Modeling of the influence of light quality on the growth of microalgae in a laboratory scale photo-bio-reactor irradiated by arrangements of blue and red LEDs

• Radiant field inside a PBR irradiated with different LEDs arrays was analyzed.
• Average absorption rates in culture with blue LEDs were higher than that with red LEDs.
• Chlorophyll content was lower in microalgal cultures irradiated with red light.
• Red light rendered greater energy efficiency for biomass production.

Knowing the distribution of the density of radiant energy within a photo-bio-reactor and its impact on the growth of microalgae through the local rate of absorption of radiant energy is essential for the analysis, modeling and design of photo-bio-reactors. In this work we develop a physical model and a computer simulation algorithm, in order to accurately predict the rate of absorption of photons in microalgal cultures at each point of a reactor irradiated with a light source made of different arrangements of LEDs emitting in blue and red spectral regions. Results showed that the average absorption rates in the culture irradiated with blue LEDs were higher than that irradiated with red LEDs. However, the radiation emitted by red LEDs rendered greater energy efficiency for biomass production compared to that emitted by blue LEDs. The development of a computational model based on a Monte Carlo method allowed the determination of the local volumetric rate of photon absorption at each point inside the PBR at different culture times. The information obtained with this tool allowed a detailed assessment of the effect of different radiation conditions on growth of microalgae, regardless of the PBR and the light source used.

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