Soft sensor design with state estimator for lipid estimation of microalgal photobioreactor system

Microalgae have received considerable attention as a source of biodiesel since they contain large amounts of lipid. However, microalgal biodiesel is not economically competitive compared to other sources of biodiesel or petrodiesel. To improve the productivity of lipid and biomass in photobioreactor systems, real-time monitoring and control are prerequisite. However, measurement of lipid in microalgae itself is very difficult and time consuming task, and it is not easy to know the lipid concentration in real-time. In this study, estimation of lipid concentration using other online measurements from biomass or glucose sensor was studied. Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), and Particle Filter (PF) were compared in various cases for their applicability to photobioreactor systems. Furthermore, simulation studies to find appropriate types of sensors for estimating lipid have also been performed. This study suggests what filters and what type of sensors are suitable for estimating lipid concentration on-line.