Simulation of Multi-Loop PI Control Strategies for Optimizing Microalgae Cultivation and CO2 Capture in 3-Stage Bubble Column Photobioreactors

Abstract

Microalgae holds several promising applications, such as renewable sources for biofuel production and CO2 capture from industrial flue gases. There are limited studies so far focusing on the challenges of optimizing microalgae cultivation productivity and CO2 capture efficiency. The present work shows that one of the challenges to aim at high microalgae cultivation and CO2 capture efficiency is maintaining the oxygen level in water below its maximum threshold value, beyond which microalgae photosynthesis switches to respiration. The current work explores various control strategies, such as directly maintaining
the oxygen level, microalgae concentration and CO2 capture efficiency. One of the findings revealed that the conditions that increase the microalgae concentration tend to reduce CO2 capture and vice versa. The results emphasize the need to improve the mass transfer rates of CO2 and O2 across the liquid-gas phases by modification of the existing PBR design to improve microalgae productivity and CO2 capture efficiency simultaneously.