Overall, ice systems offer the densest storage capacity but the most complex charge and discharge equipment. Water systems offer the lowest storage density, but are the least complex. Eutectic salts fall somewhere in between. Comparing storage media Chilled water systems require the largest tanks, but they can easily interface with existing chiller systems. Ice systems use smaller tanks and offer the potential for the use of low-temperature air systems, but they require more complex chiller systems.
Eutectic salts can use existing chillers but usually operate at the warmest temperatures.
They operate at temperature ranges compatible with standard chiller systems and are most economical for systems greater than 2,000 ton-hours in capacity. To store energy at the temperature of ice requires refrigeration equipment that provides charging fluids at temperatures below the normal operating range of conventional air-conditioning equipment. Ice accumulates on the outside of the pipes. Storage is discharged by circulating the warm return water over the pipes, melting the ice from the outside. Storage is discharged by circulating warm coolant through the pipes, melting the ice from the inside.