We propose a simple numerical model for incorporation of oxygen and carbon impurities into multicrystalline Si during one-directional crystal growth in comparison with experimental results. The model includes parameters that are oxygen and carbon concentrations in the melt in the beginning of the growth, carbon flux form the atmosphere, oxygen fluxes from the crucible and to the atmosphere. Variation of oxygen and carbon concentrations in multicrystalline Si ingots with a diameter of 30 cm and a height of 7.5 cm solidified one-directionally was measured by infra red absorption spectroscopy at room temperature. By fitting the numerical results on the experimental results, the parameters were evaluated. In the modeling we found fruitful suggestions for suppressing and controlling the oxygen and carbon concentrations in multicrystalline Si for solar cells. (c) 2012 Elsevier B.V. All rights reserved.