Photobioreactor purpose

Along with concerns of lost production during cloudy periods, the amount of downtime associated with maintenance will also affect the overall economics. Ideally, the photobioreactor would operate continuously. If operated in batch mode, there would be a period of limited H2 production while the cell density increased at the start of a new batch. If the system needs to be emptied for maintenance purposes, or if the cell culture is lost due to equipment failure or contamination, lost production will significantly affect the economics. The length of time required to build up cell mass in a wastewater treatment plant during start-up can be weeks, for example. 

Photobioreactor Modeling and Radiative Transfer Analysis for Engineering Purposes... 

The purpose of a photobioreactor is to absorb incident light in order to convert it into biomass via coupling with photosynthesis. On the one hand, efficient light absorption usually corresponds to heterogeneous radiation fields (x) within the reaction volume (see Section 3). On the other hand, the coupling law (Eq. (4)) is usually a non-linear function of (x) (the law obtained in Section 5 is non-linear, but this is also the case for most of other models reported in the literature). Therefore, the coupling between radiative transfer and photosynthesis must be formulated locally, which implies that determination of the volumetric rate < > requires... 

In the earlier example, the local production rate was assumed to be known for the purposes of illustration. Nevertheless, as stated in Section 1 (and detailed in Section 5), is a function of the specific rate of photon absorption A. This is why photobioreactor studies require solution of the radiative transfer equation prior to estimation of the production... 

Besides hght supply, carbon dioxide uptake is most important to be considered. CO2 transfer to photobioreactors has been shown to be one of the reasons for energy dissipation. Furthermore, it influences pH value what on the other hand can be used for control purposes. CO2 kinetics is therefore an important issue for optimizing cultivation conditions. 

Also when employing more realistic and more complex models, such as Jassby and Platt with spectral resolution the same rule applies volumetric productivity of a photobioreactor is maximal when the biomass density is such that the photon flux density at the darkest zone of the reactor is equal to the compensation point of photoautotrophic growth. In practice it has also been confirmed that photobioreactors can be operated at maximal productivity when the biomass concentration is maintained at those levels that almost aU light is absorbed within the microalgal culture but at the back still a minimal amount of light is left to compensate for maintenance purposes (Barbera et al, 2015 Takache et al, 2012 Zijffers et al, 2010). 

Ifrim GA, Titica M, Cogne G, Bofllereaux L, LegrandJ, Caraman S Dynamic pH model for autotrophic growth of microalgae in photobioreactor a tool for monitoring and control purposes, AIChEJ 60(2) 585—599, 2014. 

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