Special Issue "Pumped-Storage Hydropower Plants"

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Energy".

Deadline for manuscript submissions: closed (15 July 2019).

Special Issue Editor

Prof. Dr. Giovanna Cavazzini
Website
Guest Editor
Department of Industrial Engineering, University of Padova, Padua, Italy
Interests: hydraulic machines; unstable behavior; CFD; design optimization; experimental investigation
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Special Issue Information

Dear Colleagues,

Looking at future grids with increasing shares of intermittent renewable energy solutions, pumped hydro energy storage (PHES) plants are widely recognized as an ideal solution because of their ability to provide large storage capacity with excellent grid connection properties, high cycle efficiency range, and competitive costs. However, in order to provide primary and secondary regulation services, there is a primary need to increase the PHES operational flexibility by developing new machine designs and/or new technologies, as well as by providing hybridization with different types of energy and energy storage systems. To stimulate research areas in these fields, it is important to gather the most relevant ongoing research works on new solutions for PHES (innovative design, innovative control systems, etc.) and on their hybridization with other energy and energy storage systems (sizing algorithm, forecast model, management strategies, virtual power plant, etc.). Therefore, you are kindly invited to share your recent findings in this Special Issue.

Prof. Giovanna Cavazzini
Guest Editor

Manuscript Submission Information

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Published Papers (4 papers)

