FAFCO - Hybrid Ice Storage - the Functionality:

When the ice bank is charged, the water is frozen into a solid ice-block.

In the discharge process, refrigeration energy is taken from the inner surface of the ice-block - directly or indirectly - via a glycol circuit and a water circuit simultaneously, As a result of the glycol circuit, an initial large and steadily growing inner ice surface forms, which adds to the effectiveness of the ice-water circuit.

The ice surface needed for the ice-water circuit is achieved by pre-cooling of the water fed to the load via a plate-type heat-exchanger. The glycol-water mixture heated in that process flows through the heat-exchanger system built into the storage vessel and by internal melting creates free passage for the second stage ice-water circuit.

An air-blower system, together with ice-water distributors and collectors placed in the optimum positions and with optimum dimensions, ensure the best possible flow of water through the ice and a very uniform melting process.

The inner ice surface is significantly greater than it is in ice banks with external melting. This makes it possible to achieve an extremely high discharge performance at extremely low outflow temperatures throughout the whole discharge process.

The advantage of the new ice bank design lies in the performance-enhancing hybrid melting of the ice-block after 100 per cent charging of the storage system with ice. It is also possible to achieve any desired partial charge and discharge cycles without the well-known disadvantages of the external melt system arising as a result.

In the hybrid ice bank, the water is allowed to freeze to form a solid ice-block - this is in fact desired. The performance per unit volume of this type of storage systems is therefore significantly higher than for external melt systems because there attention must be paid to the free flow of the ice water between the ice slabs. As a result, FAFCO hybrid ice banks are significantly more compact and space-saving than ice banks using the external melt system.

Direct und indirect discharge

Immediately following the start of the discharge, many spaces are formed by the first glycol circuit between the ice-block and the heat-exchanger pipes through which the ice water can flow during the second stage. When discharging, a distinction is made between direct and indirect discharge, depending on whether the water to be cooled and fed to the load comes in contact with the ice or not.

Direct discharge: The water to be cooled is fed first via the brine heat-exchanger and then directly through the ice bank

Indirect discharge: The water to be cooled, or also any other liquid, is fed first via the brine heat-exchanger and then via the ice-water heat-exchanger.

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