1. Presentation by:
Srikanth Reddy
Prakash Chandra sharma

2. Contents
 Introduction
 Basic characteristics
Components and structure
Specifications(size, material, HTF(heat transfer fluid))
 Operation and maintenance
Power generation technology(thermal cycle)
Cleaning
Drives
tracking
 Performance comparison
 Cost comparison
 Globally installed capacity of each technology

3. List of abbreviations:
 PTC: Parabolic Trough Collectors
 CRS: Central Receiver Systems
 LFC: Linier Fresnel Collectors
 SD: Solar Dish
 CR: Concentration Ratio
 HTF: Heat Transfer Fluid

4. Introduction
Parabolic Trough
collector(PTC)
Central Receiver
Systems(CRS)
Linear Fresnel
Collectors(LFC)
Solar Dish(SD)
PTC is a line focusing
system that uses a
moving parabolic
reflector to concentrate
direct solar radiation
onto linier receiver.
CRS is a point-focusing
system that uses
individually tracked
heliostat mirrors to
concentrate solar
radiation onto the
stationary receiver
located on the top of
solar tower.
Fresnel Collector is a
line-focusing system
which uses individually
tracked reflector rows to
concentrate onto a
stationary linier receiver.
Solar Dish is a point
focusing system that
uses curves solar
tracking mirrors to
concentrate direct solar
radiation on to a receiver

5. Components and Structure-PTC
 Pylons: To support the system,
these were attached to some
body or rimmed into ground.
 Torque body: Which could be
made of some kind of framework
or a simple solid tube, is
mounted onto these pylons.
 Cantilever Arms: To hold the
mirror facets.
 Absorber: To absorb the
concentrated sunlight and
convert it with high efficiency to
heat.
 Metal bellows: These are used at
either side of absorber tube to
accommodate thermal expansion
difference between steel and
glass.
 Getter: To keep and maintain
vacuum.

6. Specifications
 Size: The normal range of the collector/aperture area ranges from 817 m2 to 1000 m2
these values may reach about 1700 m2 .
 Material: The pylons, torque body and cantilever arms are made of steel with paint or
galvanization to avoid corrosion. Stainless steel, plastic is used for smaller
applications[1] and to build more rigid PTCs concrete structures are fabricated on-site[2].
 Heat Transfer Fluid (HTF):
 Thermal oil(biphenyl-diphenyl oxide) : Up to 300oC[3]
Advantage: Low vapour pressure
Disadvantage: Low viscosity
which is critical in start-up after the plant is cooled down.
 Water/steam:
Advantages: Reduction in thermal loss through elimination of thermal oil.
lower pressure drop resulting in lower pump work
Disadvantages: Eventual instabilities at the two-phase flow.
 Molten nitrate salt: 1000oC[3] and above
Advantages: High operating temperatures
Disadvantage: The freezing points were typically too high to prevent freezing
during off-sun and winter periods

7. Operation and maintenance
 Cleaning: The mirrors should be cleaned/washed at least once in 2 months. Demineralized
water must be used for wet cleaning. The reflectivity of surface washed with hard water is
lower than that of the surfaces left with dirt. Usually spraying washer is used.
 Maintenance of HTF quality[4]: The normally used HTF is synthetic oil with lower and
upper temperature levels of 14 and 400 degrees respectively. For satisfactory operation it
should be operated in that limit. Operating at higher temperatures increases the thermal
degradation.
 Drives: Most of the currently installed systems are using hydraulic drives which are robust
and can provide strong forces with small steps(typically 1/10mm).
 Tracking system: Either one or two dimensional to attribute the daily and seasonal
variations, the sensor is located on parabolic trough.

