Abstract: Thin magnesium plate 101, which contains metal magnesium, is enclosed by separator 102, which is made of fluid-permeable material and is used as magnesium fuel assembly 100 in magnesium battery 120 in this invention. Magnesium fuel assembly 100 is enclosed from both sides by cathode 103 and provided with electrolyte retention unit 106, which stores electrolyte 107, at its bottom. When magnesium fuel assembly 100 is pushed down from above, separator 102 is impregnated with electrolyte 107, thereby initiating the battery reaction.

Abstract: A magnesium fuel element (100) comprises the magnesium thin plate (101), the front surface separator (102), and the back separator (103), and functions as a fuel for the magnesium air battery. The front surface separator (102) and the back separator (103) are folded, and the plurality of magnesium thin plates (101) are arranged in a stacked manner. The front surface separator (102) and the back separator (103) will be expanded, if the magnesium thin plate (101) moves parallel to the front surface.

Abstract: A water treatment system (220) heats raw water, gasifies a portion thereof by an evaporator (34), and condenses the gasified steam at a condensation area (240) to obtain condensed water. The water treatment system (220) includes a heater (32) for heating raw water, a steam conducting part (35, 36) for conducting, to the condensation area (240), steam gasified from the raw water heated by the heater (32), and a pipe (221) for conducting circulating water from the condensation area (240) to the evaporator (34), causing heat exchange between the steam conducted to the condensation area (240) by the steam conducting part (35, 36) and the circulating water, as well as causing heat exchange between the raw water and the circulating water at the evaporator (34).