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Pumped hydro energy storage system: A technological review
... The rapid growth in variable RESs is increasing the necessity to develop reliable and stable storage solutions with the ability to operate in utility-scale applications and overcome the technical issues that might occur due to the high integration of RESs [31]. The flexibility and resilience provided by PHS, in addition to its ancillary network services, are hugely significant in securing the power stability of modern EPSs. ...
... With a high round-trip efficiency (75%-85%), PHS offers multiple services such as frequency control, fast response times for pumping and generating (ranging from seconds to minutes), and voltage regulation. The long discharge time and large capacity of PHS are critical in averting curtailment, limiting congestion, decreasing total costs, and reducing emissions [31,32]. Furthermore, PHS provides the flexibility to start and stop with rapid load tracking, and has the advantages of a long lifetime (50-100 years), high power rating (100-5000 MW), and non-reliance on raw materials. ...
... Furthermore, PHS provides the flexibility to start and stop with rapid load tracking, and has the advantages of a long lifetime (50-100 years), high power rating (100-5000 MW), and non-reliance on raw materials. Hence, despite its high initial cost (60-160 $/kWh) and geographical restrictions, PHS is one of the best options for increasing the integration of RESs into EPSs [30][31][32][33][34]. There are two main types of PHS: open-loop (OL), in which at least one of the reservoirs is connected to a natural source of water (e.g., a river), and closed-loop (CL), in which neither reservoir has a connection to any naturally flowing source of water. ...
Over the past decade, energy storage in renewable energy-dominated systems has received increasing interest. Effective energy storage has the potential to enhance the global hosting capacity of renewable energy in power systems, accelerate the global energy transition, and reduce our reliance on fossil fuel-based generation. Pumped hydro storage (PHS) is the most common storage technology due to its high maturity, reliability, and effective contribution to the integration of renewables into power systems. Accordingly, it is essential to achieve the optimal operation of energy systems combined with PHS. Therefore, this paper comprehensively reviews recent efforts toward the optimal operation of PHS-based energy systems (PHS-BES), considering the diversified energy sources, configurations, grid connectivity, and research directions. The evaluation criteria for the optimal operation of these systems are mathematically addressed and discussed. Moreover, methods of solving the studied problem are categorized and several improvements are suggested. It is observed that more flexible energy policies are urgently needed to encourage new investments in PHS, and the existing environmental and social criteria require further research. Moreover, the hybridization of PHS with other storage devices should be further investigated, and the development of robust hybrid methods for solving the optimal operation of PHS-BES, especially for real-time applications, is highly promising. Based on an in-depth analysis, this paper provides a compendium of real-world research and industry-oriented challenges, and presents future research and industry trends for the optimal operation of PHS-BES.
... Pumped hydro energy storage and CAES are prevalent in off-grid and remote electrification applications. PHES is considered the most promising and economically viable energy storage system for handling large electricity networks [13]. Moreover, it is a clean and reliable energy storage system that works like a conventional hydropower plant, but unlike traditional hydropower plants, they do not require constant water input [14]. ...
... However, the problem with the development of PHES is the lack of favourable topography and geography [13]. More precisely, the topography found in most European countries is appropriate for developing PHES. ...
Pumped hydro energy storage (PHES) solutions enable greater diffusion of renewable energy into the electricity grid. However, accelerated development of PHES is complex due to the numerous spatially relevant technical, environmental, social, and economic criteria that must be assessed to determine a pumped hydro sites feasibility. With the goal to rapidly narrow down feasible sites from a large land area, this study developed a Geographic Information System (GIS) and Analytic Hierarchy Process (AHP) based technique to autonomously identify PHES sites based on a range of environmental and technical criteria. Following GIS-AHP analysis, Levelized Cost of Energy (LCOE) scenario analysis was conducted with a limited number of feasible sites, as well as their carbon abatement potential. The developed approach was demonstrated for the case of Northern Queensland (NrQLD), Australia. The developed GIS-AHP PHES site selection approach identified 14 potentially feasible sites. For the base case scenario, these sites could generate 366.94 TWh over their lifetime while abating 300 ktCO2eq. The LCOE of these 14 PHES sites ranged between 0.04 AU$/kWh and 0.27 AU$/kWh for the base case scenario. The developed approach has implications for energy planning managers seeking to efficiently narrow down feasible PHES sites, which are essential storage enablers for transitioning to a zero-emissions economy.
... Ahora bien, el almacenamiento energético está en pleno auge en el panorama mundial y se prevé un incremento de la capacidad instalada mundial de más de un 200% en el periodo 2014-2050 [139], y las tecnologías se desarrollan con mayor rapidez debido al impulso procedente de instituciones y empresas [140]. La tecnología PHES lleva años en el mercado [133], sin embargo, muchos países deberían evaluar su potencial para diseñar una correcta política energética que sirva de base para la ejecución de los futuros proyectos de las centrales PHES, pues todavía es una tecnología que tiene un papel clave en el panorama energético [139]. ...
... El PHES es, desde hace décadas, y hasta la actualidad, la tecnología de almacenamiento energético más consolidada a nivel mundial [133,141]. Existen diversas metodologías de evaluación del potencial PHES [138,[150][151][152][153][154], sin embargo algunas no consideran una optimización de los resultados, mientras que otras aplican la optimización al final de la metodología, con lo cual queda ligada a las restricciones incluidas en el proceso de evaluación, arrastrando hasta el final del procedimiento cierto grado de subjetividad implícito en la elección de las restricciones. Hasta el momento de inicio de la presente tesis se desconocían referencias que incluyeran una optimización antes de aplicar las restricciones. ...
In order to achieve the minimum targets for the penetration of renewable energy sources (RES) and the development of energy storage set by the different organisations, this thesis provides two contributions: a methodological proposal for the evaluation of the potential for pumped hydro energy storage (PHES) and a dynamic operation model for PHES systems. In "Contribution 1", the objective is to propose a universal, modularised methodology for simple replication that serves as a tool for the evaluation of the viable potential of PHES in a given territory, through the use of a package of predesigned constraints. An optimisation algorithm is included. Furthermore, the results are classified in basins or interbasins of ravines and demonstrate that the high potential assumed a priori is considerably reduced, showing how important it is that the restrictions applied are adapted to the territory in question. The methodology is applied to the island of Gran Canaria, because of its large number of large dams and the fact that it does not have any large scale hydroelectric power plants at present. In "Contribution 2", the main objective is to create a dynamic operation model that studies the contribution of a PHES system to a given electricity market in a scenario of increased RES penetration. The model is applied to the case of the Salto de Chira power plant on the island of Gran Canaria. The results demonstrate the optimisation of the plant's operation strategy and the need to: take advantage of other PHES plants; use other storage technologies; and continue using conventional energy sources (CES) until the RES can cover the electricity demand on their own. The model is validated by providing reliable results within the margins established in the power plant project and also because they are within the range of the different forecasts made so far.
... They also indicate that PHES based on photovoltaic energy has only been used on a very small scale. As a result of all the above, a renewed interest is emerging worldwide in the use of PHES along with demands for the rehabilitation of old small hydropower plants [10]. According to Javed et al. [11], a large number of studies in the literature recommend high levels of wind penetration in order to energize remote areas and the use of PHES as energy storage to fill and decrease the energy gaps caused by variations in wind availability. ...
... Some PHES systems are already in operation [21][22][23], while others are in the construction stage [24]. However, according to [10], PHES systems require, in addition to advances in turbine design to improve plant efficiency and flexibility, new strategies to optimize storage capacity and maximize the rate of return of the plant. Safe and stable operation of hydropower plants must be guaranteed to achieve clean energy production and renewable integration in the system [25]. ...
The present paper proposes the implementation of a new algorithm for the control of the speed regulators of Pelton wheel turbines, used in many of the pumped hydroelectric energy storage systems that operate in isolated electrical systems with high renewable energy participation. This algorithm differs substantially from the standard developments which use PID or PI governors in that, in addition to acting on the nozzle needles and deflectors, it incorporates a new inner-loop pressure stabilization circuit to improve frequency regulation and dampen the effects of the pressure waves that are generated when regulating needle position. The proposed algorithm has been implemented in the Gorona del Viento wind–hydro power plant, an installation which supplies the primary energy needs of the island of El Hierro (Canary Islands, Spain). Although, as well as its wind and hydro generation systems, the plant also has a diesel engine based generation system, the validation of the results of the study presented here focuses on situations in which frequency control is provided exclusively by the hydroelectric plant. It is shown that implementation of the proposed algorithm, which replaces the previous control system based on a classical PI governor, is able to damp the pressure wave that originates in the long penstock of the plant in the face of variations in non-dispatchable renewable generation, a situation which occurred with a high degree of relative frequency in the case study. The damper has enabled a substantial reduction in the cumulative time and the number of times that frequency exceeded different safety margins. Damper incorporation also reduced the number of under-frequency pump unit load shedding events by 93%.
... The excessive amount of fossil fuel consumption in this era of globalization causes air pollution, global warming, climatechanging, which leads to systematic ecological destruction. Thus, ample source of sustainable and clean energy is highly desirable for modern society [1][2][3][4][5][6][7][8] . One of the most fascinating abundant sources of such inexpensive and clean energy is the salinity gradient energy or the 'blue energy' by its another common name, which generates from the entropy changing or the Gibbs free energy associated with mixing of two solutions having different concentrations 9 . ...
... As depicted in Figure 9(a), we can extract a maximum power density of 23.5 kW/m 2 , which is almost eighteen (18) times higher than that of a conical nanopore, albeit keeping other relevant parameters identical. Moreover, as witnessed in Figure 9(b), the efficiency also gets enhanced by more than six (6) times in comparison to the setup discussed at the beginning. The reasons behind this substantially enhanced power density as well as the augmented efficiency are attributed to the raise in pore selectivity (cf. Figure S6(a)) and also the reduction in the cross-sectional area. ...
