A Simple Model for Algal Photosynthesis for Better Light Utilization with Flashing Light

A simple mathematical model of the algal growth in a flashing light regime is proposed. The model is based on reduction state of fast and slow charge carriers in PS-II. The model constants were fitted to the published experimental data. Chlorophyll a fluorescence measurement was used for estimating the reduction time scale of the fast charge carriers. The data suggest that the reduction time scale of fast charge carriers exponentially drops with an increase in the light intensity. For the studied light intensities, the fast carrier’s reduction time varies between 1 and 16 ms. The reduction time constant of slow charge carriers and average re-oxidation time constant of all charge carriers are estimated to be 300 and 250 ms respectively. First time the model was able to predict the photosynthesis rate for a wide range of light duty values with reasonably good accuracy. The model also accurately predicted 3X improvement in the light utilization efficiency observed in the experiments. In the second part, a simple modelling approach to simulate algal growth in a flat panel photo-bioreactor is presented. Incident light intensity and cell density were used for estimating the thickness of light region and the lateral velocity was used for modelling the movement of cells from one region to another. The model highlighted the impact of boundary layer thickness on the PBR performance and demonstrated that increasing the lateral velocity beyond 0.1 m/s does not help in further improving the productivity. Graphical Abstract