8. Layout of PTC plant[5]

9. LOCE[5] and Resource Requirements[6] of PTCs

10. Performance and cost analysis[7]-PTC

11. Components and structure-CRS
 A CRS includes solar tower and heliostat field.
 Tower: Normally the tower is a monopole whose
structure is similar to that of a wind turbine or
steel framework constructions. The shape can be :
1.Cylindrical
2.Rectangular
 Heliostat field: It is made up of individual
heliostats. Each heliostat follows the sun in two
dimensions with the help of dual axis tracking
system and concentrates the radiation onto
receiver area.
 Receiver: The receiver shape can be flat,
cylindrical, pyramidal depending upon the
heliostat field. To minimize thermal loss receiver
is covered by cavity of quartz glass.
 Tower Reflector: In this the receiver is placed on
ground[8]. The radiation from the heliostats is
reflected on to hyperboloidal mirror which is
placed on tower and then the radiation reaches to
receiver. It helps in solar chemistry where the
reactants are solids.

12. Specifications
 Size: The height of tower depends on the area of
heliostat field, varies from as low as 150 ft. to
order of hundreds with the tallest tower in world
is 750ft. [9] high in California.
 Material: Towers are mainly constructed of steel
or concrete. Factory made tower structure which
are used for wind turbine were also been
available, old models used the microwave relay
towers.
 Heat Transfer Fluid(HTF):
Water/Steam: It is used as HTF for a long
time as it is used in conventional steam
cycles with good thermal conductivity,
absence of heat exchanger and high
specific heat capacity as advantages and
storage, two phase flow and corrosion as
disadvantages.
Molten salt: The molten salt for both heat
receiver and storages yields high capacity
factors[10].It is best developed CRS
technology today. It can be operated only
in open cycle.
Air: Air as HTF is environmentally Benin
and free. The disadvantage being low flow

13. Operation and Maintenance-CRS
 Cleaning: Cleaning is normally carried at night times. The adjacent heliostat rows
were driven in opposite direction to facilitate cleaning.
 Drives: Depending upon the size of heliostats either hydraulic or electrical
drives(stepper motor) were used.
 Tracking: Two dimensional tracking is used in most of the cases. Separate
microwave towers are used to hold sensors which detects the reflected sun rays and
tracks the sun accordingly.

14. Layout of CRS plant

15. Performance and cost Indicators[11]

16. Components and Structure-LFC
 It consists of a collector consists of a receiver with selectively coated absorber tube,
concentrator, cover plate and thermal insulation.
 Reflectors: The reflectors were long flat linear mirrors which were tracked individually.
The adjacent reflectors should be spaced carefully to avoid shading losses.
 Receiver: The receiver is based on a vacuum tube and a secondary reflector on top of it.
 Secondary Reflector: It has the task not to concentrate but to direct the radiation that
misses the entrance of the absorber aperture again to the absorber tube. Most common
are CPCs which are designed for temperatures above 1200oC.Hexagonal shapes were
often used.

17. Specifications:
 Size: The size width of the mirrors should be carefully co-ordinated with the gaps
between mirrors and height of receiver[12]. Todays power plants with Fresnel
collectors have a typical size of 50MW gross electrical output. The risk is high
due to limited experience and the technology has not yet proven in full-scale size.
 Material: These uses flat glass mirrors and has a significant material reduction
compared to parabolic trough collectors.
 HTF: Water, air or oil is used as HTF. When using Direct Steam Generator(DSG)
no heat exchanger is required but with thermal oil heat exchanger is imperative.

18. Layout of LFC plant

19. Components and structure-Solar Dish
 The major parts are solar concentrator(dish) and power
conversion unit.
 Dish: It is mounted on a structure that tracks the sun
continuously. The solar concentrators are supported
with a truss structure in order to hold the mirrors of the
concentrator.
 Power conversion unit: It includes the thermal receiver
and the engine/generator.
 Thermal Receiver: It is the interface between dish and
engine. It absorbs the radiation and transfers the heat to
engine. The thermal energy cab be either transported to
central generator or converted directly into electricity.
The receiver transfers its heat to HTF.
 Engine/Generator: It is the sub system that takes heat
from thermal receiver and uses it to produce
electricity[13].
 Stirling Engine: It heated HTF to move pistons and
create mechanical power which rotates the generator. It
has higher efficiency high power density, low
maintenance and long life.

