Abstract A multi-crystalline silicon (Si) ingot was simulated and grown using the improved directional solidification (DS) process. Numerical simulations were performed with two different cooling paths and two different coolant flow rates in order to demonstrate the thermal characteristics in the improved DS furnace during the crystal growth. The temperature distributions in the furnace and locally (at the silicon ingot) were predicted as a function of time. From these result, a multi-crystalline Si ingot weighing 300 kg was grown within 40 h using the improved DS process. The Si ingot had a grain size that was larger than 5 mm, and the structure of the ingot was in the form of vertical columns. From the analysis results, the Si ingot exhibited a resistivity below 2 Ω cm and a life time above 3 μs.