Advanced Design and Characterization of a Flat Panel Photobioreactor Equipped with a Customizable Light-Emitting Diode Lighting System
Michele Carone, Graziano Frungieri, Lorenzo Costamagna, Mariachiara Zanetti, Marco Vanni, Vincenzo Riggio
Abstract
Microalgae-based biorefinery processes are gaining particular importance in producing high-quality biomass and energy feedstock for several industrial markets. However, there are still several factors that contribute to poor yields of microalgae growth in the current technologies. These include inadequate light management, inefficient gas exchange, limited control over temperature and pH, and susceptibility to contamination. Additionally, challenges associated with the scalability and high operational costs of photobioreactors (PBR) further hinder the achievement of optimal yields in microalgae cultivation. This work presents a detailed characterization of a novel flat-panel PBR equipped with a tunable LED lighting system. A computational fluid dynamics (CFD) study was conducted to characterize in detail the equipment from a hydrodynamics point of view. CFD results showed that the flow field has several peculiar features, such as vortices and a bypass current, that can be expected to affect the light absorbance statistics and the microalgae and nutrients spatial distributions. Considerations for both the system optimization and modeling of its behavior during operation were drawn. Additionally, two different microalgae strains, namely, the green microalga Acutodesmus obliquus and the red extremophile Galdieria sulphuraria, each with specific growth parameters and spectra irradiation requirements, were successfully cultivated using tailored light spectra. The biomass concentrations and yields achieved (yields on light of 0.58 and 0.45 g mol ph –1 for A. obliquus and G. sulphuraria, respectively) were consistent with currently reported productivities for both species, highlighting the effectiveness of the adopted strategy for light management and the PBR overall design.