Patent application number | Description | Published |
20080292921 | RECOVERY OF INERT GAS FROM A FUEL CELL EXHAUST STREAM - A fuel cell system is provided including a fuel cell stack having a fuel cell having an anode, an anode outlet, an anode inlet, and a cathode. The fuel cell system further includes a hydrogen pump in communication with the anode outlet and the anode inlet. The hydrogen pump features a proton exchange membrane disposed between a first electrode and a second electrode. The first electrode is configured to accept an anode outlet stream from the anode outlet, the anode outlet stream including a hydrogen gas and an inert gas, the first electrode being configured to exhaust the inert gas. In one embodiment, the hydrogen pump is in communication with a PROX unit and configured to provide the hydrogen gas to the fuel cell stack. Further provided are methods employing the hydrogen pump wherein a start-stop degradation of the fuel cell is militated against and a hydrogen feed stream is humidified. | 11-27-2008 |
20080311437 | METHOD FOR FUEL CELL START-UP WITH UNIFORM HYDROGEN FLOW - A fuel cell system is provided having a fuel cell stack including a plurality of fuel cells. The fuel cell system includes an anode supply manifold in fluid communication with the plurality of fuel cells, the anode supply manifold adapted to deliver a anode supply stream to the plurality of fuel cells; an anode exhaust manifold in fluid communication with the anodes of the plurality of fuel cells, the anode exhaust manifold adapted to receive an anode exhaust stream from the plurality of fuel cells; a first valve in fluid communication with the anode supply manifold; and a second valve in fluid communication with the anode exhaust manifold. A method of starting the fuel cell system is also provided. The fuel cell system and method militates against a non-uniform distribution of the anode supply stream to the anodes of the plurality of fuel cells. | 12-18-2008 |
20080312849 | Anode Bleed Control Strategy for Improved Water Management and Hydrogen Utilization - A control strategy for bleeding an anode side of fuel cell stack in a fuel cell system that improves water management and addresses durability and performance concerns. The method includes determining when to begin the anode bleed, typically by estimating or measuring the amount of nitrogen in the anode side of the stack. The method also includes determining when to end the anode bleed based on the volume of gas that has been bled. The method determines the mole flow rate of the anode gas flowing through a bleed valve, integrates the mole flow rate to get the number of moles of the gas that have passed through the bleed valve, determines a desired amount of moles to be bled, and ends the bleed when the actual number of moles of the gas equals the desired number of moles of the gas. | 12-18-2008 |
20090081491 | Method for Fast and Reliable Fuel Cell System Start-Ups - A method for providing a fast and reliable start-up of a fuel cell system. The method uses a stack voltage response to a load to assess if hydrogen and oxygen are being sufficiently distributed to all of the fuel cells by coupling an auxiliary load to the fuel cell stack until a predetermined minimum cell voltage has been reached or a first predetermined time period has elapsed. The method then determines whether a minimum cell voltage has dropped to a first predetermined voltage and, if so, reduces the maximum power allowed to be below the first predetermined voltage value, determines whether the minimum cell voltage in the stack is below a second predetermined voltage, or determines whether the minimum cell voltage drop rate is greater than a predetermined voltage drop rate. If none of these conditions are met, the method returns to loading the stack with system components. | 03-26-2009 |
20090081496 | FUEL CELL SYSTEM AND START-UP METHOD - A fuel cell system including a fuel cell stack having a plurality of fuel cells is provided. An anode supply manifold and an anode exhaust manifold are in fluid communication with the anodes of the plurality of fuel cells. A first valve is in fluid communication with the anode supply manifold and a second valve is in fluid communication with the anode exhaust manifold. A pressure sensor is adapted to measure an anode pressure. In operation, the first valve and the second valve are controlled in response to the anode pressure, thereby militating against an undesired exhausting of an anode supply stream. | 03-26-2009 |
