Water electrolysis system

Abstract

A water electrolysis system includes a water electrolysis stack, a gas-liquid separator, a water supply path, a water introduction unit, a water lead-out unit, a water discharge path, and a circulation pump. The water lead-out unit includes a first water lead-out unit and a second water lead-out unit, which are provided in the water electrolysis stack. The water introduction unit is positioned in a stacking direction between the first water lead-out unit and the second water lead-out unit, together with being disposed in a water electrolysis cell which is positioned between both ends in the stacking direction among a plurality of the water electrolysis cells.

What is claimed is: 
     
         1 . A water electrolysis system equipped with a water electrolysis stack provided with a water introduction unit and a water lead-out unit, and in which a plurality of water electrolysis cells, which produce hydrogen and oxygen by electrolysis of water, are stacked together mutually, and a circulation pump through which water is circulated in a manner so that water which is stored in a gas-liquid separator is supplied from the water introduction unit into the water electrolysis stack via a water supply path, and so that unreacted water which was not subjected to electrolysis inside the water electrolysis stack is discharged from the water lead-out unit into the gas-liquid separator via a water discharge path;
 wherein the water lead-out unit comprises:   a first water lead-out unit provided on one end side of the water electrolysis stack in a stacking direction of the water electrolysis cells; and   a second water lead-out unit provided on another end side of the water electrolysis stack in the stacking direction;   wherein the water introduction unit is positioned in the stacking direction between the first water lead-out unit and the second water lead-out unit, together with being disposed in a water electrolysis cell which is positioned between both ends in the stacking direction among the plurality of water electrolysis cells.   
     
     
         2 . The water electrolysis system according to  claim 1 , wherein the water introduction unit is disposed in a water electrolysis cell which is located in a central region in the stacking direction among the plurality of water electrolysis cells. 
     
     
         3 . The water electrolysis system according to  claim 1 , wherein, in each of the water electrolysis cells, there are formed:
 a water introducing communication passage adapted to allow the water introduced from the water introduction unit to flow in the stacking direction; and   a water lead-out communication passage adapted to allow the unreacted water which was not subjected to electrolysis to flow in the stacking direction, and to guide the unreacted water to the first water lead-out unit and the second water lead-out unit.   
     
     
         4 . The water electrolysis system according to  claim 1 , wherein each of the first water lead-out unit and the second water lead-out unit is disposed at a position which is shifted in phase from the water introduction unit by 180° in a circumferential direction of the water electrolysis stack. 
     
     
         5 . The water electrolysis system according to  claim 1 , wherein:
 the first water lead-out unit is provided in a water electrolysis cell positioned at one end in the stacking direction among the plurality of water electrolysis cells; and   the second water lead-out unit is provided in a water electrolysis cell position at another end in the stacking direction among the plurality of water electrolysis cells.   
     
     
         6 . The water electrolysis system according to  claim 1 , further comprising:
 a drain flow passage connected to a lowermost part of the water discharge path; and   an opening-closing valve adapted to open and close the drain flow passage;   wherein the water electrolysis stack is installed in a manner so that the stacking direction is arranged along a vertical direction; and   the second water lead-out unit is positioned lower than the first water lead-out unit and the water introduction unit.   
     
     
         7 . The water electrolysis system according to  claim 6 , wherein the second water lead-out unit is positioned lower than each of the gas-liquid separator, the water supply path, and the circulation pump. 
     
     
         8 . The water electrolysis system according to  claim 6 , wherein the opening-closing valve is a solenoid valve, the water electrolysis system further comprising:
 an air supply path through which air is supplied to the gas-liquid separator;   an air supplying device provided in the air supply path;   a freeze prediction unit adapted to predict freezing of the water inside the water electrolysis system; and   a control unit adapted to control the solenoid valve and the air supplying device;   wherein, when performing a process to stop driving of the water electrolysis system, in the case it is predicted by the freeze prediction unit that there is a possibility that the water inside the water electrolysis system may become frozen, the control unit controls the solenoid valve in a manner so as to open the drain flow passage, and controls driving of the air supplying device in a manner so that air is supplied to the gas-liquid separator via the air supply path.   
     
     
         9 . The water electrolysis system according to  claim 2 , wherein the central region is a middle region obtained by dividing the plurality of water electrolysis cells into three equal parts in the stacking direction. 
     
     
         10 . The water electrolysis system according to  claim 6 , wherein the second water lead-out unit is connected to a lowermost part of the water discharge path.