Abstract: In order to cause a plurality of cells in a fuel cell to be recovered to a desired humidity state, it is configured to determine that the cells present a mixture of dry and overly humid states in the case where a predetermined condition is satisfied, and in the case where it is determined that the cells present the mixture, humidifying control is carried out to cause all the cells to attain the overly humid state, and thereafter, drying control is carried out to dry all the cells, to thereby cause the plurality of cells to be recovered to a predetermined humidity state.

Abstract: A fuel cell system suppresses the deterioration of an electrolyte membrane of a fuel cell. The fuel cell system comprises: a temperature rise speed calculation unit for calculating a target temperature rise speed of the fuel cell using a temperature of the fuel cell and a water content of the fuel cell; and a drive control unit for controlling a drive of the cooling water pump using the temperature rise speed of the fuel cell and the target temperature rise speed calculated by the temperature rise speed calculation unit. The drive control unit controls the drive of the cooling water pump such that a circulation amount of the cooling water is decreased when the temperature rise speed of the fuel cell is below the target temperature rise speed and controls the drive of the cooling water pump such that the circulation amount of the cooling water is increased when the temperature rise speed of the fuel cell is equal to or greater than the target temperature rise speed.

Abstract: Provided is a fuel cell system including: a fuel cell which generates power by an electrochemical reaction between an oxidant gas supplied to an oxidant gas flow path and a fuel gas supplied to a fuel gas flow path; and a controller which adjusts an amount of the oxidant gas supplied to the fuel cell and a voltage of the fuel cell. The controller has an obstruction degree determining unit which determines a degree of obstruction of the oxidant gas flow path based on a stoichiometric ratio of the oxidant gas and the voltage of the fuel cell during a low-efficiency operation in which the stoichiometric ratio of the oxidant gas is reduced from the stoichiometric ratio of the oxidant gas during a normal operation and heat discharged from the fuel cell is increased from that during the normal operation. This improves stability of the low-efficiency operation of the fuel cell system.

Abstract: A fuel cell system comprises: a fuel cell formed of a plurality of cells stacked therein, each cell generating electric power through an electrochemical reaction between a fuel gas and an oxidant gas; a cell monitor capable of detecting a group voltage for each group wherein each group is composed of two or more cells; and an estimation device that estimates a minimum cell voltage. The estimation device comprises a maximum cell voltage estimation part that estimates a maximum cell voltage, and the estimation device estimates the minimum cell voltage by using an estimated value of the maximum cell voltage and a minimum group-average voltage, where an average voltage of a group having the lowest voltage value among the group voltages is defined as the minimum group-average voltage.

Abstract: A fuel cell system includes: a fuel cell supplied with fuel gas for power generation; a fuel supply flow passage flowing fuel gas, supplied from a fuel supply source, to the fuel cell; a pressure regulating valve regulating a pressure of fuel gas flowing through the fuel supply flow passage; a fuel circulation flow passage returning gas, emitted from the fuel cell, to the fuel supply flow passage; a circulation pump delivering gas in the fuel circulation flow passage to the fuel supply flow passage; an emission valve emitting gas in the fuel circulation flow passage to an outside; and a control device controlling the pressure regulating valve, the circulation pump and the emission valve such that the sum of losses of crossover hydrogen, circulation pump power and purge hydrogen is minimum while a hydrogen stoichiometric ratio required for power generation of the fuel cell is ensured.

Abstract: A fuel cell system suppresses the deterioration of an electrolyte membrane of a fuel cell. The fuel cell system comprises: a temperature rise speed calculation unit for calculating a target temperature rise speed of the fuel cell using a temperature of the fuel cell and a water content of the fuel cell; and a drive control unit for controlling a drive of the cooling water pump using the temperature rise speed of the fuel cell and the target temperature rise speed calculated by the temperature rise speed calculation unit. The drive control unit controls the drive of the cooling water pump such that a circulation amount of the cooling water is decreased when the temperature rise speed of the fuel cell is below the target temperature rise speed and controls the drive of the cooling water pump such that the circulation amount of the cooling water is increased when the temperature rise speed of the fuel cell is equal to or greater than the target temperature rise speed.

