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.
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December 2016
Research-Article
Measuring the Effect of Vegetated Roofs on the Performance of Photovoltaic Panels in a Combined System
Hamid Ogaili,
Hamid Ogaili
Mechanical and Materials
Engineering Department,
Portland State University,
Portland, OR 97207
Engineering Department,
Portland State University,
Portland, OR 97207
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David J. Sailor
David J. Sailor
School of Geographical Sciences and
Urban Planning,
Arizona State University,
Tempe, AZ 85287
e-mail: David.Sailor@asu.edu
Urban Planning,
Arizona State University,
Tempe, AZ 85287
e-mail: David.Sailor@asu.edu
Search for other works by this author on:
Hamid Ogaili
Mechanical and Materials
Engineering Department,
Portland State University,
Portland, OR 97207
Engineering Department,
Portland State University,
Portland, OR 97207
David J. Sailor
School of Geographical Sciences and
Urban Planning,
Arizona State University,
Tempe, AZ 85287
e-mail: David.Sailor@asu.edu
Urban Planning,
Arizona State University,
Tempe, AZ 85287
e-mail: David.Sailor@asu.edu
1Corresponding author.
Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received November 13, 2015; final manuscript received August 19, 2016; published online October 3, 2016. Assoc. Editor: Carlos F. M. Coimbra.
J. Sol. Energy Eng. Dec 2016, 138(6): 061009 (8 pages)
Published Online: October 3, 2016
Article history
Received:
November 13, 2015
Revised:
August 19, 2016
Citation
Ogaili, H., and Sailor, D. J. (October 3, 2016). "Measuring the Effect of Vegetated Roofs on the Performance of Photovoltaic Panels in a Combined System." ASME. J. Sol. Energy Eng. December 2016; 138(6): 061009. https://doi.org/10.1115/1.4034743
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