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Effect of Side Reflectors on the Performance of Flat Plate Solar Collector: A Case Study for Asir Region, Saudi Arabia

  • Research Article - Mechanical Engineering
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Abstract

The solar collector’s efficiency is directly depended upon the solar radiation intensity falling on its surface. In order to increase the solar concentration over the collector, side reflectors are introduced which will concentrate both diffuse and direct radiations from the sun toward the collector surface. Therefore, in this study the influence of side (left and right) reflectors on efficiency improvement of the flat plate solar collector (FPSC) was analyzed. For determining the optimum tilt angles of side reflector and collector, a simulation model was developed by using TRNSYS software. The results obtained from simulation were validated with the experimental results for whole year during the daytime of semiarid Asir region of Saudi Arabia. Both simulation and experimental results indicate that optimal left side reflector angle is lowest in winter with the value of 38° and highest in summer with the value of 68°, while the optimal angle of right side reflector is lowest in summer with the value of 43° and highest in winter with the value of 74.5°. The thermal efficiency of FPSC has been improved significantly by adding side reflectors. The average thermal efficiency of FPSC without reflector was 46% which was increased to 58% by adding side reflectors. The addition of side reflectors increases the concentration of solar radiation falling on the collector surface and thus increases the output temperature of water by 12 °C as compared to input water temperature. Thus, the effective size of the system was reduced by adding side reflectors as thermal efficiency was enhanced which implies less space requirement for heating an appropriate quantity of water.

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Abbreviations

α :

Angle of solar altitude (°)

β :

Tilt angle of collector (°)

γ 1 :

Angle between the horizontal plane and left side reflector (°)

γ 2 :

Angle between the horizontal plane and right side reflector (°)

δ :

Angle of sun declination (°)

η coll :

Solar collector thermal efficiency

ω :

Sun hour angle (°)

ϕ :

The solar collector latitude (°)

\( \varepsilon_{\text{g}} ,\varepsilon_{\text{p}} \) :

Emissivity of plate glass and absorber plate

ρ Αlum :

Aluminum sheet reflectance

ρ g :

Ground reflectance

σ 1 :

Angle of incident from the left side reflector (°)

σ 2 :

Angle of incident from the right side reflector (°)

θ :

South facing solar zenith angle (°)

AM:

Optical air mass

D :

Daylight saving time (h)

d :

Performance coefficient of collector

e :

Root mean square deviation (°)

EOT:

Equation of time

G dif :

Diffuse solar radiation on horizontal surface (W/m2)

G 0 :

Solar constant (1366 W/m2)

G dif_col :

Total diffuse solar radiation (W/m2)

G dif_sky :

Sky-diffuse solar radiation (W/m2)

G dir_col :

Direct solar radiation on collector surface (W/m2)

G h :

Global solar radiation on horizontal surface (W/m2)

G in :

Global solar incident radiation (W/m2)

G sr1_incident :

Solar radiation incident on the left side reflector (W/m2)

G sr2_incident :

Solar radiation incident on the right side reflector (W/m2)

G gr_reflected :

Ground-reflected solar radiation (W/m2)

G sr1_reflected :

Solar radiation reflected from the left side reflector reaches the collector surface (W/m2)

G sr2_reflected :

Solar radiation reflected from the right side reflector reaches the collector surface (W/m2)

G net_col :

Net incoming solar radiation on the collector surface without the additional solar input from reflected solar radiation from reflectors (W/m2)

G tot_col :

Total solar radiation on the collector surface (W/m2)

H :

Altitude above the sea level (m)

I :

Intensity of solar radiation (W/m2)

L long :

Longitude of the solar collector (°)

L STM :

Local standard time meridian (°)

L ST :

Local solar time (h)

LT:

Local time (h)

N :

Day number of the year

r :

Correlation coefficient

T in :

Temperature distribution inside the tank (°C)

T a :

Ambient temperature (°C)

T out :

Outlet fluid temperature (°C)

T c :

Temperature of glass cover (°C)

T sky :

Sky temperature (°C)

T p :

Temperature of absorber plate (°C)

\( \dot{m} \) :

Mass flow rate

C p :

Specific heat capacity

\( \dot{Q}_{\text{useful}} \) :

Heat gain useful

F R :

Heat removal factor

A p :

Absorber plate area

F′:

Collector efficiency factor

Φ :

Plate effectiveness

U l :

Overall loss coefficient

S :

Absorber plate radiation absorption per unit area

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Acknowledgements

The authors of the present work feel grateful and would like to thank King Khalid University, Abha, and Center of Research Excellence in Renewable Energy (CoRE-RE), King Fahd University of Petroleum and Minerals, Dhahran, Saudi Arabia, for providing facilities and supports in performing experiments.

Author information

Authors and Affiliations

  1. Department of Mechanical Engineering, King Khalid University, P.O. Box 9004, Abha, 61413, Saudi Arabia

    Baiumy El-Assal

  2. Center of Research Excellence in Renewable Energy (CoRE-RE), King Fahd University of Petroleum and Minerals, Dhahran, 31261, Saudi Arabia

    Kashif Irshad & Amjad Ali

Authors
  1. Baiumy El-Assal
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  2. Kashif Irshad
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  3. Amjad Ali
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Corresponding author

Correspondence to Kashif Irshad.

Appendices

Appendix A

Time

T in

T out

T 3

T 4

T amp

I

8:30

31.9

43.5

34.8

33.7

17

230

9:00

34.5

47.3

33.1

35.1

17

305

9:30

36.5

50.1

32.1

36.1

18

370

10:00

38.1

54.6

33.6

37.5

18

397

10:30

40.5

59.4

34.8

38.4

18

479

11:00

42.1

65.3

35.1

39.4

19

535

11:30

43.7

67

36.9

40.8

19

606

12:00

44.7

68

37.8

42.7

19

708

12:30

45.8

70

38.7

43.1

20

788

13:00

46.3

72

39.4

44.5

20

805

13:30

47.9

70

40.5

41.8

21

847

14:00

48

68

41.5

43.8

21

793

14:30

44

55

42.6

41.5

21

787

15:00

42

50.6

43.1

41.3

20

732

15:30

40

48.2

52.6

40.8

20

645

16:30

38

46.3

50.7

39.2

19

585

17:00

37

44.5

41.8

37.5

19

483

Appendix B

See Table 4.

Table 4 Data for graph 17
Full size table

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El-Assal, B., Irshad, K. & Ali, A. Effect of Side Reflectors on the Performance of Flat Plate Solar Collector: A Case Study for Asir Region, Saudi Arabia. Arab J Sci Eng 45, 1035–1050 (2020). https://doi.org/10.1007/s13369-019-04221-x

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  • DOI: https://doi.org/10.1007/s13369-019-04221-x

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