The Simple, yet Effective Thermosyphon Solar Water Heaters

Thermosyphon refers to a method of passive heat exchange based on natural convection, which circulates a substance (liquid, or gas such as air) without the necessity of a mechanical pump. It makes it a very attractive water heating solution to heat domestic water for small scale installations such as villas and commercial facilities, since simplicity and minimal electromechanical intervention is required to operate the system.

In Thermosyphon solar water heaters, the natural circulation of the thermal fluid inside the closed collectors-tank loop results when water heated in the Solar Collector expands and rises, pushing cooler water in the rest of the loop into flowing. Cooler water is pushed out of the bottom of the tank and into the bottom of the solar collector. Once circulation starts, the process continues unabated all day.

Thermosyphon – Solar Water Heating System Operation

• The absorber in the flat solar collector converts the solar energy to heat and transfers the heat to the thermal fluid inside the solar collectors
• The solar fluid in the absorber heats up quickly. The result is that the heated solar fluid (1) rises because its density is reduced
• The rising solar fluid enters the domestic hot water cylinder and flows through the heat exchanger (2)
• During this process the thermal fluid releases energy to the drinking water
• The cooled thermal fluid (3) sinks back into the collector because its density is now higher
• Heated thermal fluid rises and cooled thermal fluid sinks to circulate through the system

Fitted with a back up electric heating rod, submersed inside the tank, the Thermosyphon solar water heater from Vaillant guarantees 24 hours coverage of hot water demand. The system consists of a high performance flat plate collector and high performance thermal insulation for the 150L, 200L and 300L tanks.

The inclination angle of the collectors can be adjusted to optimize the system performance based on the geographical location of the house, thanks to the smart aluminum A-frames which are provided with Vaillant systems.

Other safety features are developed for the Thermosyphon solar water heating system from Vaillant to prevent system damage due to high temperature in summer and pressure build up inside the system.