Types Of Flat Plate Collector

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Simply put, flat plate collectors are components of a solar panel responsible for converting solar power into thermal energy. The flat plate collector is one of the most popular and efficient heat exchangers that are commonly employed in industrial applications as well as in residential boilers.

These heat exchangers are mainly used to reduce the energy consumption of heating systems and improve the efficiency of the power generation equipment.

Flat plate collector

The performance of a flat plate collector is greatly influenced by heat loss through convection. Utilizing double glass may reduce convective heat loss, but due to double reflection, less radiation will reach the absorber. Therefore, single glazing provides greater efficiency than double glazing at low temperatures where this loss is minimal, while the usage of glazing is encouraged for better performance at higher temperature differences.  

Categories of Flat Plate Collector

The categories of flat plate collectors are divided into two, they are Air heaters and Water or Liquid heaters. 

1. Air Heaters

Air solar heater system

Air heaters are commonly used these days in a domestic environment and are less expensive compared to water or liquid heaters. The air heaters have a relatively small heat loss, low cost, and simple thermal design.

The solar air heater is designed using an aluminum sheet which is a cheaper option than steel sheets. This heater uses air to absorb the heat from the sun.

The air heaters are available in sizes ranging from 1 m to 15 m and they are used as supplemental heat because they are more efficient than direct heating.

Air heaters are commonly used as a primary source of heating to supplement the primary energy supply. In large buildings where sunlight is insufficient for the heating of water, these kinds of heaters are employed however, they can also be used in commercial buildings and homes.

2. Water Or Liquid Heaters

Flat Plate Solar Water Heater

Water or liquid heaters were originally invented in the 19th century and have been used in several countries for heating water or fluid. The water heater collector is used in many commercial and industrial buildings, but their large size and high initial cost make them less common for homes.

A fluid can be heated by heat transferred from the absorber via a fluid circulating in the external tank, which is then returned to the absorber.

There are two types of solar water heating systems. Active water heating systems have circulating pumps and control while the passive system is devoid of circulating pumps and control. Let’s take a closer look at both of them.

1. Active Water Heating Systems 

Active water heaters have two types. These are Direct circulation systems and Indirect circulation systems.

In direct circulation systems, pumps move the water used for household purposes through the collectors and into the building. They perform well in regions with infrequent freezing.

Indirect water heating systems on the other hand work by ensuring that pumps move a non-freezing fluid that transfers heat through the collectors and a heat exchanger. This warms the water before it enters the house. They are common in regions with frequent freezing temperatures.

2. Passive Water Heating Systems

Passive solar water heating systems are less expensive than active systems although, they are frequently less effective. This system, however, may be more dependable and durable. Passive systems have two types which are integral Collector storage systems and thermosyphon systems.

  • Integral collector-storage passive systems

Integral collector-storage passive systems are made out of a storage tank that is wrapped in a transparent material to let the sun heat the water. The water supply is then filled with the heated water from the tank.

The best areas for this type of heating are areas where it doesn’t often get below freezing. They are also effective in homes with high daytime and nighttime hot water demands

  • Thermosyphon systems

Thermosyphon systems are a bit more conservative. They usually have a 40-gallon capacity due to the system of heating involved. When a hot water faucet is opened, water that has been heated in a roof-mounted collector begins to flow through the plumbing system.


Water-heater collectors are the most widely used and the easiest to install. Air-heater collectors are a good option if you have a limited amount of money.

For more details on flat plate collectors, check out the advantages and disadvantages of flat plate collector

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