Abstract: Recirculation arrangements and methods are disclosed for high temperature fuel cell systems or electrolysis cell systems. Exemplary embodiments recirculate gas exhausted from at least one of an anode side and a cathode side. A desired recirculated flow rate is provided by an ejector supplied with at least one primary feedstock fluid and a supplementary fluid to a nozzle with a convergent-divergent flow channel. A respective ratio of the primary and supplementary fluids of the ejector maintains a desired motive flow and pressure at the nozzle to accomplish desired recirculated flow rate. The supplementary fluid is cutoff when a level of system loading is such that the primary feedstock fluid alone maintains the desired motive flow and pressure at an ejector inlet.

Abstract: A method and system for high temperature fuel cell system or electrolysis cell are disclosed which include recirculating a fraction of gas exhausted from at least one of sides an anode side and a cathode side; accomplishing a desired flow rate of the recirculated flow by using an ejector via at least one primary feedstock fluid to a nozzle of the ejector, which nozzle has a convergent-divergent flow channel through which fluid is expanded from an initial higher pressure to lower pressure; providing supplementary fluid to the nozzle of the ejector; regulating respective ratio of the fluids of the ejector to maintain a desired motive flow and pressure at the nozzle of the ejector in order to accomplish desired recirculated flow rate; and cutting off the supplementary fluid when a level of system loading is the primary feedstock fluid alone maintains desired flow and pressure at ejector inlet.

Abstract: A start-up transition process is disclosed for a fuel cell system operation state, which includes utilization of predefined first and second temperature limits for the fuel cells, specifying a low temperature operating state of cells below the first limit, at which presence of carbonaceous species at the cells is precluded, a transition temperature range of cells above the first and below the second limit at which fuel flow supply is initiated to the fuel system in a mixture with air, combined with anode tail gas recirculated at a recirculation rate over 70, and an intermediate temperature operating state of the cells above the second temperature limit, at which free oxygen at the anodes.

Abstract: A control arrangement in a fuel cell system for producing electricity with fuel cells, the fuel cell system including means for recirculating fuel through the anode sides of the fuel cells, and at least one system controller in a control processor for controlling the operation of the fuel cell system. The control arrangement includes means for performing a substantially asynchronous chemical reaction rates calculation process of at least one of fuel composition and fuel flow rate to accomplish information in a substantially iterative process on at least recirculation ratio of the fuel recirculation through anodes and means for generating, in a substantially synchronous process with the system controller process, fuel utilization (FU) information and Carbon formation information by utilizing the latest available recirculation ratio information provided by said asynchronous process.

Abstract: A start-up transition process is disclosed for a fuel cell system operation state, which includes utilization of predefined first and second temperature limits for the fuel cells, specifying a low temperature operating state of cells below the first limit, at which presence of carbonaceous species at the cells is precluded, a transition temperature range of cells above the first and below the second limit at which fuel flow supply is initiated to the fuel system in a mixture with air, combined with anode tail gas recirculated at a recirculation rate over 70, and an intermediate temperature operating state of the cells above the second temperature limit, at which free oxygen at the anodes.

Abstract: An arrangement utilizing recirculation for high temperature fuel cell system, each fuel cell including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, wherein the fuel cell system can perform anode side recirculation flow of reactants. The arrangement can accomplish a recycle ratio of 70% or more for the recirculation flow, feed to the recirculation a feed-in flow, which can include substantially high oxygen content, the feed-in flow being 30% or less of entire flow, perform heat exchanging to provide substantially reduced low temperature conditions in the recirculation flow, perform catalytic partial oxidation in the recirculation flow to produce a substantially high amount of hydrogen for the recirculation flow in fuel cell system start-up or shutdown situations, and exhaust 30% or less of the entire flow from the anode side recirculation.

Abstract: An exemplary arrangement and method for controlling operating conditions of a fuel cell device are disclosed. The fuel cell device having plural fuel cells, each including an anode side, a cathode side, an electrolyte between the anode side and the cathode side, and being arranted in a stack. The control arrangement includes at least one controllable electrical heater configured to produce controllable heat quantities, at least two controllers that control fuel cell quantities including at least a portion of air flowing to the fuel cells and heat applied to the stack environment. The controllable heat quantities and controllable fuel cell quantities are controlled to meet a target value. The fuel cell device includes a low level high speed controller configured to control at least one controllable electrical heater to operate the heater as a buffer for excess energy of the fuel cell device.

Abstract: Exemplary systems and methods for adjusting current values in a fuel cell system for producing electricity with fuel cells, include drawing major part of the current from at least one serial connection. An adjusting circuit adjusts current values by drawing or supplying current of at least one stack of individual fuel cell stacks or current of at least one group of the groups of stacks within the serial connection. The adjusting circuit is integrated with the at least one stack of individual fuel cell stacks or with the at least one group of the groups of stacks. Compensation current of the at least one stack or group is a small percentage of a major part of the current in the serial connection of stacks.

Abstract: A control arrangement in a fuel cell system for producing electricity with fuel cells, the fuel cell system including means for recirculating fuel through the anode sides of the fuel cells, and at least one system controller in a control processor for controlling the operation of the fuel cell system. The control arrangement includes means for performing a substantially asynchronous chemical reaction rates calculation process of at least one of fuel composition and fuel flow rate to accomplish information in a substantially iterative process on at least recirculation ratio of the fuel recirculation through anodes and means for generating, in a substantially synchronous process with the system controller process, fuel utilization (FU) information and Carbon formation information by utilizing the latest available recirculation ratio information provided by said asynchronous process.

