Patent ID: 7687182

Claim:
A fuel cell stack, comprising: a bi-polar plate assembly; an active feed region including a stack of fuel cells, each fuel cell including a membrane electrode assembly having a cathode side and an anode side, a cathode side diffusion media layer on the cathode side of the membrane electrode assembly, an anode side diffusion media layer on the anode side of the membrane electrode assembly, and an active feed region of the bipolar plate assembly positioned between opposing diffusion media layers in adjacent fuel cells, wherein the active feed region of the bipolar plate assembly includes nested bipolar plates defining cathode side flow reactant channels and anode side flow reactant channels; and an inactive feed region including a stack of membranes that form part of each membrane electrode assembly in the stack of fuel cells and an inactive feed region of the bipolar plate assembly, wherein the inactive feed region of the bipolar plate assembly includes non-nested bipolar plates defining cathode side flow reactant channels and anode side flow reactant channels; wherein the cathode side flow reactant channels in the inactive feed region are in fluid communication with, and are substantially the same size as, the cathode side flow reactant channels in the active feed region; wherein the anode side flow reactant channels in the inactive feed region are in fluid communication with, and are substantially the same size as, the anode side flow reactant channels in the active feed region; wherein the fuel cells are free of diffusion media layers in the inactive feed region; wherein the non-nested bipolar plates of the inactive feed region of the bipolar plate assembly are mutually non-bonded with respect to each other; wherein clearance gaps are selectively present between the non-nested bipolar plates of the inactive feed region of the bipolar plate assembly; wherein the non-nested bi-polar plates of the inactive feed region of the bipolar plate assembly of the inactive feed region also define coolant flow channels, wherein the nested bipolar plates of the active feed region of the bi-polar plate assembly of the active feed region also define coolant flow channels, and wherein the coolant flow channels in the inactive feed region are in fluid communication with the coolant flow channels in the active feed region; and wherein coolant flow pressure provides, in combination with said non-bonding and clearance gaps of said non-nested bipolar plates of the inactive feed region, a general uniformity of height of the reactant channels in said inactive feed region.