Improving Energy Efficiency of Akaki Well-Field Submersible Pumps by Implementing Variable Speed Drive Controls

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Addis Ababa University


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.



Groundwater,, Submersible Pumps, Energy Conservation, Variable Speed/Frequency Drives, Pulse Width Modulation, Affinity Laws, Matlab/Simulink Model