Pumped-storage Station Research Articles

Calibration of flow differential pressure coefficients on pump-turbine by thermodynamic method

On-line monitoring of flow rate is rather important to evaluate the water consumption of the pump-turbine and the overall efficiency of the pumped storage station. Flow rate can be worked out based on the flow differential pressure measured in the flow passage and coefficients determined on model test. But the coefficients must be calibrated to obtain the reliable flow rate. As thermodynamic method is a common way to measure the discharge of prototype pump-turbine, site test is carried out on a vertical pump-turbine with 600 m rated head to calibrated the coefficients in this paper. Measuring devices are designed to satisfy both the turbine and pump operating conditions, and test results of flow rate at both turbine and pump operating conditions are presented and show that the calibrated coefficients are different to the predicted values. The calibrated results indicate the importance of site calibration on prototype turbine to ensure the monitoring validity on real-time flow rate.

Study on the hydraulic effect of Tesla valve structure on the end roadway of abandoned coal mine pumped storage

The use of abandoned mine for pumped storage has garnered significant attention as a novel energy storage technology. The hydraulics of utilizing underground reservoirs constructed in mine roadways represent a key issue for the application of abandoned mines in pumped storage. This study focuses on the practical situation of the Longdong Coal Mine in Jiangsu Province, China. By employing numerical simulation methods, the research investigates the phenomenon of water wave reflection at the end of the roadway in an abandoned mine pumped storage station, as well as the improvement effect of the Tesla valve structure on the reflected water waves. It was found that under the condition of the hydraulic turbine, the reflected wave height at the end of the roadway could reach 1–1.5 times that before reflection. The Tesla valve structure was found to be an effective means of reducing the water level height at the end of the roadway. The average water level was reduced by 0.55 m and 0.35 m under the two flow rates of 1 m/s and 1.4 m/s, respectively. Under the pump condition, the Tesla valve structure has little obstruction to the reverse flow of water. This study has to a certain extent addressed the issue of excessive wave height from water wave reflections at the end of the roadway, thereby enhancing the operational stability of the abandoned mine pumped storage station.

Study on dynamic stress variation of head cover bolt during transient operation of pump turbine

Abstract The head cover bolt is an important connecting part of pump turbine, if it is damaged, it will affect the operation safety of the unit and the power station. During the transient process, such as start-up and load rejection in extreme case, the head cover bolt is subjected to complex load action, and its stress also changes, and extreme cases may occur. The dynamic stress level of the bolt will have a certain influence on its fatigue life, therefore, in order to further study the dynamic stress level and variation law of the bolt, this paper relies on a pumped-storage station, the dynamic stress of the head cover bolt during the start-up and load rejection is measured, and the pressure pulsation between the head cover and the runner and the bladeless zone are collected synchronously. Through the data analysis, the bolt dynamic stress level and variation law and the correlation between stress and pressure fluctuation under the power generation and pumping conditions are summarized.

Study on hydraulic characteristics of two-direction flow at the inlet/outlet of a large pumped storage station

Abstract The inlet/outlet is one of the most important parts of a pumped storage power station. Improper designs will cause problems such as suction vortex and increased head loss, which will affect the operation efficiency of the power station. This paper takes the inlet/outlet of a pumped storage power station in Zhejiang Province as an example for research. The upper reservoir inlet/outlet takes itself and the surrounding terrain, gully, and dam as the research object, and conducts physical model tests; the lower reservoir inlet and outlet take itself and the surrounding stone factory and other mountain terrain as the research object, and conduct numerical simulation studies. On this basis, the rationality of the scheme is explored and the optimization scheme is found, which can be used as a reference for similar engineering designers.

Reasonable Energy-Abandonment Operation of a Combined Power Generation System with an Ultra-High Proportion of Renewable Energy

With large-scale grid-connected renewable energy, new power systems require more flexible and reliable energy storage power sources. Pumped storage stations play an important role in peak shaving, valley filling, and promoting renewable energy consumption. This paper presents the reasonable energy-abandonment operation of a combined power generation system (CPGS), in which a pumped storage station is the core control power, with an ultra-high proportion of renewable energy. Firstly, based on the seasonal characteristics of wind, solar, and load demand, typical days are selected through improved clustering analysis algorithms. Then, a daily optimal scheduling model for combined power generation systems (CPGS) is developed with the goals of economy, low-carbon, and stable operation. Finally, the correlation between the energy-abandonment rate and pumped storage station peak shaving and system optimization operation indicators is obtained by a reasonable energy-abandonment calculation method considering source-grid-load coordination. Taking the operation data of an energy base in the western region of China as an example, when the penetration rate of renewable energy is 60–70% in the future, the operating cost on the power side is greatly affected by the construction of the source side. When the system operates at a planned reasonable energy-abandonment rate of 2%, electricity regulation, load tracking, and daily operating costs all show better performance.

