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Photobioreactor design for microalgae cultivation using a thermoelectric cooler for temperature control

Blagotinsek, Vincent (2018) Photobioreactor design for microalgae cultivation using a thermoelectric cooler for temperature control. Honours thesis, Murdoch University.

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This thesis aims to design a photobioreactor that has a low capital investment so microalgae cultivation becomes cheaper. Implementation of temperature control is achieved by a thermoelectric cooling (TEC) device by pulse width modulation.

Materials of cheap cost from local vendors are availabe including low thermal conductivity materials like foam insulation and temperature sensors that have accurate measurement. Arduino based sensors of low cost are used to obtain process variable information of the system such as lux intensity, internal ambient temperature, and the temperature of a 500 mL flask of water. Power supplies are used to supply a 12 VDC connection to the LED lights, mixing motor and TEC. Switching of these voltages is done with MOSFETs to achieve a variable voltage.

Understanding the capabilities of a temperature feedback control by implementation of temperature sensors is investigated and it was found that high-frequency feedback signals cause antireset windup and overheating of components. On/off switching is also implemented to negate the high frequency switching issues while PI controller installation is discussed and favours the PBR sensor over the internal ambient temperature sensor.

The lower temperature regions of the PBR are unatainable which results in PV offset and hardly noticable temperature changes that are not desirable. A remedy to solve the issue suggests that materials with high thermal conductivities should provide better heat energy transfers when using TECs. Lux lighting sensor illustrates the maximum achievable LED intensity. Undesirable heat energy generated by the LED lights will increase the internal PBR temperature.

Overall TECs are very costly to run because heatsinks and fans for heat extraction are required for heat removal, while the TEC devices for this research is not efficient enough to get to the lower temperature regions. This research concludes that cheap quality electrical components will achieve strict control of variables while it is possible to create low budget microalgae monitoring systems.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Engineering and Information Technology
Supervisor(s): Parlevliet, David
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