New correlations for determination of optimum slope angle of solar collectors

Ali Khosravi*, Oscar Ricardo Sandoval Rodriguez, Behnam Talebjedi, Timo Laukkanen, Juan Jose Garcia Pabon, Mamdouh El Haj Assad

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

6 Citations (Scopus)
110 Downloads (Pure)


The energy coming from solar radiation could be harvested and trans-formed 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.

Original languageEnglish
Pages (from-to)249-265
Number of pages17
JournalEnergy Engineering: Journal of the Association of Energy Engineering
Issue number5
Publication statusPublished - 1 Jan 2020
MoE publication typeA1 Journal article-refereed


  • Flat-plate collector
  • Linear regression
  • Optimum slope angle
  • Photovoltaic system
  • Slope angle
  • Solar energy


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