The salinity gradient energy or the 'blue energy' is one of the most promising inexpensive and abundant sources of clean energy, having immense capabilities to serve modern-day society. In this article, we overlay an extensive analysis of reverse electrodialysis (RED) for harvesting salinity gradient energy in a single conical nanochannel, grafted with a pH-tunable polyelectrolyte layer (PEL) on the inner surfaces. We primarily focus on the distinctiveness of the solution pH of the connecting reservoirs. In spite of acquiring a maximum power density of ∼1.2 kW m-2 in the chosen configuration, we notice a counter-intuitive patterning of the ion transport for a certain span of pH, leading to diminishing power. To this end, we discuss the possible strategic avenues essentially to achieve a higher amount of power density. In order to achieve a desirable outcome within that pH zone, we employ two separate approaches intending to counter the underlying physics. Results reveal a great enhancement in the power density as well as in the efficiency even under the framework of both strategies proposed herein. Moreover, as shown, the window of solution pH has increased by three times, implicating the maximum power density mentioned above. We expect that the strategic procedure of augmented energy harvesting as discussed in this analysis can be of importance from the perspective of fabricating state-of-the-art nanodevices aimed at blue energy harvesting.
... Roundtrip electric efficiency is usually in a range of 70-80% (some references refer to a range of 65-85%) and plant lifetime can be assumed to be in the order of about 80 years (60-150 years) (with shorter periods for certain components) (Bauer et al., 2007;Deane, Ó Gallachóir and McKeogh, 2010;Oliveira et al., 2015;Rehman, Al-Hadhrami and Alam, 2015;Immendoerfer et al., 2017;Rahman et al., 2020;Vilanova, Flores and Balestieri, 2020;VSE, 2020;wikipedia, 2021). ...
... 1: Overview of PHES costs and other key parameters for economic assessment as reported by different studies(Deane, Ó Gallachóir and McKeogh, 2010;Rehman, Al-Hadhrami and Alam, 2015;Andrey et al., 2020;Rahman et al., 2020;Vilanova, Flores and Balestieri, 2020; VSE, 2020). n.a.: not available. ...
This report is an extension or continuation of the technology monitoring of the Swiss Federal Office of Energy (Bauer et al., 2017, 2019) and covers – after electricity production – two additional technological areas: Hydrogen (production, storage and transport, conversion with CO2 into methane) and electricity storage (batteries, compressed air and pumped hydro storage, re-electrification of
hydrogen in fuel cells). In addition, an update of costs and potentials of electricity production with photovoltaic systems and wind turbines in Switzerland is provided. Fact sheets regarding further technologies are provided in the appendix.
The cost analysis for the various energy technologies was performed before the summer of 2021, so that the increase in commodity prices and the market uncertainties since the fall of 2021 have not been taken into account in the present study. This applies in particular to the power generation costs of natural gas-fired power plants (section 21.5), for which a natural gas price for large consumers in
Switzerland of 5-7 Rp./kWh (natural gas) was assumed until 2050, based on the IEA scenarios.
The report contains an overview of the current state of the art and the expected future development of hydrogen and electricity storage technologies. It also provides information on the corresponding costs and their development up to 2050, as well as life-cycle greenhouse gas emissions. System aspects – i.e. answering the question what role hydrogen and electricity storage will play in the overall
energy system of the future – are not subject of this report. For this, we refer to the recently published Energy Perspectives (Kirchner et al., 2020) and similar analysis (Panos et al., 2021).
... Six aspects of interaction (interconnections) between elements of nuclear-renewable hybrid energy systems are identified: Thermal, electrical, chemical, hydrogen, mechanical, and information. Rehman et al (Rehman, Al-Hadhrami, and Alam 2015). ...
Global energy demand has consistently increased in recent decades, owing to the rapid population increase. Energy consumption is higher than it has ever been, and most fossil supplies are on the verge of exhaustion with the current rate of exploitation. Facing the double pressure of meeting energy demands and reducing carbon emissions, the integration of renewable energy into different aspects of the energy ecosystem has become a unified agreement for all countries globally. Hybrid renewable energy systems that integrate multiple energy sources can effectively solve this problem. In the hybrid renewable energy system, optimizing the unit size is the key to achieving efficient utilization of renewable energy. Research trends show that artificial intelligence methods are gaining attention from researchers and can provide good system optimization in the absence of long-term weather data to provide good system optimization. While different studies have presented articles in this research domain, it is important to give a comprehensive collation/summary of the research trend while highlighting key models/methods utilized in this research domain. Hence, based on the published literature, this paper provides a comprehensive bibliographical review of the current trends/status of hybrid renewable energy systems research. Key research articles published in the Web of Science between the years 2000 and 2022 in this research domain have been reviewed. This paper describes the hybrid renewable energy systems, summarizes many different energy systems in existing literature, compares the differences between various energy systems, and analyzes the physical models of different systems, as well as the optimization methods and the optimization of the systems. Further, the uncertainty of electricity generation from renewable energy sources is analyzed in the literature review and the future challenges of hybrid renewable energy systems are summarized.
... Compressed air and pump hydroelectric storage systems are part of mechanical energy storage systems that, in terms of power, the duration of energy storage and the lifetime of the system are the highest, and their construction and maintenance costs are lower than other energy storage systems [3]. The storage pump system requires a specific site for construction, and construction is not possible in every region and with every scale [4]. Moreover, common storage pump systems have adverse effects on the environment, and due to the high volume of evaporation, the use of freshwater sources in them is not economical [5]. ...
The system presented in this paper can change the energy storage landscape by having the advantages of a compressed air storage system and pump storage, as well as minimizing the disadvantages of these two systems. One of the advantages of this system compared to similar systems is the lack of combustion of natural gas. Correspondingly, for construction, it does not require specific specifications for the executive site, and control of the energy and heat of the system (due to the use of water as an operational fluid) is easier than similar systems. In addition, this system is very scalable and can be designed in low capacities to high capacities, energy analysis of this research to identify the basic and effective parameters of the system and determine the limitations and relationships between them. The amount of energy saved in the current research system compared to previous research is significant, and 92% efficiency can be achieved. The energy analysis of this research determined the effect of the parameters on each other and their limitations so that the path of its feasibility design was paved.
... Due to the intermittency of some of these renewable energies (wind, solar power (particularly photovoltaics), etc.), storage is thus the only way to operate in accordance with the time lag between the production of electricity (by solar panels working only during the day) and the satisfaction of demand (lighting at night). Today, the most widely used system for storing large quantities of primary energy during overproduction is hydraulic storage by pumping water uphill from a downstream dam, and then pouring it into the latter's reservoir [22,23]. ...
This survey article has explored a number of energy storage-related topics.
We start by outlining the main challenges and objectives related to energy storage.
Second, we went over a number of energy storage techniques and the standards used to choose the best available technology. We also talk about the problems and restrictions that currently exist with energy storage methods. Thirdly, we provide information on the battery technologies that are most often employed in a variety of energy storage applications. Together with their market share, social and environmental factors, and usage and kind, batteries are detailed. Also, an overview of current developments in cell balancing techniques and battery state estimation is provided.
... Although pumping storage has been proven to have a long-life cycle, it requires a large amount of land and needs to be located near water resources. Moreover, the pumping energy storage system is not extensible upon completion and faces significant challenges in meeting the expected market growth due to the high cost and environmental impacts of constructing man-made reservoirs [4]. Some chemical components in other forms of renewable energy storage technologies, such as Energies 2023, 16, 1575 2 of 15 lithium-ion battery technology, require scarce raw materials (such as cobalt) to produce batteries. ...
In the future, there will be more and more abandoned oil-gas wells with the exploitation of onshore oilfield resources. However, the large height difference in abandoned oil-gas wells can be used as building blocks for gravity power generation, thus maximizing the economic value of abandoned oil-gas wells. In this study, a scheme of gravity power generation by virtue of the spud-in casing depth of oil-gas wells is proposed, and a gravity power generation model based on abandoned oil-gas wells is established. The parameters and economic benefits of gravity energy storage are calculated for oil-gas wells in the Huabei oilfield, the Daqing oilfield, and the Xinjiang oilfield. It is shown that the power density and discharge time of the gravity energy storage system in abandoned oil-gas wells are suitable for distributed power generation. In addition, the fast response characteristics of energy storage in abandoned oil-gas wells are verified, which makes the system suitable for correcting continuous and sudden frequency and voltage changes in the power grid but not suitable for energy arbitrage under a high number of annual cycles. Furthermore, the leveling cost of storage of the gravity system in abandoned oil-gas wells is more economical with the high number of annual cycles. The analysis of this work provides a significant investigation of the feasibility of gravity power generation by using abandoned oil-gas wells.
... Pumped storage is the most mature large-scale energy storage method at present [5]. It is a key regulator for "net zero" targets and modern power systems because of its excellent regulating ability. ...
Multi‐energy complementation is an important means to improve the capacity of renewable energy consumption and the key to achieving the goal of “net zero” globally. The hydro‐wind‐photovoltaic‐storage hybrid system is an important technical approach, and in this system, pumped storage and battery energy storage are both key components for regulation. In order to study the problem of coordinated control of the two storage systems, a model of a pumped storage‐battery integrated system (PSBIS) for simulating small disturbances of pumped storage units and the battery charge and discharge characteristics was established by MATLAB/Simulink in this study firstly. Then, two control strategies (“priority regulation of pumped storage” and “priority regulation of battery storage”) are studied, and simulation calculations under ideal input and measured wind power disturbances are carried out to compare two control strategies by using the integrated system model under grid‐connected conditions. The simulation results revealed that the “priority regulation of pumped storage” control strategy has a better performance on active power balance, compared with the “priority regulation of battery storage” control strategy. This work could provide technical support for coordinated control of the practical PSBIS in the future. This article is protected by copyright. All rights reserved.
