The storage of 'cold' with ice slurries-a special type of thermally multi-functional fluids or phase change slurries (PCS)-is discussed. At first an example of a calculation of a thermal energy storage tank in an ice slurry system with a peak load demand is presented. Then a new concept of ice slurry storage without mixing is introduced. It leads to ice particle stratification and front propagation in the storage vessel. The stratification of ice particles in ice slurry is theoretically described by multi-component multi-phase fluid dynamics. The resulting stratification process is calculated and front propagation times are compared with experimental results; they compare fairly well. Copyright (C) 2007 John Wiley & Sons, Ltd.