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Research Papers

Finite Element Modeling, Analysis, and Life Prediction of Photovoltaic Modules

[+] Author and Article Information
Osama Hasan

Research Assistant
Department of Mechanical Engineering,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: osamahasan@kfupm.edu.sa

A. F. M. Arif

Professor
Mem. ASME
Department of Mechanical Engineering,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: afmarif@kfupm.edu.sa

M. U. Siddiqui

Department of Mechanical Engineering,
King Fahd University of Petroleum and Minerals,
Dhahran 31261, Saudi Arabia
e-mail: musiddiqui@kfupm.edu.sa

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received December 20, 2012; final manuscript received November 3, 2013; published online December 19, 2013. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 136(2), 021022 (Dec 19, 2013) (14 pages) Paper No: SOL-12-1336; doi: 10.1115/1.4026037 History: Received December 20, 2012; Revised November 03, 2013

A Photovoltaic (PV) module consists of layers of different materials constrained together through an encapsulant polymer. During its lamination and operation, it experiences mechanical and thermal loads due to seasonal and daily temperature variations, which cause breakage of interconnects owing to fatigue. This is due to the fact that there is a coefficient of thermal expansion (CTE) mismatch because of the presence of unlike materials within the laminate. Therefore, thermomechanical stresses are induced in the module. The lifetime of today's PV module is expected to be 25 yr and this period corresponds to the guarantee of the manufacturer. Its high reliability will help it to reach grid parity. But, the problem is that it is not convenient to wait and assess its durability. In this work, material of each component of PV module is characterized and finite-element (FE) structural analysis is performed to find the initial condition of the components of the module after manufacture. It was found that the copper interconnects undergo plastic deformation just after the lamination process. A thermal model was numerically developed and sequentially coupled to the structural model. By using the meteorological data of Jeddah, Saudi Arabia, average life of PV module was estimated to be 26.5 yr.

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Figures

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Fig. 1

Cross-section of a PV module

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Fig. 2

Failure modes of PV modules [5]

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Fig. 3

Flow chart of the modeling process

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Fig. 4

Structure of silicon crystal

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Fig. 5

The Maxwell–Weichart or the generalized Maxwell model

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Fig. 6

Isothermal relaxation curves for EVA obtained by experiments performed by Eitner et al. [18]

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Fig. 7

Prony series fit of the master curve in Ref. [18]

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Fig. 8

Dimensions of the shell model

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Fig. 9

Layered configuration of areas along transverse direction

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Fig. 10

Interconnection approximation in shell model

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Fig. 12

Cell gap displacements measured for validation

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Fig. 13

Validation of 2D model with 3D model using maximum von-Mises stress

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Fig. 14

von-Mises stress (left) and von-Mises plastic strain (right) at room temperature after the lamination process at the interconnect region between two adjacent cells (shaded region A)

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Fig. 15

Max von-Mises stress and first principal stress through the thickness of the module at lowest temperature on Day 4

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Fig. 16

First principal stress contours of (a): glass at region A, (b): backsheet at region A, (c): cells at region B, and (d) encapsulant at region A at lowest temperature on Day 4

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Fig. 17

First principal stress contours of (a): interconnect region over the cells at region A and (b): interconnect region between two adjacent cells at region B at lowest temperature on Day 4

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Fig. 18

Stress variation on module along (a) longitudinal path AB and (b) transverse path CD at lowest temperature on Day 4

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Fig. 19

Transient change in von-Mises stress and first principal stress for Day 3 on copper interconnect. A represents the time of max. stress, min. temperature and B represents the time of min. stress, max. temperature.

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