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TUT: Tutorials

TUT 2: Energy Concepts of the Future (AGjDPG, AKE)

TUT 2.3: Tutorium

Sonntag, 13. März 2011, 17:20–17:55, HSZ 03

Physical aspects of photobioreactors for growing biomass — •Hilmar Franke — Applied. physics, Univ. Duisburg-Essen, Duisburg, Germany

Using photosynthesis CO₂ can be converted in the presence of water and light into biomass and O₂. On hot summer days one may observe the blossoming of algae on seashores or lakes. Often this phenomenon occurs in the presence of high concentrations of nutrients. The function of photobioreactors is to transfer this blossoming or high growth rate of biomass into the laboratory or a large scale industrial plant.
The climate gas CO₂ is produced during the oxidation of carbon or hydrocarbon compounds.
On earth there are many natural and industrial sources for CO₂, but only few sinks. The process of photobiological fixation of carbon dioxide in photobioreactors may contribute to the installation of a recycling technology for CO₂!
In this talk we will focus on the different physical aspects of photobioreactors (PBR) which may lead to efficient large scale plants:
A major problem is the light exposure. The exposure has to be optimized with respect to the wavelengths and the intensity. Using sunlight or LED’s as an efficient system for collecting, guiding and distribution of light has to be developed.
Microalgae in PBR*s form a suspension in an aqueous environment with various ions of dissociated water and nutrient components. There are algae with an electric charge distribution. Depending on their shape even in an aqueous ionic environment this may cause an electric dipole moment. The electrical properties of a microalgae suspension may be used for characterization of important process parameters or the control of the system.
Photosynthesis requires CO₂, while O₂ is formed. Therefore an additional gas phase is present in the PBR. Especially in high columns gravitation controls any sedimentation profile. On the other hand clouds of gas bubbles form the reactive interface and the rising speed of gas bubbles depends on the bubble size which again depends on the local pressure.

Examples for potential applications of these physical aspects will be discussed.