20090197125 | Method for Maximum Net Power Calculation for Fuel Cell System Based on Online Polarization Curve Estimation - An algorithm for determining the maximum net power available from a fuel cell stack as the stack degrades over time using an online adaptive estimation of a polarization curve of the stack. The algorithm separates the current density range of the stack into sample regions, and selects a first sample region from the far left of the estimated polarization curve. The algorithm then calculates the cell voltage for that current density sample region, and determines whether the calculated cell voltage is less than or equal to a predetermined cell voltage limit. If the calculated cell voltage is not less than the cell voltage limit, then the algorithm selects the next sample region along the polarization curve. When the calculated cell voltage does reach the cell voltage limit, then the algorithm uses that current density for the sample region being analyzed to calculate the maximum power of the fuel cell stack. | 08-06-2009 |
20090197127 | Algorithm for Stack Current Controller Based on Polarization Curve Estimation of a Fuel Cell Stack - A method for providing a current density set-point for a fuel cell stack in response to a power request from the stack where the set-point is determined based on system parameters that identify the life and degradation of the stack. The method includes dividing a current density range of the fuel cell stack into a predetermined number of sample regions, and selecting the sample regions in order from low to high during the current set-point analysis. The method calculates an average cell voltage for the current density of the selected sample region, and stack power from the average cell voltage. The method then determines whether a power request signal is less than the stack power for the selected sample region and greater than the calculated power for the previous sample region, and if so, calculates the current density set-point at the requested power based on these values. | 08-06-2009 |
20090197155 | Online Low Performing Cell (LPC) Prediction and Detection of Fuel Cell System - A system and method for detecting and predicting low performing cells in a fuel cell stack. When the fuel cell stack is running and certain data validity criteria have been met, an algorithm collects the data, such as stack current density, average cell voltage and minimum cell voltage. This information is used to estimate predetermined parameters that define the stack polarization curve. The system defines a predetermined minimum current density that is used to identify a low performing cell. The system then calculates an average cell voltage and a minimum cell voltage at the minimum current density set-point, and calculates a cell voltage difference between the two. If the cell voltage difference is greater than a predetermined low voltage threshold and the minimum cell voltage is less than a predetermined high voltage threshold, the algorithm sets a flag identifying a potential for a low performing cell. | 08-06-2009 |
20090263679 | SHUTDOWN OPERATIONS FOR AN UNSEALED CATHODE FUEL CELL SYSTEM - Processes to shut down a fuel cell system are described. In one implementation ( | 10-22-2009 |
20100003546 | SYSTEM AND METHOD FOR SHORTING A FUEL CELL STACK - A fuel cell system is provided that includes a fuel cell stack with a plurality of fuel cells and a power converter in electrical communication with the fuel cell stack. The power converter is configured to selectively regulate a power of the fuel cell stack and short circuit the fuel cell stack, as desired. A method for starting the fuel cell stack is also described including the steps of causing a short circuit of the fuel cell stack by placing the power converter in a short circuit mode; introducing a hydrogen to the anodes of the fuel cell stack to displace a quantity of air on the anodes; and placing the power converter in a power regulation mode. A degradation of the fuel cell stack during start-up is thereby militated against. | 01-07-2010 |
20100035090 | OFF-STATE DEGRADATION PREVENTION IN A FUEL CELL WITHOUT ON-STATE LOSSES USING SELF CONTROLLED ELEMENT - A fuel cell system that employs a technique for reducing MEA degradation during system shut-down that occurs as a result of the hydrogen and air being present in the fuel cell stack flow channels. The fuel cell system includes a non-linear load element, such as a positive temperature coefficient resistor, electrically coupled to each fuel cell in the fuel cell stack. The non-linear element operates such that it has high electrical conduction at low cell voltages and low electrical conduction at high cell voltages. During system shut-down, the voltage that is generated as a result of the hydrogen and air interaction in the fuel cells that creates a low cell voltage is drawn from the fuel cell and dissipated by the element. During system operation, the fuel cell potentials are relatively high and the resistance of the element goes up so that less current flows through the element, thus reducing electrical losses. | 02-11-2010 |
