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Flat-plate Collector Solar Systems versus Evacuated Tubes

One of the most frequently-asked questions in the South African solar industry at present is whether one should purchase a Flat-Plate Collector Solar System or an Evacuated Tube Solar System. Before we elaborate on this it is important to understand the key differences between the two systems:

Flat Panel CollectorThe Flat-Plate Collector System is the traditional solar system comprising of a solar panel which is approx 80mm thick and ranges in size anywhere from 1.5 sq. m to 4 sq. m. The solar panel is mounted on the roof and is connected to a solar geyser which can also be installed on top of the roof (above the panel) or inside the ceiling. Flat-plate collector panels have been around since the 1950's and whilst the materials used in the manufacture of the solar panels have improved over time, the technology within the system is largely the same. The system utilizes the thermosyphon principle whereby cold water is fed into the bottom of the solar panel, and as the panel is heated by the sun the water in turn is heated and automatically starts to rise to the top of the solar panel from where it is then fed into the solar geyser. The Flat-Plate Collector System is a tried and tested system which has provided thousands of people with solar-heatedwater for decades.


The Evacuated Tube Collector SystemThe Evacuated Tube Collector System is a much newer system which has been available in South Africa for around 2 years. With this system a series of cylindrical glass tubes are attached to a frame and installed on top of a roof. Each tube is approx 1.9m long and inside each tube is a copper rod which extends from the bottom to the top of the tube and then into a manifold. A special chemical formula inside each tube starts to boil between 30 and 40 degrees celsius. This quickly heats up the copper rods in each tube which in turns heats the water which passes through the manifold. The manifold in turn is connected to a geyser (some evacuated tube systems are connected directly to a geyser instead of a manifold).


Which Solar Geyser Should I purchase?

There are two main technologies on the market, namely Flat Plate Collectors and Vacuum Tube Collectors. There are advantages and disadvantages to both systems, and the debate over which technology to use has been going on for many years. It is important that the sales person you are speaking to understands both technologies and can offer you both options depending on your budget, geographical area, water quality and number of people that will be utilizing the hot water from the solar geyser.