Research on the Short-Term Economic Dispatch Method of Power System Involving a Hydropower-Photovoltaic-Pumped Storage Plant

The auxiliary regulation capacity of pumped-storage power stations can be utilized as an effective method to regulate the output of a hydro-photovoltaic complementary system, further mitigating the power fluctuations of the system and enhancing the photovoltaic absorption. This study aims to minimize power fluctuations and maximize the economic benefits of electricity generation in a hydropower-photovoltaic-pumped-storage complementary system (HPPCS), which are treated as the objective functions. It explores the participation of the HPPCS in grid active power balance auxiliary services. By modulating the participation ratio of the HPPCS in the grid’s active balance service, the system output is aligned to fluctuate proportionally with the daily load curve trend. Consequently, a short-term economic dispatch model for the integrated HPPCS is developed. The case study focuses on the considerable impact of weather conditions on photovoltaic (PV) power generation. In this model, the outputs of cascading hydro-power stations and pumped-storage power stations are considered as the decision variables. A decomposition-based multi-objective evolutionary algorithm is applied to derive an optimized intra-day dispatch Pareto solution set for the cascading HPPCS in each of these scenarios. Additionally, this study compares the Pareto solution sets for the HPPCS in various extents of its participation in grid auxiliary services. The results of the case study suggest that the system is capable of timely adjustments during the peak and trough periods of load demand. Considering the economic benefits, it enables the pumped-storage station to generate electricity for the grid during periods of high electricity prices and to store energy by pumping water when prices are low.

Multi-attribute decision-making method of pumped storage capacity planning considering wind power uncertainty

Pumped storage technology plays a crucial role in achieving balance in power systems and enhancing the stability of energy systems. Scientific planning can help optimize the operation of power systems, promote the development of renewable energy, and conserve energy. This paper addresses the capacity planning problem of pumped storage stations in hybrid operation systems considering wind power uncertainty. A comprehensive decision-making method is proposed, based on the Delphi method, interval intuitionistic fuzzy theory, grey relational theory, entropy weight method, and prospect theory. This method comprehensively evaluates decision alternatives by considering various factors such as the uncertainty of qualitative indicators, the interrelationships between indicators, and the impacts of different risk environments. The test system in this paper is conducted on a hybrid wind-thermal-pump storage output model based on the IEEE 30-bus system. The optimal capacity planning scheme determined by the proposed method is 190 MW when decision-makers are risk-neutral or risk-averse, and 200 MW when they are risk-appetite. Subsequently, the case study verifies the impact of different load levels and proportions of wind power access on the optimal decision-making scheme, and compares it with decision-making method such as principal component analysis, technique for order preference by similarity to an ideal solution, and a combined method of Pythagorean fuzzy theory and cumulative prospect theory, validating feasibility and effectiveness.

An efficient generator maintenance scheduling model based on unit clustering and linear relaxation

The formulation of periodic maintenance schedules for generators is crucial for the efficient and reliable operation of power systems. Traditional generator maintenance scheduling models often have low temporal resolution and ignore significant information. To solve this problem, this paper proposes a mid/ long-term generator maintenance scheduling model with an hourly time resolution. Given the challenges of large integer variable quantities and computational complexity in directly solving mid/ long-term maintenance schedules for power system generation units, an efficient solution method is proposed based on unit clustering and linear relaxation. Initially, a basic maintenance model is established based on the Unit Commitment (UC) model. Subsequently, the basic UC maintenance model is linearly relaxed to obtain an efficient approximate model, termed the Relaxed Clustered Unit Commitment (RCUC) maintenance model, which involves the operation of annual regulating hydropower stations, energy storage devices, pumped storage stations, wind power plants, and photovoltaic (PV) plants. Simulation results from an adapted IEEE RTS-79 system and a provincial scale system case study are provided to demonstrate the effectiveness of the proposed model in coping with mid/long-term maintenance scheduling and annual hydropower allocation problems of large-scale power systems.

