Hydrogen system and method of operation

A method of providing hydrogen, comprising

• receiving a hydrogen demand signal;
• when the hydrogen demand signal is greater than zero and a first gas comprising hydrogen is available, operating a first electrochemical cell or cell stack comprising a first membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, and an inlet for the first gas in fluid communication with the anode side of the first electrochemical cell or cell stack, to provide hydrogen at an outlet in fluid communication with the cathode side of the first membrane electrode assembly, and controllably operating a second electrochemical cell or cell stack comprising a second membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, and a water inlet in fluid communication with the second membrane electrode assembly, in response to the hydrogen demand signal and/or the hydrogen output of the first electrochemical cell or cell stack to provide hydrogen at an outlet in fluid communication with the cathode side of the second membrane electrode assembly;
• and
• when the hydrogen demand signal is greater than zero and the first gas is not available at the first electrochemical cell or cell stack inlet, operating the second electrochemical cell or cell stack to provide hydrogen at the outlet in fluid communication with the cathode side of the second membrane electrode assembly.

A system for providing hydrogen, comprising:

• a first electrochemical cell or cell stack comprising a first membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, an inlet in controllable fluid communication with a variably-available source of a first gas that comprises hydrogen in fluid communication with the anode side of the first electrochemical cell or cell stack, and an outlet in fluid communication with the cathode side of the first membrane electrode assembly;
• a second electrochemical cell or cell stack comprising a second membrane electrode assembly comprising a cathode and an anode separated by a proton exchange membrane, a water inlet in fluid communication with the anode side of the second membrane electrode assembly, and an outlet in fluid communication with the cathode side of the second membrane electrode assembly;
• and
• a first volume of liquid water in fluid communication with the water inlet of the second electrochemical cell or cell stack and in fluid communication with the anode side of the first electrochemical cell or cell stack proton exchange membrane, or a second volume of liquid water in fluid communication with the cathode side of the first membrane electrode assembly and the cathode side of the second electrochemical membrane electrode assembly.