Abstract: A method and system for high temperature fuel cell system or electrolysis cell are disclosed which include recirculating a fraction of gas exhausted from at least one of sides an anode side and a cathode side; accomplishing a desired flow rate of the recirculated flow by using an ejector via at least one primary feedstock fluid to a nozzle of the ejector, which nozzle has a convergent-divergent flow channel through which fluid is expanded from an initial higher pressure to lower pressure; providing supplementary fluid to the nozzle of the ejector; regulating respective ratio of the fluids of the ejector to maintain a desired motive flow and pressure at the nozzle of the ejector in order to accomplish desired recirculated flow rate; and cutting off the supplementary fluid when a level of system loading is the primary feedstock fluid alone maintains desired flow and pressure at ejector inlet.

Abstract: An arrangement utilizing recirculation for high temperature fuel cell system, each fuel cell including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, wherein the fuel cell system can perform anode side recirculation flow of reactants. The arrangement can accomplish a recycle ratio of 70% or more for the recirculation flow, feed to the recirculation a feed-in flow, which can include substantially high oxygen content, the feed-in flow being 30% or less of entire flow, perform heat exchanging to provide substantially reduced low temperature conditions in the recirculation flow, perform catalytic partial oxidation in the recirculation flow to produce a substantially high amount of hydrogen for the recirculation flow in fuel cell system start-up or shutdown situations, and exhaust 30% or less of the entire flow from the anode side recirculation.

Abstract: An arrangement utilizing recirculation for high temperature fuel cell system, each fuel cell including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, wherein the fuel cell system can perform anode side recirculation flow of reactants. The arrangement can accomplish a recycle ratio of 70% or more for the recirculation flow, feed to the recirculation a feed-in flow, which can include substantially high oxygen content, the feed-in flow being 30% or less of entire flow, perform heat exchanging to provide substantially reduced low temperature conditions in the recirculation flow, perform catalytic partial oxidation in the recirculation flow to produce a substantially high amount of hydrogen for the recirculation flow in fuel cell system start-up or shutdown situations, and exhaust 30% or less of the entire flow from the anode side recirculation.

Abstract: An arrangement for improved operability of a high temperature fuel cell device at higher fuel cell voltage values than nominal voltage values, each fuel cell in the fuel cell device including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, and the arrangement includes means for determining temperature information of the fuel cells and main power converter for loading fuels cells at least up to their rated power level.

Abstract: An offset control arrangement is disclosed for controlling voltage values in a fuel cell system including an anode side, a cathode side and an electrolyte between the anode side and the cathode side. The fuel cell system can include at least one fuel cell array of at least two fuel cells, and at least one load for performing load function. The offset control arrangement can include voltage monitoring for monitoring an input voltage of the load, a control processor for processing the monitoring information, and at least one offsetting source in serial connection to the at least one fuel cell array, with a power level of the offsetting source being substantially low compared to the power level of the fuel cell array, and the offsetting source being arranged to perform at least unidirectional shifting of fuel cell array output voltage.

Abstract: A method is disclosed for producing electrical current by a fuel cell device, which inputs electrical current to an electrical network. A fuel cell device can be arranged to be parallel connected to the electrical network. A phase reference signal can be utilized in the inputting of the electrical current, and electrical current inputted to electrical network can be current controlled by a power transformer having a power stage. The fuel cell device can be switched off from the electrical network when a malfunction occurs in the electrical network. The fuel cell device can be changed, using the phase reference signal, to the switched off operation mode for performing voltage controlled operation of the power transformer. A controllable load can be used for maintaining a power stability between the voltage controlled power transformer and other parts of the fuel cell device.

Abstract: An offset control arrangement is disclosed for controlling voltage values in a fuel cell system including an anode side, a cathode side and an electrolyte between the anode side and the cathode side. The fuel cell system can include at least one fuel cell array of at least two fuel cells, and at least one load for performing load function. The offset control arrangement can include voltage monitoring for monitoring an input voltage of the load, a control processor for processing the monitoring information, and at least one offsetting source in serial connection to the at least one fuel cell array, with a power level of the offsetting source being substantially low compared to the power level of the fuel cell array, and the offsetting source being arranged to perform at least unidirectional shifting of fuel cell array output voltage.

Abstract: An arrangement is disclosed for reducing use for safety gases in a high temperature fuel cell system, each fuel cell in the fuel cell system including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side. The fuel cells can be arranged in fuel cell stacks. The fuel cell system can include a fuel cell system piping for reactants, and feeding of fuel to the anode sides of the fuel cells. Electrical anode protection can be achieved by supplying a predefined voltage separately to at least two fuel cell stacks or groups of fuel cell stacks to prohibit oxidation of anodes.

Abstract: An arrangement for improved operability of a high temperature fuel cell device at higher fuel cell voltage values than nominal voltage values, each fuel cell in the fuel cell device including an anode side, a cathode side, and an electrolyte between the anode side and the cathode side, and the arrangement includes means for determining temperature information of the fuel cells and main power converter for loading fuels cells at least up to their rated power level.

Abstract: A method and system are disclosed for reducing the consumption of safety gas in a fuel cell system having at least one fuel cell unit whose fuel cells include an anode side and a cathode side, as well as an electrolyte interposed therebetween. A supply is provided for supplying the anode with a safety gas, and an exhaust is provided for exhausting the fuel cell unit of a spent safety gas coming from the anode side. The method can adapt a specific percentage of the spent safety gas flow coming from the anode side of the fuel cells to be re-supplied into the anode side of the fuel cells.

Abstract: A method is disclosed for monitoring galvanic isolation of a fuel cell device. At least one stack of fuel cells and at least one load circuit for fuel cells are arranged to an electrically freely floating configuration towards at least one structure near fuel cells. A controlled switching is performed via at least two switching points to at least one measurement element having known impedance in connection to the at least one structure. Measurements are performed from the measurement element to form voltage information. The voltage information and at least voltage information between switching points are processed to check floatages of fuel cells in relation to said at least one structure.