One limitation of this system is that there may not always be sufficient heat supply from the sun for the collector to absorb. Because of this, a back-up system, such as a booster,  is almost always required. The figure above shows the required booster that is used as a back-up secondary system, when there is not a sufficient solar heat supply.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As shown in the figure above, another drawback is that the system can be damaged by the expansion of freezing transfer fluid. In order to prevent this, the collectors need to be drained when freezing is expected. This can be done manually, or using drainback systems. Alternatively, anti-freeze can be used in the heat transfer fluid.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Overheating needs to be addressed as well. When hot water is not used for a few days, the fluid in the collectors and storage unit can reach high temperatures. A typical solar hot water storage tank is shown above.