Tilted photovoltaic energy outputs in outdoor environments

Siwei Lou, Wenqiang Chen, Danny H.W. Li, Mo Wang, Hainan Chen, Isaac Y.F. Lun, Dawei Xia

Research output: Journal PublicationArticlepeer-review

4 Citations (Scopus)


The direction and environment of photovoltaics (PVs) may influence their energy output. The practical PV performance under various conditions should be estimated, particularly during initial design stages when PV model types are unknown. Previous studies have focused on a limited number of PV projects, which required the details of many PV models; furthermore, the models can be case sensitive. According to the 18 projects conducted in 7 locations (latitude 29.5-51.25N) around the world, we developed polynomials for the crystalline silicon PV energy output for different accessible input variables. A regression tree effectively evaluated the correlations of the outcomes with the input variables; those of high importance were identified. The coefficient of determination, indicating the percentage of datasets being predictable by the input, was higher than 0.65 for 14 of the 18 projects when the polynomial was developed using the accessible variables such as global horizontal solar radiation. However, individual equations should be derived for horizontal cases, indicating that a universal polynomial for crystalline silicon PVs with a tilt angle in the range 0°-66° can be difficult to develop. The proposed model will contribute to evaluating the performance of PVs with low and medium tilt angles for places of similar climates.

Original languageEnglish
Article number6052
JournalSustainability (Switzerland)
Issue number21
Publication statusPublished - 1 Nov 2019


  • Photovoltaic efficiency
  • Polynomial
  • Real-time estimation
  • Regression tree
  • Universal model

ASJC Scopus subject areas

  • Geography, Planning and Development
  • Renewable Energy, Sustainability and the Environment
  • Environmental Science (miscellaneous)
  • Energy Engineering and Power Technology
  • Management, Monitoring, Policy and Law


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