... However, due to the instability of wind power, large-scale wind power generation has system voltage fluctuations, flicker, harmonics and other issues, and will have an adverse impact on the frequency , supply and demand control of independent power supply and load system. The pumped storage power station has the advantages of fast response, high performance to price ratio, flexible start and stop, good adjustment ability and so on [3] . So, it has obvious advantages in the application of large-scale power grid energy storage, as shown in Figure 1. ...
... Untuk mengatasi masalah tersebut dipilih sebuah tempat penyimpanan energi menggunakan sistem penyimpanan energi air ( water energy storage ) yang lebih ramah lingkungan daripada baterai [3]. Karakteristik dari water energy storage yang lebih fleksibel dan mempunyai kapasitas penyimpanan energi yang lebih besar daripada baterai membuat water energy storage memiliki lifecycle yang lebih lama [4]. Prinsip kerja dari sistem ini adalah dengan menggunakan daya berlebih yang dihasilkan oleh PV untuk memompa air menggunakan motor pompa dari lower reservoir ke upper resevoir, lalu air pada upper reservoir akan dialirkan ke generator sebagai sumber untuk memutar turbin sehingga generator akan menghasilkan daya [3]. ...
Photovoltaic (PV) menjadi pembangkit listrik dengan sumber energi terbarukan yang paling banyak digunakan karena biaya perawatan yang murah. Karakteristik yang dimiliki oleh pembangkit listrik ini ialah fluktuasi daya yang dihasilkan karena bergantung pada intensitas cahaya matahari. Solusi untuk mengatasi hal tersebut adalah dengan menambahkan penyimpan energi (energy storage) ke dalam sistem pembangkit ini agar kebutuhan daya yang dikirim ke beban dapat dijaga. Energy storage yang biasa digunakan adalah baterai karena mudah dalam pemasangannya. Namun, kandungan baterai seperti timah dan bahan kimia menjadi sebuah kekurangan bagi lingkungan. Untuk mengatasi masalah tersebut, maka dipilih penyimpanan energi dengan media energi air (Water Storage) karena sifatnya yang ramah lingkungan serta memiliki kapasitas lebih besar dari baterai. Prinsip kerja dari sistem ini adalah dengan menyimpan daya berlebih yang dihasilkan PV dalam bentuk energi air dan menyalurkan menjadi daya listrik ke beban. Namun, daya listrik yang mengalir ke beban tersebut belum memiliki tegangan dengan sesuai regulasi beban. Pada penelitian ini akan dirancang sebuah kontrol aliran daya pada sistem water pumped storage sehingga sistem ini dapat memberikan daya yang memiliki tegangan sesuai regulasi beban. Berdasarkan hasil simulasi penelitian ini, dapat disimpulkan bahwa dengan adanya controller aliran daya, daya yang memiliki tegangan sesuai dengan regulasi beban yaitu 220 Volt/ 50 Hz dapat disalurkan secara konstan meskipun kebutuhan daya beban bervariasi. Mekanisme kontrol ini juga dapat menciptakan keseimbangan daya pada sistem.
... Pumped hydrostorage [18] Uses potential of water to store electrical energy Can provide extended duration support. ...
Inertia reduction due to high-level penetration of converter interfaced components may result in frequency stability issues. The paper analyses different frequency strategies for both solar photovoltaic (PV) and wind generators to support inertia, and also evaluates the contribution of synchronous condensers (SCs) to the system inertia of the power grid. Decommissioned power plants can potentially be retrofitted to SC mode in order to provide inertia support after they are retired. This paper investigates the various frequency control strategies available to the South Africa power grid in the face of increasing renewable energy integration, and makes a case for the modification of the many mothballed coal-fired power plants to SC mode.
... One of the greatest challenges for decarbonization is addressing the difficulty in maintaining power grid stability given the imbalance between fluctuating power demand and real-time electricity production by renewable sources 30 . Pumped hydro energy storage is a tested technology with great potential for worldwide development 31 . Potential river power plant sites with large reservoirs may in some cases be suitable for pumped storage plants. ...
The benefits of developing the world’s hydropower potential are intensely debated when considering the need to avoid or minimize environmental impacts. However, estimates of global unused profitable hydropower potential with strict environmental constraints have rarely been reported. In this study we performed a global assessment of the unused profitable hydropower potential by developing a unified framework that identifies a subset of hydropower station locations with reduced environmental impacts on the network of 2.89 million rivers worldwide. We found that the global unused profitable hydropower potential is 5.27 PWh yr−1, two-thirds of which is distributed across the Himalayas. Africa’s unused profitable hydropower is 0.60 PWh yr−1, four times larger than its developed hydropower. By contrast, Europe’s hydropower potential is extremely exploited. The estimates, derived from a consistent and transparent framework, are useful for formulating national hydropower development strategies. The development of hydropower offers a renewable energy source that can help reduce society’s dependence on fossil fuels. A global assessment of the unused profitable hydropower potential can be performed by incorporating strict constraints to identify hydropower station locations with reduced environmental and societal impacts.
... These hybrid Renewable-PHES systems are helpful in the seawater desalination units. These can ensure the continuous operation of the desalination plants by providing an energy storage facility [15]. A Hybrid Wind-PHES system is described in the next section. ...
The use of natural resources like coal, nuclear and other fossil fuels for electricity generation exhausts the natural reserves and puts adverse effects on the environment. For assuring an unlimited energy supply and environment friendly generation of electricity, the renewable energy sources are utilized. But these sources are irregular sources of energy generation due to inconsistent natural situations. These fluctuations in the output of renewable energy sources can be omitted by employing a promising and huge energy storage system. The pumped hydroelectric-energy storage systems (PHES) are widely used for large-scale energy storage. The use of such systems along the natural renewable energy sources (RES) can enhance the penetration of renewable energy into the conventional grid and helps stabilize their fluctuating output. Such systems are economically feasible and help save the environment by reducing the use of fossil fuels for energy generation. This paper presents a review of the studies conducted related to hybrid pumped storage systems. Further, a novel method for increasing the efficiency of a hybrid solar-wind-pumped hydroelectric energy storage system is proposed. It is concluded that the pumped hydroelectric energy storage systems help stabilize the output from the renewable energy sources as well as increase the penetration of renewable sources in the conventional power grids.
... The storage systems ensure the continuity of the energy supply to the different consumers even in case of a sudden variation of the renewable energy production systems. Among the existing types of energy storage systems, the most widely used is pumped hydro storage systems [6,7] since they have long life spans and a minimal cost of energy as compared to battery and thermal energy storage systems [8,9]. The total installed PHS capacity reached 127 GW and represented more than 99% of the total installed storage capacity worldwide [10]. ...
Access to inexpensive, clean energy is a key factor in a country’s ability to grow sustainably The production of electricity using fossil fuels contributes significantly to global warming and is becoming less and less profitable nowadays. This work therefore proposes to study the different possible scenarios for the replacement of light fuel oil (LFO) thermal power plants connected to the electrical network in northern Cameroon by renewable energy plants. Several scenarios such as the combination of solar photovoltaic (PV) with a pumped hydro storage system (PHSS), Wind and PHSS and PV-Wind-PHSS have been studied. The selected scenarios are evaluated based on two factors such as the system’s total cost (TC) and the loss of load probability (LOLP). To achieve the results, metaheuristics such the non-dominated sorting whale optimization algorithm (NSWOA) and non-dominated sorting genetic algorithm-II (NSGA-II) have been applied under MATLAB software. The optimal sizing of the components was done using hourly meteorological data and the hourly power generated by the thermal power plants connected to the electrical grid. Both algorithms provided satisfactory results. However, the total cost in the PV-PHSS, Wind-PHSS, and PV-Wind-PHSS scenarios with NSWOA is, respectively, 1%, 6%, and 0.2% lower than with NSGA-II. According to NSWOA results, the total cost for the PV-Wind-PHSS scenario at LOLP 0% is 4.6% and 17% less than the Wind-PHS and PV-PHSS scenarios, respectively. The profitability study of all three scenarios showed that the project is profitable regardless of the scenario considered.
... Renewability, long lifetime (around 40 years), availability and low cost of materials and low maintenance cost are the main advantages of PHS. On the other hand, high capital cost and difficulties related to finding appropriate location for the facilities are the main disadvantages of PHS system [2]. Among chemical storage devices, batteries are the most common one. ...
This research focuses on the design optimization of an off‐grid hybrid energy system including photovoltaic (PV) and diesel generator considering energy storage system (ESS). For this aim, the techno‐enviro‐economic feasibility assessment of PV/diesel, PV/diesel/battery, and PV/diesel/pumped hydro storage (PHS) hybrid energy systems is investigated in a multi‐objective framework. Levelized cost of energy (LCOE) and total pollutant emission (TPE) are defined as the problem objectives and the design problem is solved for determination of the components size. The impact of PV tracking is also investigated on the system sizing. Over the case study, simulation results reveal that the most cost‐effective hybrid energy system is PV/diesel/PHS with fixed panels in which LCOE and TPE are 0.198$/kWh and 208120 kg/year, respectively. Moreover, the most environmentally friendly hybrid energy system is PV/diesel/battery with double‐axis tracker in which LCOE and TPE are 0.2816$/kWh and 112760 kg/year, respectively.
... Pumped storage is currently the most mature technology and has the best economy and the most large-scale development conditions for the power system, which is green, low-carbon, clean, and flexible, and has a good coordination effect with wind power, solar power, nuclear power, and thermal power [12][13][14]. The pumped-storage power station is mainly composed of upper reservoirs, water-delivery systems, underground powerhouse systems, lower reservoirs, and other buildings, which can convert low-value energy into high-value energy. ...
