Energy storage apparatus and method for cooling the energy storage apparatus

The present invention relates to an energy storage system and a method for cooling the energy storage system. An objective of the present invention is to provide an energy storage system having a high energy density. The other objective of the present invention is to provide the energy storage system and the method for cooling the energy storage system, which are capable of improving cooling efficiency of battery racks. The energy storage system according to an embodiment of the present invention comprises: a chamber in which an accommodation space is formed; battery racks which are located in the accommodation space and include a first battery rack group and a second battery rack group that are separated to face each other based on the center of the accommodation space; an upper duct which is located in an upper part of the accommodation space, and supplies a cooling fluid to a cooling space that is a space between the first battery rack group and the second battery rack group; a cooling unit which is located outside the accommodation space, and cools the cooling fluid; and a fluid moving member having a moving space in which the cooling fluid heated after cooling the battery racks is moved to the cooling unit, wherein the cooling unit receives the heated cooling fluid from the moving space and cools the same to supply the cooled cooling fluid to the upper duct.