Modelling and Control Issues of pH in Tubular Photobioreactors

This paper presents the modelling and control issues about the pH regulation in a microalga tubular photobioreactor. The aim is to control the pH level minimizing CO2 losses. These kinds of photobioreactors are usually controlled by means of on-off valves and thus classical on-off switching controllers are implemented, where system dynamics and disturbances are not considered in the control system design. This work tries to improve this control results by means of a PI control system with PWM and including a feeforward term to compensate solar radiation influence. The process was simulated under different conditions to validate the proposed control system. Furthermore, experimental results were performed in a real plant obtaining promising results.