A solar water heater uses energy from the sun to heat water. A solar water heater works on two
basic principles. Firstly when water gets hot it rises due to density differences between hot and
cold water (thermosiphon effect) and secondly that black objects absorb heat.
A solar water heater comprises three main parts: the collector, the storage tank and an energy
transfer fluid.
Solar water heaters are classified as either active or passive and direct or indirect systems. They
may make use of either flat plate collectors or evacuated tubes. Below the differences are briefly
discussed
