2025
Shen, Jiawei; Pei, Ji; Wang, Wenjie; Yuan, Shouqi; Pavesi, Giorgio
In: Renewable Energy, vol. 253, 2025, ISSN: 18790682.
Abstract | Links | BibTeX | Tags: Acceleration transition process, Flow instability, High-efficiency operation, Micro-pumped hydro storage, Reversible mixed-flow pump, Variable-speed regulation
@article{Shen2025,
title = {Broader high-efficiency zone of micro-pumped hydro storage enabled by a variable-speed reversible mixed-flow pump: Taking acceleration as an example},
author = {Jiawei Shen and Ji Pei and Wenjie Wang and Shouqi Yuan and Giorgio Pavesi},
doi = {10.1016/j.renene.2025.123642},
issn = {18790682},
year = {2025},
date = {2025-01-01},
journal = {Renewable Energy},
volume = {253},
publisher = {Elsevier Ltd},
abstract = {Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.},
keywords = {Acceleration transition process, Flow instability, High-efficiency operation, Micro-pumped hydro storage, Reversible mixed-flow pump, Variable-speed regulation},
pubstate = {published},
tppubtype = {article}
}
Given the burgeoning renewables-based microgrids, it is crucial for a stable power supply to enable more flexible micro-pumped hydro storage by the reversible mixed-flow pump (RMFP) with a broad high-efficiency zone (HEZ). Variable-speed operation is the most effective method to regulate operating conditions for scenarios of the RMFP without the guide vane. To reveal the effect of variable-speed regulation on the HEZ, we test the energy characteristics of RMFP at four speeds based on a bidirectional hydraulic test bench. The experiment shows that the RMFP receives an HEZ that is expanded by 53.4 % in pump mode and 60.3 % in turbine mode by accelerating from 830 r/min to 980 r/min. Moreover, the transition process of the acceleration regulation under full load is simulated based on a validated CFD numerical scheme. It is indicated that the acceleration regulation not only improves the efficiency and hydraulic dissipation but also alleviates the flow instabilities. The peak-to-peak value and the amplitude of the dominant frequency of the pressure fluctuation in the runner can be reduced by up to 49.4 % and 46.2 %, respectively. This study highlights the broad high-efficiency zone and stable internal flow that variable-speed regulation contributes to the RMFP, aiming at enhancing the flexibility of micro-pumped hydro storage.
2016
Pavesi, Giorgio; Cavazzini, Giovanna; Ardizzon, Guido
Numerical analysis of the transient behaviour of a variable speed pump-turbine during a pumping power reduction scenario Journal Article
In: Energies, vol. 9, iss. 7, pp. 1-15, 2016, ISSN: 19961073.
Abstract | Links | BibTeX | Tags: Adjustable Speed Hydro Plants, Dynamic response, Dynamic response of hydro plants, Hydro plant control, Pump as Turbine, Variable Speed, Variable-speed regulation
@article{pop00005,
title = {Numerical analysis of the transient behaviour of a variable speed pump-turbine during a pumping power reduction scenario},
author = {Giorgio Pavesi and Giovanna Cavazzini and Guido Ardizzon},
url = {http://www.mdpi.com/1996-1073/9/7/534 http://www.mdpi.com/1996-1073/9/7/534/htm},
doi = {10.3390/en9070534},
issn = {19961073},
year = {2016},
date = {2016-01-01},
urldate = {2016-01-01},
journal = {Energies},
volume = {9},
issue = {7},
pages = {1-15},
publisher = {mdpi.com},
abstract = {To achieve the carbon free electricity generation target for 2050, the penetration of renewable energy sources should further increase. To address the impacts of their unpredictable and intermittent characteristics on the future electricity grid, Pumped Hydro Energy Storage (PHES) plants should enhance their regulation capability by extending their continuous operating range far beyond the optimal normal working range. However, for the time being, the regulation capability of the new generation of PHES, equipped with reversible pump-turbines due to their cost-effectiveness, is limited at part load by instability problems. The aim of this paper is to analyse, during a pumping power reduction scenario, the onset and development of unsteady phenomena leading to unstable behaviour. A 3D transient numerical simulation was carried out on the first stage of a variable-speed two-stage pump-turbine from full load to the unstable operating zone by progressively reducing the speed from 100% to 88% rpm corresponding to a power reduction from full load to about 60% with a ramp rate of 1.5% per s. Two three-dimensional unsteady flow structures affecting the return channel and the wicket gates at the end of the first stage were identified and their evolution in the power regulation scenario was fluid-dynamically and spectrally characterized to determine the fluid-dynamical conditions causing the head drop in the hump zone.},
keywords = {Adjustable Speed Hydro Plants, Dynamic response, Dynamic response of hydro plants, Hydro plant control, Pump as Turbine, Variable Speed, Variable-speed regulation},
pubstate = {published},
tppubtype = {article}
}
To achieve the carbon free electricity generation target for 2050, the penetration of renewable energy sources should further increase. To address the impacts of their unpredictable and intermittent characteristics on the future electricity grid, Pumped Hydro Energy Storage (PHES) plants should enhance their regulation capability by extending their continuous operating range far beyond the optimal normal working range. However, for the time being, the regulation capability of the new generation of PHES, equipped with reversible pump-turbines due to their cost-effectiveness, is limited at part load by instability problems. The aim of this paper is to analyse, during a pumping power reduction scenario, the onset and development of unsteady phenomena leading to unstable behaviour. A 3D transient numerical simulation was carried out on the first stage of a variable-speed two-stage pump-turbine from full load to the unstable operating zone by progressively reducing the speed from 100% to 88% rpm corresponding to a power reduction from full load to about 60% with a ramp rate of 1.5% per s. Two three-dimensional unsteady flow structures affecting the return channel and the wicket gates at the end of the first stage were identified and their evolution in the power regulation scenario was fluid-dynamically and spectrally characterized to determine the fluid-dynamical conditions causing the head drop in the hump zone.
