HEAT STORAGE APPARATUS

A heat storage apparatus includes: a container sealed, with a heat storage material encased in the container, the above material including a thermosensitive polymer gel including a thermosensitive polymer and a solvent selected from the group consisting of water, organic solvents, and compounds of water or organic solvents; and a heat exchanger that is housed in the container to transfer heat between the above material and a heating/cooling fluid to heat or cool the material, and store heating energy or cooling energy in the material, and that transfers heat between the material and a heat utilization fluid to receive heat from the material and to transfer heat from the material. The material makes a reversible hydrophilic-hydrophobic transition at a lower critical solution temperature, and the solvent included in the thermosensitive polymer gel is kept in a liquid state in hydrophilic-hydrophobic transition.