Abstract

 Experiments of algal bio-productivity have demonstrated significantly higher biomass production in thin flat plate bioreactors (thickness of 1-3 cm) than in conventional biomass systems (open ponds).  More important, culture-production rates grow persistently as radiation levels are increased above one sun and do not reach saturation or photo-inhibition at light intensities of up to several suns.

Whereas in open ponds algae are exposed to continuous illumination, in thin flat plate reactors they are exposed to light flashes because of the ultra-high cell density; light intensity falls off rapidly into the depth of the reactor.

We characterize the dynamics of biomass production in thin flat plate bioreactors by two types of time scales: physical time scales, capturing the random motion of algae cells through the reactor, and biological time scales that characterize periods, during which cells do not utilize impinging photons, as well as decay processes of absorbed photons. The physical and biological time scales approach approximate synchronization. Consequently, higher photosynthetic rates are expected. These expectations are borne out by a simple random walk model, which is based on the fundamental timescales. The predictions of the model are consistent with available data.