Abstract: The ice storage reservoir (1) comprises a container (2) filled with water (3) and containing first heat exchangers (4) through which a cooled medium flows when the ice storage reservoir is charged. The water in the container thus turns to ice. For discharging the ice storage reservoir, a medium can be conveyed through the first heat exchangers which is passed through a second heat exchanger (11). Coolable in the second heat exchanger is a working medium which circulates in a working-medium circuit (14) and can be supplied after cooling to a cooling plant. At the same time, during the discharge operation water is withdrawn from the container via drainage facilities (22), conveyed over a third heat exchanger (18), and returned to the container through supply facilities (27). The working medium precooled by the second heat exchanger is led through the third heat exchanger in which further heat is withdrawn from the working medium.