20. Specifications:
 Size: They were flexible in terms of size and scale since they can be operated
individually or a in cluster. The dish/engine systems produce relatively small
amounts of electricity typically 3-25 kW.
 Materials: concentrators use a surface of Aluminium or silver, deposited on glass
or plastic. Since the focal length is low thin glass mirrors are required to
accommodate required curvatures low iron content ,silvered solar mirrors can
have high reflectivity up to 94%[14].
 HTF: Usually liquid hydrogen or helium is used as HTF to facilitate the heat
transfer between receiver and engine[13].

21. Operation and maintenance
 Cleaning : The key difference between solar dish and
other systems is that the solar dish technology does not use
water in the power conversion process(neither for steam
nor for cooling),and water is used only for
washing/cleaning.
 Maintenance: Scheduled maintenance can be done on
individual units while the others continue to generate
power.
 Tracking and control: The solar dish system is mostly
controlled by microprocessor based control which also
enables switching off from solar to fuel operation is a
hybrid system is integrated.

22. Layout of solar dish system/plant

23. Performance and cost analysis[15]:

24. Performance and economic comparison:
Parabolic Trough Dish/Engine Power Tower
Size 30-320 MW 5-25 kW 10-200 MW
Operating Temperature
(ºC/ºF)
390/734 750/1382 565/1049
Annual Capacity Factor 23-50 % 25 % 20-77 %
Peak Efficiency 20%(d) 29.4%(d) 23%(p)
Net Annual Efficiency 11(d)-16% 12-25%(p) 7(d)-20%
Commercial Status
Commercially Scale-up
Prototype
Demonstration AvailableDemonstration
Capital
requirements($/kW)
3000 1690 2605
O&M costs $/kW-yr 43 11 30
Technology
Development Risk
Low High Medium
Storage Available Limited Battery Yes
Hybrid Designs Yes Yes Yes

25. Globally installed capacity of each
technology

26. References:
 [1] Anthrakidis A, Kroker J, and Rusack M, et al,(2009) technical improvement of
small parabolic trough collector. Berlin, Germany: solarPACES
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stage solar trough concentrator based on pneumatic polymeric structures. Berlin,
Germany: solarPACES.
 [3]Comprhensive Renewable Energy- Elsevier.
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heat transfer fluid in concentrating solar facilities.Proceedings solar PACES.
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1996. Report ISBN 3-9804901-0-6.
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Endesa, Cologne,Germany: June 1994.
 [8]Segal A and Epstein M(2006) practical considerations of designing large scale
beam down optical systems solarPACES conference.19-23 june,Sevilla, Spain.

27. References(cntd.):
 [9] http://www.treehugger.com/renewable-energy/worlds-tallest-solar-
tower-be-erected-california-twice.html
 [10]Ortega JI, Burgaleta JI, and Tellez FM (2008) central receiver
system(CRS) solar power plant using molten salt as heat transfer fluid.
Journal of Solar Energy Engineering.
 [11] Stoddard, M.C., et. al., SOLERGY - A Computer Code for Calculating the
Annual Energy from Central ReceiverPower Plants, Sandia National Laboratories,
Livermore, CA: May 1987. Report SAND86-8060.
 [12]Mertins M, Lerchenmuller H, and Haberle A (2004) Geometry optimization of
Fresnel collectors with economic assessment, proceedings Eurosun conference,
Freiburg.
 [13]Kroposki B, Morgolis R, and Ton D (2009) An overview of solar technologies.
IEEE power & Energy magazine.
 [14]Winter C-J, Sizmann RL, and Vant-Hull LL (1991) solar power plants. Berlin,
Germany: Springer.
 [15] Kolb, G.J., “Evaluation of Power Production from the Solar Electric
Generating Systems at Kramer Junction: 1988 to 1993,” Solar
Engineering 1995, Proceedings of the ASME Solar Energy Conference,
Maui, HI (1995).