Water electrolysis device and method of controlling water electrolysis device

A method of controlling a water electrolysis device,

• the water electrolysis device comprising:
• an anode configured to oxidize water to produce oxygen;
• a cathode configured to reduce a hydrogen ion to produce hydrogen;
• an anode flow path through which an anode solution containing water and a metal ion flows, the anode flow path facing on the anode;
• a cathode flow path facing on the cathode;
• an electrolyte membrane provided between the anode and the cathode;
• an anode supply flow path connected to an inlet of the anode flow path;
• an anode discharge flow path connected to an outlet of the anode flow path;
• a circulation flow path branching into a first circulation flow path and a second circulation flow path, the first circulation flow path connecting the anode supply flow path and the anode discharge flow path, and the second circulation flow path connected in parallel with the first circulation flow path;
• an ion filter provided in a middle of the second circulation flow path and configured to remove some of the metal ion in the anode solution, the first circulation flow path being connected to the anode supply flow path without the ion filter, and the second circulation flow path being connected to the anode supply flow path via the ion filter;
• a metal supply source configured to supply the metal ion to the anode solution;
• a metal supply flow path connecting the metal supply source and the anode supply flow path;
• a first valve provided in a middle of the first circulation flow path;
• a second valve provided in a middle of the second circulation flow path;
• and
• a third valve provided in a middle of the metal supply flow path;
• the method comprising:
• measuring a concentration of the metal ion in the anode solution from the anode flow path;
• and
• controlling opening and closing of the first valve, opening and closing of the second valve, and opening and closing of the third valve, according to the measured concentration of the metal ion,
• the method further comprising:
• opening the first valve and the third valve and closing the second valve when the measured concentration of the metal ion is less than 0.05 μmol/l;
• opening the second valve and closing the first valve and the third valve when the measured concentration of the metal ion is larger than 0.5 μmol/l;
• and
• opening the first valve and closing the second valve and the third valve when the measured concentration of the metal ion is 0.05 μmol/l or more and 0.5 μmol/l or less.

A water electrolysis device comprising:

• a membrane electrode assembly comprising
• an anode configured to oxidize water to produce oxygen, the anode containing iridium,
• a cathode configured to reduce a hydrogen ion to produce hydrogen, the cathode containing platinum, and
• an electrolyte membrane provided between the anode and the cathode;
• an anode flow path through which an anode solution containing water and at least one metal ion flows, the anode flow path facing on the anode, and the at least one metal ion being selected from the group consisting of a nickel ion, an iron ion, a cobalt ion, and a manganese ion;
• a cathode flow path facing on the cathode;
• an anode supply flow path connected to an inlet of the anode flow path;
• an anode discharge flow path connected to an outlet of the anode flow path;
• a circulation flow path branching into a first circulation flow path and a second circulation flow path, the first circulation flow path connecting the anode supply flow path and the anode discharge flow path, and the second circulation flow path connected in parallel with the first circulation flow path;
• an ion filter provided in a middle of the second circulation flow path and configured to remove some of the at least one metal ion in the anode solution, the first circulation flow path being connected to the anode supply flow path without the ion filter, and the second circulation flow path being connected to the anode supply flow path via the ion filter;
• a metal supply source configured to supply the at least one metal ion into the anode solution;
• a metal supply flow path connecting the metal supply source and the anode supply flow path;
• a first valve provided in a middle of the first circulation flow path;
• a second valve provided in a middle of the second circulation flow path;
• a third valve provided in a middle of the metal supply flow path;
• a sensor configured to measure a concentration of the at least one metal ion in the anode solution from the anode flow path;
• and
• a controller configured to control opening and closing of the first valve, opening and closing of the second valve, and opening and closing of the third valve, according to the measured concentration of the at least one metal ion,
• wherein the controller is configured to control
• a first operation of opening the first valve and the third valve and closing the second valve when the measured concentration of the at least one metal ion is less than 0.05 μmol/l,
• a second operation of opening the second valve and closing the first valve and the third valve when the measured concentration of the at least one metal ion exceeds 0.5 μmol/l, and
• a third operation of opening the first valve and closing the second valve and the third valve when the measured concentration of the at least one metal ion is 0.05 μmol/l or more and 0.5 μmol/l or less.