Laboratory-scale reproduction of lighting conditions for an outdoor vertical column photobioreactor: Theoretical fundamentals and operation of a programmable LED module

Abstract

The development of tools aimed to predict the productivity of photobioreactors (PBRs) implies immense efforts in the Algae Biotechnology field. Mainly, bubble column systems are widely used for microalgae cultivation. Here, we sought to present a methodology to reproduce the solar lighting conditions of a vertical bubble column reactor located in Santa Fe, Argentina, utilising a commercial laboratory-scale reactor, with a programmable LED module attached. Based on solid, rigorous modelling of solar radiation properties and radiation transfer between surfaces, and keeping constant the effects of geometry and orientation of PBR, and those related to geography such as photoperiod and solar radiation composition (direct and diffuse), the same amount of photosynthetically active radiation (PAR) per volume unit (volumetric radiant flux) has been provided to the indoor unit. Lastly, since the deliverance of radiant energy between the indoor and outdoor units is not the same, the radiant energy field (REF) is obtained for both reactors and compared using the Monte Carlo methodology. Comparisons were made in terms of the distribution and average volumetric absorption rate of PAR photons (〈rPAR〉) for different scenarios (time, day of the year, biomass concentration and photosynthetic pigments concentration). Taken together, the 〈rPAR〉 turned out to be similar for both PBRs, highlighting the potentiality of this approach for its usage either in real or simulated units under varying outdoor conditions.