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New Correlations for Determination of Optimum Slope Angle of Solar Collectors

Ali Khosravi1,*, Oscar Ricardo Sandoval Rodriguez2, Behnam Talebjedi1, Timo Laukkanen1, Juan Jose Garcia Pabon3, Mamdouh El Haj Assad4

1 Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland
2 Graduate Program in Mechanical Engineering Federal University of Minas Gerais, Belo Horizonte, Brazil
3 Institute of Mechanical Engineering, Federal University of Itajubá, Itajubá, Brazil
4 Sustainable and Renewable Energy Engineering Department, University of Sharjah, Sharjah, United Arab Emirates

* Corresponding Author: Ali Khosravi. Email: email

Energy Engineering 2020, 117(5), 249-265.


The energy coming from solar radiation could be harvested and transformed into electricity through the use of solar-thermal power generation and photovoltaic (PV) power generation. Placement of solar collectors (thermal and photovoltaic) affects the amount of incoming radiation and the absorption rate. In this research, new correlations for finding the monthly optimum slope angle (OSA) on flat-plate collectors are proposed. Twelve equations are developed to calculate the monthly OSA by the linear regression model, for the northern and the southern hemisphere stations from 15° to 55° and –20° to –45°, respectively. Also, a new equation for calculating the yearly tilt angle is developed and compared with several other calculation methods from the literature. Results confirm a 20% increase in solar energy absorption by adjusting the collectors’ tilt angle in monthly time periods. This is while the adjusted collectors with the yearly optimum slope angle receive approximately 7% higher solar radiation compared to the horizontal collectors. Furthermore, the proposed equations outperformed the other calculation methods in the literature.


Cite This Article

Khosravi, A., Ricardo, O., Talebjedi, B., Laukkanen, T., Jose, J. et al. (2020). New Correlations for Determination of Optimum Slope Angle of Solar Collectors. Energy Engineering, 117(5), 249–265.


cc This work is licensed under a Creative Commons Attribution 4.0 International License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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