COMPARISON OF USEFUL SURFACE OF DIFFERENT TYPE OF SOLAR COLLECTORS

CIOSTA 29 June - 1 July 2011, Vienna

Department of ep e oPhysics and

Process ControlINSTITUTE FOR

ENVIRONMENTAL ENGINEERING SYSTEMS

FACULTY OF MECHANICALENGINEERINGENGINEERING

SZENT ISTVÁNUNIVERSITYUNIVERSITY

Gödöllő, Páter K. u. 1. H-2103 Hungary

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Ivett KocsányE-mail: Kocsany.Ivett@gek.szie.hu

Tel: +36 28 522055Fax: +36 28 410804

Fizika.Tanszek@gek.szie.huhttp://fft.szie.hu

CONTENTS

• IntroductionIntroduction• Objectives• Geometrical model scheme of flat plate and • Geometrical model scheme of flat plate and

vacuum tube collectors• R lt• Results• Conclusion

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BACKGROUND

Due to a different of geometry under the same incomingDue to a different of geometry, under the same incomingradiation and the same incidence angle the two solarcollectors showed many differences, like:y ,

• different efficiency,f l• useful area,

• reflected radiation.

Several reasons e.g. shape (active surface), convective heatloss and spectral sensitivity are different.p y

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OBJECTIVESO J C V S

• Analyze the developed geometrical model.

•Determine the active surface for separately flat plate and vacuum tube collector under different incoming radiation.g

• To get a know-how about the differences of each type of collector operationcollector operation.

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The equipment

Measured parameters:

• temperature of inlet and outlet solar fluid temperature of inlet and outlet solar fluid, • solar liquid volume flow rate, • solar radiation, • environmental temperature

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• environmental temperature.

Measuring system• Temperature of outlet and inlet solar fluid (Pt1000 platinum ohm

temperature sensor)

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•Volume rate of solar fluid (Zenner Zelsius )

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•Incoming radiation (Kypp & Zonen piranometer)g ( ypp p )

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Geometrical model Based on results of spectral measurement the geometrical model wasBased on results of spectral measurement the geometrical model wasimproved with the angle dependence of the absorption at the differentparts of the active surface to determine the daily incoming radiation.

The calculation is presented on all-glass evacuated tube solar collector and also on flat platesolar collector.

na.) Flat plate collector

ϕ

ϕ

AusefulAuseful=A*cos ϕ(t)

.

ϕ : the angle between the beam radiation on a surface and the normal to the surface

The rate of absorbed radiation is principally depends on the angle of incident radiation.

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e ate o abso bed ad at o s p c pa y depe ds o t e a g e o c de t ad at o .

b.) Vacuum tube collector

D=5,2 cm l = 2 cmL=180 cm

Parameters:D: glass tube diameter, cmd: absorber tube diameter, cml di b b D 5,2 cm l 2 cm

d=4,5 cml: distance between tubes, cmL: length of tube, cm

Scheme of vacuum tubes

R.

Determine limit angler

r

ϕlimit

R RDetermine limit angle(ϕ) of the incoming light which passes between two tubes r

.two tubes

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ϕlimit = 38°40’

Shading effectWhen the incoming radiation angle is lower than limit angle ( ϕ < ϕo ) there will beappear an overshadow from one tube to the neighbor.

g

d

r

x y

cd-c

ϕϕy

r

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Sets of equations:x

ydyxtg

−

=ϕ

'

I.

rt

cdyd

−=ϕcosII.

III cdtg

−=ϕIII.

tgrdy −=ϕr

d

ytgxtg⋅= ϕ

ϕ

x y

cd-c

rϕϕ

r

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Measurment analysis

Used equations:Used equations:

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The useful area under different angle of incoming radiation on a horizontal plain surface

Results

1.4Vacuum tube collector

0.6

0.8

1

1.2

area

[m2]

0

0.2

0.4

0 10 20 30 40 50 60 70 80 90

Use

ful a

0 10 20 30 40 50 60 70 80 90Angle of incoming radiation [°]

Flat plate collector

11.21.41.61.8

l are

a [m

2]

00.20.40.60.8

1

Use

ful

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00 10 20 30 40 50 60 70 80 90

Angle of incoming radiation [°]

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Result

1 20

Efficiency of FP and VC

0.80

1.00

1.20

ency

0.20

0.40

0.60E

ffic

ie

0.00

10:23 11:35 12:47 13:59 15:11 16:23

Time

FPEnergy production (MJ/m2)

VCFPTime intervall (MJ) 21,014Area (MJ/m2) 13,470

VC14,94412,351

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CONCLUSIONCONCLUSION

•Based on such observation data analysis was elaborated for understanding thebehavior of different technologies. Due to the discrepancy it can be concludedwhen the angle of incidence radiation is between 40-60° when ray of sunlight arewhen the angle of incidence radiation is between 40-60 when ray of sunlight arelateral better used for vacuum tube collector then flat plate which active surface isbigger at near to the vertical rays (60-90°).

•In the future work it is planned to determine the rate of the reflected and absorbedpower as a function of the incidnent angle.

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Thank you for your attention!

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