Numerical Study on the Thermal Characteristics of Large Sized Silicon Polycrystal Growth by DS Method

The development of the manufacturing processes of solar silicon ingot is one of the more important issues to guarantee the growth of the photovoltaic industry, because of the saving of manufacturing costs of ingots, wafers, solar cells and of solar modules. Several solidification processes have been developed by industries, including casting, heat exchanger method and electromagnetic casting. However, the market growth using mono- and polycrystalline Si wafers might be saturated due to the shortage of Si feedstock. One of the methods to solve this problem is to make higher quality polycrystalline Si wafers which are capable of producing higher efficiency solar cells. In this paper, the effects of changing several geometrical configurations of cooling path were evaluated to improve the directional solidification (DS) method and to achieve the main issues. The developed DS method has the advantages of the small heat loss, short cycle time and efficient directional solidification. Based on the CFD (computational fluid dynamics) model, the simulation was performed on the thermal characteristics during the DS process. Using a commercial CFD code, Fluent, the thermal characteristics in the DS system are calculated, and the results are graphically depicted.