Light/dark cycle enhancement and energy consumption of tubular microalgal photobioreactors with discrete double inclined ribs

Qin, Chao; Lei, Yuling; Wu, Jing

doi:10.1186/s40643-018-0214-8

Cited by 15 publications

(11 citation statements)

References 30 publications

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“…Therefore, knowing the spectral properties of microalgae could enhance biofuel production by producing more biomass and lipids, although this will depend on improving photobioreactor designs. Models of photobioreactor mixing that have incorporated scalar irradiance [61][62][63][64] and spectral irradiance [65] have shown that continuous mixing in strong light is needed to achieve high biomass production [66]. To enhance biomass and lipid production, the light spectrum could be matched to algal absorption in a well-mixed photobioreactor so that algal cells would experience a high, time-averaged light field with no dead zones to trap cells in suboptimal light levels.…”

Section: Bio-opticsmentioning

confidence: 99%

The influence of bio-optical properties of Emiliania huxleyi and Tetraselmis sp. on biomass and lipid production when exposed to different light spectra and intensities of an adjustable LED array and standard light sources

et al. 2019

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The effects of bio-optical characteristics on lipid and biomass production rates for Emiliania huxleyi and Tetraselmis sp. were studied under different irradiances and spectra. Biomass and lipid production increased from irradiances of 50-800 μE m −2 s −1 but differed for each spectrum. The highest biomass and neutral lipid production rates for E. huxleyi occurred under a red-blue LED array, which mimicked the absorption spectra of the cell's chlorophyll a and accessory pigments, especially fucoxanthins. Biomass and neutral lipid production for Tetraselmis sp. were enhanced under broader spectra of cool white and grow lights. Neutral lipids per cell volume were similar for the two species and inversely proportional to chlorophyll a concentrations. High biomass and neutral lipid production rates were associated with high total quantum absorption and low quantum absorption per cell. Generally, quantum efficiencies were highest for high light treatments with high total quantum absorption and high production rates. Using reconstructed quantum absorption by pigments, the bio-optical model showed that photoprotective pigments were dependent on light intensity and spectra. Quantum efficiencies increased when excluding the contribution of photoprotective pigments to total quantum absorption since they did not directly contribute to photosynthesis, but did promote higher production rates.

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Section: Bio-opticsmentioning

confidence: 99%

The influence of bio-optical properties of Emiliania huxleyi and Tetraselmis sp. on biomass and lipid production when exposed to different light spectra and intensities of an adjustable LED array and standard light sources

et al. 2019

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“…The motions of the microalgae particles between the light and dark zones form L/D cycles. A complete duration of the L/D cycle is [22,23,25] t c = t l + t d (13) where t l and t d are the durations for which a particle stays in the light and dark zones [s].…”

Section: The Average L/d Cycle Frequencymentioning

confidence: 99%

“…Gómez-Pérez et al [21] simulated the effect of wall turbulence promoters in a tubular PBR and found that the mixing behavior of the PBR was enhanced after the addition of wall turbulence promoters. Qin et al [22] modified the tube structure and found that the addition of discrete inclined ribs on the tube wall increased the L/D cycle frequency of the algae cells. The highest L/D cycle frequency was obtained when two pairs of ribs with a rib length ratio of 5 were used.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, it is suggested to pay attention to the increase in energy consumption while increasing the average L/D cycle frequency using a built-in static mixer or by modifying the tube structure. To comprehensively consider the effects of mixer addition or the reactor structure on the average L/D cycle frequency and the energy consumption, Qin et al [22] proposed the concept of the efficiency of the L/D cycle enhancement and used this parameter to evaluate the economic performance of mixers or rib structures in enhancing the L/D cycles [24,25].…”

Section: Introductionmentioning

confidence: 99%

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Optimization of Tubular Microalgal Photobioreactors with Spiral Ribs under Single-Sided and Double-Sided Illuminations