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Research

Open AccessArticle
Large-Scale Pumped Thermal Electricity Storages—Converting Energy Using Shallow Lined Rock Caverns, Carbon Dioxide and Underground Pumped-Hydro
Appl. Sci. 2019, 9(19), 4150; https://doi.org/10.3390/app9194150 - 03 Oct 2019
Abstract
A fast-paced energy transition needs a higher penetration of renewables, of heating and cooling in the worldwide energy mix. With three novelties 1-of using shallow high-pressure LRC (Lined Rock Cavern) excavated close to storage needs, 2-of using a slow-moving CO2 piston applying [...] Read more.
A fast-paced energy transition needs a higher penetration of renewables, of heating and cooling in the worldwide energy mix. With three novelties 1-of using shallow high-pressure LRC (Lined Rock Cavern) excavated close to storage needs, 2-of using a slow-moving CO2 piston applying steady pressure on the hydro part of UPHES (Underground Pumped Hydro Energy Storage) and 3-of relying on inexpensive thermal stores for long-duration storage, CO2 UPHES coupled with PTES (Pumped Thermal Electricity Storage) could become, at expected Capex cost of only 20 USD/kWh electrical, a game-changer by allowing the complete integration of intermittent renewable sources. Moreover, even though this early conceptual work requires validation by simulation and experimentation, CO2 UPHES as well as UPHES-PTES hybrid storage could also allow a low-cost and low-emission integration of intermittent renewables with future district heating and cooling networks. Full article
(This article belongs to the Special Issue Pumped-Storage Hydropower Plants)
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Open AccessArticle
Research on an Output Power Model of a Doubly-Fed Variable-Speed Pumped Storage Unit with Switching Process
Appl. Sci. 2019, 9(16), 3368; https://doi.org/10.3390/app9163368 - 15 Aug 2019
Cited by 1
Abstract
The doubly-fed variable-speed pumped storage (DFVSPS) is an effective method to balance the fluctuation of renewable energy generation and is an important means of frequency and voltage regulation of a power grid. Firstly, this paper introduces the structure and mathematical model of the [...] Read more.
The doubly-fed variable-speed pumped storage (DFVSPS) is an effective method to balance the fluctuation of renewable energy generation and is an important means of frequency and voltage regulation of a power grid. Firstly, this paper introduces the structure and mathematical model of the DFVSPS unit. Secondly, the control methods of each switching stage in generating mode and pump mode are proposed, and the simulation study of each stage of DFVSPS switching process is carried out by MATLAB/Simulink. Thirdly, when studying the regulating effect of DFVSPS unit in the power system, due to the high switching frequency of converter in the electromagnetic transient model, the simulation speed is very slow and the data volume is large, so the model of DFVSPS unit needs to be simplified. By analyzing the dynamic behavior of the pumped storage power station, the mathematical model of output power of the DFVSPS unit is established, which includes start-up stage, load ramping stage, stable operation stage, load rejection stage and shutdown stage of generating mode and pump mode. Finally, the simplified model of DFVSPS unit is applied to a simple power system to verify its regulating effect on grid power. Full article
(This article belongs to the Special Issue Pumped-Storage Hydropower Plants)
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Open AccessArticle
Analysis of the Guide Vane Jet-Vortex Flow and the Induced Noise in a Prototype Pump-Turbine
Appl. Sci. 2019, 9(10), 1971; https://doi.org/10.3390/app9101971 - 14 May 2019
Cited by 1
Abstract
The start-up process of a pump-turbine in pump mode is found with obvious noise, especially at the small guide vane opening angle. The turbulent-flow-induced noise is an important part and must be reduced by flow control. Therefore, the computational fluid dynamics (CFD) method [...] Read more.
The start-up process of a pump-turbine in pump mode is found with obvious noise, especially at the small guide vane opening angle. The turbulent-flow-induced noise is an important part and must be reduced by flow control. Therefore, the computational fluid dynamics (CFD) method is used in this study to predict the internal flow in a high head prototype pump-turbine (the specific speed nq is 31.5) under an extremely off-design condition (Cφ = 0.015 and Cα = 0.096). The acoustic analogy method is also used to predict the near-field noise based on the turbulence field. Special undesirable flow structures including the flow ring between the runner trailing-edge and the guide vane, guide vane jet, twin-vortexes adjacent to guide vane jet, inter stay vane vortex, stay vane jet, and volute vortex-ring are found in a pump-turbine. These complex jet-vortex flow structures induce local high turbulence kinetic energy and an eddy dissipation rate, which is the reason why noise is generated at small guide vane opening angle. Three dominating frequencies are found on the turbulence kinetic energy pulsation. They are the runner blade frequency fb = 64.5 Hz, the dominate frequency in the guide vane and the stay vane fgsv = 9.6 Hz, and the dominate frequency in volute fvl = 3.2 Hz. The flow pulsation tracing topology gives a good visualization of frequency propagation. The dominating regions of the three specific frequencies are clearly visualized. Results show that different flow structures may induce different frequencies, and the induced specific frequencies will propagate to adjacent sites. This study helps us to understand the off-design flow regime in this prototype pump-turbine and provides guidance when encountering the noise and stability problems during pump mode’s start-up. Full article
(This article belongs to the Special Issue Pumped-Storage Hydropower Plants)
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Open AccessArticle
Internal Mechanism and Improvement Criteria for the Runaway Oscillation Stability of a Pump-Turbine
Appl. Sci. 2018, 8(11), 2193; https://doi.org/10.3390/app8112193 - 08 Nov 2018
Cited by 1
Abstract
The runaway oscillation process of the pump-turbine in a high head pumped-storage power plant is usually unstable. The root cause of its instability is still unclear. In this paper, its internal mechanism and the improvement method were studied in depth. First, the flow [...] Read more.
The runaway oscillation process of the pump-turbine in a high head pumped-storage power plant is usually unstable. The root cause of its instability is still unclear. In this paper, its internal mechanism and the improvement method were studied in depth. First, the flow characteristics in a model pump-turbine during the runaway process at four guide-vane openings (GVOs) were investigated by 3D transient numerical simulations. Then, the energy dissipation characteristics of different types of backflow vortex structures (BFVSs) occurring at the runner inlet and their impacts on the runaway stability were investigated by the entropy production theory. The results show that the location change of BFVSs between the hub side and the mid-span of the runner inlet around the no-load point leads to the sharp change in the energy dissipation rate, which makes the slope of dynamic trajectory positive and the runaway oscillation self-excited. If the occurrence of BFVSs at the hub side is suspended, the runaway process will be damped. Finally, the pump-turbine runner was improved to obtain a wider stable operating range. Full article
(This article belongs to the Special Issue Pumped-Storage Hydropower Plants)
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