Thermo-Siphon Solar Systems

If you look out of the plane window as your holiday flight is about to land at Zhejiang or Jiangsu in China, you will see that virtually every house has a thermo-siphon system, which is simply a way of water heating. There are usually a collection of solar collector and sometimes a random collection of tanks on the roof. Cyprus has more solar systems per capita than any other European country.  It can use its predictable and strong sunshine to provide almost all its hot water needs.

Thermo-siphon systems work very simply. A solar collector, usually with vacuum tubes, converts light into heat. The heat transfers into the water tank on the roof and heats the water. Sometimes the potable water flows through the tank. The installation is usually simplicity itself, with the domestic cold water being taken by one pipe into the roof and the hot water drawn from another pipe in the roof.

Cost is a critical factor and many of these systems have a “heath-Robinson” look about them but they do provide hot or warm water, and people tend to make do with and get used to what they have, rather than thinking about what they can get.

These thermo-siphon systems will work in the hot weather area (above -15 Celsius), depending on weather.
The better quality thermo-siphon systems come with solar collector that was selectively coated. These provide much better performance and much hotter water temperatures. In China, for example, a good quality thermo-siphon system with selective coating will recharge a two hundred litre tank in less than three hours and can provide tank temperatures in excess of 80° Celsius although the norm is around 60°C. These thermo-siphon systems can have excellent performance criteria in hot countries.