20100035097 | FUEL CELL STACK USED AS COOLANT HEATER - A system and method for increasing the temperature of a fuel cell stack quickly, especially at cold stack start-up. The method includes determining whether the fuel cell stack is below a first predetermined temperature threshold, and, if so, starting a cooling fluid flow through the stack and engaging a shorting circuit across the stack to short circuit the stack and cause the stack to operate inefficiently. The method then determines a desired heating rate of the fuel cell stack and calculates a cathode airflow to the fuel cell stack based on the desired heating rate. The method reduces the flow of cathode air to the stack if a minimum cell voltage is below a predetermined minimum cell voltage threshold and disengages the shorting circuit and applies vehicle loads to the stack when the stack temperature reaches a predetermined second temperature threshold. | 02-11-2010 |
20100114513 | ESTIMATING MINIMUM VOLTAGE OF FUEL CELLS - A method of estimating minimum voltage of fuel cells, and a product using same. | 05-06-2010 |
20100143754 | SHUTDOWN STRATEGY TO AVOID CARBON CORROSION DUE TO SLOW HYDROGEN/AIR INTRUSION RATES - A fuel cell system including a fuel cell stack having a plurality of fuel cells, each of the fuel cells including an electrolyte membrane disposed between an anode and a cathode, an anode supply manifold in fluid communication with the anodes of the fuel cells, the anode supply manifold providing fluid communication between a source of hydrogen and the anodes, an anode exhaust manifold in fluid communication with the anodes of the fuel cells, and a fan in fluid communication with the anodes of the fuel cells, wherein the fan controls a flow of fluid through the anodes of the fuel cells after the fuel cell system is shutdown. | 06-10-2010 |
20110014535 | METHOD TO IMPROVE RELIABILITY OF A FUEL CELL SYSTEM USING LOW PERFORMANCE CELL DETECTION AT LOW POWER OPERATION - A system and method for detecting a low performing cell in a fuel cell stack using measured cell voltages. The method includes determining that the fuel cell stack is running, the stack coolant temperature is above a certain temperature and the stack current density is within a relatively low power range. The method further includes calculating the average cell voltage, and determining whether the difference between the average cell voltage and the minimum cell voltage is greater than a predetermined threshold. If the difference between the average cell voltage and the minimum cell voltage is greater than the predetermined threshold and the minimum cell voltage is less than another predetermined threshold, then the method increments a low performing cell timer. A ratio of the low performing cell timer and a system run timer is calculated to identify a low performing cell. | 01-20-2011 |
20110091780 | IN-SITU FUEL CELL STACK RECONDITIONING - A method for reconditioning a fuel cell stack. The method includes periodically increasing the relative humidity level of the cathode input airflow to the stack to saturate the cell membrane electrode assemblies to be greater than the relative humidity levels during normal stack operating conditions. The method also includes providing hydrogen to the anode side of the fuel cell stack at system shut down while the membrane electrode assemblies are saturated without stack loads being applied so that the hydrogen crosses the cell membranes to the cathode side and reacts with oxygen to reduce stack contaminants. | 04-21-2011 |
20110143241 | FUEL CELL OPERATIONAL METHODS FOR OXYGEN DEPLETION AT SHUTDOWN - A method for creating an oxygen depleted gas in a fuel cell system, including operating a fuel cell stack at a desired cathode stoichiometry at fuel cell system shutdown to displace a cathode exhaust gas with an oxygen depleted gas. The method further includes closing a cathode flow valve and turning off a compressor to stop the flow of cathode air. | 06-16-2011 |
20110143243 | FUEL CELL OPERATIONAL METHODS FOR HYDROGEN ADDITION AFTER SHUTDOWN - A method for reducing the probability of an air/hydrogen front in a fuel cell stack is disclosed that includes closing anode valves for an anode side of the fuel cell stack to permit a desired quantity of hydrogen to be left in the anode side upon shutdown and determining a schedule to inject hydrogen during the time the fuel cell stack is shutdown. The pressure on an anode input line is determined and a discrete amount of hydrogen is injected into the anode side of the stack according to the determined schedule by opening anode input line valves based on the determined pressure along the anode input line so as to inject the hydrogen into the anode side of the stack. | 06-16-2011 |
