Induction Coil System for Multicrystalline Silicon Melting
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Solution Overview
Problem
Current methods for obtaining high-purity multicrystalline silicon for photovoltaic cells require precise control of thermal flows and consume high energy, with long melting times and inefficient equipment.
Innovation Solution
A device comprising a crucible in a graphite container with induction coils and cooling means, allowing for adjustable heat control through selectively connecting windings of the bottom induction coil and varying its distance from the susceptor, enabling flexible heat management during melting and solidification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional directional solidification is used to obtain high-purity multicrystalline silicon, then the purity of the silicon is improved, but the energy consumption and melting time increase significantly
Solution Approach 1:
The induction coil system is divided into multiple independent coils (first induction coil for heating, second induction coil for cooling) that can operate separately and simultaneously. This segmentation allows the melting and solidification processes to be controlled independently, reducing the total energy required while maintaining the directional solidification necessary for high purity silicon production.
Solution Approach 2:
The patent employs parameter changes by varying the power supply to different induction coils during different stages of the process. The first induction coil receives power during melting, while the second induction coil receives power during solidification. This dynamic parameter adjustment optimizes energy consumption at each stage while achieving the required purity through controlled thermal gradients.
2Manufacturing precision
If precise control of thermal flows is implemented to achieve directional solidification, then the quality of multicrystalline silicon is improved, but the device complexity increases
Solution Approach 1:
The thermal control system is segmented into multiple independent induction coils, each responsible for a specific thermal function (heating, cooling, gradient control). This modular approach simplifies the control architecture by assigning specific functions to specific coils, making the system easier to manage despite the increased precision requirements.
Solution Approach 2:
The induction coil system is designed with multi-functionality, where the same basic component type (induction coil) serves multiple purposes: heating during melting, cooling during solidification, and creating thermal gradients for directional solidification. This universality reduces device complexity by using a single type of component for multiple functions rather than requiring different specialized components.
3Manufacturing precision
If long melting times are used to ensure complete melting and directional solidification, then the purity of the final product is improved, but the productivity decreases
Solution Approach 1:
The patent implements periodic action by alternating the operation of different induction coils in distinct phases: a melting phase with the first induction coil, followed by a solidification phase with the second induction coil. This periodic switching of functional modes accelerates the overall process by optimizing each stage independently, reducing total processing time while maintaining product purity through controlled phase transitions.
Solution Approach 2:
The process explicitly utilizes phase transitions (melting and solidification) as controlled stages rather than continuous processes. By applying heat during the melting phase and then applying cooling during the solidification phase, the system efficiently progresses through phase changes that are essential for purity separation, thereby improving productivity without compromising the purification mechanism.
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
This solution allows for simplified and energy-efficient control of thermal flows, reducing equipment dimensions and energy consumption while maintaining high-purity silicon production for photovoltaic cells.
Implementation Method 1
at least one top induction coil (12), the induction coil being set facing, with interposition of a graphite plate, a mouth of the graphite container (4); at least one lateral induction coil (16), set around a side wall (17) of the graphite container (4); and a bottom induction coil (18), set facing a bottom wall (19) of the graphite container (4)
Implementation Method 2
the melting step is performed by heating the semiconductor material contained in a crucible by means of graphite susceptors, each operatively associated to at least one respective induction coil
Implementation Method 3
cooling means (21) for supplying a coolant within respective hollow turns (13) of the induction coils (12, 16, 18)
Implementation Method 4
cooling means (21) for supplying a coolant within respective hollow turns (13) of the induction coils (12, 16, 18)
Implementation Method 5
heating the semiconductor material contained in a crucible by means of graphite susceptors, each operatively associated to at least one respective induction coil
Data Source
Figure 1
Figure 2
Figure 3a~4c
AI summary
A device (1) for obtaining multicrystalline silicon, including: at least one crucible (3) made of quartz for the silicon, removably housed in a cup-shaped graphite container (4); a fluid- tight openable casing (5); a top induction coil (12), set facing, with interposition of a graphite plate (14), the crucible, a lateral induction coil (16), set around a side wall (17) of the graphite container, and a bottom induction coil (18), set facing a bottom wall (19) of the graphite container and vertically mobile for varying the distance (D) from the bottom wall; and first means (20) for a.c. electrical supply of the induction coils separately from one another, and second means (21) for supply of a coolant within respective hollow turns of the induction coils; the bottom induction coil includes four spiral windings (31-34), arranged alongside one another according to a chequered scheme in one and the same plane of lie, which is defined by an insulated supporting plate (35); electrical switching means (40) enable in use selective connection of the four windings (31-34) to one another according to different configurations.