With the rapid development of pumped storage, the vibration problems caused by the operation of power stations have become increasingly prominent. In this paper, a large-scale pumped-storage power station is taken as the research object, and a three-dimensional refined finite element model of the underground powerhouse including the surrounding rock mass is established. Based on the analysis of the vibration source of the powerhouse and the water diversion pipeline, the modal and dynamic response analysis of the underground powerhouse of the hydropower station is carried out, and the distribution law of the larger vibration displacement position is revealed. The calculation results show that under the premise that the vibration source is selected reasonably and the numerical model is accurate, the main frequency of the underground powerhouse structure can be obtained more accurately. After optimizing the design of the underground powerhouse based on the calculation results, the resonance problem of the underground powerhouse of the hydropower station can be avoided. The dynamic elastic modulus of the rock mass around the underground powerhouse has little influence on the mode shape of the powerhouse, but has a great influence on its fundamental frequency. When the dynamic elastic modulus of the rock mass increases by 50%, the fundamental frequency of the plant increases by about 29%. At the same time, the mode shape of each order of the underground powerhouse structure does not change much, mainly manifested as the vibration of the beam system structure, which is mainly caused by the stiffness of the beam system components being much smaller than the structural stiffness of the windshield, machine pier, and mass concrete around the volute. The research results can provide references for the design of underground powerhouses of large-scale pumped-storage power stations and the analysis of vibration problems.
... It is expected that the installed capacity of hydropower nationwide will reach 470 million kilowatts in 2025, and the per capita electricity consumption will be close to the level of moderately developed countries [43]. Moreover, hydropower has a relatively obvious advantage, which is that it can pump hydro energy storage, convert electricity waste, and improve the efficiency of electricity use [44]. Due to its cost advantages, solar energy has become the best tool in developing countries to maintain the energy needs of the poor [45]. ...
Renewable energy technological innovation (RETI) will be a significant way to stimulate the growth of renewable energy. This paper investigates the effect of RETI on green total factor productivity (GTFP) of 30 provinces in China from 2006 to 2019 applying the instrumental variable generalized method of moment (IV-GMM) method, as well as geographic heterogeneity and mediating effect analysis. The results indicate that RETI significantly improves GTFP in China; put differently, a 1% increase in the RETI index will cause a 0.049% growth in GTFP. Moreover, the RETI of various renewables plays a significant role in promoting GTFP, among which hydropower technological innovation, solar energy technological innovation, and geothermal and ocean energy technological innovation have more obvious promotion effects. In addition, RETI negatively affects GTFP in eastern China, and RETI positively affects GTFP in central and western China. Finally, we further reveal that energy structure and energy efficiency are the mechanisms that impact the relationship between RETI and GTFP.
... Figure 9a shows the storage capacity and power of each accumulation system. The capacity of the largest pumped hydroelectric energy storage system in the world (Fengning Pumped Storage Power Station, China) is currently up to 3.6 GW [42], with the storage capacity primarily being determined by the water reservoir volume. A thermochemical accumulation and hydrogen system capacity is primarily determined by the storage, gasholder, tank, subterranean cavity size, and its power is limited by the performance of the equipment. ...
The daily non-uniform power demand is a serious problem in power industry. In addition, recent decades show a trend for the transition to renewable power sources, but their power output depends upon weather and daily conditions. These factors determine the urgency of energy accumulation technology research and development. The presence of a wide variety of energy storage mechanisms leads to the need for their classification and comparison as well as a consideration of possible options for their application in modern power units. This paper presents a comparative analysis of energy storage methods for energy systems and complexes. Recommendations are made on the choice of storage technologies for the modern energy industry. The change in the cost of supplied energy at power plants by integrating various energy storage systems is estimated and the technologies for their implementation are considered. It is revealed that in the large-scale power production industry, the most productive accumulation methods for energy systems and complexes are the following: pumped hydroelectric energy storage systems, thermal and thermochemical accumulations, and hydrogen systems. These methods have the best technical and economic characteristics. The resulting recommendations allow for the assessment of the economic and energy effect achieved by integration of storage systems at the stage of designing new power units.
... In the context of the growing participation of intermittent renewable energies, PHES has re-emerged as an economically and technologically acceptable option to manage electricity production during peak hours and storing wind and solar energy, ensuring its quality and continuity [7]; Kougias et al. [8], mentioned that some of these PHES are under-utilized for energy control and management. Hendena et al. [9] evaluated the convenience of installing a PHES and compared it to expanding the transmission network in its capacity, proving it is more favorable to install a PHES when managing energy. ...
Pumped-storage hydroelectric plants are an alternative to adapting the energy generation regimen to that of the demand, especially considering that the generation of intermittent clean energy provided by solar and wind power will cause greater differences between these two regimes. In this research, an optimal operation policy is determined through a simulation tool that allows the annual benefits under the energy arbitration service (purchase–sale) to be estimated, considering the variations of the energy price in Mexico. A case study is proposed in the Zimapán hydroelectric facility, where reservoir operation at the hourly level is simulated with records for a period of 3 years, considering historical values. The results establish that this type of pumped storage power plant obtains greater benefits by generating electrical energy during 8 h of high demand and pumping for more than 11 continuous hours in times of low demand. With this configuration, the PHES consumes 82.33 GWh/year more energy than it produces, and the energy generated is 210.83 GWh/year; however, when considering the energy arbitration service, a net income of more than USD 3.25 million per year is identified, which represents a 123.52% increase for the annual energy purchase.
... Pumped hydroelectric energy storage (PHES) systems operate using two water reservoirs at different elevations (Figure 2.1). The system stores energy as gravitational potential energy in the water, consuming power to pump the water from the lower reservoir to the upper reservoir (Rehman et al. 2015;Sorensen 2007). To produce power, the water is transferred from the upper reservoir to the lower reservoir, where the energy is extracted by a hydraulic turbine as the fluid flows between the reservoirs, recovering 70-85% of the stored energy. ...
The current work was undertaken to perform a basic review of the different high capacity and long-term energy storage solutions, concepts, and initiatives currently being developed globally. The purpose is to identify and further develop concepts that make use of geological media for energy storage.
The work also maps the scientific opportunities and pending knowledge gaps related to the different concepts for sub-surface energy storage; those that could be potentially addressed by GNS Science in future research projects.
... Some energy storage processes have been investigated and proven to be highly efficient, such as batteries (Zakeri and Syri, 2015), pumped hydroelectric energy storage (PHES) (Rehman, Al-Hadhrami, and Alam, 2015), and compressed air energy storage (CAES) (Arabkoohsar et al., 2015). Liquid air energy storage (LAES) (Damak et al., 2020) is a promising energy storage technology that is limited by its low round-trip efficiency (RTE). ...
Energy storage technologies are required to ensure stability of energy systems when the share of renewable energy forms (wind and solar) is increasing. Liquid air energy storage (LAES) is a promising technology for storing electricity with certain advantages, such as high energy density and being geographically unconstrained. However, one drawback of a standalone LAES is the relatively low round-trip efficiency (RTE). In this work, the performance of a standalone LAES system with different number of compression and expansion stages is studied. All cases are optimized by using a particle swarm optimization (PSO) algorithm. The optimal results show that the highest RTE of 66.7% is obtained when there is a 2-stage compressor and a 3-stage expander in the LAES system. When the number of compression stages is fixed, the highest RTE is obtained when hot and cold streams have close to parallel temperature profiles in the preheaters of the expansion section.
Deprived electrochemical performance and declining cycle constancy of electrode materials restrict the capacity of energy storage systems like batteries and supercapacitors. To obtain significantly larger performance and stability, which are essential characteristics to assess the electrode material for energy conversion applications, nanostructured materials must be created. These materials must have enhanced specific surface area (SSA) and electrical conductivity. In the current work, samarium selenide (SmSe) supported on multiwalled carbon nanotubes (MWCNTs) nanohybrid is produced using a simple and inexpensive hydrothermal approach. The structure, chemical composition, and morphology of the sample were investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-rays diffraction analysis (XRD), respectively. The SmSe/MWCNTs nanohybrid shows excellent stability of 5000th cycles, with 2152 F/g of specific capacitance, and 160 Wh/Kg of specific energy at a current density of 1 A/g. The nanohybrid exhibits a greater double-layer capacitance (Cdl) value of 21.9 mF and small charge transfer hindrance (Rct) of 0.32 Ω than pure materials. Hence, the SmSe/MWCNTs nanohybrid material has outstanding electrochemical capabilities with significant technological implications in the future.
Solar energy is currently dispatched ahead of other renewable energy sources. For the first time, this study presents a concept of exploiting temporary–periodical runoff discharge in the Shire River. Pumped hydro storage–photovoltaic plant (PHS–PV) was optimized to satisfy the all-day peak electricity demand in Malawi. The effect of varying the net head on the PHS system in both the generation and pumping operation modes was investigated. The bi-objective optimization evaluated the system reliability for day-time and night-time operation together with implied costs of investment for the whole system. The optimized system generated above 53% of added power as contrasted to single-source power generation from the existing hydropower plants. The estimated optimal capacities were 182 MWp (solar PV) and 86 MW (PHS plant). These additional optimal capacities achieved a 99.8% maximum system reliability (Loss of Power Supply Probability—LPSP—of 0.2%) and Levelized Cost of Energy—LCOE—of 0.13 USD/kWh. The overall investment cost of the PHS–PV system was estimated at 671.23 USD for an LPSP of 0.20%. The net head varies from 15.5 to 17.8 m with an impact on electricity generation of the PHS–PV system. More notably, the PHS–PV production matches with daily day-time and night-time peak loads and functions as a peaking plant.
