Thermosyphon Solar Water heaters

Whenever you see a solar panel and a cylinder located immediately above it, you are looking at a thermosyphon solar water heater system. Thermosyphon solar water heaters are simple and reliable and the most common solar water heater worldwide.

How thermosyphon solar systems work

Thermosyphon solar water heaters do not have pumps or controls in their most typical configuration. They are based on a basic convection principle: hot water rises and cold water sinks.

As the potable water (or an antifreeze fluid, in colder climates) entered into the solar panel it warms and rises to the top and to the tank, where it is stored (that’s the reason why thermosyphon tanks are always above the collector).

Thermosyphon Solar Water Heaters & Collectors

Thermosyphon systems can be equipped with either tube solar panels or flat solar panels, which gives them the possibility (and the advantage) of responding to different needs and climates.

Thermosyphon Systems & Advantages

Thermosyphon solar water heaters are cheap, reliable and because they do not have pumps or controls they do not demand any significant maintenance cares.

Contrary to batch systems, since the hot water is stored in a well-insulated tank, thermosyphon solar systems do not pose heat loss problems during night-time.

Thermosyphon Image: EERE

Thermosyphon Solar Water Heaters Disadvantages

Thermosyphon systems depend largely on ambient temperatures, which is a major disadvantage.

In fact, they will stop working if outdoor temperatures drop below the freezing point and stay there for long. In that case the system needs to be drained or warmed.

To overcome this limitation some manufacturers are equipping their thermosyphon solar systems with small circulating pumps, that are turned on in very cold weather conditions in order to move the water and to prevent it from freezing. Only in this case, thermosyphon systems are truly an all-climate solution.

Another possible disadvantage of thermosyphon solar water heaters – when installed on a roof – is their high weight. A tank full of water is a very heavy object that may require the reinforcement of the roof.

Thermosyphon Solar Water Heaters Installation

Thermosyphon systems are easy to install and to connect to the existing hot water piping.

The installation involves mounting a cold water supply line, a cold water inlet and a hot water outlet... Which doesn't mean that thermosyphon solar do not pose the same problems that other systems pose in their integration with backup systems. See: Solar Backup.

Prices

Thermosyphon solar water heaters are relatively inexpensive. Prices are now much lower than some years ago.

In USA you may find a 40 gallons thermosyphon kit with a tube solar panel (standard 20 tubes) at prices of $1,000-$1,200. A larger thermosyphon solar system (80 gallons) with the same 20 tube solar panel may cost you $1,200-$1,500.