Proofing the concept of a segmented biophotovoltaic process to produce electricity from marine cyanobacteria: an indoor and outdoor approach

This study presents an innovative biophotovoltaic (BPV) process with three components: a cyanobacteria reservoir that serves as the biological engine; an electron-capture reactor that redirects transmembrane electrons; and a radiation-harvesting tower designed to maximize energy input and enhance system scalability. For the indoor (LED) and outdoor (solar radiation) tests, the most suitable resistances to yield the maximum current density were 164 Ω and 220 Ω, respectively. Indoor electricity generation peaked at 227 mW m − 2 , with an average of 175 ± 47 mW m − 2 , while outdoor tests peaked at 215 mW m − 2 , with an average of 166 ± 26 mW m − 2 , indicating similar efficiency under both conditions. To explain these efficiencies, the 5% loss in performance is most likely related to the increase in temperature from 20 °C to 32 °C and the resistivity of electrode materials. To confirm this, complementary experiments (in triplicate) demonstrated that an increase in incubator temperature to 32 °C also resulted in lower electricity generation (125 ± 25 mW m − 2 ). The heat conduction to the cyanobacteria medium led to harsher environmental conditions for Synechocystis pevalekii , and the increased resistivity caused voltage drops. Overall, the proof of concept of our BPV process demonstrated that it is technically possible to run in the system in an external laboratory environment using the segmentation approach and the radiation-harvesting tower.