We report on the fabrication of a tungsten disulphide (WS2) nanosheet (NS)-based single-electrode triboelectric nanogenerator (STENG) for possible application in nanoscale power generators and motion sensors. STENG devices in flexible and wearable modes were fabricated with chemically exfoliated WS2 NS-coated cellulose paper and silk textile as active layers. The triboelectric characteristics of the devices comprising a different counter triboelectric layer such as metallic aluminium (Al), polytetrafluoroethylene (PTFE), etc., confirm that WS2 has strong affinity towards donating electrons to the counter layer. The STENG device with the WS2-PTFE pair is found to exhibit the highest open-circuit voltage (Voc) of ~ 11.02 V amongst all devices. The device delivers maximum output power of ~ 1.7 μW and can accumulate ~ 2 nC of charge in a storing capacitor within 3 s of impact. The adequate response of the STENG to small impacts with an estimated sensitivity of 0.2VN−1 (0.15 V kPa−1) indicates the possible application of the device as force sensors. Apart from that, upon attaching the flexible and wearable STENG on different parts of the human body, the device exhibits the scope for motion sensing application. The biomechanical actions like finger, neck and hand movement at different angles can generate different output signals in terms of voltage values and signal shape. The present study demonstrates the possible scope of WS2-based TENG for tactile, motion sensing applications and may pave the path for futuristic self-powered sensors.Graphical Abstract
Energy storage solutions for grid applications are becoming more common among grid owners, system operators and end-users. Storage systems are enablers of several possibilities and may provide efficient solutions to e.g., energy balancing, ancillary services as well as deferral of infrastructure investments. To ensure that an energy storage investment is guaranteed a reasonable payback period and a good return of investment it is advantageous to consider the possibility of service stacking. By offering additional services in turns or in parallel with the main service it is possible to create important revenue streams. The aim of this review is to provide an up-to-date status of service stacking using grid connected energy storage systems by presenting current research and on-the-table ideas. Results from the review show that frequency regulation services are the most common services to offer together with energy arbitrage and integration of renewable energy sources. The results also show that it is strategically favorable to offer additional services for storage units which are used seasonally or with low frequency. It can be concluded that service stacking is a promising method to implement for storage operators to increase the degree of utilization of storage units. It may also be concluded that the increased need for ancillary services increases the opportunity for storage units to participate in markets for energy and ancillary services. Future studies could focus on the correlation between service stacking possibilities and actual placement of the storage, and how hybrid storage configurations would affect the potential of service stacking.
With the expansion of renewables in the electricity markets, research on electricity storage economics is needed for a better understanding of the utilization of these systems and for improving the performance of intermittent variable generation. Collected up-to-date research of electricity storage systems published in a wide range of articles with high impact factors gives a comprehensive review of the current studies regarding all relevant parameters for storage utilization in the electricity markets. Valuable research of technical characteristics from the literature is broadened with the electricity storage analyses from an economic point-of-view. Analysis of selected technologies, considering different perspectives such as their profitability, technical maturity, and environmental aspect, is a valuable addition to the previous research on electricity storage systems. Comparing conducted analysis with the selected literature, electricity storage technologies are analyzed concerning their viability in the electricity markets. Given the current outlook of the electricity market, the main problems for storage's wider integration are still energy storage costs. These can be overcome with different applications of energy storage systems, integration of new market players, or a combination of storage technologies along with the implementation of new energy policies for storage.
The study explores the techno-economic feasibility and viability of a Photovoltaic-Diesel Hybrid system for rural electrification in sub-Sahara Africa with a case study of Chilubi island, a remote district without access to electricity in the Northern Province of Zambia. Using HOMER (Hybrid Optimization of Multiple Electric Renewables) Pro software, the best and most feasible technical solutions through different hybrid system configurations, combinations and the district's rate of access to electricity were considered based on the least Levelized Cost of Energy (LCoE) and life cycle costs of the project. The results show that operating diesel generators as stand-alone is not economically sustainable and has a high LCoE. Influencing factors include variability in diesel pump prices, high fuel transportation costs, high cost of operation and maintenance, among other factors of concern. 100% photovoltaic (PV) with a battery system gave the lowest LCoE. However, the initial capital cost of solar energy projects in Zambia is relatively high compared to the equivalent diesel-based plants, as shown herein. It explains why diesel power plants are favoured for off-grid settlements. On the hand, the low operational cost and LCoE of PV power plants favour rural districts as they offset the high initial capital costs. Additionally, the continued downward trend in the cost of PV installations per kWp has opened discussions among policymakers and energy planners in Zambia to favour rural electrification with renewable energy-based power generation. This study contributes to this discussion.
Hydraulic vibration is a common phenomenon in pumped storage power stations (PSPS) and hydropower plants. Evaluating the performance of the PSPS and water conveyance system under the hydraulic vibration condition is significant for the safety of the electric power and the PSPS system. In this study, the one‐dimensional (1D) and three‐dimensional (3D) coupling model for the entire PSPS system is established based on the open‐source software OpenFOAM and in‐house C++ codes. The coupling data exchange is realized by writing and reading files. The coupling model is validated by comparing the results with the pure 1D method under small load disturbance conditions. The forced vibration source is modeled by the pipe walls vibration method in the 3D region, and the 1D method takes charge of other parts in the PSPS system. The combination of the pipe walls vibration and 1D–3D coupling could fully consider the incident and reflected characteristics of the pressure waves. The established model could evaluate the overall performance of the PSPS system under forced vibration. Sensitive analysis of the vibration magnitude is carried out, and the results are consistent with the theoretical analysis, demonstrating that the established model is applicable for the forced vibration analysis. This study proposed a novel forced vibration model based on pipe vibration and 1D–3D coupling methods. The established model could evaluate the overall performance of the pumped storage power station system under forced vibration
The Chinese government has been encouraging to accelerate the development of energy storage systems to support the rapid growth of renewable energy power generation. For the purpose of achieving flexible and economic energy storage, in this study, a combined transcritical CO2 power cycle is added to biomethane plants to form a liquefied-biomethane energy storage system. A mathematical model that includes terms of energy, exergy, and economy is established to assess the performance of the combined transcritical CO2 power cycle. The effects of critical parameters on the thermo-economic performance are studied. A sensitivity analysis is used to evaluate the extent of the influence of critical parameters. According to the simulation results, the characteristics of the liquefied-biomethane energy storage system are calculated and evaluated. The results show that at a liquefied-biomethane mass flow rate of 1 kg/s, the maximum net power output of the combined transcritical CO2 power cycle reaches 909.81 kW by adjusting the pressure and temperature. High turbine inlet temperature, pump pressure ratio, and methane purity have positive effects on system performance. Among these, the inlet temperature of turbine 2 is the most sensitive factor. Simultaneously, the maximum energy storage density and round-trip efficiency of the liquefied-biomethane energy storage system are 106.8 Wh/L and 52.7 %, respectively. Benefiting from less upfront equipment investment, the lowest power capital cost of the liquefied-biomethane energy storage system is 885.3 $/kW. In conclusion, the liquefied-biomethane energy storage system integrated with a combined transcritical CO2 power cycle exhibits good performance in terms of power output and economy.
The use of energy storage devices is essential for the development and maintenance of zero-energy structures. They are necessary for optimal usage of renewable energy sources and for managing the intermittent nature of energy supply and demand. Many different types of storage systems (electrochemical, thermal, mechanical, etc.) are either commercially available or close to being developed for usage on a building scale. Different technologies have different capabilities and features, therefore it's important to find a system for evaluating your possibilities before diving into a techno-economic study. All aspects of current and emerging energy storage technologies, as well as their uses, future prospects, and historical contexts, are subjected to a rigorous evaluation. Energy storage techniques such as electrochemical and battery storage, thermal storage, thermochemical storage, flywheel storage, compressed air storage, pumped storage, magnetic storage, chemical and hydrogen storage, and redox flow storage are all covered. New studies on alternative energy storage methods, along with major advancements and discoveries in the field, are also discussed.
With the development of the social economy and the demand for environmental protection, people's requirements for clean and renewable energy are gradually increasing. Generally, renewable energy, such as wind power and photovoltaic energy, has natural intermittency to varying degrees. Consequently, renewable energy sources, due to their fluctuating nature, cannot provide a continuous supply of power and hence require bulk electricity storage. Additionally, energy storage is important to electrical systems, allowing load levelling, peak shaving, frequency regulation, damping energy oscillations, and improving power quality and reliability. Pumped storage power stations are notable for their ability to efficiently store energy on a large scale. The construction of a reservoir inevitably changes the water temperature situation of the original river channel. The expansion of pumping and storage units on a pre-existing reservoir, namely, a mixed pumped storage power station, is different from a conventional power station in terms of the thermal structure of the reservoir area. This study focuses on the Jinshuitan hydropower station and uses the MIKE3 model to analyse the influence of different outlet elevations and pumping flows on the water temperature structure of the reservoir area. The water pumping had no impact on the surface water body but did have a significant impact on the middle and bottom water bodies. The vertical water temperature stratification intensity weakened under different pumping scenarios, and the temperatures of the middle and bottom water bodies increased. The influence of the outlet elevation on the water temperature structure in the reservoir area was much greater than that of the pumping flow. The lower the elevation of the water outlet was, the greater the impact. For the Jinshuitan hydropower station, when the elevation of the water outlet was 130 m, the water temperature of the bottom column rose significantly, the stratification intensity of the water column weakened significantly, and the reservoir reached a vertically isothermal state in December. In summary, water pumping dramatically changed the original water temperature structure in the reservoir. The final research results can provide an effective reference for follow-up studies on relevant ecological and environmental issues associated with the development of pumped storage power stations and for setting the outlet elevation and pumping flow.
