Experimental investigation of a local recirculation photobioreactor for mass cultures of photosynthetic microorganisms

Hydrodynamic Light Flashing in Thin Layer Wavy Photobioreactors

“…A quantitative validation of the numerical model was performed by comparing the corresponding numeric values of the parameters describing the hydraulic features of potential photobiological significance, and of most concern for microalgal technology. The recirculation period (tc) of the liquid elements were calculated as tc= 2π/(∂u/∂z) from the velocity plot, by considering the (nearly) constant value of the velocity gradient within the vortex (∂u/∂z) and the characteristic dimension of the vorticose structure according to a previously described procedure [19]. The comparison between the values of the light flash-related hydrodynamic parameters predicted by the CFD and those computed from the post-processed experimental data is reported in Table 1.…”

“…Model setup was based on experimental data collected in a test rig substantially analogous to that described by Moroni and others [19]. Image processing was achieved in three steps: 1) a pre-processing step aimed to remove the background and improve image contrast; 2) particle detection and temporal tracking via HLPT to isolate particles and track them in consecutive frames; 3) post-processing to obtain the relevant flow parameters [19].…”

“…Compared to many conventional culture systems this photobioreactor design: 1. features an optically thin culture that is amenable to high cell concentration which is amongst the top requirements for lowering biomass harvest costs [17]; 2. provides an efficient gas-liquid mass transfer, with a positive dependence upon specific flow rate [16] 3. features a low equipment cost (can be produced from low cost semi-finished materials); 4. has hydrodynamic features leading to regular, specific flow ratedependent light-dark alternation which might result in increased photosynthetic activity with respect to other frequently adopted (e.g., tubular and bubble column) photobioreactor geometries [19]. It was shown that in a 15-cavity wavy-bottomed lower surface photobioreactor a local recirculation zone establishes in each cavity only at low inclinations (≤ 6°) and that its location changes according to the inclination slope from the lower (0° and 3°) to the upper part of each cavity (6°) [19].…”

“…Compared to many conventional culture systems this photobioreactor design: 1. features an optically thin culture that is amenable to high cell concentration which is amongst the top requirements for lowering biomass harvest costs [17]; 2. provides an efficient gas-liquid mass transfer, with a positive dependence upon specific flow rate [16] 3. features a low equipment cost (can be produced from low cost semi-finished materials); 4. has hydrodynamic features leading to regular, specific flow ratedependent light-dark alternation which might result in increased photosynthetic activity with respect to other frequently adopted (e.g., tubular and bubble column) photobioreactor geometries [19]. It was shown that in a 15-cavity wavy-bottomed lower surface photobioreactor a local recirculation zone establishes in each cavity only at low inclinations (≤ 6°) and that its location changes according to the inclination slope from the lower (0° and 3°) to the upper part of each cavity (6°) [19]. Sforza and others' warning that the combination between species, external irradiance and hydrodynamic mixing Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 5 June 2019 doi:10.20944/preprints201906.0043.v1 frequency must be carefully checked before investing on a specific photobioreactor installation [20] and the consideration of how burdensome experimentally investigating fluid dynamics is [19], was chosen to track the interface between microalgal suspension phase and the upper gas phase [24].…”

“…It was shown that in a 15-cavity wavy-bottomed lower surface photobioreactor a local recirculation zone establishes in each cavity only at low inclinations (≤ 6°) and that its location changes according to the inclination slope from the lower (0° and 3°) to the upper part of each cavity (6°) [19]. Sforza and others' warning that the combination between species, external irradiance and hydrodynamic mixing Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 5 June 2019 doi:10.20944/preprints201906.0043.v1 frequency must be carefully checked before investing on a specific photobioreactor installation [20] and the consideration of how burdensome experimentally investigating fluid dynamics is [19], was chosen to track the interface between microalgal suspension phase and the upper gas phase [24].…”