Liquid power generation apparatus and liquid power generation system

A liquid power generation apparatus comprising:

• a movable liquid tank which is vertically movable;
• a linear-rotation conversion mechanism which comprises a male screw shaft and a female screw body screwed to the male screw shaft, one of the male screw shaft and the female screw body being displaced in an axial direction in tandem with the movable liquid tank, the other generating a rotation output;
• liquid introducing means for introducing a liquid into the movable liquid tank when the movable liquid tank is placed at an upper position;
• controlling means for lowering the movable liquid tank having the liquid introduced therein from the upper position;
• liquid discharging means for discharging the liquid in the movable liquid tank when the movable liquid tank is lowered;
• movable liquid tank returning means for moving up the movable liquid tank, which has been lowered and has discharged the liquid, and returning it to its original position, the movable liquid tank returning means comprising:
• an outer tank which surrounds the movable liquid tank and stores the liquid that has been discharged from the movable liquid tank;
• and a float which allows the movable liquid tank to float on the discharged liquid;
• and
• a generator which is driven by a desired rotation output from the linear-rotary conversion mechanism and generates electricity.