An Analysis of Two Case Studies on the Construction of Underground Caverns-A Focus on the Tiantai Pumped Storage Station

This paper presents a numerical analysis of two case studies on the construction of underground caverns by FLAC3D, with a specific focus on the Tiantai Pumped Storage Power Station. During the construction period, two main problems, which are crane beam stability and rock support, have been numerically analysed and addressed. The first case study examines the influence of rock wall crane beam support on excavation stability. It has been proven that The reinforcement of connected concrete enhances integrity but may lead to localized cracking. Moreover, over-excavation reinforcement marginally improves anchor safety. The second case study investigates abnormal anchor stress in a powerhouse resulting from excavation. Recommended measures include conducting timely stability evaluations, identifying weakened zones to control rock stress relaxation effects, and establishing effective feedback mechanisms. By enhancing the safety of pumped storage power stations, promoting sustainable energy infrastructure, and improving the design and construction processes of such stations, this research paper aims to contribute to the overall development and success of these projects. In conclusion, the paper has discussed the rock wall crane beam stability and rock support effect, which implement the lack of this type of numerical analysis in underground cavern group construction. Also, it is recommended to accurately determine the rock mass mechanics parameters and timely support the excavated spaces to prevent abnormal increases in anchor stress.

Seepage and Deformation Analysis of Tailing Dam regarding the Upper Reservoir of Tiantai Pumped Storage Station

This paper has studied on the seepage and deformation analysis of a tailing dam in the upper reservoir of the Tiantai Pumped Storage Station. The analysis of seepage and deformation is crucial for evaluating the stability and safety of the dam and its impact on the surrounding environment. The study uses numerical simulation software (Phase2 and FLAC3D) to analyse the behaviour of the dam under different drainage conditions and construction phase. The results indicate that two drainage schemes in different filling stages are effective. In the same cross-section of the rock and soil basement, the flow rate of the no dumped and dumped slope is 0.0315 L/s and 0.0319 L/s respectively. The filling of the tailing dam has no predominant impact on the internal deformation magnitude of the auxiliary dam, but it changes the direction of the slope deformation from being squeezed out towards the lower slope to being towards the near-vertical direction, achieving a stable slope. Therefore, it is necessary to ensure the drainage function of the anti-filter layer and the deep interceptive drainage ditch and strengthen the monitoring of slope deformation during the construction phase.

Power grid load frequency control based on Fractional Order PID combined with pumped storage and battery energy storage

With the increasing proportion of installed renewable energy power generation capacity and the introduction of quantitative energy storage policies for new energy power generation. In view of the influence of intermittent and volatility of distributed generation on the safe of power grid, it is​ particularly important in the future to equip reasonable energy storage to ensure the flexibility of power system. In this paper, a load frequency control (LFC) strategy of hybrid energy storage based on fractional order proportion integral derivative (FOPID) is proposed to solve the frequency modulation problem of battery energy storage system (BESS) and pumped storage station (PSS) participating in the interconnection network. Firstly, the LFC model is established under the nonlinear factors such as regulator dead zone and generation rate constraint on a two-area reheat steam turbine. Secondly, a FOPID controller is designed. Furthermore, the combined LFC simulation is carried out by adding BESS under the two working operations of PSS generating and pumping. Finally, the influence of demand response is considered in the hybrid energy storage control.

Study on pump mode cavitation characteristic of variable speed pump turbine

The continuous variable speed technology is a key technology in the development of pumped storage units. When the operating range of the rotation speed is widened, the unit's stable and safe operation range will be constrained by conditions, such as cavitation, hump, and power limit. This paper uses a traditional fixed-speed pumped storage station as the research object. Based on the complete characteristic curves of the unit, the modification hypothesis after the application of variable speed technology is carried out, and the preferred operation curve of the pump working condition is obtained. The improvement of the cavitation characteristics of the fixed speed unit by the variable speed technology is studied in this paper, and the problems in the prediction of cavitation of prototypes based on model tests are also analyzed. In this paper, the cavitation characteristics of the model and prototype of a pump turbine are analyzed using computational fluid dynamics simulation, with the initial cavitation coefficient as the basis for judging the cavitation. This paper points out that there is a deviation in the direct prediction of the cavitation characteristics of the prototype through the model test and provides a more accurate method to predict the cavitation limit range of variable speed units, which provides a reference for practical engineering.

