Types of Collectors in Solar Power

Types of Collectors

There are two main types of collectors :

(A) Flat plate collectors.

(B) Concentrating collectors.

(A) Flat plate collector

• The construction is shown below :

Figure A

• Absorber plate with number of tubes is prepared by copper tubes and sheets by soldering.
• This plate is layered by black paint so as to absorb and retain sunlight heat.
• In order to prevent heat losses it is enclosed in box which has insulation on bottom side and transparent cover on the top side.
• This complete assembly is placed at proper Inclined angle to absorb solar radiations.
• Fluid, water, oil is circulated through tubes which carry heat to heat exchanger where steam is formed and goes to drive steam turbine-generator set to produce electrical energy.
• There are different types of fat-plate collectors.
• Flat plate collectors are used for small works.

Advantages of flat plate collectors :

1. Construction is very simple in comparison with concentrating type.
2. Cost is low.
3. Maintenance is less.
4. Suitable for direct and diffused solar radiations.

Disadvantages of flat plate collectors :

1. Suitable for low temperature works (upto 100°C) like water heater, space heater.
2. Not suitable for large capacity power generation.
3. Weight is much more.
4. Dirt, dust, moisture deposits an glass surface so to be cleaned.
5. These are at fixed position so loose solar collection.

(B) Concentrating collectors (Generally used for Power Generation Plants)

• These are the focusing collectors by which heat is concentrated and temperature Increased upto 200 to 300°c.
• These collectors are more effective but very costly. 
• Parabolic or fresnel mirror is used for this.
• Acrylic material is suitable for fresnel type lense.
• Types of concentrating collectors are shown below.

1. Parabolic trough concentrator :

• There are many parabolic trough shaped mirrors arranged.
• The arrangement of these mirrors are in parallel rows.
• These collect solar radiations over the area of reflecting surface.
• Absorber is along focus axis.
• Receiver pipe runs along focal point over which concentrated solar radiations fall.
• There is an arrangement of rotating the reflector about the axis of absorber as per the sunlight direction.

2. Parabolic dish concentrator :

• It has point focus collector in parabolic shape in dish form. This reflects solar radiations on the receiver mounted at focal point.
• Highest concentration ratio is obtained in such construction. This is flexible and efficient type. 
• This is suitable for small or medium, large scale power generation.

3. Fresnel lens concentrator :

Figure B