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

  • Baiumy El-Assal
  • Kashif IrshadEmail author
  • Amjad Ali
Research Article - Mechanical Engineering
  • 26 Downloads

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.

Keywords

Flat plate collector Reflector Solar energy Energy efficiency 

List of Symbols

α

Angle of solar altitude (°)

β

Tilt angle of collector (°)

γ1

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

γ2

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

δ

Angle of sun declination (°)

ηcoll

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

ρΑlum

Aluminum sheet reflectance

ρg

Ground reflectance

σ1

Angle of incident from the left side reflector (°)

σ2

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

Gdif

Diffuse solar radiation on horizontal surface (W/m2)

G0

Solar constant (1366 W/m2)

Gdif_col

Total diffuse solar radiation (W/m2)

Gdif_sky

Sky-diffuse solar radiation (W/m2)

Gdir_col

Direct solar radiation on collector surface (W/m2)

Gh

Global solar radiation on horizontal surface (W/m2)

Gin

Global solar incident radiation (W/m2)

Gsr1_incident

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

Gsr2_incident

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

Ggr_reflected

Ground-reflected solar radiation (W/m2)

Gsr1_reflected

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

Gsr2_reflected

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

Gnet_col

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

Gtot_col

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

H

Altitude above the sea level (m)

I

Intensity of solar radiation (W/m2)

Llong

Longitude of the solar collector (°)

LSTM

Local standard time meridian (°)

LST

Local solar time (h)

LT

Local time (h)

N

Day number of the year

r

Correlation coefficient

Tin

Temperature distribution inside the tank (°C)

Ta

Ambient temperature (°C)

Tout

Outlet fluid temperature (°C)

Tc

Temperature of glass cover (°C)

Tsky

Sky temperature (°C)

Tp

Temperature of absorber plate (°C)

\( \dot{m} \)

Mass flow rate

Cp

Specific heat capacity

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

Heat gain useful

FR

Heat removal factor

Ap

Absorber plate area

F

Collector efficiency factor

Φ

Plate effectiveness

Ul

Overall loss coefficient

S

Absorber plate radiation absorption per unit area

Notes

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.

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Copyright information

© King Fahd University of Petroleum & Minerals 2019

Authors and Affiliations

  1. 1.Department of Mechanical EngineeringKing Khalid UniversityAbhaSaudi Arabia
  2. 2.Center of Research Excellence in Renewable Energy (CoRE-RE)King Fahd University of Petroleum and MineralsDhahranSaudi Arabia

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