In the present study, two novel annular photobioreactors (PBR) were developed to enhance microalgae growth. One of these photobioreactors used mirrors outside the PBR, while the other one utilized phosphorescence materials inside the PBR. The results of the study suggested that the use of mirrors and phosphorescence materials led to 70% and 30% increase, respectively, in the light intensity without any additional energy consumption. Further, the results revealed that when compared with the base case, the biomass concentration increased by 91% and 24% in PBR with mirrors and phosphorescence materials, respectively. In conclusion, an improvement in PBRs resulted in efficient light to biomass conversion and economical technology for microalgae production. © 2018