Experimental and Numerical Parametric study of horizontal photobioreactor on the growth rate of Chlorella vulgaris microalgae

Microalgae have gained considerable attention due to their extensive application in the production of biofuels and water treatment. In this paper, the effects of three main parameters, namely the light intensity, aeration rate, and diameter of the photobioreactors (PBR), were simultaneously examined on the microalgae growth rate and energy cost of the horizontal PBR. Regarding the number of variables, the response surface method in the Design Expert software was employed to attain a deeper insight into the influence of these factors on biomass production and energy costs. The biomass and energy equations were obtained based on the numerical analysis. The highest biomass production rate (1.9 g/L per day) was attained under a light intensity of 625 µmol/s/m², photobioreactor diameter of 5 cm, and aeration rate of 0.18 L/min with the cost of 504.6 cents per day. At the optimum point, although the biomass production showed a 26.8% decline, it resulted in a 53% decrement in the energy costs. Therefore, the investigation of microalgae production at the highest efficiency and lowest costs in this research can promote the application of this useful and renewable biomass.