Nature paints a serene backdrop with lush greenery, towering trees, and a gentle stream under the warm embrace of the setting sun. The air is filled with the delicate scents of blooming flowers, creating a tranquil atmosphere. Birds add a musical touch, their chirps blending harmoniously with the rustling leaves and the soft babble of the brook. Life thrives in this natural haven, as playful squirrels leave tiny footprints in the soft soil, and colorful butterflies gracefully flutter through the air. The environment resonates with the soothing sounds of insects, contributing to the lively symphony of nature. Each element, from the vibrant hues of the flora to the intricate movements of the fauna, collaborates to form a captivating ecosystem. This idyllic setting invites observers to appreciate the delicate balance of life in nature. It serves as a sanctuary where the beauty of the environment lies in its simplicity, offering a peaceful retreat and a moment of connection with the wonders of the natural world. Nature paints a serene backdrop with lush greenery, towering trees, and a gentle stream under the warm embrace of the setting sun. The air is filled with the delicate scents of blooming flowers, creating a tranquil atmosphere. Birds add a musical touch, their chirps blending harmoniously with the rustling leaves and the soft babble of the brook. Life thrives in this natural haven, as playful squirrels leave tiny footprints in the soft soil, and colorful butterflies gracefully flutter through the air. The environment resonates with the soothing sounds of insects, contributing to the lively symphony of nature. Each element, from the vibrant hues of the flora to the intricate movements of the fauna, collaborates to form a captivating ecosystem. This idyllic setting invites observers to appreciate the delicate balance of life in nature. It serves as a sanctuary where the beauty of the environment lies in its simplicity, offering a peaceful retreat and a moment of connection with the wonders of the natural world. Nature paints a serene backdrop with lush greenery, towering trees, and a gentle stream under the warm embrace of the setting sun. The air is filled with the delicate scents of blooming flowers, creating a tranquil atmosphere. Birds add a musical touch, their chirps blending harmoniously with the rustling leaves and the soft babble of the brook. Life thrives in this natural haven, as playful squirrels leave tiny footprints in the soft soil, and colorful butterflies gracefully flutter through the air. The environment resonates with the soothing sounds of insects, contributing to the lively symphony of nature. Each element, from the vibrant hues of the flora to the intricate movements of the fauna, collaborates to form a captivating ecosystem. This idyllic setting invites observers to appreciate the delicate balance of life in nature. It serves as a sanctuary where the beauty of the environment lies in its simplicity, offering a peace

1. Module_2
Solar Thermal Energy Collectors

2. Solar Thermal Energy Collectors: Types of Solar Collectors,
Configurations of Certain Practical Solar Thermal Collectors, Material
Aspects of Solar Collectors, Concentrating Collectors, Parabolic Dish –
Stirling Engine System, Working of Stirling or Brayton Heat Engine, Solar
Collector Systems into Building Services, Solar Water Heating Systems,
Passive Solar Water Heating Systems, Applications of Solar Water Heating
Systems, Active Solar Space Cooling, Solar Air Heating, Solar Dryers,
Crop Drying, Space Cooing, Solar Cookers, Solar pond.

3.  Sun’s heat energy is a diffuse energy. It is always first collected and then
concentrated.
 In residential systems, simple and cheap solar panels are used to collect the
solar heat energy below 60°C.
 Residential panels for heat collection are referred to as flat plate collectors.
 In utility scale systems, solar heat energy is required to be concentrated at
high temperature level in the range 70°C–80°C at the collectors.
 The utility panels are, therefore, called concentrators.
 Solar energy collectors are special kind of heat exchangers that transform
solar radiation energy into internal energy of the transport medium.
 The solar collector absorbs the incoming solar radiation, converts it into heat,
and then transfers this heat to a fluid (usually air, water, or oil) flowing through
the collector.
 The solar energy, thus, collected is carried from the circulating fluid either
directly to the hot water or space conditioning equipment or to a thermal
energy storage tank, from which it can be drawn for use at night and/or cloudy
days.
Diffuse Radiation (Gd) is the part of total radiation that reaches earth's surface after a change of its
directions due to scattering by the atmosphere.

