A fuel cell system 100 includes: a fuel cell 1 for generating a power by causing an electrochemical reaction between an oxidant gas supplied to an oxidant electrode 34 and a fuel gas supplied to a fuel electrode 67; a fuel gas supplier HS for supplying the fuel gas to the fuel electrode 67; and a controller 40 for controlling the fuel gas supplier HS to thereby supply the fuel gas to the fuel electrode 67, the controller 40 being configured to implement a pressure change when an outlet of the fuel electrode 67 side is closed, wherein based on a first pressure change pattern for implementing the pressure change at a first pressure width ΔP1, the controller 40 periodically changes a pressure of the fuel gas at the fuel electrode 67.

A first representative value is acquired representing an amount of liquid water in a hydrogen gas passage (30) when a fuel cell stack (10) is to be started up. Based on the first representative value, a first purge gas amount is calculated. A second representative value is acquired representing a concentration of hydrogen gas in a hydrogen gas passage when the fuel cell stack is to be started up. Based on the second representative value, a second purge gas amount is calculated. The greater of the first purge gas amount and the second purge gas amount is set as a startup purge gas amount. When the fuel cell stack is to be started up, hydrogen gas is fed to the fuel cell stack while the purge control valve 38 is temporally opened to purge the gas by the startup purge gas amount.

Disclosed is a high-temperature operating fuel cell system including: a fuel cell stack; a combustor that combusts a cathode off-gas and an anode off-gas; a heat insulator that covers at least part of the fuel cell stack and at least part of the combustor; a first preheater that covers at least part of the heat insulator and preheats an oxidant gas; an oxidant gas feeder that supplies the oxidant gas to the first preheater; a vacuum heat insulator that covers at least part of the first preheater; a sensor that detects information indicating stopping of a power generation operation; and a controller. When a determination is made that the power generation has stopped, the controller controls the oxidant gas feeder to supply the oxidant gas to the first preheater so that the temperature of the vacuum heat insulator is equal to or lower than a prescribed temperature.

A fuel cell system includes a first temperature sensor to detect a valve temperature of a sealing valve. A second temperature sensor is provided in a refrigerant circulation circuit to detect a fuel cell temperature of a fuel cell through a refrigerant. The circuitry is configured to calculate a sealing valve estimated temperature by subtracting a correction value from the fuel cell temperature detected by the second temperature sensor after the fuel cell stops generating electric power and after the sealing valve is closed. The circuitry is configured to determine whether at least one of the valve temperature and the sealing valve estimated temperature is lower than a predicted freezing temperature. The circuitry is configured to open the sealing valve when it is determined that the at least one of the valve temperature and the sealing valve estimated temperature is lower than the predicted freezing temperature.

Provided is a method of operating a fuel cell system equipped with a fuel cell stack, a liquid hydrogen storage unit configured to store liquid hydrogen, a boil-off gas recovery unit configured to recover boil-off gas generated from the liquid hydrogen storage unit, and a hydrogen concentration estimation unit configured to estimate the hydrogen concentration at a hydrogen electrode in the fuel cell stack in a standby state, the method including: in a case in which a hydrogen concentration at a hydrogen electrode in the fuel cell stack in a standby state has become less than a predetermined value, supplying boil-off gas recovered by the boil-off gas recovery unit to the hydrogen electrode in the fuel cell stack.

This specification describes a system and method for controlling the voltage produced by a fuel cell. The system involves providing a bypass line between an air exhaust from the fuel cell and an air inlet of the fuel cell. At least one controllable device is configured to allow the flow rate through the bypass line to be altered. A controller is provided to control the controllable device. The method involves varying the rate of recirculation of air exhaust to air inlet so as to provide a desired change in fuel cell voltage.

This disclosure relates to module level redundancy for fuel cell systems. A monitoring component monitors a set of operational parameters for a fuel cell group. The fuel cell group includes a set of fuel cell units, each having a set of fuel cell stacks. The fuel cell stacks include a set of gas powered fuel cells that convert air and fuel into electricity using a chemical reaction. The monitoring component determines that the set of operational parameters do not satisfy a set of operational criteria, and, in response, a load balancing component adjusts the electrical output capacity of the set of fuel cell units included in the fuel cell group.

A method of cleaning power cells in an array of power cells, comprising coupling at least one first power cell to second power cells in an array of power cells and causing the second power cells to drive the at least one first power cell with a voltage to clean catalyst on the at least one first power cell.

Provided is an incorporated device that incorporates therein an electrolytic cell and a power control device that is capable of suppressing temperature rise in the electrolytic cell to thereby suppress a reduction in the life of electrodes, and a method for controlling an incorporated device. The incorporated device incorporates therein an electrolytic cell and a power control device that is capable of suppressing temperature rise in the electrolytic cell to thereby suppress a reduction in the life of electrodes. The power control device includes: a voltage-current control circuit that supplies, in a constant current control mode, an electrolysis current to the electrolytic cell while the voltage-current control circuit controls the electrolysis current not to exceed a current value of a reference current, the current value of the reference current being preliminary set according to a rated current of a unit cell constituting the electrolytic cell; and a temperature detecting part that detects an environmental temperature of an outside of the electrolytic cell, the environmental temperature being a temperature of an inside of the incorporated device. The voltage-current control circuit stops supply of the electrolysis current when a detected temperature of the temperature detecting part falls outside of a preliminarily set rated temperature range, and resumes supply of the electrolysis current when the detected temperature of the temperature detecting part returns within the rated temperature range.

In various aspects, systems and methods are provided for operating a molten carbonate fuel cell at increased fuel utilization and/or increased CO.sub.2 utilization. This can be accomplished in part by performing an effective amount of an endothermic reaction within the fuel cell stack in an integrated manner. This can allow for a desired temperature differential to be maintained within the fuel cell.