Access to clean, cost-effective, and available energy is essential for the sustainable development of a country. Nowadays, the production of energy from fossil fuels has environmental and economic disadvantages. In this context, this work proposes to study the technical and economic aspects of the replacement of a 20 MW Light Fuel Oil (LFO) thermal power plant by a hybrid Photovoltaic Pumped Hydro Storage System (PV-PHSS) power plant in northern Cameroon. The objective is to minimize the total life cycle cost (TLCC) of the proposed hybrid system with a loss of power supply probability (LPSP) below a defined limit. To obtain optimal results, several meta-heuristics such as Artificial Bee Colony (ABC), Water Cycle Algorithm (WCA), Grey Wolf Optimizer (GWO), and African Vulture Optimization Algorithm (AVOA) have been used. Moreover, the optimal sizing of the hybrid system components was performed under MATLAB software using real-time information and meteorological data from the selected site. All the algorithms achieved good results. However, the WCA algorithm delivered a slightly better result than the other algorithms.
Generation of energy has to increase due to society's demand escalation. However, generation from conventional sources is one of the major reasons for greenhouse gas emission, which is a key reason for global warming and climate change issues. To mitigate the emission of greenhouse gas and to protect the environment from pollution, renewable energy sources (RESs) are the one and only effective solution till date. To reduce the fluctuation of RESs on energy generation, a RES-based hybrid system is an innocuous solution. Here, a brief discussion of hybrid systems and their opportunities are presented and reviewed the role of the different combinations of renewable energy-based hybrid systems to reduce environmental pollution, generation costs, improve efficiency, and achieve a continuous power output of the system. A discussion is made on the importance of the site selection and the importance of different kinds of storage systems for energy generation. Result of article gives a brief idea regarding different factors to design future hybrid energy system (HES).
Pump-turbines (RTP) are the most common mechanical equipment adopted in pumped-hydro power plants and, for grid balancing purposes, are required to sharply switch from pumping to generating mode, and to extend their operative, jeopardizing not only the machine operability but also its life. New design approaches to avoid the onset of unstable behaviours are still far from being defined, and control strategies for accelerating start-up/shut-down procedures are still not effective since these are based on semi-empirical approaches, due to the lack of identification of precursors of the unstable behavior.
In this paper, a numerical analysis of the unstable behavior of an RPT during the transition from partial load up to the turbine-brake area was carried out. The fluid-dynamics in different operating points (partial load, run-away condition, turbine brake) was deeply investigated, identifying the rotor-stator mechanisms causing the 3D evolution of the flow field leading to the development of the unstable behavior. Three evolution phases (inception, growth and consolidation) were identified and clearly correlated with the runner geometry and with the S-Shape of the RPT characteristic curve. Customized signal processing strategies were adopted for spectrally characterizing each phase so as to identify potential triggers for new monitoring and control strategies. Moreover, for the first time, a clear fluid-dynamic explanation of the empirical results found in literature on the influence of the runner geometry is provided.
Studying the property of the combination of renewable energy sources in the existing power systems is of great importance, and especially in the case of deregulated systems. The uncertainty of renewable sources is the largest barrier to integrating renewable-energy-producing units into the existing electrical infrastructure. Due to its uncertainty, integrating wind power into an existing power system requires extra consideration. In this work, the impacts of wind farm (WF) integration and a pumped hydroelectric storage system (PHES) on the electric losses, voltage profiles, generation costs, and system economy in a deregulated power market were studied. A comparative study was performed to determine the impact of wind farm integration on regulated and deregulated environments. Four locations in India were chosen at random for this work, and we used the real-time statistics for the actual wind speeds (AWSs) and forecasted wind speeds (FWSs) for each chosen location. To determine the system economy, surplus charge rates and deficit charge rates were developed to evaluate the imbalance cost resulting from the mismatch between the predicted and actual wind speeds. Considering the effect of the imbalance cost, the system profit/day varies by an average of 1.6% for the locations studied. Because of the reorganization of the power system, consumers constantly look for reliable and affordable power that is also efficient. As a result, the system security limit may be breached, or the system may run in a dangerous state. Lastly, in this paper, an economic risk analysis is presented with the help of heuristic algorithms (i.e., artificial bee colony algorithm (ABC) and moth–flame optimization algorithm (MFO)), along with sequential quadratic programming (SQP), and the way in which the PHES is used to compensate for the deviation in the WF integration in the real-time electricity market is also presented. The value at risk (VaR) and conditional value at risk (CVaR) were used as the economic risk analysis tools. According to the work, with the increase in the wind generation, the system risk improves. The results show that, as the wind generation increases by three times, there is an improvement in the risk coefficient values by 1%. A modified IEEE 14-bus test system was used for the validation of the entire work.
In light of the energy transition and the need to reduce emissions, efficient and capable energy storage devices are needed. Different concepts will have their individual pros and cons, an energy storage device placed subsea would provide high energy densities, long lifetime, and high efficiencies given that the unit could be designed so that it takes advantage of the cooling effects of the ocean.
To fully evaluate a conceptual subsea energy storage device based on PHS (Pumped Hydro Storage), the theoretical efficiency limits were derived. Although several different subsea PHS concepts have been presented in various papers, a study outlining the basic thermodynamic limits has not been widely published, the intention of this paper is to fill this gap. Different standard thermodynamic cycles such as the Otto and Joule cycles have been analyzed. The best possible efficiency for an adiabatic process is achieved by compressing/expanding the gas in a combined Otto-Joule cycle which for a compression ratio of 50 would give a maximum possible efficiency of 93.2%. If enough time for heat transfer is given during the compression/expansion process an isothermal process would be achievable which would result in an isothermal process with a theoretical efficiency of 100%. It is interesting to note the difference between CAES (Compressed Air Energy Storage) and the subsea-PHS where in the former case the energy that is utilized is the expansion energy of the gas and for the PHS system the energy of the water flowing into the tank is the energy that is converted into electrical power where the compression energy of the gas reduces the available energy.
The main criteria for the ideal cycle are low compression energy and high expansion energy. In addition, the heat generated in the compression process is not utilized so a very slow compression process where there are no finite heat transfers and thus very small entropy generation is desired. If a slow process is not possible, the entropy generation could be lowered by splitting the compression process into smaller steps. A case where an adiabatic compression process is split into several steps was investigated and it was found that splitting an adiabatic compression process into two steps with enough time for heat transfer in between would lower the amount of compression energy needed by 15% for an adiabatic case with a compression ratio of 100.
The theoretical study provided in this paper will form the basis for detailed parameter studies and subsequent publications.
Electricity demand has grown in the Kingdom of Saudi Arabia at a very fast pace and there are large differences between the summer and winter peak loads as well as between morning and evening peak loads. Thus, the predicament facing the Saudi Arabia power sector is how to reduce the requirement and investment for new thermal peak plants in order to meet the rapidly increasing short-term peak demands. To ensure a reliable power supply, the system needs expensive peaking units to operate just for a few hours during the whole year. To reduce the peak thermal generation, the possibility of building pumped storage hydroelectric power plants is being considered. During the off peak generating hours, when surplus generation is available, the pumped storage plant will pump water to an upper reservoir, and then use this stored water for hydro generation during peak load hours.
Wind power, a green energy, has become another primary renewable resource of great value in economic utility and industrialization development, like hydraulic power at the time when comes with the pressure from energy crisis and environmental protection. This paper considers a wind-powered pumped storage system based on an 8 MW wind farm. The effect of pumped storage power station to wind power regulation is calculated, and an economic evaluation model was developed. This paper shows that a significant smoothing of the produced power is realized, dispatchable output power can be offered to the system, whereas extra economic benefit can also be achieved.
Renewable energy sources, such as wind and solar, have vast potential to reduce dependence on fossil fuels and greenhouse gas emissions in the electric sector. Climate change concerns, state initiatives including renewable portfolio standards, and consumer efforts are resulting in increased deployments of both technologies. Both solar photovoltaics (PV) and wind energy have variable and uncertain (sometimes referred to as intermittent) output, which are unlike the dispatchable sources used for the majority of electricity generation in the United States. The variability of these sources has led to concerns regarding the reliability of an electric grid that derives a large fraction of its energy from these sources as well as the cost of reliably integrating large amounts of variable generation into the electric grid. In this report, we explore the role of energy storage in the electricity grid, focusing on the effects of large-scale deployment of variable renewable sources (primarily wind and solar energy).
The transient performance of a small-scale plant consisting of a photovoltaic (PV) and a pumped hydro storage (PHS) system has been evaluated. An indirect field oriented control (IFOC) based state-vector pulse width modulation (SVPWM) drive connects the plant to the distribution system. The drive system includes two six-pulse IGBT converters interconnected through a DC link, to which the PV plant is interfaced via a single-stage bidirectional boost converter. The electrical system of the PHS plant consists of a squirrel-cage induction machine supplied by the machine side converter. The hydraulic system of the PHS plant includes separate turbine and pump units where a scaled linearized model is adopted to represent the elastic water column and surge tank. In the present study, the PV generated power has a control scheme designed to regulate the performance of the overall system. Simulation results are provided that show the transient performance of the plant during pumping and generating cycles of the PHS system.
High penetration of wind power has impacts that have to be managed through proper plant interconnection, integration, transmission
planning, and system and market operations. This report is a summary of case studies addressing concerns about the impact of wind
powers variability and uncertainty on power system reliability and costs. The case studies summarized in this report are not easy to
compare due to different methodology and data used, as well as different assumptions on the interconnection capacity available.
Integration costs of wind power need to be compared to something, like the production costs or market value of wind power, or
integration cost of other production forms. There is also benefit when adding wind power to power systems: it reduces the total
operating costs and emissions as wind replaces fossil fuels.
