Improving Energy Efficiency of Akaki Well-Field Submersible Pumps by Implementing Variable Speed Drive Controls
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Date
2019-03
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Addis Ababa University
Abstract
In Ethiopia water pumping system is given less concern regarding to energy saving and in groundwater
management. The amount of groundwater recharging is affected by many factors like seasonal rain
variation, global warming, drought and also groundwater withdrawal. This changes significantly show
in a water pumping system hydrodynamic head and flowrate changes. Since, the draw down in the
system increases because of the ground water recharging is less in the system, the amount of water
discharge decreases.
When the amount of the water availability in the ground decrease we need such control mechanisms
to run the pumping system. The most commonly used controlling system in the country for water
pumps are throttling.
This thesis is focused on ten deep-well pumps at Akaki well-field Phase-3A ground water pumping
system. Studying and evaluate the efficiency the actual groundwater pumping system, make energy
efficiency/saving analysis and economic analysis for the improved system.
The actual water pumps used to withdraw water from ground at this sites are fixes speed centrifugal
submersible pumps, and throttled to the amount of water availability. This types of control techniques
are characterized by low efficiency and high energy consumption. Therefore, this pumps draw nearly
full horsepower and consume maximum energy full time regardless of water availability in the ground.
This research carried out the simulation and performance analysis of such pump motors by
implementing a variable frequency drive control between the power supply and motor, using
MATLAB/SIMULINK model and shows the motor perform in its maximum efficiency. Successfully
achieved the control of the speed of the induction motor by varying the frequency of the applied
voltage using pulse width modulation method. Affinity laws also used to predict the pump
performance change to re-design the system in variable speed pump analysis. The economic analysis
is shown through comparison between the pumps operating energy consumption cost and investment
cost to implement the VFD control system.
The results of this thesis provides a potential energy efficiency/ saving for using VFD in Akaki wellfield
submersible pumps. The redesigned VSD control system provides low energy consumption in
KWh, depends on the actual groundwater discharge capacity and economically viable to implement
the variable speed drive control system to the existing pumps.
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Keywords
Groundwater,, Submersible Pumps, Energy Conservation, Variable Speed/Frequency Drives, Pulse Width Modulation, Affinity Laws, Matlab/Simulink Model