Pumped Storage Hydro Plant Research Articles

Realistic coordination and sizing of a solar array combined with pumped hydro storage system

This paper presents a realistic coordination and sizing of a photovoltaic (PV) plant connected with pumped-hydro storage (PHS) system at King Talal dam (KTD), Jordan. KTD is proposed to serve as the upper reservoir of the PHS. Two scenarios are investigated. First, both recombination loss in the two-diodes PV power and effective head loss in the PHS plant are not considered. Second, those two losses are considered, so the output power of the system's components is accurately modelled. Data of system demand, air temperature, water flow rate and solar irradiance are collected from different formal institutions in Jordan. This paper employs particle swarm optimization to find the optimal value of the index of reliability (IR). Results show that the optimal values of the IR are 99.67% and 99.90% for the first and second scenarios, respectively. The required number of PV panels (NPV) and the volume of the lower reservoir (VLR) are 44,063 panels and 69.348 M.m3, respectively. In the second scenario, these decision variables are decreased by 14.33% and 5.39%. Uncertainty analysis, on the measured inputs, is performed to assess the system's effectiveness. The proposed methodology is recommended anywhere to get reliable renewable systems with true-sizes and realistic performance.

A multi-objective stochastic tri-level programming for highlighting the role of the pumped-storage power plant on electric grid defense budget

This paper attempted to highlight the impact of a pumped-storage hydro plant on the electricity grid defense budget, which is spent to increase the power system resilience against terrorist attacks. A stochastic tri-level programming approach known as the defender-attacker-defender technique was applied to detect the defense plan by considering the pumped-storage hydro plant. The stochastic parameter was related to the water volume of the upper reservoir during the disruptive attack. In the stochastic tri-level programming model, the upper level was formulated to identify the components that should be defended for mitigating the system vulnerability against disruptive agent attacks. A terrorist agent seeks to find a set of components for maximizing power system damage. Therefore, the middle level was used to model the disruptive behavior. Finally, the lower level modeled the system operator behavior during the attack. The system operator generally applied flexible sources such as storage to reduce the effects of the attack. Thus, the role of the pump-storage hydro plant was evident at this level. The proposed tri-level problem was solved by transforming it into an equivalent bi-level program, which was solved by using an enumeration algorithm. Simulation results illustrate the effectiveness of the pump-storage hydro plant in reducing the power system defender budget

Hybrid Modular Multilevel Converter for Variable DC Link Voltage Operation

Modular Multilevel Converter (MMC) secured its place in applications where high reliability, efficiency and effortless voltage/power scalability are of paramount importance. Without compromising these benefits, this paper proposes a novel control and appropriate design approach for Hybrid-MMC topology, comprising a mix of Full-Bridge and HalfBridge submodules in converter branches, as a grid-side stage of a back-to-back MMC, enabling operation at variable DC link voltage and arbitrary power factor. In the midst of transition to Renewable Energy Sources-dominated power systems, variable DC link voltage operation opens door to the use of Hybrid-MMC in retrofit of large Pumped Hydro Storage Plants to variable speed operation, where existing machines would not tolerate high common-mode voltage stress imposed by fixed-DC-link-voltage operated machine-side MMC stage. In this way, highly flexible grid-scale energy storage use of existing hydro capacities is enabled. Converter design approach and additional control layers have been developed and verified through a set of test scenarios. Sizing and operation at typical operating points are compared to equally-rated Full-Bridge-based MMC. Improvements over the existing Hybrid-MMC solutions include unity-power-factor operation at the entire attainable DC link voltage range and equal loading of upper and lower phase-leg branches regardless of the operating poin.

Comparing CO2 emissions impacts of electricity storage across applications and energy systems

Summary Electricity storage systems can support the decarbonization of energy systems. However, the effect of electricity storage use on greenhouse gas emissions is complex because of roundtrip efficiency losses of the storage and its effects on the dispatch of different electricity-generation technologies. The limited literature examining this issue focus on individual electricity storage applications and the geographies where they are applied. Here, we systematically compare the effects of electricity storage on CO2 emissions across four applications in electricity systems resembling seven European countries. Our findings reveal large emission impact differences between applications and countries. Among other findings, we find that when compared with wholesale arbitrage, storing electricity in other applications exhibits much lower effects on CO2 emissions. We also investigate different policy options to reduce CO2 emissions from storing electricity. We find that although a higher carbon price can have a substantial effect on reducing the CO2 emissions from wholesale arbitrage, other applications require alternative approaches.

