Multi-Physics Modeling of Light-Limited Microalgae Growth in Raceway Ponds

Abstract

This paper presents a multi-physics modeling methodology for the quantitative prediction of microalgae productivity in raceway ponds by combining a semi-mechanistic model of microalgae growth describing photoregulation, photoinhibition and photoacclimation, with models of imperfect mixing based on Lagrangian particle-tracking and heterogeneous light distribution. The photosynthetic processes of photoproduction, photoregulation and photoinhibition are represented by a model of chlorophyll fluorescence developed by Nikolaou et al. (2015), which is extended to encompass photoacclimation. The flow is simulated with the commercial CFD package ANSYS, whereas light attenuation is described by the BeerLambert law as a first approximation. Full-scale simulation results are presented on extended time horizons. Comparisons are made in terms of areal productivities under both imperfect and idealized (CSTR) mixing conditions, and for various extraction rates and water depths.

Microalgal kinetics — a guideline for photobioreactor design and process development

“…The first one is the temporal aspect. Photo‐acclimation ranges from fractions of a second to hours or days . The differences in time scales prohibit the transfer of short‐term measurements to outdoor cultivations.…”

Deep learning‐based surrogate modeling and optimization for microalgal biofuel production and photobioreactor design

“…However, the complexity of the interactive hydrodynamics and kinetic mechanisms makes it challenging to construct a multiscale physical model, which is capable of simulating cell growth and product synthesis accurately in large‐scale PBRs. Although a few studies have attempted to couple kinetic models and CFD models, these have been restricted to the analysis of open ponds instead of PBRs. Moreover, the execution of mathematical optimization on multiscale physical models is infeasible in most cases due to the high nonlinearity and stiffness of the models; while using the integrated models for the sampling of large numbers of different combinations of reactor configurations and operating conditions is also impractical due to the substantial computational costs of running each design scenario.…”

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

“…By applying this simple scaling rule to literature results, the found t I values are larger than 10 2 s for raceways , or close to 1 s in falling‐film devices . Considering a microalgae characteristic time around 0.3 s as observed in this work, the raceway could be simulated using the hypothesis of a full integration kinetic.…”

“…In recent years, numerous works proposed some advances regarding one or several of the aforementioned points. Wu and Merchuk , Hartmann et al , or Nikolaou et al coupled the light fluctuations to the growth rate using the photosynthetic unit model of Eilers and Peeters .…”