How Mixing and Light Heterogeneity Impact the Overall Growth Rate in Photobioreactors

• Published in: Chemical engineering & technology Vol. 42; no. 8; pp. 1663 - 1669
• Main Authors: Gernigon, Vincent, Chekroun, Mohammed A., Cockx, Arnaud, Guiraud, Pascal, Morchain, Jérôme
• Format: Journal Article
• Language: English
• Published: Frankfurt Wiley Subscription Services, Inc 01.08.2019; Wiley-VCH Verlag
• Subjects: Algae; Biotechnology; Design parameters; Growth models; Growth rate; Irradiance; Life Sciences; Light distribution; Light heterogeneity; Microalgae; Particle tracking; Photobioreactor; Simulation; Time constant; Variations; micro-algue; photobioréacteur; effet de la lumière; light heterogeneity; simulation; microalgae; photobioreactor; growth models
• ISSN: 0930-7516; 1521-4125
• DOI: 10.1002/ceat.201900102

The microalgae growth rate in photobioreactors responds with inertia to light stimuli. Here, light variations experienced by the algae are accessed through a coupling of an irradiance field calculation and a Lagrangian particle tracking. The response of algae to fluctuating light is then described by a relaxation model involving a single time constant, the value of which is identified from published data. The overall growth rate is calculated as the sum of individual growth rates of all particles. Instantaneous adaptation and full integration asymptotic behaviors are recovered whilst a finite time constant reveals that the overall growth rate is dependent both on mixing and light distribution. This methodology thus quantitatively relates the design parameters to the photobioreactor performance. A general methodology is developed and applied for the calculation of the overall growth rate in a heterogeneous photobioreactor. The light exposition experienced by the cells obtained from their Lagrangian tracking on two‐phase non‐stationary computational fluid dynamics simulations is coupled to a biological growth model based on an experimental characteristic relaxation time.