Several issues that impact on the amount of wind power that can be integrated have been identified. Large balancing areas and
aggregation benefits of large areas help in reducing the variability and forecast errors of wind power as well as help in pooling more
cost effective balancing resources. System operation and working electricity markets at less than day-ahead time scales help reduce
forecast errors of wind power. Transmission is the key to aggregation benefits, electricity markets and larger balancing areas.
From the investigated studies it follows that at wind penetrations of up to 20% of gross demand (energy), system operating cost
increases arising from wind variability and uncertainty amounted to about 14 /MWh. This is 10% or less of the wholesale value of
the wind energy.
With current technology, wind power plants can be designed to meet industry expectations such as riding through voltage dips, supplying
reactive power to the system, controlling terminal voltage, and participating in system operation with output and ramp rate control. The
cost of grid reinforcements due to wind power is very dependent on where the wind power plants are located relative to load and grid
infrastructure. The grid reinforcement costs from studies in this report vary from 50 /kW to 160 /kW. The costs are not continuous;
there can be single very high cost reinforcements, and there can also be differences in how the costs are allocated to wind power.
Wind generation will also provide some additional load carrying capability to meet forecasted increases in system demand. This
contribution can be up to 40% of installed capacity if wind power production at times of high load is high, and down to 5% in higher
penetrations and if local wind characteristics correlate negatively with the system load profile. Aggregating larger areas benefits the
capacity credit of wind power.
State-of-the-art best practices so far include (i) capturing the smoothed out variability of wind power production time series for the
geographic diversity assumed and utilising wind forecasting best practice for the uncertainty of wind power production
(ii) examining wind variation in combination with load variations, coupled with actual historic utility load and load forecasts
(iii) capturing system characteristics and response through operational simulations and modelling and (iv) examining actual costs
independent of tariff design structure.
This paper presents a power production system for the isolated insular power system of the islands Karpathos and Kasos. Karpathos and Kasos are two small islands, located in the South-East Aegean Sea (Dodecanese complex) that are not connected to the main power distribution network. Energy production is based exclusively on an autonomous thermal power plant and a small wind park, installed on the island of Karpathos. The maximum annual power demand has been estimated to exceed 12 MW by 2014. The mean specific annual energy production cost from the existing system has been calculated at 0.249 €/kW h in 2008.
Electricity generation from renewable energy sources (RES) in Greece is regulated by the energy law 2244/94 which provides incentives to attract private investments in the RES sector. The wind energy sector is highly attractive due to the verified large wind potential in many regions of the country. This paper presents the current situation concerning wind energy exploitation, analyses the technical problems following the penetration of wind power into electricity grids, and the consequent technical solutions proposed by the Public Power Corporation (PPC). It also describes the perspectives for high wind power penetration into Greek power system.
Pumped hydroelectric energy storage (PHES) is the largest and most mature form of energy storage currently available. However, the capital costs required for PHES are extremely large and the availability of suitable sites is decreasing. Therefore, identifying the remaining sites available for PHES is becoming vital so that the most beneficial location is chosen: in terms of capacity and economics. As a result, the aim of this work is to develop a computer program that will scan a terrain and identify if there are any feasible PHES sites on it. In this paper, a brief description of the program is provided, including the limitations identified during the initial development. Also, the program was used to evaluate a 20km × 40km area in the South West of Ireland so the results obtained from this study are discussed. Finally, future improvements to advance the program's capabilities are identified. The program has proven to date that it can identify feasible locations for PHES, however, further investigation is necessary to improve the site selection.
Pumped hydroelectric storage (PHES) is the most established technology for utility-scale electricity storage and has been commercially deployed since the 1890s. Since the 2000s, there has been revived interest in developing PHES facilities worldwide. Because most low-carbon electricity resources (e.g., wind, solar, and nuclear) cannot flexibly adjust their output to match fluctuating power demands, there is an increasing need for bulk electricity storage due to the increasing adoption of renewable energy. PHES has been the traditional way of storing energy. This chapter introduces PHES technology, its pros and cons, its historical developments, and its prospects.
This chapter details how pumped storage hydroelectric projects differ from conventional hydroelectric projects. The concept of electrical energy storage has become a controversial issue in recent years. Many questions are raised in the electricity sector: Why is energy storage needed? What are the alternatives? One of the answers is pumped storage hydropower plants, using mainly pump-turbines. In this chapter, details of some remarkable examples of pumped storage power plants are given: Okinawa Seawater in Japan, Goldisthal in Germany, Tianhuangping in China, and Coo-Trois Ponts in Belgium.
Hydropower is not only a renewable and sustainable energy source, but its flexibility and storage capacity also makes it possible to improve grid stability and to support the deployment of other intermittent renewable energy sources such as wind and solar power. As a result, a renewed interest in pumped-hydro energy storage plants (PHES) and a huge demand for the rehabilitation of old small hydropower plants are emerging globally. As regards PHES, advances in turbine design are required to increase plant performance and flexibility and new strategies for optimizing storage capacity and for maximizing plant profitability in the deregulated energy market have to be developed. During the upgrading of old small hydropower plants, the main challenges to be faced are the design of new runners, that had to match the existing stationary parts, and the development of optimal sizing and management strategies to increase their economic appeal. This paper traces an overview of the prospects of pumped-hydro energy storage plants and small hydro power plants in the light of sustainable development. Advances and future challenges in both turbine design and plant planning and management are proposed. PHES and hybrid wind/solar-PHES are illustrated and discussed, as well as the limits and peculiarities of the new design strategies, based on computational fluid dynamics, for both PHES and small hydropower plants.
With the rapid development of the Chinese economy and society, differences in the electric power system load between the peak and valley values are increasing, and inefficient small capacity coal-fired plant units must be involved in load adjustment because gas units and pumped storage units that act as peak-load units are lacking. In addition, due to concerns about energy saving and emissions reduction, clean energy sources are rapidly being developed and deployed. This presents a significant challenge for the construction and planning of peaking power solutions in China. Pumped storage plants provide a means of reducing the peak-to-valley difference and increasing the deployment of wind power, solar photovoltaic energy and other clean energy generation into the grid. Pumped storage plants represent the most mature approach among the peaking power sources and thus are one of China's major investments for the future. This paper presents China's current development of pumped storage plants, their role in the electric power system, the management models for pumped storage plants and the electricity price patterns utilising them. Here, we also analyse China's future plans for pumped storage plants, including the influencing factors and related policies.
This paper presents the characteristics of a power plant that combines renewable energy sources (RES), that is, a photovoltaic (PV) power plant and pump storage hydroelectric (PSH), to achieve sustainable production of green electric energy equal to that of conventional energy sources. The proposed solution does not produce CO 2 and does not significantly use freshwater or other resources. The PSH storage is the main element of the proposed power plant system, which provides a continuous and reliable supply of green energy. Its size significantly affects the size of the PV generator and operation characteristics of the hybrid plant. The paper elaborates in detail the functional relationship between the choice of the PV generator power and the PSH upper storage volume and presents the basic mathematical relations. The algorithm of the system development is presented, along with the procedure choice solutions. The results from the case study show that the concept is flexible in design, construction, and operation.
The Renewable Energy Law has been formulated by China government in 2005. During the next few years, there has been dramatic progress in China's renewable energy industries, along with the formation of the policy system of renewable energy in China. It is widely recognized that a reasonable and effective policy system can lay the solid foundation for the development of renewable energy. Regarding the rapid growth of renewable energy With a host of relevant policies issued in China, there is an urgent need to study the policy system of renewable energy in view of the latest situations to further promote the development of renewable energy. This paper is a systematical review about the promotion of China's policy system of renewable energy since Renewable Energy Law issued. Achievements on the policy system of renewable energy in 2011 as of 2005 are discussed. Experiences from recent periods are drawn and factors limiting the policy system of renewable energy are also addressed in details to probe the policy predicament and solutions. The development tendency of renewable energy is presented and the framework is drafted to set the framing constraints for China's policy system of renewable energy. Finally, policy suggestions are proposed for the successful implementation of renewable energy policies within the framing constraints of the policy system and the long-term healthy development of renewable energy in China.
With the integration of increased variable renewable energy generation and advent of liberalized electricity market, much attention has been devoted on the development of pumped hydro energy storage (PHES) as it has many prominent advantages of ensuring the safe and steady operation of power grid. In China, PHES has met a booming periods for the last ten years. Currently, there are 24 PHES stations with an installed capacity of 16.95 GW while government's target of 2020 is 50.02 GW. In this paper we provide an overall review of China's PHES development with a detailed presentation of the installed capacity and distribution of existing and proposed PHES stations, examine 4 typical stations in order to give a good description for the practical functions of PHES in power grid, analyze the management mode and price mechanism of PHES operation and point out the barriers in PHES development in China. State Grid Corporation of China (SGCC), which are making great efforts on China's PHES development, is discussed as a role model. On that basis we suggest PHES in the fast developing period should be temporarily operated and scheduled by grid companies in terms of exertion of its positive effects, while government should also take responsibility to subsidize on the stations' operation to relieve the price pressure of the ever-growing integration of renewable energy.
Pumped storage is generally viewed as the most promising technology to increase renewable energy source (RES) penetration levels in power systems and particularly in small autonomous island grids, where technical limitations are imposed by the conventional generating units. In this chapter, an operating policy is proposed for hybrid wind-hydro power stations (HPS) in island grids, in order to increase wind penetration levels, while at the same time minimizing the impact on the conventional generation system and ensuring the viability of the HPS invest-ment. The proposed operating strategy is applied to different autonomous island systems using a dedicated logistic model, in order to evaluate the effect on the overall operation and economics of the island systems and to assess the feasibility of HPS investments. In addition, the real study case of the HPS in Ikaria island, Greece, which is currently in the construction stage and will be one of the first wind-hydro-pumped-storage hybrid stations in the world, is examined and the ex-pected benefits from its operation according to the proposed policy are presented. The material presented in this chapter is based on publications [36] and [38] avail-able in IET-Renewable Power Generation and IEEE Transaction on Sustainable Energy.
