Flat Plate Collectors: An Informative Overview

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A Flat plate collector is a solar panel device that uses solar energy to generate thermal energy. It converts solar power into thermal energy, i.e., cheaper energy utilising water as an operating fluid. 

A Flat plate solar collector takes in solar radiation and transmits heat to the functioning medium. It is suitable for several thermal applications. The average temperature range of FPC devices is 100° C. Besides, these devices have an economical cost of investment. 

The FPC devices are the backbone of solar thermal devices. They have diverse applications from household to commercial sectors. Flat plate collector devices are commonly used for active space heating and water heating for further usage.

How does A Flat Plate Collector Work?    

The working of a flat plate collector (FPC) involves the transfer of heat or thermal energy. The operating medium exchanges heat from the sun’s rays.

The heat-absorbing plate of the collector is exposed to sunlight. As the sun rays hit the flat plate surface, a portion of their energy is transformed into heat. This leads to a rise in the temperature of the flat plate solar collector.

When a fluid is passed inside the collector, the temperature of the fluid increases as the heat from the absorbing plate heat is transmitted to the fluid. 

Eventually, the fluid transmits the thermal energy from collectors to the functioning energy systems for different uses. It works on the principles of the 1st & 2nd Laws of Thermodynamics. 

Types Of Flat Plate Collector Devices 

We can categorise flat plate collector devices on two main grounds – 

A] Based on Glaze 

  • Glazed Panels – Glazed or Glazing Panels are insulated panels that embrace a glaze covering. They block infrared radiation and provide insulation to the solar plate. Under the glazing, there is an absorbent in which the working fluid flows. Glazed FPCs are commonly used in household water heating installations. 
  • Unglazed Panels: These flat plate collector devices are not glazed. Unglazed panels are usually utilised for swimming pool heating installations. They are inexpensive but less popular. Their temperature range is less than 30° C.

B] Based on Configuration 

  • Parallel Absorbing Plate: In a Parallel flat plate collector, the heat can be dispersed with a larger volume of circulating fluid via the branches present inside. It can be installed in both horizontal and vertical orientations.  
  • Series Absorbing Plate: Such FPCs include a sole continuous circuit. It has a high heat jump and a lesser volume of circulating fluid. 

Components Of Flat Plate Collector 

Here are the typical components of a flat plate collector:

  • Absorbing Plate: It is a component inside the collector that traps solar radiation. The absorbing plate converts the solar power into thermal power. It is a dark plate, generally made of copper foil.   
  • Tubes or Passages: The absorbing plate in a flat plate collector has a grid of conduits. These are tubes or passages for circulation of the heat transfer fluid. It aids in conducting the working fluid from the inlet to the outlet.
  • Insulation & Glazing Cover: Insulation minimises heat loss from the absorbing plate. It is present on the sides & back of the plate collector. The insulation is typically made up of synthetic foam sheets (fibreglass, polyurethane, etc.)
  • Casing or Container: The casing acts as a resting surface or closure for the components of the flat plate solar collector. It is made up of aluminium and holds all elements in place.

Sizing of A Flat Plate Collector     

The size of a flat plate collector depends on the temperature and consumption requirements. 

The flat plate solar collector devices generally range in:

  • 4 x 6.5 ft
  • 4 x 8 ft
  • 4 x 10 ft

The most commonly available size of plate collectors is 4 x 8 ft (32 sq ft). It can weigh beyond 200 pounds (or 100 kgs). 

On average, a one sq ft collector plate heats around ten litres (2 gallons) of water beyond 60°C every day. Hence, a single panel of 20 to 30 sq ft can heat about 300 litres (60 gallons) of water. This is approximately equal to the capacity of a standard hot water storage tank.

Flat Plate Collectors Without Cover    

Most flat plate solar collectors come with a cover (glass sheet), but those without a cover are also available. 

A flat plate collector without cover includes an absorber element made up of plastic, rubber, polypropylene, etc. Such solar plate collector devices are very reasonable. 

  • They have flexible configurations, so they can be placed on any surface.
  • Also, a flat plate collector without a cover resists corrosion and facilitates direct heating systems, for example – swimming pool heating.

Notably, the collector plates without cover having synthetic absorbers have efficient functioning. But, they may rapidly lose their efficiency when the atmospheric temperature is less than the working temperature, or strong winds are flowing.

Advantages of a Flat Plate Collector     

Some advantages of a flat plate collector include –  

  • A Flat plate collector facilitates the collection of direct energy from all directions and diffuses thermal radiation.
  • It is a clean, pollution-free system of energy generation.
  • The power utilised by FPCs is natural & renewable.
  • Flat plate collector devices have relatively low maintenance costs and longer working life.
  • It is easy to fabricate and economical.
  • It can be installed effortlessly. FPCs are fixed to a mounting structure in tilt and orientation in which they receive maximum sunlight.
  • With FPCs, more energy can be generated even at low temperatures.


A Flat Plate Collector is a device acting as a heat exchanger. It converts solar power into thermal energy. 

It can gather solar energy and use it to heat water in the house for bathing, washing, etc. Also, it can be used to heat hot tubs and swimming pools. 

The FPCs prove to be more feasible than other water heating systems due to their economical price, simple design, and easy installation. They greatly help to save on energy bills.


1. What are the uses of a flat plate collector?

Some common uses of a flat plate collector are:

  • Space heating.
  • Heating the swimming pool or hot tubs.
  • Support for household solar water heating systems. 
  • Preheating of fluids in industrial sectors.
2. Where should I install a flat plate collector?

A Flat plate solar collector should be either fixed on the rooftop of a building or installed on the ground at a 45° angle using the mounting kit (optional). 

While mounting the FPCs, one should take care that they are facing the sun.

3. What is the primary drawback of a flat plate solar collector?

The primary drawback of a flat plate collector is the deprivation of optical concentration. Due to this, there is a larger area from which the heat energy is lost.