20110178742 | DETECTION METHOD FOR MEMBRANE AND ELECTRODE FAILURES IN FUEL CELL STACKS - A method for determining a failure of a membrane in a fuel cell in a fuel cell stack. The method includes measuring the voltage of each fuel cell in the fuel cell stack, calculating an average cell voltage from all of the cell voltages of the fuel cells in the fuel cell stack, and identifying a minimum cell voltage from all of the cell voltages of the fuel cells in the fuel cell stack. The method then determines an absolute delta voltage value as the difference between the average cell voltage of the fuel cells and the minimum cell voltage of the fuel cells at a plurality of sample points during the sample period. A plurality of absolute delta voltage values determined over a plurality of sample periods, filtered for low current density are used to determine whether there is a membrane failure and, by filtering for high current density, to determine whether there is an electrode failure. | 07-21-2011 |
20110189573 | ONLINE ANODE PRESSURE BIAS TO MAXIMIZE BLEED VELOCITY WHILE MEETING EMISSION CONSTRAINT - A method that employs a model based approach to determine a maximum anode pressure set-point based on existing airflow in the exhaust gas line. This approach maximizes anode flow channel velocity during bleed events while meeting the hydrogen emission constraint, which in turn increases the amount of water purged from the anode flow channels to increase stack stability. | 08-04-2011 |
20120040264 | HYDROGEN CONCENTRATION SENSOR UTILIZING CELL VOLTAGE RESULTING FROM HYDROGEN PARTIAL PRESSURE DIFFERENCE - A hydrogen concentration sensor for measuring the hydrogen concentration in an anode sub-system of a fuel cell system. The hydrogen concentration sensor includes a membrane, a first catalyst layer on one side of the membrane and a second catalyst layer on an opposite side of the membrane where the sensor operates as a concentration cell. The first catalyst layer is exposed to fresh hydrogen for the anode side of a fuel cell stack and the second catalyst layer is exposed to an anode recirculation gas from an anode exhaust of the fuel cell stack. The voltage generated by the sensor allows the hydrogen partial pressure in the recirculation gas to be determined, from which the hydrogen concentration can be determined. | 02-16-2012 |
20120082917 | FUEL CELL ELECTRODES WITH GRADED PROPERTIES AND METHOD OF MAKING - A graded electrode is described. The graded electrode includes a substrate; and at least two electrode layers on the substrate forming a combined electrode layer, a composition of the at least two electrode layers being different, the combined electrode layer having an average level of the property that changes across the substrate. Fuel cells using graded electrodes and methods of making graded electrodes are also described. | 04-05-2012 |
20120251908 | VOLTAGE RECOVERY AND CONTAMINANT REMOVAL BY EX-SITU WATER FLUSH - A system and method for removing contaminants from a fuel cell stack. The method includes exposing the cathode and anode of the stack to an air purge, then exposing the cathode and anode of the stack to a water flush and then again exposing the cathode and anode of the stack to an air purge to dry the stack. In one technique, the stack is removed from the vehicle at a maintenance facility to perform the air purge and water flush, and in another technique, the stack remains in the vehicle and appropriate hoses are connected to the stack for the air purges and water flush. | 10-04-2012 |
20120274332 | ALGORITHM FOR IN-SITU QUANTIFICATION OF PEMFC MEMBRANE HEALTH OVER ITS LIFE - A method for determining the health of the membranes in a fuel cell stack. The total parasitic current of the fuel cells in the stack is determined. From the total parasitic current, the shorting resistance and the cross-over parasitic current are determined. The health of the membranes is then determined from the cross-over parasitic current and the shorting resistance. | 11-01-2012 |
