This paper presents the numerical simulation of heat transfer and solidification process in an industrial silicon directional solidification system. The energy efficiency in the production system is analyzed. The effects of the heating power and the position of the side insulation layer on the solidification interface position/shape are investigated. The numerical results indicate that the directional solidification of the silicon can be controlled by adjusting the heating power and moving the side insulation layer. The knowledge gained from the thermal analysis can be used to improve the energy efficiency in the Current silicon production system. An easy method to detect the solidification interface shape was proposed and has been conceptually proven. (C) 2009 Elsevier B.V. All rights reserved.