Civil Engineering Reference
In-Depth Information
storage system that operates with a chiller that produces chilled water between 4 to
6 C can be expected to conserve the energy up to 85 %. The most commonly
preferred ice thermal storage systems for meeting out the cooling requirements in
buildings are explained below.
5.1 External Melt Ice Thermal Storage
The term external melt basically refers to the extraction of cool thermal energy
from the ice that is being melted from the outside of the primary cooling coil circuit
(EVAPCO Inc.
2007
and Yau and Rismanchi
2012
). The schematic representation
and pictorial view of the external melt ice TES system are shown in Fig.
13
.
During the charging mode, glycol (or brine) solution at low temperature is
pumped through the primary cooling coils by the standard chiller configured with
the ice storage tank. By this, the water in the tank starts freezing, thereby forming a
thick ice layer over the primary cooling coil circuit. The storage tank is designed in
such a way that at complete freezing of water to become ice, the ratio of ice build
to water would be 70-30 %.
This aspect ratio would facilitate for better circulation of warm chilled water
inside the storage tank in order to retrieve the heat energy from the ice layers. The
merits of external ice melt system include the following:
• the energy extraction rate can be modulated based on the cooling load demand
persisting in the conditioned spaces,
• the melting of ice with warm water can be done in single stretch, or on timely
basis depending on the fluctuating thermal load conditions, and
• the overall cooling system efficiency is appreciable in terms of reduced energy
consumption in the secondary chiller and the associated chilled water pumps, as
they may be turned off at on-peak conditions.
• As the secondary cooling loop and the storage tank utilize water, appreciable heat
transfer mechanism can be expected during charging and discharging cycles.
Fig. 13 The charging and
discharging procedures of an
external melt ice storage
system
