The pump as a turbine: A review on performance prediction, performance improvement, and economic analysis

Pumps as Turbines (PATs) are known for their ability to replace conventional turbines in Pico/ micro-hydropower plants. However, selecting a suitable pump and estimating its performance in reverse mode is a challenging task. The overall efficiency of PATs is also lower when compared to purpose-made turbines. Numerous attempts have been made to analyze the performance of PAT in power-generating applications, and many scholars have presented their research on performance improvement and economic analysis. In this paper, a detailed review is conducted to show the historical development and current status of PAT technology. The review also presents the findings of performance prediction, performance improvement techniques, and economic analysis. The results of the literature survey demonstrate that the choice of an appropriate pump for a specific application significantly affects the performance of the PAT system. Among the various options, the Shear Stress Transport (SST) k-omega and standard k-epsilon turbulence models are widely used for simulating the pump as a turbine. Blade grooving and blade tip rounding are recognized as the most promising techniques for improving efficiency, with gains of 4.91% and 4.00%, respectively. Except for impeller diameter trimming, blade modification techniques proposed by various scholars have a significant impact on the efficiency of PATs; however, further research is needed to investigate the economic advantages of impeller modification.