In this PPT, types of solar thermal power generation technology has been explained

1. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 1
Autumn Semester
Solar Thermal Energy Conversion
By
Prof. A.K Ranjan

2. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 2
Autumn Semester
• A solar collector is a special kind of heat exchanger that transforms solar radiant
energy into heat.
• A solar collector differs in several respects from more conventional heat exchangers.
The latter usually accomplish a fluid-to-fluid exchange with high heat transfer rates
and with radiation as an unimportant factor.
• In the solar collector, energy transfer is from a distant source of radiant energy to a
fluid. The flux of incident radiation is, at best, approximately 1100 W/m2 (without
optical concentration), and it is variable.
• The wavelength range is from 0.3 to 3 µm, which is considerably shorter than that of
the emitted radiation from most energy-absorbing surfaces. Thus, the analysis of solar
collectors presents unique problems of low and variable energy fluxes and the
relatively large importance of radiation.
Introduction

3. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 3
Autumn Semester

4. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 4
Autumn Semester
• Flat-plate collectors can be designed for applications requiring energy delivery at
moderate temperatures, up to perhaps 100◦C above ambient temperature.
• They use both beam and diffuse solar radiation, do not require tracking of the sun,
and require little maintenance.
• They are mechanically simpler than concentrating collectors.
• The major applications of these units are in solar water heating, building heating, air
conditioning, and industrial process heat. Passively heated buildings can be viewed
as special cases of flat-plate collectors with the room or storage wall as the
absorber.
Flat-plate collectors

5. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 5
Autumn Semester
DESCRIPTION OF FLAT-PLATE COLLECTORS
• The important parts of a typical liquid heating flat-plate solar collector, as shown in Figure
6.1.1, are the ‘‘black’’ solar energy-absorbing surface with means for transferring.
• The absorbed energy to a fluid, envelopes transparent to solar radiation over the solar
absorber surface that reduces convection and radiation losses to the atmosphere, and back
insulation to reduce conduction losses.
• Figure 6.1.1 depicts a water heater, and most of the analysis of this chapter is concerned
with this geometry. Air heaters are fundamentally, the same except that the fluid tubes are
replaced by ducts.
• Flat-plate collectors are almost always mounted in a stationary position (e.g., as an integral
part of a wall or roof structure) with an orientation optimized for the particular location in
question for the time of year in which the solar device is intended to operate.
• For many applications, it is desirable to deliver energy at temperatures higher than those
possible with flat-plate collectors.

6. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 6
Autumn Semester

7. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 7
Autumn Semester
CONCENTRATORS
• Concentrators can be reflectors or refractors can be cylindrical or surfaces of revolution
and can be continuous or segmented.
• Receivers can be convex, flat, or concave and can be covered or uncovered.
• Many modes of tracking are possible.
• To avoid confusion of terminology, the word collector will be applied to the total system,
including the receiver and the concentrator.
• The receiver is that element of the system where the radiation is absorbed and converted to
some other energy form; it includes the absorber, its associated covers, and insulation.
• The concentrator, or optical system, is the part of the collector that directs radiation onto
the receiver.
• The aperture of the concentrator is the opening through which the solar radiation enters the
concentrator.

8. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 8
Autumn Semester
Concentrator geometry
Aperture (W): The plane at the opening of the concentrator through which
solar radiation enters the concentrator
Concentration ratio (C): This is the ratio of the aperture to the area of the
absorber pate.
Intercept factor: This is the ratio of the incident radiation on the absorber
plate after concentration to the actual incident radiation crosses the aperture
Acceptance angle: This is the measurement of the deviation in the incident
angle from the normal to the aperture area.
a
D
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a
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m C
C
focus
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For

 2
3
,
2
,
sin
1
focus
point
and
sin
1



9. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 9
Autumn Semester

10. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 10
Autumn Semester
Parabolic Trough Systems
Description: Parabolic troughs consist of long, curved mirrors that focus sunlight onto a
receiver tube (absorber) located along the focal line of the parabola. The mirrors track the sun
along one axis.
Heat Transfer: A heat transfer fluid (HTF), such as synthetic oil or molten salt, flows
through the tube, absorbing the concentrated solar energy and heating up to high
temperatures.
Electricity Generation: The heated HTF is then used to generate steam in a heat exchanger,
which drives a conventional steam turbine for electricity production.
Applications: This is the most mature and widely deployed solar thermal technology, with
several commercial-scale power plants operating worldwide.

11. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 11
Autumn Semester
Parabolic Trough Systems
Utilize parabolic mirrors to
concentrate light onto a receiver that
runs parallel to the mirror.
-Second surface silvered
glass
Low iron glass, 4mm thick,
with very high transmittance
Solar weighted reflectivity
~93.5%
Each mirror is ~2m^2

12. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 12
Autumn Semester

13. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 13
Autumn Semester
Fresnel Reflectors
•Design:
Linear Fresnel collectors consist of an array of nearly flat, slightly curved mirrors (reflectors)
that focus sunlight onto a linear receiver positioned above the mirrors. These mirrors track the
sun's path across the sky to maximize solar energy absorption.
• Receiver:
The receiver is a tube that runs parallel to the mirror array and contains a working fluid (such
as water or thermal oil) that is heated by concentrated sunlight.
• Efficiency and Cost:
Fresnel collectors are generally less expensive to manufacture and install than parabolic
troughs or central receiver systems due to the simpler mirror design. However, they typically
have lower thermal efficiency because of the less precise focus of sunlight on the receiver.
•Applications:
They are used for electricity generation, desalination, and industrial process heat
applications, offering a cost-effective solution for moderate temperature requirements.

14. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 14
Autumn Semester
Fresnel Reflectors
 Similar to Trough
Design
 Easy to cover
ground area and
track the sun
effectively, single
axis
 An entire row of
mirrors reflect to a
single overhead
receiver

15. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 15
Autumn Semester

16. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 16
Autumn Semester
Central Receiver System
Description: : Solar tower systems use a large field of flat, movable mirrors called heliostats
to focus sunlight onto a receiver located on top of a central tower.
Heat Transfer: In the receiver, the concentrated sunlight heats a fluid, which can be air,
water, molten salt, or another HTF, to very high temperatures.
Electricity Generation: The thermal energy is used to produce steam that drives a turbine
connected to a generator. Some systems use molten salt as the HTF and for thermal energy
storage, allowing for electricity generation even when the sun is not shining.
Applications: Solar tower systems can achieve higher temperatures and efficiencies
compared to parabolic trough systems.

17. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 17
Autumn Semester
Rankine cycle
system
Central receiver
•Tower height- 80m
• Reflectic area- 71000 sq. m
• 1800 heliostat
• Steam as fluid
• 10MW
Central receiving power plant

18. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 18
Autumn Semester
Solar-1, 10 MW plant

19. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 19
Autumn Semester
Central Receiver System
The central-receiver, or ‘‘power tower,’’ concept for generation of electrical energy from
solar energy is based on the use of very large concentrating collectors.
The optical system consists of a field of a large number of heliostats, each reflecting beam
radiation onto a central receiver. The result is a Fresnel-type concentrator, a parabolic
reflector broken up into small segments, as shown in Figure 7.1.1(f).
Several additional optical phenomena must be taken into account. Shading and blocking can
occur (shading of incident beam radiation from a heliostat by another heliostat and blocking
of reflected radiation from a heliostat by another which prevents that radiation from reaching
the receiver).
As a result of these considerations, the heliostats are spaced apart, and only a fraction of the
ground area ψ is covered by mirrors. A ψ of about 0.3 to 0.5 has been suggested as a
practical value.

20. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 20
Autumn Semester
Central Receiver System
The maximum concentration ratio for a three-dimensional concentrator system with radiation
incident at an angle θi on the plane of the heliostat array (θi = θz for a horizontal array), a rim
angle of φr, and a dispersion angle of δ, if all reflected beam radiation is to be intercepted by
a spherical receiver,
For a flat receiver, the concentration ratio is
As with linear concentrators, the optimum performance may be obtained with intercept factors
less than unity.
The designer of these collectors has additional considerations to take into account. The
heliostat field need not be symmetrical, the ground cover ψ does not have to be uniform, and
the heliostat array is not necessarily all in one plane. These collectors operate with high
concentration ratios and at relatively high receiver temperatures.

21. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 21
Autumn Semester
Water heating
Ironing
Pressure
cooking
Fraying

22. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 22
Autumn Semester
Parabolic Dish System
Description: Parabolic dish systems consist of a parabolic-shaped reflector that focuses sunlight
onto a receiver located at the focal point of the dish.
 A parabolic dish or solar furnace is a large reflector that concentrates thermal energy into a
single focal point
 The focal point can contain a Stirling Engine to generate electricity or the energy can be focused
and used in industrial processes
 On a small scale, a reactor can be used in the same way a solar oven is used
Heat Transfer: The receiver absorbs the concentrated sunlight, converting it into thermal energy
that heats up a HTF or directly heats air.
Electricity Generation: Instead of heating water to drive a steam turbine, each dish is typically
equipped with a Stirling engine or a microturbine at the focal point that converts thermal energy
directly into mechanical energy to generate electricity.
Applications: Parabolic dish systems are highly efficient on a small scale and can be used in
standalone applications or grouped together for larger power demands.

23. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 23
Dish/Stirling Designs
 Large(5-7m dia) individual
parabolic dish mirrors
reflect onto a thermal
receiver and stirling engine
which powers a generator
 Advantage for distributed
power
 Typically, same fluid is
used for heat transfer and in
engine
 3-25 kW each unit typical
electricity generation
 Net 30% efficiency
achieved

24. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 24

25. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 25
Future Improvements
 Advanced optical materials are key
 Reflective flexible coatings with ultra high
reflectance and which are durable and easy to clean
 Materials which have high heat capacities and good
thermal conductance
 Continued optimization of design to drive down
capitol costs and increase efficiency
 Strategic management of heat transfer fluids which
also double for thermal storage so plant can generate
electricity at night

26. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 26
Benefits of using CSP
 Extremely limited environmental impacts, essentially no
CO2/NO2 emissions
 Evolutionary instead of revolutionary technology,
resembles and uses much of the same equipment as current
fossil fuel plants, easy to incorporate into the existing
electricity infrastructure
 Already proven to be dependable and efficient(SEGS)
 Though initial investments are larger than other forms, the
fuel used is unlimited, we don't have to mine or discover
more which leads to heavy environmental impacts
 Fast approaching costs of fossil fuels

27. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 27
Solar Steam Cooking System for 15000
people (worlds largest)
Tirumala Tirupati Devasthanams (TTD)
Andhra Pradesh, India
Cooking by parabolic disk

28. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 28
Autumn Semester
Cocker installed in Saidham

29. GEC Bhojpur
DEE
Solar thermal energy conversion Slide 29
Autumn Semester
Name of system Contributing
radiation
Temp (oC) Efficiency
(%)
Cylindrical parabolic
collector
Direct 100 to 400 50 - 60
Parabolic point focus Direct Up to 1000 70-80
Concentrated collector: comparison