Abstract
BackgroundUnlike conventional cultivation systems, liquid mixing in floating photobioreactors (PBRs) is solely induced by their hydrodynamic movement in response to waves, and this movement is affected by the wave conditions (wave height and wave period), the PBR configuration and the culture depth. However, to the best of our knowledge, a practical study of the hydrodynamic movements of PBRs has not been previously conducted.ResultsThis study aims to investigate the hydrodynamic performance of floating PBRs in response to wave conditions. First, the effects of the experimental wave height (2–10 cm) and wave period (0.8–1.8 s) on movement was investigated using two 1.0 m2 PBR models: a square PBR (1.0 m/1.0 m; length/width) and a rectangular PBR (1.7 m/0.6 m). The results indicated that wave movement became not only more intense with increasing wave height, but also less intense when the wave period decreased. However, the square PBR experienced more intense movement than the rectangular PBR, but also little mooring force. The effects of culture depth (0.5, 1.0 and 2.0 cm) were investigated and the results showed that the culture depth significantly affected the hydrodynamic movements of the PBRs; however, the mooring forces were unaffected. Finally, the movement and mooring-line forces of PBRs equipped with different mooring systems were investigated. The use of two different mooring systems had little effect on PBR movement; however, a mooring system with floaters was able to significantly reduce the mooring line forces compared to a system without floaters. During this study, the greatest force (10.5 N) was found for the rectangular PBR using a mooring system without floaters, whereas the lowest force (0.67 N) was observed for a rectangular PBR using a mooring system with floaters.ConclusionsThese studies have provided basic data describing the fluid dynamics of floating PBRs; as well as their structural design and scale up. These results also provide guidance for the selection of ocean fields with suitable wave conditions; as well as a proper mooring methods to ensure safe operation.
Highlights
Unlike conventional cultivation systems, liquid mixing in floating photobioreactors (PBRs) is solely induced by their hydrodynamic movement in response to waves, and this movement is affected by the wave conditions, the PBR configuration and the culture depth
The square model experienced more intensive movement than the rectangular model at the tested wave heights, during which the square PBR experienced horizontal movement ranging from − 4.73 to 5.56 cm and vertical movement ranging from − 4.80 to 4.55 cm; whereas, the rectangle PBR experienced horizontal movement ranging from − 2.65 to 4.5 cm and vertical movement ranging from − 2.80 to 2.19 cm
This finding was consistent with the results of the movement trajectories, which showed that the square model had a wide range of movement trajectories (Fig. 5). These results indicated that PBR geometry can significantly affect floating PBR hydrodynamics
Summary
Liquid mixing in floating photobioreactors (PBRs) is solely induced by their hydrodynamic movement in response to waves, and this movement is affected by the wave conditions (wave height and wave period), the PBR configuration and the culture depth. Microalgae have higher efficiency than plants for capturing C O2 from the atmosphere. Microalgae are more efficient at capturing solar energy than are terrestrial plants [2] Zhu et al Biotechnol Biofuels (2019) 12:54 and considerably higher production costs due to the high energy required for their operation and maintenance, as well as high capital costs [9, 10]. A floating cultivation system known as the Bicarbonate-based Carbon Capture and Algal Production System on Ocean (BICCAPSO) was developed [16, 19, 20], in which inorganic carbon was supplied via bicarbonate to develop a simple PBR that did not require aeration and agitation with the aim of reducing the costs of PBR manufacture and installation. During outdoor culturing in the ocean, the biomass productivity of BICCAPSO can yield up to 18.9 g m−2 day−1, which indicates that this system can effectively produce microalgal biomass
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
