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BRIDGING THE GAP BETWEEN ACCELERATED AND FIELD AGING OF PHOTOVOLTAIC BACKSHEETS

Wang, Yu
http://orcid.org/0000-0003-1353-2578
http://rave.ohiolink.edu/etdc/view?acc_num=case155445993551404

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, Materials Science and Engineering.
The photovoltaic (PV) industry has grown tremendously for the past decades, benefi ting from the continuous reduction of cost. PV modules are expected to work functionally for 25-30 years with a future goal of up to 50 years. Backsheets play an important role in maintaining the long-time reliability and durability of PV modules.There is a gap in application of indoor experimental results to the prediction of backsheet`s lifetime in the field. In order to reduce this gap, a comprehensive study of backsheets degradation was conducted to investigate the effects of outdoor degradation factors and the changes of backsheet materials. This work includes studies of backsheet degradation with three thrusts: fi eld-exposed, field-retrieved, and indoor accelerated test exposed backsheets. Field surveys were conducted on 1310 field-exposed PV module backsheets at 4 PV sites, and a generalized spatio-temporal model was developed to t each site. Spatially non-uniform backsheet degradation within a rack level in the field is observed, arising from inhomogeneous backside irradiance of PV modules. The non-uniform backsheet degradation is also affected by ground cover and the air-side material of backsheet. The generalized spatio-temporal models, with adjusted R-2 up to 0.89 capture this spatial and temporal variation in backsheet degradation in real-world PV power plant sites. This model can be used to identify the backsheets that will degrade faster in a specific PV site, due to the backsheet air-side polymer and the PV rack`s design, and enable replacement of those modules before potential safety concerns become extreme. A total of 33 PV module backsheets were retrieved from the fi eld worldwide, and the degradation induced color change, gloss loss, and physical and chemical material changes analyzed. Principle components analysis (PCA) of field-retrieved backsheets indicates that the discoloration of poly(ethylene terephthalate) (PET) and polyamide (PA) air-side backsheets has a strong correlation with exposure time (accumulated irradiance) and with the concentration of the air pollutant NO2, respectively. The non-uniform degradation within an individual module is also studied using Fourier transform infrared spectroscopy (FTIR), and the faster photo-degradation of backsheets between the PV cells is assumed to be associated with the severe cracking in PA/PA/PA backsheets. Four types of backsheets were exposed in the laboratory to 6 indoor accelerated tests, and the predictive < Stressor|Response > models were developed for the yellowness index (YI) and gloss. The high adjusted R-2 (up to 0.99) show that the models are able to capture the features of data. The degradation mechanisms for PET and PA are investigated with FTIR and ultra-violet visible spectroscopy (UV-Vis). The photo-oxidation of PET and PA involves chain scission, formation of carbonyl and hydroxyl species. The presence of water spray during accelerated exposures also induced the cracking of PA/PA/PA backsheets exposed outdoors by removing the air-side layer and causing degradation of the core layer. In addition the presence of water spray induces PVF degradation that is not observed in the field. The comparison between indoor predictive models and the degradation of fi eld retrieved backsheets shows the similarity and dissimilarity of different indoor accelerated test conditions with degradation observed under real-world climatic zone exposure conditions. The xenon-light exposure with an irradiance level of 0.25 W/m2/nm at 340 nm, temperature of 80 centigrade and water spray induces similar discoloration and FTIR spectra for PET/PET/EVA backsheets with BSk climate zone. The xenon light exposure with irradiance level of 0.8 W/m2/nm at 340 nm, temperature of 65 centigrade or 80 centigrade and no water spray induces similar gloss retention for PA/PA/PA backsheets with Cfa climate zone.
Bruckman Laura (Advisor)
French Roger (Committee Chair)
Willard Matthew (Committee Member)
Ishida Hatsuo (Committee Member)
Hore Michael (Committee Member)
212 p.
Materials Science; Polymers
Photovoltaic Backsheet, polymer degradation, predictive model

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Citations

  • Wang, Y. (2019). BRIDGING THE GAP BETWEEN ACCELERATED AND FIELD AGING OF PHOTOVOLTAIC BACKSHEETS [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case155445993551404

    APA Style (7th edition)

  • Wang, Yu. BRIDGING THE GAP BETWEEN ACCELERATED AND FIELD AGING OF PHOTOVOLTAIC BACKSHEETS. 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case155445993551404.

    MLA Style (8th edition)

  • Wang, Yu. "BRIDGING THE GAP BETWEEN ACCELERATED AND FIELD AGING OF PHOTOVOLTAIC BACKSHEETS." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case155445993551404

    Chicago Manual of Style (17th edition)

case155445993551404
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© 2019, some rights reserved.Creative Commons License BRIDGING THE GAP BETWEEN ACCELERATED AND FIELD AGING OF PHOTOVOLTAIC BACKSHEETS by Yu Wang is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.