Abstract: The fuel cells (16, 18) adjacent or near the end plate (15) of a fuel cell stack (14) are warmed either by (a) a heater wire (48, 50) within the fuel cell (16) adjacent to the end plate, (b) heater wires (53) disposed in a heater element (52) located between the end plate and the fuel cell closest to the end plate (15), (c) one or more heaters (56) are disposed in holes (55) within the end plate (15), (d) a catalytic heater (61) disposed on the inner surface of the end plate, or (e) catalytic burner (78, 100) disposed adjacent a current collector (70) between an end cell (16) and insulation (81) on an end plate (82). The fuel cells (16, 18) may be heated before or during startup at sub-freezing temperatures to prevent loss of fuel cell performance.

Abstract: The fuel cells (16, 18) adjacent or near the end plate (15) of a fuel cell stack (14) are warmed either by (a) a heater wire (48) within the fuel cell (16) adjacent to the end plate, (b) heater wires (53) are disposed in a heater element (52) located between the end plate and the fuel cell closest to the end plate (15), (c) one or more heaters (56) are disposed in holes (55) within the end plate (15), (d) electric heating elements (59) on a surface of the end plate (15), or (e) a catalytic heater (61) disposed on the surface of the end plate. The fuel cells (16, 18) may be heated before or during operation at sub-freezing temperatures to prevent loss of fuel cell performance, or may be heated after operation at sub-freezing temperatures to restore fuel cell performance.

Abstract: A PEM fuel cell system includes a plurality of PEM fuel cells arranged in a stack having two opposed, outwardly facing end surfaces; pressure plates positioned relative to said end surfaces for securing said PEM fuel cells in said stack; and spacer members between said end surfaces and said pressure plates for thermally insulating said end surfaces from said pressure plates.

Abstract: A method for operating a fuel cell stack assembly having a plurality of fuel cells arranged in a stack to define opposed end fuel cells, wherein the plurality of fuel cells include intermediate fuel cells between the opposed end fuel cells, including feeding fuel and oxidant to the intermediate fuel cells whereby the at least one end fuel cell transports hydrogen across the cell and produces heat.

Abstract: A cell stack assembly (102) coolant system comprises a coolant exhaust conduit (110) in fluid communication with a coolant exhaust manifold (108) and a coolant pump (112). A coolant inlet conduit (120) enables transportation of the coolant to the coolant inlet manifold. The coolant system further includes a bypass conduit (132) in fluid communication with the coolant exhaust manifold and the coolant inlet manifold, while a bleed valve (130) is in fluid communication with the coolant exhaust conduit and a source of gas. Operation of the bleed valve enables venting of the coolant from the coolant channels, and through a shut down conduit (124). An increased pressure differential between the coolant and reactant gases forces water out of the pores in the electrode substrates (107, 109). An ejector (250) prevents air form inhibiting the pump. Pulsed air is blown (238, 239, 243, 245) through the coolant channels to remove more water.

Abstract: Recovery of PEM fuel cell performance is achieved by evacuating (61, 62) or by flowing water absorbing gas (46) through, or both, the fuel flow field (12, 13, 19, 20), the air flow field (25, 26, 30, 31), and the water flow field (36, 39), while resistance of the individual cells, or of the fuel cell stack, is measured; the dry out process is continued until the resistance of the cells (or the resistance per cell, measured across the fuel cell stack as a whole), has increased by at least 5 to 1 (preferably 10 to 1) over the normal resistance of the cells. The water absorbing gas may be air (23) or nitrogen (47); it may be at ambient temperature or heated (50).

Abstract: A PEM fuel cell system includes a plurality of PEM fuel cells arranged in a stack having two opposed, outwardly facing end surfaces; pressure plates positioned relative to said end surfaces for securing said PEM fuel cells in said stack; and spacer members between said end surfaces and said pressure plates for thermally insulating said end surfaces from said pressure plates.

Abstract: A vehicle (150) includes a fuel cell stack (151) started when the stack is below freezing, by connection (158) to the vehicle propulsion system (159) within a few seconds of starting the flow of fuel (179) and oxidant (173), or when open circuit voltage (155, 156) is detected. The fuel is in excess of stochiometry requirement and the oxidant is in excess of at least twice stochiometric requirement, either may be at about atmospheric pressure or at 4 kPa (0.6 psi) or more above the pressure of any water in said water passages, and either may be below freezing. Water transport plates (84, 86, 88, 89) have water passages connected to a water circulation loop (170) including a reservoir (164) having an auxiliary heater (161) connected (160) to the stack. Warming of cell stack materials and ice in the water transport plates, heat of fusion of melting ice, warming of melted water, and evaporative cooling of water melted in the water transport plates keep the fuel cell cool until liquid coolant can be circulated.

Abstract: A vehicle (150) includes a fuel cell stack (151) started when the stack is below freezing, by connection (158) to the vehicle propulsion system (159) within a few seconds of starting the flow of fuel (179) and oxidant (173), or when open circuit voltage (155, 156) is detected. The fuel is in excess of stochiometry requirement and the oxidant is in excess of at least twice stochiometric requirement, either may be at about atmospheric pressure or at 4 kPa (0.6 psi) or more above the pressure of any water in said water passages, and either may be below freezing. Water transport plates (84, 86, 88, 89) have water passages connected to a water circulation loop (170) including a reservoir (164) having an auxiliary heater (161) connected (160) to the stack. Warming of cell stack materials and ice in the water transport plates, heat of fusion of melting ice, warming of melted water, and evaporative cooling of water melted in the water transport plates keep the fuel cell cool until liquid coolant can be circulated.

Abstract: A method for shutting down a fuel cell system including a plurality of fuel cells arranged in a stack, includes cooling the fuel cells to a shutdown temperature while maintaining a substantially uniform water vapor pressure through the fuel cells whereby migration of water within the fuel cells during cooling is reduced.

Abstract: Recovery of PEM fuel cell performance is achieved by evacuating (61, 62) or by flowing water absorbing gas (46) through, or both, the fuel flow field (12, 13, 19, 20), the air flow field (25, 26, 30, 31), and the water flow field (36, 39), while resistance of the individual cells, or of the fuel cell stack, is measured; the dry out process is continued until the resistance of the cells (or the resistance per cell, measured across the fuel cell stack as a whole), has increased by at least 5 to 1 (preferably 10 to 1) over the normal resistance of the cells. The water absorbing gas may be air (23) or nitrogen (47); it may be at ambient temperature or heated (50).