Solar Water Heating

Thermosyphon Systems

Thermosiphon Systems as indicated in Figure 6 use the natural tendency of heated water to rise and cooler water to fall to perform the heat collection task.
As the sun shines on the collector, the water inside the collector flow-tubes is heated. As it heats, this water expands slightly and becomes lighter than the cold water in the solar storage tank mounted above the collector. Gravity then pulls heavier, cold water down from the tank and into the collector inlet. The cold water pushes the heated water through the collector outlet and into the top of the tank, thus heating the water in the tank.


Figure 6

A thermosiphon system requires neither pump nor controller. Cold water from the city water line flows directly to the tank on the roof. Solar heated water flows from the rooftop tank to the auxiliary tank installed at ground level whenever water is used within the residence.

This system features a thermally operated valve that protects the collector from freezing. It also includes isolation valves, which allow the solar system to be manually drained in case of freezing conditions, or to be bypassed completely.

Material from: Florida Solar Energy Center
Credits:
John Harrison & Tom Tiedeman FSEC-EN-9 Revised May 1997