Abstract: A fuel cell system is disclosed that employs a thermal sensor for measuring an amount of heat generated in the fuel cell system, wherein a sensor signal from the thermal sensor is used to adjust operation of the fuel cell system when the fuel cell system is operating outside of desired thermal operating conditions.

Abstract: A method for controlling relative humidity (RH) of a cathode side of a fuel cell stack in a fuel cell system that includes an RH sensor on a cathode inlet line for providing an RH signal indicative of the RH of cathode inlet air. If the RH sensor is providing a valid RH signal, the RH signal is calculated as an RH average of the cathode inlet air. When the RH sensor is not providing a valid RH signal, the calculated RH average is utilized to control the cathode inlet air RH. If the RH sensor is not providing a valid signal during start-up, then the stack power is temporarily set at an optimum level for a known cathode inlet air RH.

Abstract: A method for increasing the temperature of a cooling fluid used to control the temperature of a fuel cell stack at a system freeze start-up. The method includes determining that the cooling fluid is frozen or nearly frozen, and if so, deactivating excessive power draw on the fuel cell stack to minimize stack waste heat and activating a cooling fluid heater to heat the cooling fluid. Once it is determined that the cooling fluid is not frozen or is flowing, then the method initiates a normal system start-up.

Abstract: A method for controlling cathode air flow at system start-up by controlling a stack by-pass valve. The method includes determining a concentration of hydrogen in a cathode side of the fuel cell stack. The method also includes determining a volumetric flow rate through a cathode compressor, determining a volumetric flow rate through the cathode side and determining a fraction of volumetric flow rate through the cathode side to the total flow through the compressor. The method determines a modeled hydrogen outlet concentration from the fuel cell stack based on the volumetric flow rate through the compressor, the fraction of volumetric flow rate through the compressor to the total flow through the compressor and the concentration of hydrogen in the cathode side. The method uses a desired fraction of volumetric flow rate through the cathode side and the total flow through the compressor to determine the position of the by-pass valve.

Abstract: A fuel cell system having an adaptable compressor map and method for optimizing the adaptable compressor map is provided. The method includes the steps of establishing an initial operating setpoint for an air compressor based on the adaptable compressor map; monitoring a surge indicator; adjusting the adaptable compressor map based on the monitored surge indicator; determining a desired operating setpoint based on the adjusted adaptable compressor map; and establishing an adapted operating setpoint for the air compressor based on the adaptable compressor map following the adjustment thereof. The steps are repeated until the adaptable compressor map for the air compressor is optimized.

Abstract: A system and method for controlling the speed of a compressor in the event that an airflow meter that measures the airflow from the compressor to the cathode input of the stack fails. When a failure of the airflow meter is detected, an algorithm first deactivates the primary feedback control algorithms used to control cathode pressure and flow, and sets the cathode exhaust valve to a fully open position. The speed of the compressor is controlled by an open loop set-point and the airflow from the compressor is estimated by a model using compressor discharge pressure and the compressor speed. The cathode by-pass valve position is determined by calculating the difference between the requested cathode airflow and the modeled compressor output flow. The position of the by-pass valve is then adjusted using the valve characteristics and the compressor discharge pressure. The estimated airflow to the stack is used to control the maximum stack current.

Abstract: A fuel cell system is disclosed, wherein the fuel cell system is heated by a fluid during a starting operation to mitigate against vapor condensation and ice formation in a fuel cell assembly and to decrease a warm up time of the fuel cell system.

Abstract: A system and method for controlling the speed of a compressor that provides air to the cathode side of a fuel cell stack in the event that a cathode by-pass valve fails. If a by-pass valve failure is detected, a failure algorithm first disengages the normal flow and pressure algorithms used to control the airflow to the cathode side of the stack. Next, the failure algorithm opens the cathode exhaust gas valve to its fully opened position. Then, in response to a stack power request, the compressor control will be put in an open-loop control where a look-up table is used to provide a particular compressor speed for a power request. An airflow meter will measure the airflow to the stack, and the stack current will be limited based on that airflow.

Abstract: A fuel cell system that includes a compressor for providing cathode air to the cathode side of a fuel cell stack and an air filter for filtering the air sent to the compressor to prevent particulates and other contaminants from entering the compressor and the fuel cell stack. The fuel cell system also includes a mass flow meter that measures the flow of air to the compressor and a pressure sensor that measures the pressure of the airflow at the output of the compressor. An electronic compressor map is provided that defines the operating characteristics of the compressor. By knowing the flow through the compressor and the pressure at the outlet of the compressor, an algorithm can determine where on the compressor map the compressor is operating, and from that determine the inlet pressure to the compressor, which in turn shows whether the air filter is clogged or otherwise damaged.

Abstract: A method of operating a fuel cell system comprising a fuel cell and a compressor that provides air to the fuel cell. The method comprises sensing a temperature indicative of the temperature of a fuel cell, providing a restriction in an air flow path to the fuel cell when the sensed temperature is below a threshold, and increasing the speed of the compressor to provide a desired air flow to the fuel cell. In at least some implementations, increasing the speed of the compressor increases the power drawn from the fuel cell to power the compressor and helps to increase the heat of the fuel cell. The increased speed of the compressor can also result in warmer air flow from the compressor that can further increase the temperature of the system components.

