Growth Rate Estimation of Algae in Raceway Ponds: A Novel Approach

Microalgae mass cultiviation is a promising future source of biomass for energy and food production. In order to optimize productivity of large scale plants and to make them environmentally and economically sustainable, energy requirements have to be minimized. In particular, mixing of the growth medium is a major energy input, and its effect on overall productivity should be better understood. Several dynamic models have been developed to represent the effect of a rapidly varying light on the photosynthesis process especially for the effect of photoinhibition on growth. In order to assess the mixing effects in a complex hydrodynamic regime, we propose to reconstruct the light profile received by a single cell. A multi-layer Saint-Venant approach is used to simulate the hydrodynamics of the system. It allows for the computation of Lagrangian trajectories, and finally, when knowing the light distribution, the light pattern perceived by a cell. This pattern is then used with the dynamical model for photosynthesis. In a last step, the growth rate of the whole system is estimated as the average over a set of trajectories.