How does an indirect pumped or closed loop solar water heating system work?
This system design is common where freezing weather occurs more frequently. An antifreeze solution circulates through the collector and a heat exchanger transfers the heat from the antifreeze solution to the tank water. The system illustrated below is an example of this system type. Here a heat transfer solution is pumped through the collector in a closed loop. The loop includes the collector, connecting piping, the pump, an expansion tank and a heat exchanger. A heat exchanger in the solar energy pack located on the storage tank transfers heat from the heat transfer solution to the potable water in the solar storage tank. The brain of the system is a differential controller. In conjunction with collector and tank temperature sensors, the controller determines when the pump should be activated to direct the heat transfer fluid through the collector. The fluid used in this system is a mixture of distilled water and a non-toxic, food grade antifreeze (propylene glycol). This type of flui
