A comprehensive modeling method for the simulation of outdoors algal cultivation in bubble column photobioreactors is presented. The compartmental modeling approach presented earlier by Nauha and Alopaeus (2013) [1] is used and extended to consider changes in the directionality of light during the day. The nightly loss of biomass due to darkness is also considered. The model is capable of predicting the system hydrodynamics, mass transfer and growth of algae. Model results are verified against measurements and show good agreement. The predictive capability of the model is validated. The model is used to make suggestions for optimization of outdoors algal cultivation. (C) 2014 Elsevier B.V. All rights reserved.