Solar Thermal Panels: Flat Plate or Evacuated Tubes?

Solar thermal panels come in 2 types, either flat plate or evacuated tubes. In the UK evacuated tubes are on average more efficient and resilient.

evacuated tubes solar thermal panels

Solar thermal panels come in 2 types.  Flat Plate or Evacuated Tube panels. But which is best for your home or project?


Solar Thermal Panels: Flat-Plate Collectors:

Flat-plate solar thermal panels are comprised of an absorber and transparent layer, held within a frame and insulation. The transparent cover layer is normally made of ion-poor solar safety glass, which helps transmit greater amounts of short-wave light.

The CO2 emissions of Flat-Plate Collectors are minimal and energy wastage is kept low by the cover. This enables the solar thermal panel to prevent any heat loss due to wind drawing the heat away by convection.

The frame is usually made of aluminium and galvanized steel although fibreglass-reinforced plastic is sometimes used instead.

The insulation, usually mineral wool or polyurethane, is fitted on the back of the absorber and on the sidewalls and reduces any conduction heat loss.

Solar Thermal Panels: Evacuated Tube Collectors:

Evacuated Tube Collectors are made up of numerous tubes. Within the pressure-proof tubes is a vacuum housing the absorber strip. The heat transfer fluid is sent through the absorber in a U-tube. It can flow counter-current in tube-in-tube systems.

When fitting the pipes, they must be angled at a certain degree over a horizontal position to make sure that the vaporizing and condensing of the system works properly.

The solar collector can be connected to the solar circulation system in one of two ways: by a wet connection, or a dry connection. Wet connections are where the heat exchanger flows straight into the manifold.

Dry connections are where the heat exchanger is connected to the manifold with the use of a heat-conducting material. Dry connections enable the exchanging of single tubes without needing to empty the whole solar thermal system.

Solar Thermal Panels or Evacuated Tubes 500x385 Solar Thermal Panels: Flat Plate or Evacuated Tubes?

Which Solar Thermal Panel is Best: Flat Plate or Evacuated Tube?

The general consensus is that evacuated tube solar thermal panels are the better due to their all-round qualities. The absorber area of these panels is greater, and the tubes are better at keeping up an impressive efficiency with various weather conditions and required heats.

Typically, very bright and sunny climates flat plate collectors may be more efficient but more overcast climates such as that of the UK make evacuated tube collectors the more efficient.


Image: Soltrac

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