PERFORMANCE ANALYSIS OF EMPIRICAL MODELS FOR ESTIMATING DAILY GLOBAL SOLAR RADIATION AT TAPLEJUNG, NEPAL
DOI:
https://doi.org/10.3126/jist.v31i1.88693Keywords:
Global solar radiation, Empirical models, Statistical evaluation, Mountain climate, Taplejung, NepalAbstract
Accurate knowledge of global solar radiation (GSR) is a fundamental requirement for solar energy system design, climate studies, and environmental modeling. In mountainous regions such as eastern Nepal, the scarcity of long-term measured solar radiation data necessitates the use of empirical estimation techniques. This study presents a comprehensive evaluation of twenty empirical models for estimating daily average GSR on a horizontal surface for Taplejung, a high-altitude region of Nepal. The models were calibrated using locally observed meteorological data, and their performance was assessed through standard statistical indicators, including Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), and the coefficient of determination (R²). The comparative analysis reveals substantial variation in predictive performance among the tested formulations. Advanced multivariable and nonlinear models significantly outperform simpler regression relations. Among all models, the Coulibaly and Ouedraogo model demonstrates the most balanced performance, characterized by near-zero bias, low dispersion error, and the highest correlation strength. The results confirm that Taplejung possesses a notable solar energy potential, with an estimated mean daily GSR of approximately 15.12 MJ m⁻² day⁻¹. The proposed findings provide a reliable framework for solar resource assessment in high-altitude regions of Nepal where direct measurements are limited.
Downloads
References
Adhikari, K. R., Gurung, S., & Bhattarai, B. K. (2013). Solar energy potential in Nepal and global context. Journal of the Institute of Engineering, 9(1), 95–106. https://doi.org/10.3126/jie.v9i1.10675
Adhikari, K. R., Gurung, S., & Bhattarai, B. K. (2014). Empirical model based on meteorological parameters to estimate global solar radiation in Nepal. BIBECHANA, 11, 25–33. https://doi.org/10.3126/bibechana.v11i0.10376
Al-Salameh, A., et al. (2025). Assessment of long-term solar radiation for energy exploitation in East Jerusalem, Palestine. International Journal of Energy and Environmental Science, 10(4), 13. https://doi.org/10.11648/j.ijees.20251004.13
Ampratwum, D. B., & Dorvlo, A. S. S. (1999). Estimation of solar radiation from the number of sunshine hours. Applied Energy, 63, 161–167. https://doi.org/10.1016/S0306-2619(99)00025-2
Angstrom, A. (1924). Solar and terrestrial radiation: Report to the International Commission for Solar Research on actinometric investigations of solar and atmospheric radiation. Quarterly Journal of the Royal Meteorological Society, 50(210), 121–126. https://doi.org/10.1002/qj.49705021008
Badescu, V. (2008). Modeling solar radiation at the Earth’s surface. Springer. https://doi.org/10.1007/978-3-540-77455-6
Chen, R., Ersi, K., Yang, J., Lu, S., & Zhao, W. (2004). Validation of five global radiation models with measured daily data in China. Energy Conversion and Management, 45(11–12), 1759–1769. https://doi.org/10.1016/j.enconman.2003.09.019
Dawadi, N., Shrestha, M. K., Khatri, K., Poudyal, K. N., Karki, I. B., & Tiwari, B. R. (2026). Estimation of global solar radiation using RadEst 3.00 software at Tribhuvan International Airport, Nepal. BIBECHANA, 23(1), 31–39. https://doi.org/10.3126/bibechana.v23i1.82026
Deng, J. M., Muot, D. Y., & Mawien, P. P. (2025). Uncovering South Sudan’s renewable energy potential: A comprehensive evaluation of favourable locations and variability. Energy, Sustainability and Society, 15, 42. https://doi.org/10.1186/s13705-025-00542-y
Dogniaux, R., & Lemoine, M. (1983). Classification of radiation sites in terms of different indices of atmospheric transparency. In Solar energy research and development in the European Community (Series F, Vol. 2). Reidel. https://doi.org/10.1007/978-94-009-7112-7_7
