Apparatus and method for variable conductance temperature control

A direct oxidation fuel cell comprising:

• (A) a membrane electrode assembly including
• (i) a protonically conductive, electronically non-conductive membrane electrolyte, having an anode aspect and an opposing cathode aspect;
• and
• (ii) a catalyst coating disposed on at least one of said anode aspect and said cathode aspect, whereby electricity generating reactions occur upon introduction of fuel solution from an associated fuel source including an anodic conversion of said fuel solution to carbon dioxide, protons, electrons and heat and a cathodic combination of protons, electrons and oxygen from an associated source of oxygen, producing water;
• (B) a heat switch thermally coupled to at least a portion of said membrane electrode assembly said heat switch comprising:
• a first contact having a first surface, said first contact being thermally coupled to at least a portion of said membrane electrode assembly;
• a second contact having a second surface and spaced apart from said first surface by a gap;
• a thermally responsive material, thermally coupled to said membrane electrode assembly such that upon said membrane electrode assembly reaching a predetermined temperature, said thermally responsive material closes said gap to bring at least a portion of said first and second surfaces together such that heat is conducted from said first surface to said second surface and ultimately to a heat sink to divert heat away from said fuel cell and to lower the temperature of said fuel cell.

A direct oxidation fuel cell system comprising:

• a direct oxidation fuel cell having a membrane electrode assembly including a protonically conductive electronically non-conductive membrane having an anode aspect and a cathode aspect;
• a fuel source coupled to deliver fuel to said anode aspect;
• an oxygen source coupled to deliver oxygen to said cathode aspect;
• and
• a heat switch coupled to at least a portion of said fuel cell to divert heat away from said fuel cell under predetermined circumstances.

A method of controlling hydration in a fuel cell system, including the steps of:

• (A) determining the hydration state of the fuel cell system;
• (B) if the hydration state is too low, then closing a heat switch associated with the system to divert heat away from the fuel cell system;
• and
• (C) if the hydration state is too high, then opening the heat switch to maintain heat within the fuel cell system in order to raise the temperature of the fuel cell system.

A heat management system for use with a direct oxidation fuel cell system that is powering a portable electronic device, comprising:

• (A) a direct oxidation fuel cell having a membrane electrode assembly including a protonically conductive electronically non-conductive membrane having an anode aspect and a cathode aspect, said fuel cell also having a temperature sensor associated with the fuel cell;
• (B) a first heat switch coupled to at least a portion of said fuel cell to divert heat away from said fuel cell under predetermined circumstances;
• and
• (C) a second heat switch coupled between a heat generating portion of said portable electronic device and said fuel cell, and said heat switch being capable of extrinsic actuation to create a heat path from said heat generating portion of said portable electronic device to said fuel cell to raise the operating temperature of said fuel cell in desired circumstances.

A heat switch for use with a direct oxidation fuel cell, comprising:

• (A) a first contact component having a first surface, said first contact component being thermally coupled to at least a portion of an associated fuel cell;
• (B) a second contact component disposed and spaced apart by a gap between itself and said first component;
• and
• (C) a thermally responsive material thermally coupled to said fuel cell such that upon said fuel cell reaching a predetermined temperature, said thermally responsive material acts to close said gap to bring at least a portion of said first and second surfaces together such that heat is conducted from said first surface to said second surface.