Seasonal power fluctuations of amorphous silicon thin-film solar modules: distinguishing between different contributions

• Published in: Progress in photovoltaics 2014-02, Vol.22 (2), p.208-217
• Main Authors: Virtuani, Alessandro, Fanni, Lorenzo
• Format: Article
• Language: English
• Subjects: Amorphous silicon; Amplitudes; Applied sciences; Energy; Equipments, installations and applications; Exact sciences and technology; Fluctuation; Indoor; Natural energy; Oscillations; Outdoor; Photovoltaic conversion; seasonal variations; Solar cells. Photoelectrochemical cells; Solar energy; Solar power generation; Spectra; spectral effects; Staebler-Wronski effect; Thin films
• ISSN: 1062-7995; 1099-159X
• DOI: 10.1002/pip.2257

ABSTRACT Several works report on seasonal fluctuations of power production of amorphous silicon (a‐Si). These oscillations are due to two overlapping phenomena (i) spectral and (ii) the Staebler–Wronski effects. It is hence difficult to assess—for a given location and climatic conditions—which one has the largest impact. By means of a straightforward approach based on two sets of single‐junction a‐Si photovoltaic modules (stored indoors/exposed outdoors) and on two different I–V measurement set‐ups (indoor and outdoor), we were able to separate the different contributions to this phenomenon. For the test‐site of Lugano, seasonal oscillations account for performance variations of a‐Si of ~10% (±5% around an annual average value with a minimum around the mid of January and a maximum around mid‐July). The time‐phase of the overall effect lies in between that of the two distinguished phenomena. (i) Spectral variations seem to have the highest impact on the outdoor performance of a‐Si with an amplitude corresponding to 10.5% (± ~5.2%). Moreover, the influence of spectral variations on the outdoor performance of a‐Si (and for comparison of c‐Si) was modeled, and the experimental data were found to be in excellent agreement with the theoretical simulation; (ii) the Staebler–Wronski effect has a slightly lower influence with an amplitude of ~8% (±4% with a minimum at the middle of February and a maximum around mid‐August). Because of the position (46°N) and average climatic conditions (southern Alpine climate) of Lugano, these observations are possibly representative of a large part of continental Europe. Copyright © 2012 John Wiley & Sons, Ltd. Several works report on seasonal fluctuations of power production of amorphous silicon (a‐Si). These oscillations are due to two overlapping phenomena (i) spectral and (ii) the Staebler–Wronski effects. In this work, we separate between the different contributions to this phenomenon. For the test‐site of Lugano (46°N), seasonal oscillations account for performance variations of a‐Si of ~10% (±5% around an annual average value with a minimum around the mid of January and a maximum around mid‐July). The time‐phase of the overall effect lies in between that of the two distinguished phenomena. (i) Spectral variations seem to have the highest impact on the outdoor performance of a‐Si with an amplitude corresponding to 10.5% (± ~5.2%); (ii) the Staebler–Wronski effect has a slightly lower influence with an amplitude of ~8% (±4%