Evaluation of the System Efficiencies of Different Pump-Primemover Combinations for Shallow Tubewell Irrigation
Arthur L. Fajardo2 and Delfin C. Suministrado3
ABSTRACT
Cost effectiveness and sustainability of shallow tubewell (STW) makes it popular in irrigated agriculture. One factor which affects STW’s cost effectiveness is efficient pump set operation. Thus, it is important to make comparative assessments of the system efficiencies of the different pump sets used for STW.
Fifty eight (58) pump-primemover combinations were set up by matching five (5) centrifugal pumps with six (6) units of diesel engine, three (3) of gasoline engine, and three (3) units of electric motor. The 58 pump sets were operated at varying pump test speeds of 1300, 1500 and 1800 rpm for non-self priming pumps; and 1500, 1800 and 2000 rpm for self priming pumps.
The average overall system efficiency of all electric motor pump sets was 23.85% compared to diesel engine pump sets with 9.39% and gasoline engine pump sets with 5.60%. The highest overall system efficiency of 41.05% was obtained using a 4×4-Electric Motor operated at 1300 rpm while the lowest overall system efficiency of 2.30% was obtained using an NS 50-Gasoline Engine 11.5 operated at 1500 rpm. The overall system efficiency of self priming pump sets was about twice as much when compared with non-self priming pump sets with the same primemover and pump test speed.
Electric motor would be the best option as primemover for STW irrigation considering its high overall system efficiency. However, due to its limitations in the field, diesel engines became popular as primemover for STW irrigation. The 5.22 kW diesel engine used for this study had shown relatively good performance when operated with all pumps especially at lower pump speeds of 1300 and 1500 rpm.
Keywords: shallow tubewells, irrigation pumps, electric motors, diesel and gasoline engines, pump system efficiencies
1Part of senior author’s graduate thesis supported by AMDP, 2University Researcher I, Land and Water Resources Division, and 3Professor, Agricultural Machinery Division, respectively, Institute of Agricultural Engineering, College of Engineering & Agro-Industrial Technology, University of the Philippines Los Baños, Philippines.