Water column separation under one-after-another load rejection in pumped storage station

A pumped storage power station operates on the principal of multiple pump-turbines sharing one tunnel. However, safety is a concern, particularly under one-after-another load rejection of multiple pump-turbines. In this study, we have implemented a model experiment based on water column separation experiment under the condition of one-after-another load rejection of a pumped storage model experimental platform with two pump-turbines sharing one tunnel. The results show that the unit with water column separation, which is Unit # 2, has the worst moment when it rejects full load 0.8 s after Unit #1. At this condition, the wall pressure of the draft tube of unit # 2 attains the vapor pressure and reverse water hammer pressure attains the maximum value of 6.8 m during water column bridging. However, the reverse water hammer pressure was 290 m in prototype unit. Under one-after-another load rejection, water column separation occurs when the draft tube attains the second extreme value, and the unit located in the turbine braking condition area. It was observed that the pressure pulsation frequency of the draft tube after one-after-another load rejection is composed of two parts. First, pressure pulsation frequency caused by swirling flow with a value of 0.4 f/fn and second, a broadband of 40–200 Hz generated by the reverse water hammer due to water column bridging and structural response of the unit.

Fluctuation in the Water Level of the Air Hole of the Gate Shaft in the Pumped Storage Power Station

In some pumped storage stations, water spray from the air hole occurs during load rejection. In order to avoid this phenomenon, it is necessary to study the change of the air hole water level during the transient process of the power station. A transient simulation of a pumped storage power station was carried out to study the variation in the maximum water level of the air hole and gate shaft. The transition process of a power station with or without a surge tank was analyzed, and the changes in the water level of the gate shaft and air hole were compared based on different gate shaft areas, and the influence of the gate shaft location on the changes in the water level of the gate shaft and air hole was determined. The following results were obtained: when the power station has a surge tank, the maximum water levels of the gate shaft and air hole are basically consistent; when the station has no surge tank, the maximum water level difference between the gate shaft and air hole gradually increases as the gate shaft area increases; the greater the distance between the gate shaft and inlet, the larger the maximum water level difference between the air hole and gate shaft; overflow measures for the air hole are required if the maximum water level of the air hole exceeds the design value.

Characteristics of Multi-Stage Auxiliary Equipment Linkage in Pumped Storage Power Station Under Double Carbon Target

The auxiliary control linkage system of the pumped storage power station has become a necessary technical means for the safe operation and production of the station. However, due to the scattered linkage control function and low control level of each subsystem of the pumped storage power station, the security system cannot play a full role, affecting the safety portion and other effects. This paper studies a multistage auxiliary equipment linkage method based on a linkage body for the pumped storage power station. In the framework of the system dividing safety intervals, five linkage bodies are constructed for multi-layer hierarchical linkage, including real-time monitoring, fire fighting, five-prevention locking, online monitoring, and video monitoring. Completing the development of the linkage method of auxiliary equipment comprehensive control based on a multi-level linkage strategy and implementing multi-stage auxiliary equipment linkage in the station can reduce the loss of auxiliary equipment in pumped storage stations and improve the carbon neutrality and carbon compliance benefit of the pumped storage stations.

Projekt Pumpspeicherkraftwerk Limberg III – besondere Herausforderungen an die Logistik sowie die Vortriebssysteme einer Großbaustelle im Hochgebirge

AbstractConstruction of the Verbund project Limberg III pumped storage power station is currently underway in the area of the Kaprun/Salzach power station group. Preliminary work started on 6 April 2021, the main construction work started on 7 January 2022 and the overall facility is scheduled to be commissioned the end of 2025. Kaprun has a long history in the construction of power stations. The Kaprun storage power stations in the 1950s were an outstanding engineering feat and is symbolic of the reconstruction efforts that took place in Austria in the wake of World War II. The power station facilities at the main and upper stage have been in existence since the 1950s and have since been continuously expanded. From 2006 to 2011 the all‐year‐round reservoirs Mooserboden and Wasserfallboden were extended to include the Limberg II pumped storage station. The group is currently expanding the Kaprun/Salzach power station group by building the Limberg III pumped storage station, for which the same design as Limberg II has been adopted for implementation purposes. In addition to the significant logistical challenges posed by the high mountain location of the construction site, this report also covers the tunnelling systems.

A unit commitment and economic dispatch model of the GB electricity market – Formulation and application to hydro pumped storage

We present a calibrated unit commitment dispatch model of the GB electricity market applied to an economic analysis of the four existing hydro pumped storage (PS) stations in GB. More variable renewable electricity (VRE) increases PS profit by an amount dependent on the generation mix. With a large share of coal, a 1 percentage point (p.p) increase in VRE increases total PS profit by an average of 2.3 p.p. With a more flexible system, to achieve a similar profitability, the share of wind and solar should rise to more than 60% of supply. Inflexible coal with high VRE increases price volatility that drives PS arbitrage revenue. Higher system flexibility smooths VRE variability and limits PS price arbitrage, increasing the role of PS balancing and ancillary service revenue. Between 2015 and 22 PS stations were inactive in managing transmission constraints but provided 18% of fast reserve, response and other reserve services in 2022. Stacking up the modelled revenue from price arbitrage and 2022 balancing and ancillary services revenues against the ongoing fixed costs suggests that the four existing PS stations are quite profitable. However, the revenues will not be enough to cover capex and opex of a new 600 MW PS station without more balancing and ancillary services market opportunities.

