchanger to recover water, a pump for supplying the water to secondary side upstream of the heat exchanger; a hot-water temperature measurement instrument that measures temperature of hot water at secondary side downstream of the heat exchanger, and a control unit that controls a supply amount by the pump.

Abstract: In a fuel cell system, when an electric current drawn from fuel cells is controlled based on a target power generation value, an upper limit of the electric current is optimally set to make suspensions of operation caused by voltage drops to be as infrequent as possible. The upper limit of the electric current is set by adding a predetermined offset value (e.g., 2 A) to an average value of the electric current before a predetermined delay time (e.g., 10 seconds). Moreover, when the electric current drawn from the fuel cells is controlled based on a target power generation value, the value of the electric current is compared with the upper limit of the electric current, to control the electric current.

Abstract: A fuel cell system including a PEFC stack in an inner space of a housing includes a sheathed heater, arranged in the inner space, for heating the inner space; the sheathed heater is placed on a bottom face side of the inner space of the housing, while a gap is provided between the bottom face and the sheathed heater; a mounting plate for mounting an inner device including the PEFC stack is provided in the inner space of the housing; and the sheathed heater is arranged between the mounting plate and the bottom face of the inner space of the housing.