Computational fluid dynamics applied for the improvement of a flat-plate photobioreactor towards high-density microalgae cultures

The application of innovative strategies to develop cost-effective closed photobioreactors (PBRs) aiming high-density microalgae culture is the way to overcome the predominance of algae ponds against closed systems in the growing market of overall microalgae products. Hence, this paper focused on the development of a flat-plate PBR (FP-PBR) with improved fluid dynamics (FD), based on the system analysis theory, to achieve the maximum possible high-density culture (HDC). Therefore, 10-L FP-PBRs were built with and without internal bubble dispersers. The computational fluid dynamics (CFD) concept based on the Euler-Euler model was applied to study the FD of FP-PBRs through the software Comsol Multiphysics®. The system was considered as a 2D lateral cut of the three FP-PBRA – no disperser; FP-PBRB – simple disperser; and FP-PBRC – complex disperser. The simulations indicated that in PBRB and PBRC the flashing light effect was achieved. To prove the applied strategy, real photoautotrophic experiments with Poterioochromonas malhamensis were designed and performed. Comparison between FP-PBRA and FP-PBRC performance showed a drastic improvement in microalgae growth, up to 270% in biomass concentration. Finally, the application of the system analysis theory along with CFD stands out as a unique and powerful tool for system modelling, optimization and design.