Competitiveness of power systems with nuclear power plants and with high participation of intermittent renewable energy sources

In the paper are presented and discussed the results of a more complex research of technology portfolio's competitiveness in power systems with high penetration of intermittent renewable energy sources (i-RES). Possible technology portfolios compositions are analyzed. The portfolios comprise very high participation of i-RES, as well as a certain participation of energy storage technologies, but also and other energy technologies like nuclear and fossil fueled power plants. Within the research are developed new competitiveness indicators i.e., dispatchability indicator and the technology portfolio?s assured capacity. The latter is defined on the basis of recently published Ulrich?s and Schiffer?s paper. Obtained results point out that inclusion of pumped-hydro storage plants improves portfolio?s dispatchability. However, within the researched interval up to PHS installed capacities relative to i-RES capacities of 0.3. Numerical values of the dispatchability indicators are still below their values for the portfolio without i-RES. Increased participation of nuclear power plants contribute to the improvement of numerical values of the dispatchability indicators. The sensitivity analysis for the case of two times smaller cost of pumped hydro storage capacities is also performed. Hypothetical change of power system?s technology structure in sense of substitution hard coal and lignite fired power plants with wind generators or with nuclear power plants is also analyzed. The analysis points out that the substitution with nuclear power plants enables much better results regarding power system?s ability to change the power on demand than substitution with wind generators, particularly in the countries with high participation of hard coal and/or lignite in electricity generation.

Day-Ahead Scheduling of a Gravity Energy Storage System Considering the Uncertainty

To overcome the topographic limitations of pumped hydro storage (PHS) system, novel gravity energy storage (GES) technologies are developing. In this paper, a pioneering work on the modeling and scheduling of a GES system is conducted. The GES system stores and releases energy by lifting and lowering concrete bricks. Since the working principle of the GES system is similar to that of a PHS plant, a double-tower based model of the GES system is established. In addition, a day-ahead scheduling model of the GES system is proposed to test the operation of such system. Specifically, the uncertainty of market price is considered with a data-driven distributionally robust optimization method. Some linearization and reformulation techniques are presented to transform the problem into a mixed integer linear programming (MILP) problem which can be solved easily. Numerical experiments indicate that the proposed model can effectively characterize the operation of the GES system. Concrete bricks are lifted up during low-price period and descend under gravity during high-price period to gain benefits. Additionally, the round trip efficiency considerably influences the total profits.

Optimal scheduling of variable speed pumped storage, solar and wind energy system

ABSTRACT The entry of renewable energy sources in the power sector has significantly affected the inter-connected power system’s safety and stability as renewable energy sources tend to generate variable power. The variability of power inflicts severe challenges for the scheduling of renewable sources. A pumped storage hydro plant (PSP) can help in integrating the variable renewable energy and balance the demand and generation on a day-ahead (DA) or real-time basis through fast response generation. An optimal PSP operation schedule has been obtained to increase the power producer’s profit by formulating it as a mixed-integer problem. The mathematical problem formulation for the hybrid system with solar, wind, and PSP operation has been made, considering the next day’s market schedule. The revenue has been computed by utilizing the energy of solar, wind, and PSP. A comparative study for the profit earned depending upon the power is regulated or not, using variable speed technology, during the pumping mode has been presented. The grid power has been utilized for the pumping operation of the pumped storage plant. A penalty factor has been utilized for the mismatch in the demand and generation. The analysis shows that the variable speed operation of PSP during pumping mode has increased the net profit by and reduced the charges paid toward the pumping operation by compared to the fixed speed operation and a rise of in profit and decline in pump charges have been recorded compared to two-speed operation.

Fuel constrained dynamic economic dispatch with demand side management

Owing to slowly reduction of fossil fuel, the cost-effective use of available fuel for electric power generation has turn out to be a very important concern of electric power utilities. Thermal power plants have to operate within their fuel confines and contractual constraints. This work recommends social group entropy optimization (SGEO) technique to solve fuel constrained dynamic economic dispatch (FCDED) with demand side management (DSM) integrating renewable energy sources and pumped hydro storage plant. Here the dynamic economic dispatch (DED) problem is solved with and without fuel constrained. The effectiveness of the recommended technique is revealed on two test systems. Simulation results of two test systems have been compared with those acquired from self-organizing hierarchical particle swarm optimizer with time-varying acceleration coefficients (HPSO-TVAC), fast convergence evolutionary programming (FCEP) and differential evolution (DE). Test results show that fuel consumption can be sufficiently controlled for fulfilling constraints imposed by suppliers. It has been observed from the comparison that the suggested SGEO has the capability to confer with superior-quality solution.

