(587az) The Role of Hydrodynamics and Radiation Transport During Light-Limited Growth of Microalgae in a Taylor Vortex Photobioreactor: Quantitative Analysis Using Computational Fluid Dynamics Coupled With Radiation Transport Simulations

Delivery of light to microorganisms plays a crucial role in the performance of algal photobioreactors, especially those operated at high biomass concentrations. The important characteristics of light delivery include not only the intensity and wavelength spectrum of irradiation, but also temporal variations in these quantities. In particular, microalgal biomass productivity and light utilization efficiency can be dramatically increased by causing them to experience light/dark cycles with frequencies greater than 1 Hz (flashing light effect).  In this paper we demonstrate that coherent flow structures known as Taylor vortices can be used to efficiently generate highly periodic light/dark cycles with tunable frequencies greater than 1 Hertz, and these light/dark cycles in turn produce significant increases in biomass productivity and light utilization efficiency that cannot be explained by mass transport effects. The evidence to support these findings includes experimental measurement of biomass productivity in the Taylor vortex photobioreactor, as well as a detailed quantitative analysis of Taylor vortex algal photobioreactors using computational fluid dynamics and multidimensional spectral radiation transport simulations developed in house. These simulations provide statistically meaningful data for microorganism trajectories in the reactor as well as the temporal exposure to photosynthetically active radiation, and provide a rational basis for reactor scaleup.