Numerical simulations were applied to analyze the effects of the power ratios between top and side heaters on the crystal-melt(c-m) interface and the thermal stress distribution during the solidification process. The simulation results showed that among the different increase velocities of the power ratio, increasing the power ratio uniformly provided a most favorable solidification process: a slightly convex (c-m) interface shape and low thermal stress were obtained. The optimized design was implemented in casting experiments, which showed that the high-performance multi-crystalline silicon ingot had a vertical columnar structure and a lower dislocation density. The average conversion efficiency of solar cells was about 0.08% higher with this design (18.24%) than with the original design (18.16%). (C) 2016 Elsevier B.V. All rights reserved.