Set-up of a pump as turbine use in micro-pumped hydro energy storage: a case of study in Froyennes Belgium

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-ω and standard k-ε 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.

Numerical and experimental characterization of splitter blade impact on pump as turbine performance

Several rivers and streams are available in Africa and Asian regions with great potentials not applicable for constructing large hydropower dams but feasible for small and mini hydro generation. This study strive for investigating the impact of splitter blade on pump as turbine performance considering different speed and flow rates. Two specific centrifugal pump models one with six blades without splitter and another with four blades and four splitters were used for the study. The inlet diameter and outlet diameters of both impellers were 104 mm/116 mm, and 160 mm respectively at a designed flow rate Q = 12.5 m3/h, head H = 16 m, rotational speed n = 1450 rpm and efficiency of 56%, outlet impeller width of 0.006 m, a blade outlet angle of 30° was used for the study. CFD simulations were conducted with the use of k-ε turbulence model. The influence of splitter blade position on the performance of pump as turbine in the selected specific pumps with and without splitter blades has been investigated both experimentally and numerically at three different flow rates and rotational speed. The simulated data were in good agreement with the experimental results, the maximum deviation error between the CFD and test for each model are 5.6%, 2.6%, for the head and efficiency; 7.5% and 3.6% at different flow conditions.

Techno-Economic Efficiency Analysis of Various Operating Strategies for Micro-Hydro Storage Using a Pump as a Turbine

Storage technologies are an increasingly crucial element in the continued expansion of renewable energy production. Micro-hydro storage using a pump as a turbine is a potentially promising solution in certain cases, for example, for extending existing photovoltaic systems (PV) and thus reducing grid load and enabling economically beneficial self-consumption of the energy produced. This paper gives an overview of various operating strategies and their technical and economic efficiencies. The evaluation was based on a simulation model of a system that uses measured characteristic maps of both the pump and turbine operations. An optimizer was employed to vary the essential system parameters, which made it possible to determine the optimal economical operation of the pump as a turbine in combination with a PV system. This in turn enabled us to determine the conditions under which the system can be operated most profitably. It was then possible to make precise calculations of the stored energy quantities, total efficiency (ηtot = 42% with speed control), and many other values critical to each operating strategy. Based on the technical findings, the economic analysis resulted in a levelized cost of energy of 0.63 €/kWh for the micro-hydro storage when using speed control.