Photobiohydrogen production and high-performance photobioreactor - Solar Energy Sciences and Engineering Applications - page 357

Figure 11.4.5 Tubular photobioreactor configurations: (a) near horizontal tubular photobioreactor
(Gebicki et al., 2009); (b) conical helical photobioreactor (Morita et al., 2000), and;
(c) α -shape tubular photobioreactor (Lee et al., 1995).
paralleled tubes connected to the base of the first set of riser tubes. Such design enables
an increase in the surface-to-volume ratio and equable photosynthetically-available
radiance, leading to a high biomass density.
11.4.2 Optimization of the operating parameters
To achieve a high performance photobioreactor, not only the improvement in photo-
bioreactor design is required but also the operation parameters need to be optimized.
Typically, the factors affecting the photobiohydrogen production performance of the
photobioreactor include the illumination conditions, temperature, pH value and so on
(Show et al., 2011).
11.4.2.1 Illumination conditions
The photobiohydrogen production by microorganisms is driven by light that func-
tions as an energy source so that the illumination conditions, both light wavelength
and light intensity, can affect the photobiohydrogen production performance (Car-
lozzi et al., 2010; Liu et al., 2010; Uyar et al., 2007). As the stimulation of the
photobiohydrogen production reaction occurs at different light wavelengths, depend-
ing on the used microorganisms and operating conditions, the appropriate wavelength
will be distinguished. Chen et al. (2006b) reported that the indigenous purple non-
sulfur bacteria Rhodopseudomonas palustris WP3-5 yielded excellent performance by
absorbing lights at the wavelengths of 522 and 860 nm. Tian et al. (2010) studied
the effect of the light wavelength on the performance of photobiohydrogen produc-
tion by Rhodopseudomonas palustris CQK 01 using monochromatic LED lamps. The
results showed that the best photobiohydrogen production performance was obtained
at 590 nm due to the existence of absorption maxima of bacteriochlorophyll α . Fur-
thermore, Tian et al. (2010) found that photobiohydrogen production was saturated
at around 5000 lx and high light intensity resulted in a striking decrease of the conver-
sion efficiency from light energy to hydrogen. This team also demonstrated that the
light conversion efficiency decreased monotonically with increasing the illumination
intensity because not all light can be absorbed at high illumination intensity (Liao et al.,