is considered to be an appropriate technology
. This process utilizes natural, renewable
resources and the basic laws of thermodynamics
to create movement of a heated supply of air or water. The energy source for this process is solar radiation: the energy of the sun is captured in a solar collection device and is transferred to either air or water via conduction. The entire process may be explained by the thermosiphoning effect
: When air or water is heated, it gains kinetic
energy from the heating source and becomes excited. As a result, the water becomes less dense, expands, and thus rises. In contrast, when water or air is cooled, energy is extracted from the molecules and the water becomes less active. It also becomes more dense, and tends to "sink." Thermosiphoning harnesses the natural density differences between cold and hot fluids, and controls them in a system that produces natural fluid movement.
The passive thermosiphoning of water is the process of heating and moving water within a system without the need or use of electricity. This process functions by utilizing natual phenomena such as solar energy, gravity, and an available water source.