Abstract: An object of the present invention is to provide a fuel cell system capable of avoiding damage to a circulation pump at a low temperature to improve system efficiency. The fuel cell system of the present invention includes a fuel gas circulation system having a circulation path which re-circulates, through a fuel cell, a fuel off gas discharged from the fuel cell, and a circulation pump which feeds under pressure the fuel off gas in the circulation path; and a controller which controls driving of the circulation pump. The controller stops the driving of the circulation pump at a predetermined low temperature.

Abstract: Provided is a fuel cell system capable of making a shift of an operation state while optically controlling an output voltage and an output voltage of a fuel cell. When an ECU judges that the time when an operation should be shifted from a low-efficiency operation to a normal operation has come, the ECU performs, as preprocessing prior to a shift to a ?V control, processing of increasing an oxidant gas supplied to a fuel cell stack by a predetermined amount. After this processing, the ECU detects output power, calculates an output power deviation, and then compares the output power deviation with a set deviation threshold. When the output power deviation exceeds the deviation threshold, the ECU carries out the ?V control, and then carries out an I-V control. Meanwhile, when the output power deviation does not exceed the deviation threshold, the ECU judges that the time when the ?V control is carried out has not come yet, and automatically starts the I-V control without carrying out the ?V control.

Abstract: The problem is that a large force is required to open a flow-dividing shut valve provided in an air supply path for supplying the air to a fuel cell stack at a start of a fuel cell system. This problem is solved by reducing a pressure difference between upstream and downstream of the flow-dividing shut valve, before the flow-dividing shut valve is opened, at a start of the fuel cell system.

Abstract: A fuel cell system includes a fuel cell, an operation controller and an air-conditioning mechanism. In response to a heating request for the air-conditioning mechanism during ordinary operation where the fuel cell is operated at an operating point on a current-voltage characteristic curve of the fuel cell, the operation controller compares a heat value-based required current value with an output-based required current value. When the output-based required current value is equal to or greater than the heat value-based required current value, the operation controller causes the fuel cell to be operated at an operating point on the current-voltage characteristic curve. When the output-based required current value is smaller than the heat value-based required current value, the operation controller controls the operating point of the fuel cell to an operating point of lower power generation efficiency than that of the operating point on the current-voltage characteristic curve.

Abstract: When starting operation of a fuel cell below the freezing point, a fuel cell system adjusts the open degree of a hydrogen pressure adjusting valve, introduces hydrogen to a hydrogen entrance of the fuel cell so as to make the total pressure of the hydrogen entrance a first pressure, and starts a hydrogen circulation pump. If at least one of the cell voltages acquired by a cell voltmeter is below a predetermined voltage, the system determines that clogging is caused in a hydrogen flow channel in the fuel cell. When it is determined that clogging is present, the open degree of the pressure adjusting valve is adjusted and hydrogen is introduced to the hydrogen entrance so that the total pressure of the hydrogen entrance is a second pressure which is higher than the first pressure. Then, the hydrogen circulation pump is stopped and the fuel cell is warmed up to dissolve the clogging of the hydrogen flow channel.

Abstract: Even if a failure occurs in a bypass valve during low-efficiency power generation, the occurrence of an excessive stoichiometry ratio in a fuel cell can be prevented. An output from a pressure sensor or a current sensor is monitored by a control device, and when a failure associated with a closed-valve malfunction of the bypass valve occurs, the degree of opening of the pressure regulating valve is increased to increase an amount of cathode-off gas exhaust, and a revolution speed of an air compressor is reduced to an amount of air discharged by the air compressor, thereby preventing an excessive stoichiometry ratio in the fuel cell.