Ertekin, C., & Yaldiz, O. (2000). Comparison of some existing models for estimating global solar radiation for Antalya (Turkey). Energy Conversion and Management, 41, 311–330. https://doi.org/10.1016/S0196-8904(99)00127-2
Evrendilek, F., & Ertekin, C. (2008). Assessing solar radiation models using multiple variables over Turkey. Climate Dynamics, 31, 131–149. https://doi.org/10.1007/s00382-007-0338-6
Gairaa, K., & Bakelli, Y. (2013). A comparative study of some regression models to estimate global solar radiation on a horizontal surface from sunshine duration and meteorological parameters for Ghardaïa site, Algeria. International Scholarly Research Notices, 2013, Article 754956. https://doi.org/10.1155/2013/754956
Glover, J., & McCulloch, J. S. G. (1958). The empirical relation between solar radiation and hours of sunshine. Quarterly Journal of the Royal Meteorological Society, 84, 172–175. https://doi.org/10.1002/qj.49708436011
Hamatti, M., Benchrifa, M., Elouardi, M., Hadine, M., Jamal, M., El-Baz, M., & Tadili, R. (2025). Prediction of daily global solar radiation on a horizontal plane using adaptive neuro-fuzzy inference system (ANFIS). Journal of Environmental and Earth Sciences, 7(1), 527–539. https://doi.org/10.30564/jees.v7i1.7079
Iqbal, M. (1983). An introduction to solar radiation. Academic Press. https://doi.org/10.1016/B978-0-12-373750-2.X5001-0
Joshi, U., Poudyal, K. N., Karki, I. B., & Chapagain, N. P. (2020). Evaluation of global solar radiation using sunshine hour, temperature, and relative humidity at lowland region of Nepal. Journal of Nepal Physical Society, 6(1), 16–24. https://doi.org/10.3126/jnphyssoc.v6i1.30429
Katiyar, A. K., & Pandey, C. K. (2010). Simple correlation for estimating global solar radiation on horizontal surfaces in India. Energy, 35, 5043–5048. https://doi.org/10.1016/j.energy.2010.08.014
Khalil, S. A., & Shaffie, A. M. (2014). The relationship between total solar radiation and biologically erythematic radiation over an urban region of Egypt. Renewable and Sustainable Energy Reviews, 38, 1092–1099. https://doi.org/10.1016/j.rser.2014.05.014
Kharel, B., Thapa, A., Khatiwada, K., Rijal, S., Rajbanshi, B. K., & Poudyal, K. N. (2025). Estimating solar energy potential in the high-altitude region of Jumla, Nepal, using RadEst 3.0 software. Journal of Information Systems Engineering and Management, 10(44s), 1013–1029. https://doi.org/10.52783/jisem.v10i44s.8698
Liou, K. N. (2002). An introduction to atmospheric radiation. Elsevier. https://www.sciencedirect.com/book/9780124514515/an-introduction-to-atmospheric-radiation
Liu, D. L., & Scott, B. J. (2001). Estimation of solar radiation in Australia from rainfall and temperature observations. Agricultural and Forest Meteorology, 106, 41–59. https://doi.org/10.1016/S0168-1923(00)00173-8
Martínez-Lozano, J. A., Tena, F., Onrubia, J., & de la Rubia, J. (1984). The historical evolution of the Ångström formula and its modifications: Review and bibliography. Agricultural and Forest Meteorology, 33(2–3), 109–128. https://doi.org/10.1016/0168-1923(84)90064-9
Ögelman, H., Ecevit, A., & Taşdemiroğlu, E. (1984). A new method for estimating solar radiation from bright sunshine data. Solar Energy, 33(6), 619–625. https://doi.org/10.1016/0038-092X(84)90018-5
Okundamiya, M. S., Emagbetere, J. O., & Ogujor, E. A. (2016). Evaluation of various global solar radiation models for Nigeria. International Journal of Green Energy, 13(5), 505–512. https://doi.org/10.1080/15435075.2014.968921
Olomiyesan, B., Oyedum, O., Ugwuoke, P., & Abolarin, M. (2017). Evaluation of some global solar radiation models in selected locations in northwest Nigeria. Open Access Journal of Photoenergy, 1(1), 1–6. https://doi.org/10.15406/mojsp.2017.01.00001
Page, J. K. (1961). The estimation of monthly mean values of daily total shortwave radiation. Proceedings of the UN Conference on New Sources of Energy, 4, 378–390. https://digitallibrary.un.org/record/3827996?utm=&v=pdf
Poudyal, K. N. (2015). Estimation of global solar radiation potential in Nepal (Doctoral dissertation, Tribhuvan University, Institute of Engineering, Nepal).
