Compact Solar Water Heater relies on density of the water, cold water down, hot water up, a cosmical physics. To circulate water through the collectors and the tank. When water in the collectors is heated up, it becomes lighter and naturally rises into the tank. Meanwhile, cooler water in the tank flows down to the collectors.
In this type of installation, the tank must be together with the collectors. These systems are reliable and relatively inexpensive but be careful with the installation, because the water tank is much heavier than that you thought.
Compact Solar Water Heater (SJK series) can work without circulating pump. when the aid electric breaks down, it cant affect the working of the whole system. This makes the systems generally more reliable, easier to maintain, and has a long living life. This type much cheaper than the others, but are also generally less efficient due to slower water flow rates through the system.

Cheap and reliable solution, Simple structure, Easy installation
High efficiency
Withstands water pressure no more than 0.1MPa
Operated without any power supplying
Electric heater can be used 1500W or 3000W
Hot water can be used directly, or can be used as a pre-heat