Optimization of Algal Photobioreactors: Design Considerations and Computational Approaches

Abstract

Talk: Regular Abstract: Delivery of light to microorganisms plays a crucial role in the performance of algal photobioreactors, especially for reactors 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 significantly increased by causing the organisms to experience light/dark cycles with frequencies greater than 1 Hz (flashing light effect). As a result of these observations, we demonstrate that commonly used reactor designs (e.g. airlift reactors) are highly inefficient and that biomass growth rate in both batch and continuous flow photobioreactors can be significantly improved by employing reactor designs with flow patterns that coherently shuttle microorganisms between light and dark regions of the reactor. We also describe the development and validation of two computational frameworks for coupling models for the three fundamental phenomena that determine reactor performance, namely multiphase turbulent fluid flow, radiation transport, and algal growth kinetics. While these computational methods provide a rational basis for photobioreactor design, optimization, and scaleup, significant challenges limit their applicability, especially for reactors operated at desirable high biomass concentrations.