Poudyal, K. N., Bhattarai, B. K., Sapkota, B. K., & Kjeldstad, B. (2012). Estimation of global solar radiation using sunshine duration in the Himalayan region. Research Journal of Chemical Sciences, 2(11), 20–25. https://www.isca.in/rjcs/Archives/v2/i11/4.ISCA-RJCS-2012-165.php?utm
Prescott, J. A. (1940). Evaporation from a water surface in relation to solar radiation. Transactions of the Royal Society of South Australia, 64, 114–118. https://www.scirp.org/reference/referencespapers?referenceid=4177006&utm
Rajbanshi, B. K., Singh, R. G., Khatiwada, K., Thapa, A., & K. C., B. R. (2024a). Comparative analysis of empirical models for estimating global solar radiation in Biratnagar, Nepal: A case study using RadEst 3.0. Nanotechnology Perceptions, 20(S16). https://nano-ntp.com/index.php/nano/article/view/4637
Rajbanshi, B. K., Singh, R. G., K. C., B. R., & Poudel, K. N. (2024b). Comparative analysis of different models within RadEst 3.0 for solar radiation estimation at Dhankuta, Nepal. Journal of Nepal Physical Society, 10(1), 70–76. https://doi.org/10.3126/jnphyssoc.v10i1.72845
Rajbanshi, B. K., Singh, R. G., Kharel, B., Thapa, A., & Khatiwada, K. (2025a). Estimation of solar energy using different empirical models at Okhaldhunga, Nepal. International Journal of Environmental Science, 11(7s), 92–102. https://doi.org/10.64252/v1y8pw19
Rajbanshi, B. K., Singh, R. G., K. C., B. R., Joshi, U., & Poudyal, K. N. (2025b). Determining the optimal empirical model for estimating global solar radiation in the eastern mid-hills of Dhankuta, Nepal. Journal of Nepal Physical Society, 11(1), 1–8. https://doi.org/10.3126/jnphyssoc.v11i1.87386
Rajbanshi, B. K., Singh, R. G., Khatiwada, K., Thapa, A., Kharel, B., & K C., B. R. (2025c). Estimation of global solar radiation in the eastern upland region of Taplejung, Nepal, using RadEst 3.0 software. Journal of Information Systems Engineering and Management, 10(16s). https://doi.org/10.52783/jisem.v10i16s.2658
Sonmete, M. H., Ertekin, C., Menges, H. O., Hacıseferogullari, H., & Evrendilek, F. (2011). Assessing monthly average solar radiation models: A comparative case study in Turkey. Environmental Monitoring and Assessment, 175, 251–277. https://doi.org/10.1007/s10661-010-1510-8
Tanyıldızı Ağır, T. (2025). Daily global solar radiation prediction with hybrid LSTM–SVM: The case of Nusaybin. Arabian Journal for Science and Engineering. Advance online publication.
https://doi.org/10.1007/s13369-025-10322-7
Tarpley, J. D. (1979). Estimating incident solar radiation at the surface from geostationary satellite data. Journal of Applied Meteorology and Climatology, 18(9), 1172–1181. https://www.jstor.org/stable/26179173
Trnka, M., Žalud, Z., Eitzinger, J., & Dubrovský, M. (2005). Global solar radiation in Central European lowlands estimated by various empirical formulae. Agricultural and Forest Meteorology, 131, 54–76. https://doi.org/10.1016/j.agrformet.2005.05.002
Yadav, A. K., Kumar, R., Wang, M., Fekete, G., & Singh, T. (2025). Comparative analysis of daily global solar radiation prediction using deep learning models inputted with stochastic variables. Scientific Reports, 15, Article 10786. https://doi.org/10.1038/s41598-025-95281-7
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2026 Institute of Science and Technology, T.U.
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.
The views and interpretations in this journal are those of the author(s). They are not attributable to the Institute of Science and Technology, T.U. and do not imply the expression of any opinion concerning the legal status of any country, territory, city, area of its authorities, or concerning the delimitation of its frontiers of boundaries.
The copyright of the articles is held by the Institute of Science and Technology, T.U.
