Pilot-scale self-cooling microalgal closed photobioreactor for biomass production and electricity generation

Abstract Excessive cooling and energy requirements limit microalgal culture in closed photobioreactors. Here, the thermal behavior and biological performance of a spectrally-selective insulated-glazed photovoltaic (IGP) flat panel photobioreactor capable of co-producing microalgal biomass and electricity, while eliminating the need of cooling water was evaluated. The viability of this novel system for culturing Nannochloropsis sp. was compared to flat panel photobioreactors based on passive evaporative cooling (PEC), infrared reflecting thin-film coating (IRF), and open raceway pond. Maximum temperature (33.8 ± 2.9 °C) was highest in the IRF reactor while no significant difference was seen between IGP and PEC photobioreactors. Specific growth rate and biomass productivity of Nannochloropsis sp. was similar in all closed photobioreactors; however, raceway pond showed significantly lower productivity. Algal cultures in these cultivation systems were not thermally stressed. Electricity generated from IGP photobioreactor was 2.5-fold higher than the mixing energy requirement. Experimental results demonstrate a stand-alone IGP photobioreactor co-producing algal biomass and electricity, requiring no cooling water and grid electricity for operation.