Nonlinear Photovoltaic Degradation Rates: Modeling and Comparison Against Conventional Methods

Although common practice for estimating photovoltaic (PV) degradation rate ( R D ) assumes a linear behavior, field data have shown that degradation rates are frequently nonlinear. This article presents a new methodology to detect and calculate nonlinear R D based on PV performance time-series from...

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Bibliographic Details
Published in:IEEE journal of photovoltaics 2020-07, Vol.10 (4), p.1112-1118
Main Authors: Theristis, Marios, Livera, Andreas, Jones, C. Birk, Makrides, George, Georghiou, George E., Stein, Joshua S.
Format: Article
Language:English
Subjects:
Analytical models
Change detection
Change-point analysis
Degradation
Least squares method
levelized cost of energy (<named-content xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" content-type="math" xlink:type="simple"> <inline-formula> <tex-math notation="LaTeX"> LCOE</tex-math> </inline-formula> </named-content>)
modeling
nonlinear degradation
Nonlinearity
Order parameters
Photovoltaic cells
Photovoltaic systems
photovoltaics (PV)
Silicon
SOLAR ENERGY
Thin films
Trends
Uncertainty
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Summary:Although common practice for estimating photovoltaic (PV) degradation rate ( R D ) assumes a linear behavior, field data have shown that degradation rates are frequently nonlinear. This article presents a new methodology to detect and calculate nonlinear R D based on PV performance time-series from nine different systems over an eight-year period. Prior to performing the analysis and in order to adjust model parameters to reflect actual PV operation, synthetic datasets were utilized for calibration purposes. A change-point analysis is then applied to detect changes in the slopes of PV trends, which are extracted from constructed performance ratio ( PR ) time-series. Once the number and location of change points is found, the ordinary least squares method is applied to the different segments to compute the corresponding rates. The obtained results verified that the extracted trends from the PR time-series may not always be linear and therefore, "nonconventional" models need to be applied. All thin-film technologies demonstrated nonlinear behavior whereas nonlinearity detected in the crystalline silicon systems is thought to be due to a maintenance event. A comparative analysis between the new methodology and other conventional methods demonstrated levelized cost of energy differences of up to 6.14%, highlighting the importance of considering nonlinear degradation behavior.
ISSN:2156-3381
2156-3403
DOI:10.1109/JPHOTOV.2020.2992432