Developing an Optimal Scheduling of Taiwan Power System With Highly Penetrated Renewable Energy Resources and Pumped Hydro Storages

Recently, Taiwanese Government has announced an ambitious energy policy: up to 20% of total power will be generated from renewable energy resources by 2025. Under such high-level penetration level of renewable energy resources, the typical net load curve will be definitely reshaped as the so-called duck curve. Operation modes of pumped hydro storage units in Taiwan power system will be totally changed. To tackle out this difficulty, the optimal scheduling of Taiwan power system is developed in this article for examining the coordination of highly penetrated renewable energy resources and pumped hydro storage plants under the required spinning reserve. The associated cost function and various constraints used in this optimal scheduling problem are described first. Physical characteristics of pumped hydro storage units in Taiwan will also be studied. By following the data format in the open source MATPOWER optimal scheduling tool, platform developments of this optimal scheduling program are reported. To validate the effectiveness of the proposed scheme, intensive simulations of both current scenarios and future scenarios are conducted. Simulation results indicate that existing pumped hydro storage units in Taiwan can indeed mitigate the impact of the duck-shaped net load curve in the generator scheduling of future Taiwan power system even under the worst scenario.

Hybrid Modular Multilevel Converter Design and Control for Variable Speed Pumped Hydro Storage Plants

Hybrid modular multilevel converter control and design for pumped hydro storage plants is presented, addressing application-specific shortcoming of conventional back-to-back half-bridge modular multilevel converter: high common-mode-voltage machine stress. Common-mode-voltage-free operation in the entire or partial frequency range is enabled by variable DC link voltage control, through introduction of minimal full-bridge submodule share in hybrid active front-end converter stage. The developed generalized converter design approach for arbitrary DC link voltage range operation and additional internal energy balancing control layers enable down-to-zero DC voltage control. The results are verified through high-fidelity switched-model simulations of 6 kV converter, with 10/6 ratio of full-bridge to half-bridge submodules in active front-end. The analyzed hybrid active front-end stage benefits from lower converter losses for equal machine operation flexibility compared to full-bridge design, while trade-off between grid-side power factor range and full-bridge submodule share is offered within the design stage. Compared to the state-of-the-art, zero-to-rated DC link voltage operation is possible at lower full-bridge submodule share (62% against 75 %), at the penalty of reduced grid-side power factor. Alternatively, operation at higher full-bridge submodule share (62% against 50% existing solution) enables grid-side reactive power support over wide speed range, without branch current overload.

Assessment of the Capacity Credit of Renewables and Storage in Multi-Area Power Systems

Capacity credit (CC) can be defined as the capacity of conventional generators that can be replaced by renewable energy sources (RES) and/or other resources such as energy storage without reducing system reliability. Conventional approaches for calculating CC typically treat the power system as a single area without considering transfer constraints and reliability of interconnectors. However, in multi-area power systems locational aspects are key to assess tradeoffs and synergies arising from transmission, storage and RES in providing adequacy of supply. In this work, we propose a new methodology to quantify the CC of RES and storage in a multi-area power system. Due to the large computational burden brought about by composite system adequacy evaluation, a new accelerated sequential Monte Carlo simulation strategy and a new adaptive sampling approach are specifically developed to achieve computation efficiency. The proposed methodology is tested by demonstrating the impact of interconnectors' transfer constraints and availability on RES-storage CC in the case of the Australian National Energy Market (NEM) multi-area power system, with applications to wind, solar, and pumped hydro storage plants. The results from several realistic NEM case studies highlight how the proposed model can inform strategic, reliability-aware integrated system planning of large-scale interconnected low-carbon power systems.

Pumped hydro storage plants: a review

Pumped hydro storage plants (PHSP) are considered the most mature large-scale energy storage technology. Although Brazil stands out worldwide in terms of hydroelectric power generation, the use of PHSP in the country is practically nonexistent. Considering the advancement of variable renewable sources in the Brazilian electrical mix, and the need to provide flexibility to the national electrical system, several official documents cite PHSP as an important alternative for the expansion of the Brazilian electrical system. This article presents the state of the art of PHSP and its use, in order to create a theoretical basis for future research on the subject, also providing theoretical support for Brazilian energy planning. The review includes a global panorama on the use of PHSP in the world, the technical and projective foundations on this type of technology, its benefits, and disadvantages, in addition to the new configurations and possible layouts for the construction of pumped hydro storage plants. Finally, the challenges and trends for the dissemination of PHSP technology are addressed.

