Abstract
Growing of Algae for biodiesel production has gained popularity in recent times. This is because
biodiesel from algae has an economic advantage over other oil crops. The oil content that can be
extracted from microalgae biomass depends on the culture conditions and microalgae species. This
means that besides selecting the best microalgae species, it is also necessary to ensure and maintain the
best culture conditions for optimal biodiesel production. Optimum algae growth conditions can be best
be provided by a Controlled Environment Bioproduction System (CEBS) for the algae called as photo-
bioreactor (PBR). This paper reports design and fabrication of a PC based control system for a PBR
production system for algae being developed at the School of Biosystems and Environmental
Engineering (SoBEE) in Jomo Kenyatta University of Agriculture and Technology (JKUAT) in Kenya.
The control system is intended to ensure that optimum PH, temperature, nutrients content; light
intensity/duration and salinity of growth medium for algae are maintained. The paper covers the design
and fabrication of the PC control and monitoring system. The control and monitoring system consists of
a computer program and a microcontroller connected to sensors and actuators. The computer program
(master) provides the graphical user interface (GUI) consisting of control buttons and means for real
time data logging and analysis as well as real-time simulation of PBR activities. It is available in
executable file that can be run in any windows OS computer. The microcontroller program (slave)
provides the means for connecting sensors and is used to measure as well as monitor the conditions in
the PBR tanks. Communication between the computer program and the microcontroller is achieved
through the universal serial bus (USB). The control system consists of both open and closed loop
systems. The open loop system is used to control the light duration at predetermined intervals of time.
The closed loop system is used to control the nutrient concentration, light intensity, PH and oxygen:
carbon dioxide ratio.
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