20120276466 | IN-VEHICLE ALGORITHM FOR FUEL CELL STACK HEALTH QUANTIFICATION - A method for determining the health of fuel cells in a fuel cell stack. The method includes maintaining a constant flow of hydrogen to the anode side of the fuel cell stack, shutting off a flow of air to a cathode side of the fuel cell stack when a predetermined concentration of hydrogen in the anode side has been achieved, and identifying a catalyst surface area and a catalyst support surface area for catalyst layers in the fuel cell stack. The method also includes determining the total parasitic current of the fuel cell stack to determine a cross-over parasitic current and a shorting resistance of the fuel cell stack. The method further includes calculating the catalyst surface area and the catalyst support surface area of the catalyst layers and comparing the difference between the identified catalyst surface area and the calculated catalyst surface area to estimate the change in the catalyst surface area. | 11-01-2012 |
20130260266 | FAST MEA BREAK-IN AND VOLTAGE RECOVERY - A system and method for breaking-in and humidifying membrane-electrode-assemblies (MEAs) in a fuel cell stack. The method includes performing voltage cycling and humidification of the MEAs in the stack, including one or more temperature steps wherein current density of the stack is cycled within a predetermined range for each of the one or more temperature steps. The method also includes maintaining a fuel cell stack voltage within a predetermined range, and maintaining anode and cathode reactant flows at an approximate set-point during the current density cycling of the one or more temperature steps to break-in and humidify the MEAs in the stack so that the stack is able to operate at a predetermined threshold for a fuel cell stack voltage output capability. | 10-03-2013 |
20140038073 | SHUTDOWN STRATEGY TO AVOID CARBON CORROSION DUE TO SLOW HYDROGEN/AIR INTRUSION RATES - A fuel cell system including a fuel cell stack having a plurality of fuel cells, each of the fuel cells including an electrolyte membrane disposed between an anode and a cathode, an anode supply manifold in fluid communication with the anodes of the fuel cells, the anode supply manifold providing fluid communication between a source of hydrogen and the anodes, an anode exhaust manifold in fluid communication with the anodes of the fuel cells, and a fan in fluid communication with the anodes of the fuel cells, wherein the fan controls a flow of fluid through the anodes of the fuel cells after the fuel cell system is shutdown. | 02-06-2014 |
20140072887 | OXIDATION OF FUEL CELL ELECTRODE CONTAMINANTS - A system for oxidizing contaminants on both the cathode and anode electrodes in a fuel cell stack by applying a suitable voltage potential across the electrodes that causes the oxidation. The system includes a battery and an electrical converter electrically coupled to the battery. The electrical converter is configured to assist in providing an oxidation potential to the fuel cell stack by converting electrical power from the battery at a time effective to oxidize contaminants on the cathode or anode electrodes in the stack. The electrical converter provides a positive potential to the fuel cell stack to oxidize contaminants on the cathode electrodes and provides a negative potential to the fuel cell stack to oxidize contaminants on the anode electrodes. If the battery is a high voltage battery, then the converter is a power converter and if the battery is a low voltage battery, then the converter is boost converter. | 03-13-2014 |
20140072893 | POWERING A FUEL CELL STACK DURING STANDBY - A system and method for limiting voltage cycling of a fuel cell stack during a stand-by mode by providing power from a battery to the stack while the stack is turned off. The method includes monitoring the voltage of each of the fuel cells in the fuel cell stack and determining an average cell voltage of the fuel cells in the fuel cell stack. The method also determines whether the average cell voltage of the fuel cells in the fuel cell stack has fallen below a predetermined voltage value and, if so, applies a voltage potential to the fuel cell stack to increase the average cell voltage above the predetermined voltage value. | 03-13-2014 |
20140205924 | SELECTIVELY REACTING TO THE MINIMUM CELL VOLTAGE DROP RATE IN A FUEL CELL SYSTEM - A system and method that monitor the rate of a voltage drop of fuel cells in a fuel cell stack to determine whether the voltage drop is a result of cathode reactant starvation or anode reactant starvation. The method looks at a falling voltage of a fuel cell to determine whether the rate of the fall in voltage indicates that hydrogen starvation of the anode of the fuel cell is occurring. The method also looks at the actual voltage of the fuel cell that is falling to determine whether it is a below a predetermined minimum voltage threshold also indicating that hydrogen starvation of the anode of the fuel cell is occurring. If hydrogen starvation is occurring, the method performs power limiting of the fuel cell stack either based on the rate or the voltage level. | 07-24-2014 |