4. Applications Solar collectors:
• Solar water heating
• Solar space heating systems
• Solar refrigeration
• Industrial process heat systems
• Solar desalination systems
• Solar thermal power generation systems

5. Types of Solar Collectors

7. Low temperature heat collectors have the following
types:
• Flat Plate Collectors
• Evacuated Solar Collectors

8. Medium Temperature Solar Heat Collectors
• These collectors produce higher temperatures than the low
temperature solar collectors.
• These are used in drying wood for construction and wood chips as a
fuel.
• These collectors are also used for cooking as Solar Cooker.
• These collectors are also used to distill the water in places where
drinking water is not easily available.
These devices are called solar still.

9. High Temperature Solar Collectors
• High temperature solar collectors like mirrors and lenses are used
to concentrate a large amount of solar energy to small area to
produce heat thereby producing electricity or
high temperature heat.
• This is achieved by the concentrating a large amount solar power
with the help of concentrating collectors.
• The temperatures may reach above 5000C.
The technologies using concentrated solar power are :
1.Parabolic Trough
2.Dish Sterling
3.Solar Power Tower
4.Fresnel Reflector

10. TYPES OF SOLAR COLLECTORS
There are two main types of collectors :
(A) Flat plate collectors.(Non concentrating)
(B) Concentrating collectors.
Flat Plate Collectors
Flat plate collectors are the most common type. They are also referred to
as non- concentrating collectors and have the same area for intercepting
and for absorbing solar radiation. A typical flat
plate collector is shown in Figure.

11. 1. Dark flat plate absorber of solar energy:
2. Transparent cover:
3. Heat-transport fluid (air, antifreeze, or water):
4. Heat insulation backing:
5. Insulated casing:

16. 1. Dark flat plate absorber of solar energy:
A black sheet that absorbers the radiation, and it is
generally made either of copper or aluminum. Copper is more
expensive, but is a better conductor and less prone to corrosion
than aluminium.
2. Transparent cover:
This allows solar energy to pass through, but reduces
heat losses.
3. Heat-transport fluid (air, antifreeze, or water):
To remove heat from the absorber, fluid is usually
circulated through tubing to transfer heat from the absorber to
an insulated water tank.

17. 4. Heat insulation backing
The function of this layer of solar collectors is to avoid
and minimise losses from the system by covering it.
5. Insulated casing:
It is made of a glass or polycarbonate cover.

18. •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.
•Flat plate collectors are used for small works.

19. WORKING PRINCIPLE

21. When solar radiation passes through a transparent cover and
impinges on the blackened absorber surface of high absorptivity,
a large portion of this energy is absorbed by the plate, and then
transferred to the transport medium in the fluid tubes to be
carried away for storage or use. The underside of the absorber
plate and the side of casing are well insulated to reduce
conduction losses. The transparent cover is used to reduce
convection losses from the absorber plate through the restraint
of the stagnant air layer between the absorber plate and the
glass. It also reduces radiation losses from the collector as the
glass is transparent to the short-wave radiation received by the
sun, but it is nearly opaque to long-wave thermal radiation
emitted by the absorber plate. For solar water heating systems
in home and solar space heating flat plate collectors are the
most common type of solar collector used.

22. 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 on glass surface so to be cleaned.
5. These are at fixed position so loose solar collection.

23. Flat-plate collectors are basically divided into two categories
according to their use,
(i) Water or liquid heaters and
(ii)Air heaters
Flat Plate Liquid Collectors:
These collectors use liquid as the heat transport
medium. Liquid flat plate collectors, heated liquid as it
flows through tubes in or adjacent to the absorber plate
as shown in Figure. The simplest liquid systems use
household water that is heated as it passes directly
through the solar collector and then flows to the house.

24. Solar pool heating uses liquid flat plate technology, but
the collectors are typically unglazed. The liquid tubes
can be welded to the absorbing plate, or they can be
an integral part of the plate. The liquid tubes are
connected at both ends by large diameter header
tubes.

26. Flat Plate Air Collectors
Schematic arrangement of a typical flat plate air collector
is shown in Figure.
It uses air as the heat transport medium.
Air flat plate collectors are used mainly for solar space
heating.
The absorber plates can be made of metal sheets, layers of
screen, or non-metallic materials.
The air flows past the absorber by using natural
convection or a fan. Since air does not conduct heat as
easily as liquid, air collectors are typically less efficient
than liquid collectors.

28. 1.With a neat sketch, discuss the important parts of any
solar flat plate collector.? Discuss the material aspect of
individual parts.
2.With a neat sketch discuss the operation of solar flat plate
air and liquid collectors.