Existing and new arrangements of pumped-hydro storage plants

The energy sector is undergoing substantial transition with the integration of variable renewable energy sources, such as wind and solar energy. These sources come with hourly, daily, seasonal and yearly variations; raising the need for short and long-term energy storage technologies to guarantee the smooth and secure supply of electricity. This paper critically reviews the existing types of pumped-hydro storage plants, highlighting the advantages and disadvantages of each configuration. We propose some innovative arrangements for pumped-hydro storage, which increases the possibility to find suitable locations for building large-scale reservoirs for long-term energy and water storage. Some of the proposed arrangements are compared in a case study for the upper Zambezi water basin, which has considerable water storage limitations due to its flat topography and arid climate. Results demonstrate that the proposed combined short and long-term cycles pumped-storage arrangement could be a viable solution for energy storage and reduce the cost for water storage to near zero.

Modeling and Solution Techniques Used for Hydro Generation Scheduling

The hydro generation scheduling problem has a unit commitment sub-problem which deals with start-up/shut-down costs related hydropower units. Hydro power is the only renewable energy source for many countries, so there is a need to find better methods which give optimal hydro scheduling. In this paper, the different optimization techniques like lagrange relaxation, augmented lagrange relaxation, mixed integer programming methods, heuristic methods like genetic algorithm, fuzzy logics, nonlinear approach, stochastic programming and dynamic programming techniques are discussed. The lagrange relaxation approach deals with constraints of pumped storage hydro plants and gives efficient results. Dynamic programming handles simple constraints and it is easily adaptable but its major drawback is curse of dimensionality. However, the mixed integer nonlinear programming, mixed integer linear programming, sequential lagrange and non-linear approach deals with network constraints and head sensitive cascaded hydropower plants. The stochastic programming, fuzzy logics and simulated annealing is helpful in satisfying the ramping rate, spinning reserve and power balance constraints. Genetic algorithm has the ability to obtain the results in a short interval. Fuzzy logic never needs a mathematical formulation but it is very complex. Future work is also suggested.

Disaggregation of energy storage operation by timescales

Abstract We discuss the ex-post disaggregation of electric storage operation by time differences between charging and discharging, i.e. by how long energy is stored prior to the discharge. This adds a new dimension to the analysis of storage time shifting revenue and allows for additional insights into the historic value loss of storage assets. We apply this method to stylized pumped hydro and battery storage systems operating on historic European (Swiss and German/Austrian) day-ahead electricity price curves (2007–2017). We find that historic trends of the disaggregated revenue are highly diverse depending on the timescales. Changes in relative revenue shares are primarily driven by the price profile distortion due to increasing photovoltaic electricity generation. In the battery storage case this results in a 1.5 h reduction of charging-discharging time differences between 2008 and 2012. The case of pumped hydro storage plants is more complex: Main revenue losses occur for time differences of 6 to 12 h. Revenues on other timescales are much more stable or even increasing. This especially holds for short transfer times between 0 and 6 h: In the German/Austrian market area, they contribute 17% to total pumped hydro storage revenue in 2016, as compared to 3% in 2008. The disaggregation also enables the analysis of contributions from hours with outlier electricity prices. These are found to be especially significant in the years 2007 and 2008. Overall, we find that storage operation has been increasingly diversified due to the historic price profile evolution. The often discussed revenue erosion offers new opportunities on different timescales.

Hydro storage reduces electricity costs and keep wind and solar unpolluted

New energy policy is caused by narrow range of operation of Thermal Power Plants, potential risks of Nuclear Power Plants, limited resources of oil, gas and coal, and new trends in ecology. Taking into account that renewable energy, solar and wind power particularly are very dependent on the climate, Hydro Power takes a new role in energy systems. Electricity conversion and storage in periods of lower consumption or available excess production, and electricity production from the stored energy in periods of higher demand or reduced production, are crucial for the maintenance of stable and efficient electrical system. This requirement has especially strengthened nowadays in the world due to the expansion of integration of new wind and solar plants. These renewable sources are characterized with inherent intermittent production both in daily periods and periods of several days, weeks or even months.A number of technologies might be considered for the electricity conversion and storage, but the only nature and high capacity available technology is based on the pumped-hydro storage plants. This article studies the potential of the pumped storage plants as the effective and economically competitive technology for the storage of wind, solar, run-of-river and other environmentally friendly energies, as well as energy from other conventional thermal plants including nuclear. Nuclear and coal fired plants can change power output to achieve demand but only at the price of extremely high maintenance cost. In addition, natural gas generators contribute to climate change and pollution only slightly less than coal. The pumped storage method is the most common storage system in the electricity sector. It is traditionally dependent on natural conditions, usually making use of rivers or lakes. However, some innovative methods have emerged in recent years, such as the use of the sea as the lower reservoir, or a proposal to use a surface reservoir as the upper reservoir and an underground reservoir as the lower. Analyses indicate that there is a strong economic incentive for further investment in pumped-storage installations when other hydro storages and sites are not available.

