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Design and construction of light guides for efficient transfer of light in to a dense algal culture in a Photo-Bio Reactor (PBR)

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  034058,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.13869) @2003
Authors:   Anil Kommareddy, Dr. Gary Anderson
Keywords:   photobioreactor, light penetration, algal concentration, light guides, pollution, animal waste, algae, biomass, light, photosynthesis

A photo-bio Reactor is a system that provides an artificial environment for photosynthetic organisms (Algae) to perform a chemical conversion. The conversion process of interest is the conversion of air and liquid pollutants from livestock housing to algal biomass. Light is an important parameter for the growth of algae. The walls of the PBR are made of acrylic material. The light is fed to the system through the sidewalls of PBR. The first proto-type built and tested in summer 1998 at South Dakota Sate University (SDSU) showed that light penetration in the growth medium is an important factor to achieve high yield. It is also noted that as the algae starts growing, its density in the growth medium increases and obstructs the light penetration in to growth medium. Acrylic rods were used as light guides to enhance light transmission into the dense (opaque) algae medium solution. Different types of light guides were designed and test results are presented. It was found that light guide light transmission improved from 57% to 97% when the guide is saw cut and ends smoothed by belt grinder compared to a guide which is saw cut and ends smoothened lathe. Better distribution of light was obtained when a cone shaped with an angle of 60 at the center on one side of the guide is cut. Transmission characteristics of light guide from air to acrylic rod, acrylic rod to air and acrylic to water interfaces are discussed their performances is compared with test results.

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