Solar water heater with double circulation by coil

Feature:
A. It is non-pressurized, safer and more dependable.
B. More enjoyable with tap water pressure.
C. The cold and hot water mix stably for balance of pressure.
D. Heat exchange is highly efficient with copper coil.
E. Heat is delivered efficiently by heat pipe.
F. The tank can be protected by antifreeze.
G. The water wouldn't polluted by former water