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Chapter 4
Solar is the monthly total solar radiation incident on the collector surface.
Load is the monthly total thermal energy demand on the system at a temperature above the
specified minimum useful temperature.
Q Tank is the monthly total energy loss from the storage tank.
Aux is the monthly total auxiliary energy which must be supplied in addition to the solar energy
to meet the demand.
f is the fraction of the load supplied by the solar energy system. The remaining fraction is
supplied by an auxiliary source.
4.9 Integral Collector-Storage Water Heating Systems
Integral collector-storage (ICS) units are passive solar water preheaters that combine solar
collection with thermal storage. They are usually roof or ground mounted in series with a
conventional domestic water heater and supplied by mains water. An ICS unit is basically a
black tank in an enclosure with an optical cover system, as shown in Figure 4.8. There are many
variations in design. Some units have several tanks plumbed in series within the enclosure.
Others have internal reflector systems, non-flat covers or finned tanks. ICS solar water heaters
usually cost less than active systems and are inherently simple to install and maintain. They
often operate without heat exchangers, pumps or controllers. Auxiliary energy must be supplied
if the solar energy collected by the ICS system is insufficient to meet the water heating load.
COLLECTO
Figure 4.9: Integral Collector-Storage Solar Water Heater
The monthly performance of an ICS system is estimated using the method of Zollner et al.
[1985]. The thermal parameters and default values in English units are listed below followed by
descriptions of the parameters.
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