Light availability inside the reactor is often the bottleneck in microalgae cultivation and the light intensity varies with its position and time in the cultivation process. An integrated model including flow, radiation and microorganism growth is presented, in which the radiation of two complementary polychromatic light sources is resolved with the finite volume method combined with a box model. The integration of the box model into radiative transport equation (RTE) is verified first and then utilized to predict the microalgae concentration evolutions in a batch and continuous culture, respectively, which are in a good agreement with the experimental data. The evolution of light transfer in the photobioreactor (PBR) is well captured in both cultures, which provides a guideline to promote the light utilization in the PBR. The model developed and verified in this contribution has the potential to be applied as an effective tool to scale up these types of reactors and achieve an optimal biomass production with the precise control of the cultivation. (C) 2012 Elsevier Ltd. All rights reserved.