Abstract: A method for operating a fuel cell stack (10) for a fuel cell system, in particular of a vehicle, in which by reversing the flow direction (14, 16) of a coolant during a cooling operation, the coolant in the fuel cell stack (10) is initially conveyed in a first direction (14). The coolant is subsequently conveyed in a second direction (16) which is at least substantially opposite to the first direction (14). A time period, after the elapse of which the flow direction (14, 16) is reversed, is changed during the cooling operation. In addition, a distance at which a coolant volume is situated from a heat source (12) that is present in the fuel cell stack (10) may be changed during the cooling operation. The invention further relates to a fuel cell system.

Abstract: A method for operating a fuel cell stack (10) for a fuel cell system, in particular of a vehicle, in which by reversing the flow direction (14, 16) of a coolant during a cooling operation, the coolant in the fuel cell stack (10) is initially conveyed in a first direction (14). The coolant is subsequently conveyed in a second direction (16) which is at least substantially opposite to the first direction (14). A time period, after the elapse of which the flow direction (14, 16) is reversed, is changed during the cooling operation. In addition, a distance at which a coolant volume is situated from a heat source (12) that is present in the fuel cell stack (10) may be changed during the cooling operation. The invention further relates to a fuel cell system.

Abstract: A method for operating a fuel cell system involves operating the fuel cell with recirculation of anode exhaust gas below a predefined maximum load limit of the fuel cell and operating the fuel cell without recirculation of the anode exhaust gas between the load limit and the full load of the fuel cell.

Abstract: 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.

Abstract: The present invention provides a method of operating a fuel cell system and a fuel cell system that can adjust the operating pressure of the fuel cell system to maximize efficiency. This present invention recognizes that under certain operating conditions appropriately matched operating pressures enable a substantially more efficient system operation. The method of the present invention and the fuel cell system of the present invention incorporate the recognition that a higher system efficiency can be achieved when the operating pressure produced by the air compressor is matched to the prevailing operating temperature of the fuel cell system.

Abstract: The present invention provides a method of operating a fuel cell system and a fuel cell system that can adjust the operating pressure of the fuel cell system to maximize efficiency. This present invention recognizes that under certain operating conditions appropriately matched operating pressures enable a substantially more efficient system operation. The method of the present invention and the fuel cell system of the present invention incorporate the recognition that a higher system efficiency can be achieved when the operating pressure produced by the air compressor is matched to the prevailing operating temperature of the fuel cell system. It is emphasized that this abstract is provided to comply wit the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that is will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).