Flat Plate Solar Thermal Collectors: Overview

Flat plate solar thermal collectors are one of the most well tested forms of solar panel. They are fairly inexpensive and can run up to 75% efficiency.


Flat-plate solar thermal collectors are one of the most traditional and well-tested forms of solar thermal panels. Having existed since the beginning of the 20th century these solar panels are sturdy and reliable and remain the dominant product in the solar energy market.

What are Flat Plate Solar Thermal Collectors made of?

Flat plate solar thermal collectors are comprised of an absorber plate (copper sheeting with a black coating or black painted surface), affixed to pipes (or ‘risers’) through which the heat-transfer liquid is passed.

These components are fixed within an insulated metal frame and covered with glazing to provide protection and create an insulating air space. This type of thermal collector is usually made of high-temperature rigid foam insulation, low-iron tempered glass, and aluminium frames.

The absorber plate can be covered with various coatings from black paint to selective-surface coatings which encourage the greatest absorption and retention of heat possible. The panels are generally available as 3x8ft, 4x12ft, or greater sizes. Each panel will likely weigh around 150lbs.

The Cost of Flat Plate Solar Thermal Collectors:

Flat plate solar thermal collectors are generally fairly inexpensive in comparison with Evacuated Solar Thermal collectors. However, the reliance upon a considerable amount of copper within the designs makes varying prices of materials an issue, therefore bringing the cost of the panels themselves up and down in turn.

Flat Plate Thrmal Collector Overview 2 500x266 Flat Plate Solar Thermal Collectors: Overview

The Efficiency of Flat Plate Solar Thermal Collectors:

Flat plate thermal collectors can run at up to 75% efficiency under perfect operating conditions, where the temperature of the inlet fluid is the same or less than the ambient air temperature. However, perfect conditions are rare.

In poor weather conditions such as heavy snow, flat plate collectors are aided by light passing through the snow or frost on the panels. The light heats the absorber plate, and the heat warms the glass which in turns melts the frost or snow. The position of flat plate solar panels is of great importance as indirect sunlight is easily reflected from the surface. It is best to locate the plates as directly towards the sun as possible.

Image: Renewable Project

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