Fuel cell system cathode inlet relative humidity control

Abstract

A fuel cell system (100) and operational methods (200, 300 and 400) are described that utilize a combination of sensor input and component models for causing the system's cathode effluent (150) to selectively bypass cathode effluent processing components (140) so as to obtain or maintain a desired cathode inlet relative humidity or dew point. The described system and methods may operate open loop (e.g., without sensor feedback to verify operation) or closed loop (e.g., relying on cathode inlet relative humidity / dew point sensors or fuel cell stack membrane conductivity measures).

Description

technical field [0001] The present invention relates to systems and methods for operating fuel cells, and more particularly to systems and methods for controlling the relative humidity or dew point of a cathode inflow to a fuel cell system. Background technique [0002] Fuel cells are used as power sources for electric vehicles, stationary power supplies and other applications. One known fuel cell is a proton exchange membrane (PEM) fuel cell, which includes a plurality of membrane electrode assemblies (MEAs). The MEA consists of a thin solid polymer membrane electrolyte having an anode on one side and a cathode on the opposite side, the MEA is interposed between a pair of conductive contact elements that serve as the anode and cathode current collector. Current collectors typically contain suitable channels and openings for distributing the fuel cell's gaseous reactants (e.g., hydrogen / H 2 and oxygen / O 2 ). [0003] A PEM fuel cell comprises a plurality of MEAs in the ...

AI Technical Summary

Problems solved by technology

In addition, if the MEA is too dry in operation, the MEA can be damaged, which can lead to immediate failure or reduce the life of the fuel cell

[0005] However, operating the fuel cell when the MEA is over-humidified can also limit the performance of the fuel cell stack

Specifically, the formation of liquid water can hinder gas diffusion to the MEA, limiting its performance

Liquid water can also create a flow blockage, reducing flow in the cell and even leading to higher fuel cell relative humidity which can cause fuel cell performance instability

Additionally, the formation of liquid water inside the cell can cause severe damage when the fuel cell is shut down and exposed to freezing conditions

That is, when the fuel cell is not in operation and the temperature in the fuel cell drops below freezing, the liquid water in it will freeze and expand, potentially damaging the fuel cell

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