Ice on Coil
Open System - Cold refrigerant or a brine solution is circulated through pipe coils submerged in an open water tank as shown below. During the charge cycle, ice forms on the pipe coils until a satisfactory thickness (typically 2" to 3") is achieved. During normal operation, chilled water is circulated to the load, and the ice remains in storage. During the discharge cycle, the chilled water flows through the storage tank(s) and is chilled by the melting ice.
Where a closed circulating system is required, a heat exchanger is used between the circulating ice water and building chilled water as shown in the following:
Closed System - Another popular variation is the modular ice storage system using a glycol brine. This system utilizes one or more polyethylene tanks and tubes. Cold brine in a closed circulating system flows in a counterflow arrangement through the tubes, freezing the water in the tanks. In the charge cycle, an automatic diverting valve bypasses the cooling coils and the refrigerated brine builds ice.