PARABOLIC TROUGH SOLAR CONCENTRATOR

29-Jul-08 1RIZWAN MASOOD.

DESIGN AND FABRICATION OF “PARABOLIC SOLAR

CONCENTRATOR”with sole objective to define future projects to

save natural gas


RESEARCH TEAM

Rizwan Masood, Student of ChemicalEngineering Department, UET Lahore.

Dr. A.R. Saleemi, Chairman, Department ofChemical Engineering, UET Lahore.

Dr. A.H. Dilawari, Professor at SNGPL Chair onGas Engineering.

29-Jul-08 RIZWAN MASOOD. 3

.

SYNOPSISThis presentation includes following topics.

1. Solar energy and it's importance in present era.

2. Potential for solar energy in Pakistan.

3. Introduction to “Solar Concentrating Collectors”.

4. Design of “Parabolic Trough Concentrator”.

5. Basic Parts and Structure.

6. Performance and efficiency calculations.

7. Applications in modern processes.


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The sun has a surface temperature of 6000°C, maintained bycontinuous nuclear fusion reactions between hydrogen atomswithin its interior. These nuclear reactions will gradually convertall of the hydrogen into heavier elements, but this is a relativelyslow process and the sun should continue to supply power foranother 5 billion years.

The sun radiates huge quantities of energy into the surroundingspace, and the tiny fraction intercepted by the Earth'satmosphere, 150 million km away, is however equivalent to about15,000 times humanity's present rate of use of fossil and nuclearfuels.


1. SOLAR ENERGY.

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Even though approximatelyone-third of the interceptedenergy is reflected away by theatmosphere before reachingthe earth's surface, this stillmeans that a continuous andvirtually inexhaustible flow ofpower amounting to 10,000times our current rate ofconsumption of conventionalfuels is available in principle tohuman civilization.


1. SOLAR ENERGY.

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In this figure the places indark orange color arehigh solar insolationregions.



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Solar energy technologies have great potentialto benefit our nation. They can diversify ourenergy supply, reduce our dependence onnatural gas and imported fuels, improve thequality of the air we breathe, offset greenhousegas emissions, and stimulate our economy bycreating jobs in the manufacturing andinstallation of solar energy systems.



.2. Potential for solar energy in Pakistan.

MONTHLY AVG DAILY TOTAL RADIATION ON HORIZONTAL SURFACE FOR LAHORE.

Month Day length(hr) Rad (cal/cm2) Rad (cal/m2) Rad (J/cm2) Rad(j/m2) flux(W/m2)

JAN 10.2 256 2560000 1075.2 10752000 292.81046

FEB 10.9 333 3330000 1398.6 13986000 356.42202

MAR 11.8 435 4350000 1827 18270000 430.08475

APR 12.8 499 4990000 2095.8 20958000 454.81771

MAY 13.6 545 5450000 2289 22890000 467.52451

JUN 14 533 5330000 2238.6 22386000 444.16667

JUL 13.8 491 4910000 2062.2 20622000 415.09662

AUG 13.1 448 4480000 1881.6 18816000 398.98219

SEP 12.2 436 4360000 1831.2 18312000 416.93989

OCT 11.2 361 3610000 1516.2 15162000 376.04167

NOV 10.4 297 2970000 1247.4 12474000 333.17308

DEC 10 244 2440000 1024.8 10248000 284.66667


.3. INTRODUCTION. Concentrator: Concentrator are oriented

to track the sun so that the beamradiation will be directed onto theabsorbing surface. Collector that directsradiation onto the receiver.

Collector: The aperture of theconcentrator is the opening throughwhich the solar radiation enters theconcentrator

Receiver: Radiation is absorbed andconverted to some other energy form(e.g. heat).


.3. INTRODUCTION.

Concentration Types

a) Parabolic trough collector

b) Linear Fresnel collector

c) Central receiver systemwith dish collector and

d) Central receiver systemwith distributed reflectors


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a) Parabolic Trough Collector

It is a principle of geometry that aparabolic reflector pointed at thesun will reflect parallel rays of lightto the focal point of the parabola.

A parabolic trough is a one-dimensional parabola that focusessolar energy onto a line. Physically,this line is a pipe with a flowingliquid inside that absorbs the heattransmitted through the pipe walland delivers it to the thermal load.


3. INTRODUCTION.

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Parabolic Trough Collector (con)

A trough captures sunlight over a large aperture area andconcentrates this energy onto a much small receiver area,multiplying the intensity of the sun by a concentrationratio in the range of 10-80. It is the process ofconcentration that allows troughs to delivery hightemperature thermal energy.

However, to achieve such concentration, a trough tracksthe sun in one axis continually throughout the day. Therequired tracking accuracy is within a fraction of a degree.


3. INTRODUCTION.

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Parabolic Geometry (CON)

A parabola is the locus of a point that moves so that its distances from a fixed line and a fixed point are equal.

The equation of a parabola is as follow.

X2 = 4a Y

where, 4a = lattice rectum

a = Focus point



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This may be found for a particular

parabola from Equation byintegrating a differential segmentof this curve and applying thelimits x = h and y = d/2 aspictured in Figure. where d is thedistance across the aperture ofthe parabola as shown in figureand h is the distance from thevertex to the aperture.



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From the Figure the result is

where S= length of parabolic arc.

The cross sectional area of the space enclosed between aparabola and a line across its aperture and normal to the axis isgiven by

Reflecting surface area of a parabolic trough can be calculatedas follow.

As = S . L where , L = length of through.


4. Design of “Parabolic Trough Concentrator”. (CON)

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There are basically five major part of a parabolic trough concentrator system, which are as follow;

a) Reflecting surface.

b) Absorber.

c) Support structure.

d) Tracking system.

e) Pumping system.


5. Basic Parts and Structure.

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5. Basic Parts and Structure (CON)

a) Reflecting surface.

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b) Absorber.


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c) Support structure.



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d) Tracking system.



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e) Pumping system.



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PERFORMANCEThere are basically two types of performances which are to beconsidered during design .

a. Optical performance.b. Thermal performance.

a) Optical performanceoptical performance of a solar concentrator depends on the

optical characteristics of reflecting surface, glass envelope,absorber and also on geometry of parabola


6. Performance and Efficiency Calculations.

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PERFORMANCEa) Optical performance

absorbed radiation per unit area of unshaded aperture isgiven by:

S=Ibρ(γτα) Kγτα

Where Ib is effective incident beam radiation on theplane of aperture, ρ is the reflectance of the concentrator, γ isintercept factor, τ is transmittance, and α is absorptance. Kγτα

is an incidence angle modifier that can be used to account fordeviations from the normal of the angle of incidence of theradiation on the aperture



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PERFORMANCE

b. Thermal performance

The actual useful energy gain:

Where Aa is the unshaded area of the concentrator apertureand Ar is the area of the receiver, S is the absorbed solarradiation per unit of aperture area, Ti and Ta are inlet fluidtemperature and ambient temperature FR is the collector heatremoval factor.



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OVER ALL EFFICIENCY

Over all efficiency of a solar collector is based on the optical

and thermal performances.

the over all efficiency can be calculated as;

η = (Qu / Ib) × 100



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Solar Concentrating Collector are currently used forCooling and air-conditioning

Steam generation (for electricity power-plants)

Desalination of sea water

Production of hot water for domestic and industrial use

Production of hydrogen gas


7. Applications

THANK YOU


PARABOLIC TROUGH SOLAR CONCENTRATOR

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