METHOD OF OPERATING WATER ELECTROLYSIS AND ELECTRICITY GENERATING SYSTEM

A method of operating a water electrolysis and electricity generating system includes, at a time of switching from the water electrolysis mode to the electricity generating mode, a water electrolysis stopping step, a purging step and an electricity generation starting step. In the purging step after the water electrolysis stopping step, an oxygen-containing gas is caused to flow from an oxygen-containing gas flow path to a first gas-liquid separator via an oxygen-containing gas introduction flow path, a first supply flow path, a first inlet port member, a first fluid flow path, a first outlet port member, and a first lead-out flow path. In the electricity generation starting step after the purging step, the cell member is caused to generate electricity based on a predetermined required load value.