Model-based feasibility assessment of a deep solar photobioreactor for microalgae culturing

A deep photobioreactor (PBR) based on cone-shaped light guides was conceived to improve the solar light utilization efficiency of microalgae cultures, optimizing light distribution over the culture surface and thus minimizing photoinhibition and photosaturation occurrence. A preliminary model based on local light intensities and local growth rates was developed in order to check its viability. The model was applied to a conceptual PBR unit using irradiance data of Santander (Spain). Areal biomass productivities of 15.17 and 34.57 g m(-2) d(-1) were predicted for the most unfavorable and favorable months respectively, both under monthly average cloud cover. These results are, in average, 2.72 times higher than predicted values for an open pond PBR under identical irradiance conditions. A procedure to scale-up the deep PBR in any location was developed. The procedure provides the optimal arrangement of the light guides and its operational parameters as a function of the surface incident light intensity. According to the obtained results, the novel configuration is highly efficient in land use, providing a low surface requirement solution.