Performance prediction of a pump as a turbine using energy loss analysis

Abstract

As interest in renewable energy sources grows, interest in small-scale hydropower development and utilization increases. The development of micro- and small-scale hydropower plants is challenging, mainly due to the high cost of hydraulic turbines. If the turbine mode performance can be predicted accurately before installation, pumps as turbines (PATs) are an excellent alternative for small-scale hydropower generation. In this study, a theoretical procedure using a detailed energy loss analysis to determine PAT's energy losses is developed, and a non-dimensional performance prediction model is presented. The models were implemented to determine the pressure, head, torque, power, and efficiency across a wide range of flow rates. This work clearly characterizes the effects of individual losses, thereby acknowledging their influence. The prediction results were tested at ten different flow rates, ranging from 50 % to 180 %. The model result was validated through experiments using a hydro-pump test rig developed at the Bahir Dar Institute of Technology at Bahir Dar University. The numerical and model results have good agreement with the experimental results. at BEP The experimental result gives a 1.6 flow rate, 1.72 head ratios, and an efficiency of 76.53 %, 78.09 %, and 74.04 % using analytical, numerical, and experimental methods, respectively. The PAT off-design efficiency decreases sharply below BEP and smoothly above BEP. At BEP, the CFD and analytical results deviated by −2.04 % and 3.08 %, respectively, from the experimental results. Further, the detailed energy loss analysis revealed that the volute frictional (12.1 %), the throat frictional (11.9 %), the inlet pipe frictional (11.2 %), the impeller frictional (9.4 %), and the volute diffusion (8.9 %) losses take the major energy losses sequentially. This provides full insight for applying performance optimization measures.