For central heating, solar liquid collectors are most appropriate. Solar domestic hot water systems, they are the same. Flat-plate collector is the most common, but the vacuum tube, can also be concentrated collectors. In the collector, the heat transfer or the "work" of the fluid, such as water, antifreeze (usually a non-toxic glycol), or other types of liquid absorbing solar heat. At the appropriate time, the controller operating a circulation pump to move the fluid through the collector.

 

The liquid flow quickly, so its temperature is only 10 ° to 20 ° F (5.6 ° to 11 ° C), because it is by moving the collector. A smaller volume of liquid is heated to a higher temperature, increasing the efficiency of the system, reducing heat losses from the collector.

 

The liquid flows either a storage tank or a heat exchanger for an immediate use. Other system components including pipes, pumps, valves, expansion tanks, heat exchangers, storage tanks, and control.

 

The flow rate depends on the heat transfer fluid.