Can solar control infrared blocking films be used to replace evaporative cooling for growth of Nannochloropsis sp. in plate photobioreactors?

Photobioreactor overheating is a significant challenge of microalgal mass production, resulting in low photosynthetic efficiency and poor biomass productivity. Due to cost and performance limitation, passive evaporative cooling systems for managing culture temperature are currently neither economical nor sustainable. In this study, the growth and photophysiology of Nannochloropsis sp. MUR 267 in four different flat plate photo-bioreactors designs, namely, solar control infrared reflecting film (IRF), insulated glazed photovoltaic (IGP), conventional water jacket (CWJ), and no heat control (NHC), were evaluated. Maximum attained culture temperature in the IRF is comparable with CWJ and 22.6% lower than NHC. Biomass productivity in the IRF (112.47 +/- 3.36 mg.L-1 d(-1)) is only 10% lower than that attained in the CWJ, and no net growth was seen in the NHC due to a high temperature. The immediate vitality of the cell photosynthetic apparatus monitored diurnally through the effective quantum yield of photosystem II (Fq'/Fm') showed values > 0.6 in IRF, CWJ and IGP. This study showed that clear infrared blocking films can significantly reduce the heat in PBRs without a dramatic reduction in culture performance.