Measuring the Effect of Vegetated Roofs on the Performance of Photovoltaic Panels in a Combined System

Hamid Ogaili, David Sailor

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


Experiments were conducted in summer using two identical photovoltaic (PV) panels at two heights using three roofing types: white, black, and green (vegetated). For experiments at an 18 cm height, the mean power output of the PV-green roof system was 1.2% and 0.8% higher than the PV-black and PV-white roofs, respectively. At a 24 cm height, the benefit of the green roof was slightly diminished with power output for the PV above a green roof being 1.0% and 0.7% higher than the black and white roof experiments, respectively. These results were consistent with measured variations in mean panel surface temperatures; the green roof systems were generally cooler by 1.5-3 °C. A unique aspect of this research is the investigation into the effect of vegetation on the convective cooling of the PV panels. Panel heat transfer coefficients for the PV-green roof were 10-20% higher than for the white and black roof configurations, suggesting a mixing benefit associated with the roughness of the plant canopy. While the best PV performance was obtained by locating PV above a green roof, the relative benefits diminish with distance between the PV and the roof.

Original languageEnglish (US)
Article number061009
JournalJournal of Solar Energy Engineering, Transactions of the ASME
Issue number6
StatePublished - Dec 1 2016


  • Sustainable roofing
  • convection
  • energy balance
  • green roofs

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Energy Engineering and Power Technology


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