1.Glazed Flat-Plate Collectors
A glazed flat-plate collector consists of a shallow rectangular box with a flat black plate behind a tempered glass cover. The plate is attached to a series of parallel tubes or one serpentine tube through which water or another liquid (such as an antifreeze or glycol solution) passes. The bottom of the box and in some designs the side of the box is lined with insulation. This flat-plate hot water system is active requiring an additional fluid circulating pump to push the heat transfer fluid through the tubes to a heat exchanger tank to heat the tap water for domestic use thus requiring external energy in the form of electricity to operate the system. When heat transfer fluids are utilized other than water the fluids must be replaced at a minimum every two years because the fluid material begins breaking down losing its transfer ability shortly after reaching heated temperatures.

2.Evacuated-Tube Collectors
Solar collector evacuated tubes collect and convert sunshine energy (radiation) into thermal energy, which is transferred to the central heat pipes in the tubes through the aluminum fins bridging the tube inner surfaces and the heat pipes. The copper heat pipes have tiny amount of purified water sealed in them at depressurized condition. When heated, the water inside the heat pipes vaporizes at low temperature (about 30˚C). The vapor (steam) rises to the pipe tips inserted into the water contained in the tank. Vapor is cooled down and becomes condensate falling to the bottom of the pipes. By continuously circulating this way, heat is carried from outside to the domestic city water inside the tank. The tubes work independently of each other with a lifespan to over 25 years. The evacuated tube requires no maintenance for the life of the tube. All the heat process technology is within a vacuum in the double tube thereby making the temperature in the environment irrelative to the heating process. Since each tube is round they directly receive sunlight from sunup to sundown without sunlight reflection as with the glazed flat-panel. Our evacuated tube Irradiation conversion rate  to thermal energy equals 92%.

 
                   FIGURE 2 – Evacuated tube cross-cut
The most powerful solar technology in the world.