(105c) Thermal Control of an Enclosed Photobioreactor (PBR) for Algae Cultivation

Microalgae and cyanobacteria are promising sources of not only biofuels but also many nutraceutical, cosmetic and pharmaceutical value-added bioproducts, thanks to their rapid growth rates and significantly higher oil yields compared to terrestrial oil crops.

Closed photobioreactors (PBRs) and open channel pools (RWPs) have been used extensively for growing microalgae. Although closed PBRs have significantly higher biomass volumetric productivity compared to open RWPs, they have several disadvantages that limit their use on a commercial scale.

Temperature control is one of the most important factors. For the proper production the temperature inside the PBR should be kept constant despite changing climatic conditions. Various solutions – using heat exchangers, direct immersion of the PBR in a thermo-regulated pool and water spraying on the PBR surface - have been suggested in the literature.

This study focused on water spraying technique. In this study numerical heat transfer model of a closed PBR was developed and validated with the experimental data. The effect of the operation parameters (cooling system on and off conditions, mass flow rate etc) on the PBR temperature was investigated during a year for the various cultivation periods.

The findings were consistent across pilot-scale reactor simulations. However, caution should be exercised when using the presented data for scaling purposes, as commercial scale experimental data must be collected and fitted to our numerical model.