Large-scale production of multi-crystalline silicon for high-efficient solar cells is a very important task of today’s photovoltaic technology. The efficiency of crystalline silicon solar cells depends on both the crystallization process and the solar cell processing sequence. As far as the crystallization process is concerned, it is very important to know the temperature distribution during the solidification of silicon ingots, to predict the solidification structure obtained and thus the materials properties. In this study the transient 2D and stationary 3D numerical simulation of the solidification process of large square mc-Si ingots is investigated, by using the software FIDAP and FluentTM. Some geometrical approximations of the real furnace and specific approaches for the radiation modelling are used in order to solve the difficulties related to numerical analysis. The results are compared to the experimental data, in order to calibrate the numerical model.