Introduction
Solar Hot Water describes active and passive solar technologies that utilize solar insolation – the sun’s naturally abundant and free solar thermal energy – in order to heat water for a desired application.
Availability of Solar Thermal Energy
Direct solar heat gain is one of the most efficient ways to heat water (in terms of energy/waste), as it requires no energy conversion, unlike electric-resistance heating or fuel burning. It is a simple transfer and concentration of heat energy from one place to another.
Hot water can be used for a number of applications, including sanitation (it's easier to wash a lot of things with hot water), and space heating.