Joint Operation Between Wind Power Generation with Pumped Hydro Energy Storage and Participation in Frequency Control: Study in Electricity Market

Due to the intermittency and fluctuation of wind speed, the integration of wind power into electric power system has been a relevant issue. Recently, Pumped-storage hydro plant (PHES) can be used to balance the unstable output of wind farm, as it can adjust its production to compensate wind power fluctuation. This paper investigated the combination of a wind farm and a PHES facility from the point of view of a generation company in a market environment. A joint operation model between the wind farm and PHES is proposed. An algorithm of energy management system (EMS) is proposed to identify the daily operational strategy to be followed in order to: 1) Minimize the penalty cost resulted from wind-PHES output imbalances; 2) Maximize the daily revenue profit taking into consideration all constraints of joint operation. Simulation results under MATLAB/SIMILINK®environment are presented and discussed.

On the Evaluation of Binary Event Probability Predictions in Electricity Price Forecasting

In this paper we present an evaluation framework for predictions of binary events in probabilistic electricity price forecasting. It employs the MSE-equivalent QPS together with the DM test and allows for further insights about deficiencies of the considered models. Additionally, techniques from the field of classification are considered, which extend our framework and are particularly suited for the evaluation of predictions of rare events. We consider binary events with direct applicability to a generators daily decision making such as profitability of a pumped-hydro storage plant and evaluate the respective forecasts statistically. We show that the task of forecast evaluation can be simplified from assessing a multivariate distribution over prices to assessing a univariate distribution over a binary outcome, fully characterized by a single probability.

An Overview of the Portuguese Energy Sector and Perspectives for Power-to-Gas Implementation

Energy policies established in 2005 have made Portugal one of the top renewable power producers in Europe, in relative terms. Indeed, the country energy dependence decreased since 2005, although remaining above EU-19 and EU-28 countries in 2015 (77.4% vs. 62.4% vs. 54.0%, respectively). Data collected from governmental, statistical, and companies’ reports and research articles shows that renewables and natural gas assumed a growing importance in the Portuguese energy mix along time, while oil followed an opposite trend. Recently, the country remarkably achieved a full 70-h period in which the mainland power consumed relied exclusively on renewable electricity and has several moments where power production exceeds demand. Currently, the main option for storing those surpluses relies on pumped hydro storage plants or exportation, while other storage alternatives, like Power-to-Gas (PtG), are not under deep debate, eventually due to a lack of information and awareness. Hence, this work aims to provide an overview of the Portuguese energy sector in the 2005–2015 decade, highlighting the country’s effort towards renewable energy deployment that, together with geographic advantages, upholds PtG as a promising alternative for storing the country’s renewable electricity surpluses.

Reliability assessment using probabilistic modelling of pumped storage hydro plant with PV-Wind based standalone microgrid

The storage system is promising as a crucial factor for maintaining the reliability of standalone microgrids for off-grid communities of India which depends on renewable energy sources. The pumped storage hydro (PSH) system is emerging as a source of green energy and overcomes the drawbacks of electrochemical energy storage devices in view of economic and environmental aspects which are the main concern across the world. The meteorological data of Kandla, India has been considered for simulation work. The mathematical models for the renewable energy sources based on meteorological data processing have been developed in the present work. In this work, a probabilistic upper reservoir multi-state model (MSMUR) of PSH plant has been developed for incorporating realistic situation using analytical technique. The reliability evaluation of PV-Wind energy system incorporating PSH has been carried out. For reliability evaluation, indices like Loss of load expectation (LOLE) and Expected energy not served (EENS) are considered in this paper. Analytical technique and Monte Carlo Simulation are used for reliability assessment, and the results of both methods are compared in this work. This study demonstrates that the proposed system based on PSH is more reliable and environmental friendly than battery storage system.