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Determination of the optimal tilt angle for a tilted solar panel in Kathmandu, Nepal using isotropic model

Author Affiliations

  • 1St. Xavier's College, Maitighar, Kathmandu, Nepal
  • 2Department of Physics, St. Xavier's College, Maitighar, Kathmandu, Nepal
  • 3Department of Physics, St. Xavier's College, Maitighar, Kathmandu, Nepal

Res. J. Physical Sci., Volume 7, Issue (2), Pages 8-14, May,4 (2019)


Different types of geographical and climatological parameters are necessary to evaluate the performance of a solar panel. A solar device will perform efficiently if it receives maximum solar radiation throughout the day. To achieve this, the angle of tilt of the panel should be optimized periodically. This project aims to calculate the optimal angle oftilt for any solar panel located in Kathmandu (27.7°N latitude) for every month using Liu and Jordan's Isotropic Model. The monthly and the annual optimum tilt angles are calculated for a south facing tilted surface which are almost equivalent to the latitude of the site. Further, the optimum tilt angle decreases from a peak value of 28° in January to a minimum of 20° in July and again rises to a maximum of 28° in December. It is found that the tilt angle should be optimized annually or monthly in order to boost the effectiveness of the sun oriented collector as opposed to setting it on the level ground which is the usual practice. However, there will be an annual loss of 0.0714% in irradiance if the optimization process is conducted annually instead of monthly.


  1. Handoyo E.A. and Ichsani D. (2013)., The optimal tilt angle of a solar collector., Energy Procedia, 32, 166-175.
  2. Willson R. (1999)., Solar Irradiance Variation., The many faces of the Sun, 19-40.
  3. Aggarwal R. (2013)., Estimation of Total Solar Radiation on Tilted Surface., Journal of Environmental Engineering and Technology, 2(1), 4-6.
  4. Fadare D. (2009)., Modelling of Solar Energy Potential in Nigeria using an Artificial Neural Network Model., Applied Energy, 86(9), 1410-1422.
  5. Glover J. and McCulloch F. (1958)., The empirical relationship between solar radiation and hours of sunshine., Q.J.R Met. Society, 84(360), 56-60.
  6. Reddy S. (1971)., An empirical method for the estimation of net radiation intensity., Solar Energy, 13(2), 291-292.
  7. Sabbagh J., Sayigh A.A.M. and El -Salam (1977)., Estimation of the total solar radiation from meteorological data., Solar energy, 19, 307-311.
  8. Pant B.P. and Poudyal K.N. (2017)., Evaluation of global solar radiation with single and multiple parameter models in mid - western region Jumla, Nepal., Research Journal of Physical Sciences, 5(8), 1-6.
  9. Jamil B., Siddiqui A.T. and Akhtar N. (2016)., Estimation of Solar Radiation and Optimum Tilt Angles for South - facing Surfaces in Humid Subtropical Climatic Region of India., Engineering Science and Technology, an International Journal, 19(4), 1826-1835.
  10. Li D.H. and Lam T.N. (2007)., Determining the Optimum Tilt Angle and Orientation for Solar Energy Collection Based on measured Solar radiance data., International Journal of Photoenergy, 9. http://dx.doi.org/10.1155/2007/85402
  11. Islam M.A., Alam M.S. and Sharker K.K. (2016)., Estimation of Solar Radiation on Horizontal and tilted surface over Bangladesh., Computational Water, Energy, and Environmental Engineering, 5(2), 54-69.
  12. Ertekin C., Evrendilek F. and Kulcu R. (2008)., Modeling Spatio-Temporal Dynamics of Optimum Tilt Angles for Solar Collectors in Turkey., Sensors, 8(5), 2913-2931.
  13. Gopinathan K. (1991)., Solar Radiation on Variously Oriented Sloping Surfaces., Solar Energy, 47(3), 173-179.
  14. Cooper P. (1969)., The Absorption of Radiation in Solar Stills., Solar Energy, 12(3), 333-346.
  15. Klein S.A. (1977)., Calculation of monthly average insolation on tilted surfaces., Solar energy, 19(4), 325-329.
  16. Liu B. and Jordan R. (1962)., Daily Insolation on Surfaces Tilted towards the Equator., ASHRAE Transactions, 67, 526-541.
  17. Muneer T. and Saluja G. (1985)., A Brief Review of Models for Computing Solar Radiation on Inclined Surfaces., Energy Convers. Manage, 25(4), 443-458. https://doi.org/10.1016/0196-8904(85)90009-3