Abstract: There is disclosed a fuel cell system including a fuel cell, a fuel supply system to supply a fuel gas to the fuel cell, an injector which adjusts a gas state on an upstream side of the fuel supply system to supply the gas to a downstream side, and a control unit which drives and controls the injector in a predetermined drive cycle. The control unit sets the drive cycle of the injector in accordance with an operation state of the fuel cell.

Abstract: There is disclosed a fuel cell system or the like capable of sufficiently reducing an exhaust hydrogen concentration even in a case where a fuel cell is operated in a state of a low power generation efficiency. A bypass valve is arranged between an oxidation gas supply path and a cathode-off gas channel. In a state in which supply of an oxidation gas to a cathode falls short, pumping hydrogen is included in a cathode-off gas. Therefore, a valve open degree of the bypass valve is regulated, and a flow rate of bypass air is regulated to control the exhaust hydrogen concentration.

Abstract: In order to determine the air stoichiometric ratio without using multidimensional mapping, a fuel cell system of the invention computes a command current value and command voltage value in a fuel cell during low-efficiency electrical power generation based on the required electrical power, estimates a reference voltage of the fuel cell from the command voltage value and the water temperature when the command current value is taken as a reference current, determines the difference between the reference voltage thus obtained and the command voltage value as an air concentration overvoltage target value, computes the air stoichiometric ratio based on the air concentration overvoltage target value, computes the air amount during low-efficiency electrical power generation based on the air stoichiometric ratio, and controls the amount of air supplied to the fuel cell according to the air amount thus computed.

Abstract: An object is to suppress the degradation of durability due to a heat concentration while performing a rapid warm-up operation as necessary, when starting a fuel cell system at temperatures below freezing point.

Abstract: There are disclosed a fuel cell system capable of inhibiting freezing at a joining part of a supply gas and a circulation gas during a system operation, and a method for calculating circulation ratio in the system. In the fuel cell system of the present invention, the circulation gas discharged from a fuel cell meets the supply gas from a gas supply source to be supplied to the fuel cell, and a flow rate of the circulation gas with respect to that of the supply gas is set in consideration of condensation latent heat of water vapor in the circulation gas. The flow rate of the circulation gas with respect to that of the supply gas can be set by heat balance calculation at the joining part in consideration of the condensation latent heat.

Abstract: A fuel cell system includes a fuel cell, an operation controller and an air-conditioning mechanism. In response to a heating request for the air-conditioning mechanism during ordinary operation where the fuel cell is operated at an operating point on a current-voltage characteristic curve of the fuel cell, the operation controller compares a heat value-based required current value that is a current value of an operating point that is located on the current-voltage characteristic curve and satisfies a required heat value for the fuel cell with an output-based required current value that is a current value of an operating point that is located on the current-voltage characteristic curve and satisfies a required output for the fuel cell. When the output-based required current value is equal to or greater than the heat value-based required current value, the operation controller causes the fuel cell to be operated at an operating point on the current-voltage characteristic curve.

Abstract: Disclosed is a fuel cell system including a fuel cell which generates a power, and control means for decreasing the amount of a reactant gas to be supplied to the fuel cell to an amount smaller than that during normal power generation to realize low-efficiency power generation of the fuel cell. The control means sets the voltage lower limit value of the fuel cell so that the amount of an anode gas (pumping hydrogen) to be formed in a cathode of the fuel cell during the low-efficiency power generation is a predetermined amount or less.

Abstract: FC current control in a fuel cell operation system can be roughly divided into two parts. The first part executes a total air feed amount calculation step, an FC air amount calculation step, and a bypass air amount calculation step. These steps are executed by using a stoichiometry map and a pumping hydrogen amount map. The second part calculates a control valve open amount instruction value and a bypass valve open amount instruction value according to the calculated FC air amount and the bypass air amount. Here, a control valve open amount map and the like are used. When generated power is output from the fuel cell stack by these instruction values, the actual FC current value is compared to the FC current instruction value and the control valve open amount is corrected according to a difference between them.