138
O. Pulz and K. Seheibenbogen
by an opalescent cone from 1.92 m- 1 to 19.0 m- 1, at a loss of effective volume
of only 15%, but a doubling of the productivity of Chlorella from
0.15 gd.wt.1 --1 d -1 to 0.31 gd.wt.1-1 d -~.
Miyamato et al. [108] used a very cost-effective variant to cultivate microalgae in vertically arranged glass tubes (qbA = 5 cm, height = 2 m) with mass
produced fluorescent lamps, and achieved an O/V-ratio of 80 m- ~ which corresponds to the ratio of the Biocoil reactor. At natural illumination, the maximum
productivities amounted to 0.3 g d.wt. 1- ~ d- ~ for cyanobacteria Nostoc and to
0.6 g d.wt. 1 - 1 d - 1 for the green alga Monoraphidium, the heating of the suspension having caused significant complications.
Jiittner [109] has solved the problem of overheating by the installation of
another internal tube which contained a cooling liquid and by reducing the dark
volume. This increased the growth rate by a factor of 1.5. This technically
expensive idea, however, has only limited capability for up-scaling.
5.2.2 Plate Type Reactors
If light energy has to be available continuously to the cells, a lamination of the
photobioreactor directed to the light source seems to be the best solution. This
basic principle of laminar concept has been practiced by plants for millions of
years. Compared with tubular systems, plate type geometries seem to have an
identical configuration potential and high surface/volume ratio, but some
advantages with respect to compactness (narrow U-turns, wall thickness). The
simplest approach is found in the application of widely used polyethylene bags.
With 501 turbidostatic cultures of Tetraselmis, Trotta [110] achieved yields of
20-30 g d.wt. m- 2 d- 1. Samson and Leduy [111] described transparent vertically arranged plates for cultivation. Illumination on both sides of the tanks
(10 cm wide) and simple aeration of the blue-green alga Spirulina maxima with
COz-enriched air have resulted in a maximum increase of 1.17 g d.wt. 1-~ d-1.
Ramos de Ortega et al. [112] were one of the first to test the horizontal
meandering channels which, then, were further developed by Fallowfield [-113].
Tredici and Materassi [80] and Pulz [59] also favoured this idea by arranging
vertically the rectangular channels in the plate geometry. In contrast to the
air-lift driven vertical alveolar panels (VAPs) of Tredici and Materassi, Pulz uses
a closed system with horizontal flow and pumps (PBR). The flow rate must be
high enough to maintain the turbulent flow in the channels (32 • 27 mm) and the
distance to the temperature-regulated degassing container must be short enough
to avoid critical gradients (e.g. 02, CO2-concentrations, T). Parallel plates can
be packed closely so that 42 plates (6 m 3 plant) will require only approximately
100 m 2 at a surface/volume ratio of 60 m- 1
Such a photobioreactor design, which was developed at the JGV (Inst. for
Cereal Processing) thus meets the requirements for improved areal outputs:
compact principle distributing over-saturating solar energy to as large a number
of cells as possible, narrow light path and strong turbulence streaming to move
O. Pulz and K. Seheibenbogen
by an opalescent cone from 1.92 m- 1 to 19.0 m- 1, at a loss of effective volume
of only 15%, but a doubling of the productivity of Chlorella from
0.15 gd.wt.1 --1 d -1 to 0.31 gd.wt.1-1 d -~.
Miyamato et al. [108] used a very cost-effective variant to cultivate microalgae in vertically arranged glass tubes (qbA = 5 cm, height = 2 m) with mass
produced fluorescent lamps, and achieved an O/V-ratio of 80 m- ~ which corresponds to the ratio of the Biocoil reactor. At natural illumination, the maximum
productivities amounted to 0.3 g d.wt. 1- ~ d- ~ for cyanobacteria Nostoc and to
0.6 g d.wt. 1 - 1 d - 1 for the green alga Monoraphidium, the heating of the suspension having caused significant complications.
Jiittner [109] has solved the problem of overheating by the installation of
another internal tube which contained a cooling liquid and by reducing the dark
volume. This increased the growth rate by a factor of 1.5. This technically
expensive idea, however, has only limited capability for up-scaling.
5.2.2 Plate Type Reactors
If light energy has to be available continuously to the cells, a lamination of the
photobioreactor directed to the light source seems to be the best solution. This
basic principle of laminar concept has been practiced by plants for millions of
years. Compared with tubular systems, plate type geometries seem to have an
identical configuration potential and high surface/volume ratio, but some
advantages with respect to compactness (narrow U-turns, wall thickness). The
simplest approach is found in the application of widely used polyethylene bags.
With 501 turbidostatic cultures of Tetraselmis, Trotta [110] achieved yields of
20-30 g d.wt. m- 2 d- 1. Samson and Leduy [111] described transparent vertically arranged plates for cultivation. Illumination on both sides of the tanks
(10 cm wide) and simple aeration of the blue-green alga Spirulina maxima with
COz-enriched air have resulted in a maximum increase of 1.17 g d.wt. 1-~ d-1.
Ramos de Ortega et al. [112] were one of the first to test the horizontal
meandering channels which, then, were further developed by Fallowfield [-113].
Tredici and Materassi [80] and Pulz [59] also favoured this idea by arranging
vertically the rectangular channels in the plate geometry. In contrast to the
air-lift driven vertical alveolar panels (VAPs) of Tredici and Materassi, Pulz uses
a closed system with horizontal flow and pumps (PBR). The flow rate must be
high enough to maintain the turbulent flow in the channels (32 • 27 mm) and the
distance to the temperature-regulated degassing container must be short enough
to avoid critical gradients (e.g. 02, CO2-concentrations, T). Parallel plates can
be packed closely so that 42 plates (6 m 3 plant) will require only approximately
100 m 2 at a surface/volume ratio of 60 m- 1
Such a photobioreactor design, which was developed at the JGV (Inst. for
Cereal Processing) thus meets the requirements for improved areal outputs:
compact principle distributing over-saturating solar energy to as large a number
of cells as possible, narrow light path and strong turbulence streaming to move