IASA-Based Capacity Allocation Optimization Study for a Hydro–Pumped Storage–Photovoltaic–Wind Complementary Clean Energy Base

Photovoltaic and wind power is uncontrollable, while a hydro–pumped storage–photovoltaic–wind complementary clean energy base can ensure stable power transmission in the whole system through power quantity regulation by the hydropower station and the pumped storage station. Reasonable allocation of installed capacities of various power sources in the system can improve the reliability and economy of systematic power supply. A system model was built generalizing the hydropower station and the pumped storage station as an energy storage unit, compensating and regulating the natural output process to match the system output and the load and to establish a correlation between the installed capacity of the base and the output index. Installed capacity allocation optimization was studied through an optimization model built with an initial investment of the base as the objective function and with power supply guarantee rate, power abandonment rate, and installed capacity as restraints and solved using improved artificial sheep algorithm (IASA) based on the shepherd dog supervision mechanism. A Yellow River clean energy base was selected for a case study analyzing the influence of power supply guarantee rate and power abandonment rate on installed capacity allocation and investment. For the two most important parameters in the optimization process, that is, the power supply guarantee rate and the power abandonment rate, after qualitative and quantitative analysis, it is found that the power supply guarantee rate has a greater impact on the initial investment. In this study, a combination of the power abandonment rate of 18% and the guaranteed rate of 90% is finally selected for the optimization calculation. The case study indicates that sole increase of installed photovoltaic or wind capacity resulted in the increase of both power supply guarantee rate and power abandonment rate; an appropriate increase in the installed capacity of the pumped storage station raised the power supply guarantee rate and lowered the power abandonment rate; and the optimal installed capacity allocation of the photovoltaic, wind, pumped storage, and hydropower under a specific load condition of the case project is 4.6:1.4:1.7:1.

Effect of the pressure balance device on the flow characteristics of a pump-turbine

Pump-turbine plays a significant role in the pumped storage station, and it is troubled by unreasonable hydraulic thrust. Some pressure balance devices have been adopted to ensure the safety of the pump-turbine unit, but the effect mechanism has not been numerical studied. This paper establishes the CFD model of the flow passage of a pump-turbine, wherein the crown gap, band gap, pressure balance pipe, and the discharge ostium are considered. Then, the flow characteristics of the pump-turbine at four typical operating conditions in turbine mode are calculated in transient scheme, and the numerical results agree with the experimental results. Finally, the effect of the pressure balance pipe and the discharge ostium on the pressure pulsation and the hydraulic thrust is discussed. The results show that the pressure balance pipe causes the direction of the axial hydraulic thrust to change from downward to upward, and the discharge ostium helps reducing the axial hydraulic thrust to a reasonable range. The pressure balance pipe and the discharge ostium have little effect on the radial hydraulic thrust. The pressure pulsation analysis provides a basis for revealing the mechanism of the hydraulic thrust frequency, and the rotor-stator interaction frequency exists in the axial hydraulic thrust. This paper provides a deeper knowledge of the impact mechanism of the pressure balance pipe and discharge ostium on the flow characteristics of the pump-turbine, which could contribute to future designs of the pump-turbine units, and is helpful for improving the safety of the pumped storage unit.

Building integrated pumped-storage potential on a city scale: An analysis based on geographic information systems

Energy storage is essential for the successful transformation of the existing power system to one based on variable renewable energy sources. The portfolio of existing possible storage technologies at a given location within the power system is often severely constrained by a multitude of factors. Therefore, there is a need to explore the potential of thus-far neglected and uncharted territories. The prefeasibility study presented in this article addresses the theoretical potential of small-scale pumped-storage stations located in urban areas and utilizing height differences provided by built infrastructure (buildings). Geographic information system tools are applied for a selected case study (Toruń, Poland). The results revealed that a city with a population of 200 000 has a hosting capacity for small-scale pumped storage of slightly over 19 MWh or 11.3 MWh if stricter building selection criteria are considered. The article also provides a preliminary discussion of a concept of several buildings with pumped-storage upper tanks that share the same lower reservoir and estimates the role of such storage in covering city lighting needs. The discussion section is based partially on strengths-weaknesses-opportunities-threats analysis highlights the concept's main limitations and some future research directions.