Abstract: A coolant injection controller for a fuel cell system, the coolant injection controller configured to actively control the flow of a coolant to a fuel cell assembly for cooling and/or hydrating the fuel cell assembly in response to a measure of fuel cell assembly performance, wherein the coolant injection controller is configured to provide for a first mode of operation if the measure of fuel cell assembly performance is below a predetermined threshold and a second mode of operation if the measure of fuel cell assembly performance is above the predetermined threshold, the first and second modes having different coolant injection profiles and wherein, in the first mode of operation, the coolant injection profile provides for control of the flow of coolant by alternating between at least two different injection flow rates.

Abstract: A method of operating a fuel cell system comprising a fuel cell assembly configured to generate electrical power from a fuel flow and an oxidant flow, the method comprising a first phase and a subsequent second phase, the first phase comprising; operating the fuel cell assembly with a first stoichiometric ratio of oxidant flow to fuel flow to generate electrical power; providing said generated electrical power to a heater element for heating a coolant for supply to said fuel cell assembly; the second phase comprising; delivering coolant heated in the first phase to the fuel cell assembly; operating the fuel cell assembly with a second stoichiometric ratio of oxidant flow to fuel flow to generate electrical power, the second stoichiometric ratio lower than the first ratio.

Abstract: A method of operating a fuel cell system comprising a fuel cell assembly configured to generate electrical power from a fuel flow and an oxidant flow, the method comprising a first phase and a subsequent second phase, the first phase comprising; operating the fuel cell assembly with a first stoichiometric ratio of oxidant flow to fuel flow to generate electrical power; providing said generated electrical power to a heater element for heating a coolant for supply to said fuel cell assembly; the second phase comprising; delivering coolant heated in the first phase to the fuel cell assembly; operating the fuel cell assembly with a second stoichiometric ratio of oxidant flow to fuel flow to generate electrical power, the second stoichiometric ratio lower than the first ratio.

Abstract: A coolant injection controller for a fuel cell system, the coolant injection controller configured to actively control the flow of a coolant to a fuel cell assembly for cooling and/or hydrating the fuel cell assembly in response to a measure of fuel cell assembly performance, wherein the coolant injection controller is configured to provide for a first mode of operation if the measure of fuel cell assembly performance is below a predetermined threshold and a second mode of operation if the measure of fuel cell assembly performance is above the predetermined threshold, the first and second modes having different coolant injection profiles and wherein, in the first mode of operation, the coolant injection profile provides for control of the flow of coolant by alternating between at least two different injection flow rates.