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Proceedings Paper

Spectral effects on latitude-tilt and vertical PV modules as affected by latitude, air mass, and climate
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Paper Abstract

Using the same SMARTS radiative code as for the development of improved reference spectra for PV rating, an analysis of the spectral sensitivity of specific PV technologies to varying air mass and other factors is presented. To the difference of previous studies, the approach taken here considers realistic atmospheric conditions, as measured at five North- American sites from widely different climatic zones. Two different PV applications (latitude-tilted flat-plates and vertical building-integrated modules) are showcased with seven possible materials, including a-Si, m-Si, and triple junctions. Considering the most frequent clear-sky conditions around the summer solstice at the selected sites, the Spectral Enhancement Factor (SEF) is calculated both for a fixed air mass (1.5) and daily-average spectral conditions. This analysis provides a preliminary assessment of how latitude, local climatic conditions, and PV geometry affect the relative merits of different technologies relatively to standard rating conditions. In particular, it is shown that, in summer, latitude-tilt PV modules experience bluer incident spectra than the reference spectrum, therefore favoring the a-Si modules (SEF > 1). For vertical-tilt PV systems, the SEF is generally lower than for latitude-tilt systems, with the notable exception of m- Si. When considering daily-average results, the effective SEF can become extremely low in the case of a-Si (down to 0.65) and moderately high for m-Si (up to 1.09). It is concluded that the effects of location, season, and PV material on the spectral effect needs to be investigated in detail, particularly for applications involving vertical building-integrated systems.

Paper Details

Date Published: 13 September 2007
PDF: 9 pages
Proc. SPIE 6652, Optical Modeling and Measurements for Solar Energy Systems, 66520C (13 September 2007); doi: 10.1117/12.735230
Show Author Affiliations
Christian A. Gueymard, Solar Consulting Services (United States)


Published in SPIE Proceedings Vol. 6652:
Optical Modeling and Measurements for Solar Energy Systems
Daryl R. Myers, Editor(s)

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