Much energy is used for water heating purposes. In a typical Australian household, water heating
accounts for up to 40% of the total energy consumption. Sources of the energy are commonly
electricity (79 %) and gas (16 %) while the rest are solar and other renewable sources (5 %) (AFFA
1998).
From this figure, it is clear that the number of systems using renewable energy sources,
especially solar, is very low due to several key problems involved in adopting this kind of energy.
Firstly, using solar energy depends on location of the site. The best site must have no shade on solar
collectors.
In addition, it is preferable to face the solar collector to the Equator to receive maximum
solar radiation.
Secondly, the available solar radiation varies with weather conditions. This means that
on a cloudy day the system may not heat water sufficiently to meet the requirements of household
applications.
Another problem in using solar water heating is that during midday the availability is
high when demands are low.
Therefore, substantial thermally insulated hot water storage is needed.