Abstract: A fuel cell system and method for controlling relative humidity in a fuel cell system. A controller can be signally coupled to one or more sensors and configured to operate at least one flow manipulation device in response to changes in a relative humidity of a reactant passing through the cathode flowpath of the fuel cell in order to maintain the relative humidity within a prescribed range. The controller correlates one or more of a temperature setpoint, pressure setpoint, stoichiometry setpoint or actual operating condition of any of them to an operating condition of the system. In this way, a desired level of relative humidity can be achieved, maintained or both while minimizing the use of power-robbing flow manipulation devices, such as a pump, compressor, fan or related component.

Abstract: A fuel cell system having an adaptable compressor map and method for optimizing the adaptable compressor map is provided. The method includes the steps of establishing an initial operating setpoint for an air compressor based on the adaptable compressor map; monitoring a surge indicator; adjusting the adaptable compressor map based on the monitored surge indicator; determining a desired operating setpoint based on the adjusted adaptable compressor map; and establishing an adapted operating setpoint for the air compressor based on the adaptable compressor map following the adjustment thereof. The steps are repeated until the adaptable compressor map for the air compressor is optimized.

Abstract: A method for increasing the temperature of a cooling fluid used to control the temperature of a fuel cell stack at a system freeze start-up. The method includes determining that the cooling fluid is frozen or nearly frozen, and if so, deactivating excessive power draw on the fuel cell stack to minimize stack waste heat and activating a cooling fluid heater to heat the cooling fluid. Once it is determined that the cooling fluid is not frozen or is flowing, then the method initiates a normal system start-up.

Abstract: A fuel cell system having an adaptable compressor map and method for optimizing the adaptable compressor map is provided. The method includes the steps of establishing an initial operating setpoint for an air compressor based on the adaptable compressor map; monitoring a surge indicator; adjusting the adaptable compressor map based on the monitored surge indicator; determining a desired operating setpoint based on the adjusted adaptable compressor map; and establishing an adapted operating setpoint for the air compressor based on the adaptable compressor map following the adjustment thereof. The steps are repeated until the adaptable compressor map for the air compressor is optimized.

Abstract: A method for controlling relative humidity (RH) of a cathode side of a fuel cell stack in a fuel cell system that includes an RH sensor on a cathode inlet line for providing an RH signal indicative of the RH of cathode inlet air. If the RH sensor is providing a valid RH signal, the RH signal is calculated as an RH average of the cathode inlet air. When the RH sensor is not providing a valid RH signal, the calculated RH average is utilized to control the cathode inlet air RH. If the RH sensor is not providing a valid signal during start-up, then the stack power is temporarily set at an optimum level for a known cathode inlet air RH.

Abstract: A method for controlling cathode air flow at system start-up by controlling a stack by-pass valve. The method includes determining a concentration of hydrogen in a cathode side of the fuel cell system. The method also includes determining a volumetric flow rate through a cathode compressor, determining a volumetric flow rate through the stack cathode and determining a fraction of volumetric flow rate through the cathode to the total flow through the compressor. The method determines a modeled hydrogen outlet concentration from the fuel cell stack based on the volumetric flow rate through the compressor, the fraction of volumetric flow rate through the compressor to the total flow through the compressor and the concentration of hydrogen in the cathode. The method uses a desired fraction of volumetric flow rate through the cathode and the total flow through the compressor to determine the position of the by-pass valve.

Abstract: A fuel cell system that includes a compressor for providing cathode air to the cathode side of a fuel cell stack and an air filter for filtering the air sent to the compressor to prevent particulates and other contaminants from entering the compressor and the fuel cell stack. The fuel cell system also includes a mass flow meter that measures the flow of air to the compressor and a pressure sensor that measures the pressure of the airflow at the output of the compressor. An electronic compressor map is provided that defines the operating characteristics of the compressor. By knowing the flow through the compressor and the pressure at the outlet of the compressor, an algorithm can determine where on the compressor map the compressor is operating, and from that determine the inlet pressure to the compressor, which in turn shows whether the air filter is clogged or otherwise damaged.

Abstract: A system and method for controlling the speed of a compressor in the event that an airflow meter that measures the airflow from the compressor to the cathode input of the stack fails. When a failure of the airflow meter is detected, an algorithm first deactivates the primary feedback control algorithms used to control cathode pressure and flow, and sets the cathode exhaust valve to a fully open position. The speed of the compressor is controlled by an open loop set-point and the airflow from the compressor is estimated by a model using compressor discharge pressure and the compressor speed. The cathode by-pass valve position is determined by calculating the difference between the requested cathode airflow and the modeled compressor output flow. The position of the by-pass valve is then adjusted using the valve characteristics and the compressor discharge pressure. The estimated airflow to the stack is used to control the maximum stack current.

Abstract: A system and method for controlling the speed of a compressor that provides air to the cathode side of a fuel cell stack in the event that a cathode by-pass valve fails. If a by-pass valve failure is detected, a failure algorithm first disengages the normal flow and pressure algorithms used to control the airflow to the cathode side of the stack. Next, the failure algorithm opens the cathode exhaust gas valve to its fully opened position. Then, in response to a stack power request, the compressor control will be put in an open-loop control where a look-up table is used to provide a particular compressor speed for a power request. An airflow meter will measure the airflow to the stack, and the stack current will be limited based on that airflow.

Abstract: A fuel cell system having an adaptable compressor map and method for optimizing the adaptable compressor map is provided. The method includes the steps of establishing an initial operating setpoint for an air compressor based on the adaptable compressor map; monitoring a surge indicator; adjusting the adaptable compressor map based on the monitored surge indicator; determining a desired operating setpoint based on the adjusted adaptable compressor map; and establishing an adapted operating setpoint for the air compressor based on the adaptable compressor map following the adjustment thereof. The steps are repeated until the adaptable compressor map for the air compressor is optimized.