Control of the Microalgae Photosynthetic Growth in a Torus Photobioreactor

The microalgae have the ability to use CO2 as carbon source and, together with the solar energy, to biosynthesize various components, generating O2. They have a huge potential in various industrial applications such as the production of therapeutic and industrial metabolites, biofuels and environmental applications. The aim of this paper is to control the photosynthetic growth of the microalga Chlamydomonas reinhardtii, in a continuous torus shape photobioreactor. The control strategy was to maintain the biomass concentration constant into the photobioreactor using the dilution rate as control variable. The main disturbance was the incident light flux. Two control laws were designed and analyzed in simulation, to wit a linear control algorithm and a nonlinear one. The linear controller was synthesized in a PI structure which was further tested in simulation at variable setpoints and incident light fluxes. The nonlinear controller was conceived in order to minimize the inconveniences encountered at the PI controller. The simulation conditions were identical for both controller types.