Lei

Wang

2019

Processes

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Microalgae can be raw materials for the production of clean energy and have great potential for development. The design of the microalgal photobioreactor (PBR) affects the mixing of the algal suspension and the utilization efficiency of the light energy, thereby affecting the high-efficiency cultivation of the microalgae. In this study, a spiral rib structure was introduced into a tubular microalgal PBR to improve the mixing performance and the light utilization efficiency. The number of spiral ribs, the inclination angle, and the velocity of the algal suspension were optimized for single-sided and double-sided parallel light illuminations with the same total incident light intensity. Next, the optimization results under the two illumination modes were compared. The results showed that the double-sided illumination did not increase the average light/dark (L/D) cycle frequency of the microalgae particles, but it reduced the efficiency of the L/D cycle enhancement. This outcome was analyzed from the point of view of the relative position between the L/D boundary and the vortex in the flow field. Finally, a method to increase the average L/D cycle frequency was proposed and validated. In this method, the relative position between the L/D boundary and the vortex was adjusted so that the L/D boundary passed through the central region of the vortex. This method can also be applied to the design of other types of PBRs to increase the average L/D cycle frequency.

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“…Designers are always seeking ways to increase algal biomass productivity in PBRs, and the way of introducing mixers to PBRs (including open ponds) has been well developed over the past several decades, such as the trapezoidal chamber mixer in a flat-plate PBR [3], the up–down chute baffles in an open pond [4], the Kenics mixer [5], the plate mixer with a V-groove at the top and a hole at the center [6–8], the inclined porous mixer [9] and the helical mixer [10] in tubular PBRs. Apart from mixers, novel structures (e.g., the discrete double-inclined ribs in a tubular PBR [11] and a wavy bottom in a pond-like PBR [12]) have also been introduced to PBRs to increase biomass productivity. These novel structures actually serve as mixers for enhancing PBR mixing performance.…”

Section: Introductionmentioning

confidence: 99%

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

Qin

Jing

2019

Biotechnol Biofuels

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Background Mixers are usually inserted into microalgal photobioreactors to generate vortices that can enhance light/dark cycles of algal cells and consequently enhance biomass productivity. However, existing mixer designs are usually developed using a trial-and-error approach that is largely based on the designer’s experience. This approach is not knowledge-based, and thus little or no understanding of the underlying mechanisms of mixer design for mixing performance of photobioreactors is attained. Moreover, a large pumping cost usually accompanies mixer introduction, and this cost is not favorable for practical applications. This study aims to improve this situation. Results In addition to the individual effects of flow and light fields, improving the synergy (coordination) between these fields may markedly enhance the L/D cycle frequency with a lower increase in pumping costs. Thus, the idea of synergy between flow and light fields is introduced to mixer design. Better synergy can be obtained if (a) the vortex core and L/D boundary are closer to each other and (b) the vortex whose core is too far from the L/D boundary is removed. The synergy idea has two types of applications. First, it can facilitate a better understanding of known numerical and experimental results about mixer addition. Second, and more importantly, the idea can help to develop new rules for mixer design. A helical mixer design is provided as a case study to demonstrate the importance and feasibility of the synergy idea. An effective method, i.e., decreasing the radial height of the helical mixer from the inner side, was found, by which the L/D cycle frequency was enhanced by 10.8% while the pumping cost was reduced by 23.8%. Conclusions The synergy idea may be stated as follows: the enhancement of L/D cycle frequency depends not only on the flow and light fields individually but also on their synergy. This idea can be used to enhance our understanding of some known phenomena that emerge by mixer addition. The idea also provides useful rules to design and optimize a mixer for a higher L/D cycle frequency with a lower increase in pumping costs, and these rules will find widespread applications in PBR design. Electronic supplementary material The online version of this article (10.1186/s13068-019-1430-y) contains supplementary material, which is available to authorized users.

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Light/dark cycle enhancement and energy consumption of tubular microalgal photobioreactors with discrete double inclined ribs

Cited by 15 publications

References 30 publications

The influence of bio-optical properties of Emiliania huxleyi and Tetraselmis sp. on biomass and lipid production when exposed to different light spectra and intensities of an adjustable LED array and standard light sources

The influence of bio-optical properties of Emiliania huxleyi and Tetraselmis sp. on biomass and lipid production when exposed to different light spectra and intensities of an adjustable LED array and standard light sources

Optimization of Tubular Microalgal Photobioreactors with Spiral Ribs under Single-Sided and Double-Sided Illuminations

Synergy between flow and light fields and its applications to the design of mixers in microalgal photobioreactors

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