The development and validation of a mathematical model of an ice storage tank with heat exchangers that can be de-iced is presented. The ice storage model was developed for heating applications using combined solar thermal and heat pump systems. Experiments were conducted with a laboratory scale ice storage of 1 m3. The model predicted successfully most of the operating modes for the main variables such as heat exchanger outlet temperature and energy transferred, mass of ice produced and melted, and time of ice formation.