PV Module Pyrolysis with Pre-Splitting for Wafer-Safe EVA Separation
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Solution Overview
Problem
Current pyrolysis methods for recycling photovoltaic modules face issues such as uneven heating leading to cell breakage and incomplete separation of EVA crystal silicon wafers due to pressure increases from temperature-induced back plate shrinkage, resulting in incomplete recovery of crystal silicon wafers.
Innovation Solution
A pyrolysis apparatus with a controlled heating mechanism, telescopic motion, and a splitting assembly that includes a cutting knife and clamping system to stabilize and separate the photovoltaic module, ensuring uniform heating and preventing pressure-induced stress on the crystal silicon wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If continuous temperature increase is applied during pyrolysis, then EVA decomposition is promoted, but pressure between glass and silicon wafer increases causing wafer breakage
Solution Approach 1:
The cutting knife performs preliminary separation of the back plate from the silicon wafer before the pyrolysis process begins. This preliminary action prevents the back plate from shrinking and generating stress on the wafer during subsequent heating, thus avoiding wafer breakage while still allowing complete EVA decomposition at high temperatures
Solution Approach 2:
The separation process is divided into distinct stages: first the cutting knife separates the back plate, then the heating mechanism performs pyrolysis. This segmentation allows each operation to be optimized independently - mechanical separation prevents stress buildup, while thermal processing achieves complete decomposition
2Productivity
If high temperature pyrolysis is used to decompose EVA, then decomposition efficiency is improved, but uneven heating causes cell breakage
Solution Approach 1:
The heating mechanism is designed with telescopic motion capability in the vertical direction, allowing it to dynamically adjust its position and maintain optimal heating uniformity throughout the pyrolysis process. This dynamic adjustment ensures even heat distribution across the photovoltaic module surface
Solution Approach 2:
The control system monitors the pyrolysis process and adjusts the heating mechanism accordingly to maintain uniform temperature distribution. This feedback control prevents local overheating while ensuring complete EVA decomposition, thus protecting the silicon wafer integrity
3Device complexity
If back plate is not separated before pyrolysis, then process simplicity is maintained, but back plate shrinkage generates stress causing wafer breakage
Solution Approach 1:
The cutting knife performs preliminary separation of the back plate from the module structure before pyrolysis begins. This simple preliminary action prevents the back plate from shrinking and generating stress on the wafer during heating, thus maintaining wafer integrity without requiring complex additional equipment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus achieves complete decomposition of EVA packaging material without residue, ensures the integrity of the crystal silicon wafer by stabilizing the module during pyrolysis, and effectively separates the glass and back plate from the silicon wafer, preventing breakage and ensuring high purity.
Implementation Method 1
The temperature is increased at a fixed temperature rising rate to reach the highest temperature and maintained for 45 min, so as to enable the EVA packaging material to be removed
Implementation Method 2
during pyrolysis, the pressure between the glass and the crystal silicon wafer is increased due to continuous temperature increase, and the back plate will shrink during heating to generate stress which causes breakage of the crystal silicon wafer
Data Source
AI summary
A pyrolysis apparatus for completely separating an EVA crystal silicon wafer from a waste photovoltaic module includes a heating mechanism controlled by a control system and mounted in a pyrolysis box and being capable of performing telescopic motion in a vertical direction; an overturning assembly for fixedly clamping and driving a photovoltaic module to overturn, the overturning assembly is arranged just under the heating mechanism; and a splitting assembly for separating the photovoltaic module, the splitting assembly is arranged at a left side of the photovoltaic module fixedly clamped by the overturning assembly. A splitting apparatus is provided for assisting in splitting EVA, and isolating glass from the crystal silicon wafer, as well as isolating a back plate from the crystal silicon wafer, and therefore, the pressure generated on the crystal silicon wafer due to large strength of the glass and shrinkage of the back plate is prevented.