A Comparative Study between Theoretical and Measured Performance of Standard Centrifugal Pumps Running as Turbines

Abstract

High cost of custom-made conventional turbines and the lack of local manufacturing facilities have created significant obstacles to the development of Pico/micro hydroelectric schemes in the country. In this context it has been identified pump as turbine (PAT) electric schemes can have distinct advantages over conventional turbines because pumps are manufactured locally at mass scale and available in various sizes. But not all pumps are suitable for use as PAT because they have different design details and manufacturing qualities. The performance of a pump used as a turbine is assessed based on two primary parameters: turbine mode head and flow at the Best Efficiency Point (BEP). There are various methods available in the literature for predicting PAT theoretical head and flow at BEP. These methods aim to estimate how the pump will perform when used as a turbine. Despite these prediction methods, there is a consistent deviation of approximately ±20% between the theoretical estimates and the actual measured performance. This indicates that real-world conditions and factors not accounted for in theoretical models can significantly affect the performance of PAT systems. The primary objective of the present study was to measure the deviation between the actual performance and the predicted performance of two PAT systems in terms of head and flow at BEP. This deviation was then compared to the commonly mentioned figure of ±20% in the literature. The study focused on using what it considered to be the most accurate prediction method among those presented in the literature to estimate PAT head and flow at BEP and involved running reverse, 1.1 kW, and 1.6 kW direct-drive standard centrifugal type water pumps in a test rig to measure the actual performance of the two PATs. The results of the study showed a deviation of +27% and -22% between the actual measured head and flow at BEP, and the values predicted by the theoretical method. This deviation is slightly outside the commonly mentioned range of ±20% found in the literature, but this is not expected to have a detrimental effect on the generation of electric power. This implies that, even with the observed slight deviation, the prediction method used in this study can be satisfactorily employed to estimate PAT head and flow at BEP.