This paper deals with the operation of a hybrid wind/hydro power system aiming at producing low cost electricity. A specific application on the island of Ikaria in Greece is analysed and typical results are presented and compared to the results produced from a simulation program. The simulation program, which is based on the stochastic behaviour of the weather conditions, uses as input data the monthly wind-speed distribution and, to a smaller extent, which is determined from the use of an appropriate weighting factor, the rate of rain water which is stored in the hydro reservoir. Useful conclusions were drawn regarding the feasibility of these applications in Greek islands and the expected electric energy saving.
Lack of electricity and water, the two fundamental resources in modern societies, is still a major issue in many developing countries and remote areas. This paper proposes a standalone renewable power system to solve the energy and water shortage in remote areas with abundant solar energy. The system utilizes a photovoltaic (PV) panel as the main energy source, which is controlled by a maximum power point tracking (MPPT) technique. A battery pack is used as the main energy storage device to smooth the fluctuation of solar power and to mitigate load transients and variations. In addition, a hydro storage system is used for water storage and supply, and also for supplying extra electric power via a hydro-turbine generator. The electricity and water demand of three households are considered for the system. The system modeling, unit sizing, control, simulation studies and the actual hardware implementation are presented and discussed in the paper.
Due to technological advancement, availability of multi-megawatt wind turbines, ease of installation and maintenance, economic compatibility and commercial acceptance, wind power is being used globally for both grid-connected and off-grid applications. The wind power is intermittently available due to the fluctuating nature of the wind and hence needs to be understood well. Its variability was studied in this paper both in time and spatial domain. The present work utilized daily mean values of wind speed from different meteorological stations spread over the Kingdom of Saudi Arabia in conjunction with wavelet transform and fast Fourier transform power spectrum techniques to understand the dynamic nature of the wind at nine stations. The study found that wind speed changed by ± 0.6 to ± 1.6 knots over a long period of about 10 years depending on the locations. The long-term mean wind speed of 5.6, 8.9, 6.25, 8.1, 6.0, 7.1, 6.0, 8.6 and 7.3 knots was obtained at Abha, Dhahran, Gizan, Guriat, Hail, Jeddah, Riyadh, Turaif and Yanbu, respectively.
The growing economy with corresponding increase in power demand causes more challenges in power sector of developing countries. In India, the increase in peak power demand necessitates energy storage schemes over and above the storage-hydro-, oil- and gas-based peak power plants to ensure power system stability. In utility energy storage schemes, the Pumped storage schemes attract more attention even in the developed countries due to its unique operational flexibility over other energy storage systems. In India, the availability of suitable topographies, hydro-thermal ratio imbalance in various regions, and optimal storage capacity for flexible power system operation gives a thought for the planers and executors to implement these schemes to meet peak demands. This paper presents a critical review of the necessity of pumped storage schemes in India. This review reveals that the major constraint for pumped storage operation in India is the deficit of off-peak power available in all the regional grids except north-east region for pumping at present. But the current adversity is likely to be gradually solved by the commissioning of newly proposed power projects. Fixing of a separate operational tariff for pumped storage schemes throughout the country is another requirement for which the government has set up a one man committee to analyze the feasibility for this peak tariff. Non-availability of lower tail pools and irrigation needs also causes poor pumping operations in some cases. However, most of the states in India are evincing interest in pumped storage schemes and proposals are being submitted to central government for securing stations clearance.
Pumped storage is generally viewed as the most promising technology to increase renewable energy source (RES) penetration levels in power systems and particularly in small autonomous island grids. Combined wind and pumped-storage “virtual power plants”, called hybrid power stations (HPS), constitute a realistic and feasible option to achieve high penetrations, provided that their components are properly sized. In this paper, the optimum sizing is investigated for a pumped storage HPS operating in an island system. The analysis addresses the sizing of the main HPS components (hydro turbines, pumps, wind farm, reservoirs), adopting either the investor’s perspective, where the objective is to maximize the return on the HPS investment, or a system perspective, where the optimization target is the maximization of RES penetration, along with maintaining the lowest possible generation cost in the system. Genetic Algorithms (GAs) are applied for the optimization and a real isolated island power system is used as a study case. The adopted operating policy and pricing principles, which critically affect the optimal sizing of an HPS project, are based on the existing regulatory framework for storage stations in Greek islands.
This paper studies pumped storage plants (PSPs) operating all over the EU, in which the key statistical indicators can be found in the European Hydropower database (HYDI), administered and managed by the European Small Hydropower Association (ESHA). The main emphasis is on mixed-type PSPs, which generate electricity from natural inflow; however, pure PSP plants are included in this study. Different analysed, independent PSP data sources (e.g., Eurostat, Eurelectric) show a great variation in the main statistical values (installed capacity and power generation) of the EU pumped storage plant fleet. Presented and analysed PSP layouts and a clear methodology for determining renewable electricity generation from mixed pumped storage plants will avoid ambiguities that actually pertain to power databases to clearly separate renewable and non-renewable electricity generation. Most of the National Renewable Energy Action Plans (NREAP) submitted to the European Commission do not correctly account for renewable electricity generation due to natural inflow into upper basins of PSPs. Moreover, renewable and non-renewable electricity generation types are mixed up. The operating mixed PSP installed capacity and electricity generation were determined in the EU countries, which is a type of renewable source, and their projected estimates in 2020 are provided.
Renewable electricity expansion highlights the need for a review of energy storage options. Wind power growth, in particular, is likely to require the support of dedicated fast-start reserve capacity. Moreover, in New Zealand, non-pumped hydroelectricity-based storage has only limited potential to meet seasonal variations of hydro inflows. This constraint has contributed to several ‘dry-year’ events over the last decade. This case study surveys New Zealand electricity sector experts as to the feasibility of meeting reserve capacity needs while reducing carbon emissions through the introduction of pumped hydro and utility-scale batteries by 2025. Most respondents project peak power demand to continue to increase, resulting in new-build centralised (∼150 MW) thermal reserve power sources. Pumped hydro is seen by most as prohibitively costly, but is almost universally viewed as technically capable of providing renewables support and peak power adequacy. Utility-scale batteries are seen as least cost-effective, with very high storage costs per kWh and most likely only to be used in NZ for very high-value applications where there is a strong technical advantage, such as the six-second instantaneous reserve. A price of carbon of around NZ$100/tCO2-e, however, was seen as making these technologies much more competitive, and climate change mitigation was seen as a strong driver of these storage options.
Integrating large amounts of wind power in energy systems poses balancing challenges due to the variable and only partly predictable nature of wind. The challenges cover different time scales from intra-hour, intra-day/day-ahead to several days and seasonal level. Along with flexible electricity demand options, various electricity storage technologies are being discussed as candidates for contributing to large-scale wind power integration and these also differ in terms of the time scales at which they can operate. In this paper, using the case of Western Denmark in 2025 with an expected 57% wind power penetration, wind power impacts on different time scales are analysed. Results show consecutive negative and high net load period lengths indicating a significant potential for flexibility measures capable of charging/activating demand and discharging/inactivating demand in periods of 1 h to one day. The analysis suggests a lower but also significant potential for flexibility measures charging/activating demand in periods of several days. In addition, the results indicate a physical potential for seasonal electricity storage. In the study, a number of large-scale electricity storage technologies – batteries, flow batteries, compressed air energy storage, electrolysis combined with fuel cells, and electric vehicles – are moreover categorised with respect to the time scales at which they are suited to support wind power integration. While all of these technologies are assessed suitable for intra-hour and intra-day/day-ahead power balancing only some are found suited for responding to several days with high/low net loads and even fewer for seasonal balancing.
The new Spanish regulations allow wind farms to go to the market to sell the energy generated by their facilities. In the case of over- or under-supply, other producers must reduce or increase their production to resolve the so-called deviation, thereby incurring financial losses. Faced with this situation, wind farms have several options. In this paper we consider one promising method: the combined optimization of a pumped-storage hydro-plant and a wind park. First, we are going to present the mathematical modelling of the resulting problem. Second, we shall solve the optimization problem using Optimal Control techniques and finally we shall present several examples of the combined optimization and analyse which strategy is the best one possible.
Energy storage constitutes an effective way to manage excess RES production, and pumped storage is a suitable and mature solution for large storage capacities. The present study aims to investigate the performance of a pumped storage unit introduced in a conventional Hydroelectric Power Plant in Greece. At first, the plant operation and the electric grid data for a reference period of one year are used to compute the time variation of water inflow into the dam, and to estimate the RES production rejections depending on the installed power. Next, a pumping station powered by the rejected RES production and raising water from an adjacent downstream reservoir is modeled. Various scenarios concerning the pumping station power rate and feeding program are examined. The operation of the combined system is simulated in detail and the energy results are analyzed. Also, an economic evaluation is carried out based on current financial conditions in Greece. The results showed that a considerable amount of excess RES production can be stored, but the economic viability of the investment depends on some critical parameters, which are identified. Certain guidelines concerning the optimum sizing and operation strategy of the pumped storage scheme are finally extracted.
This paper presents important technical details for the design, construction and operation of seawater pumped storage systems (S-PSS).S-PSS co-operating with wind parks, features as the most promising technology towards maximizing Renewable Energy penetration in insular systems with low annual rainfalls.This article summarises the fundamental points of integrated studies of S-PSS, from the feasibility study to the precise positioning of the systems' components and the selection of the main equipment. Special issues regarding the use of seawater from the PSS (pumped storage system), such as the use of materials for the construction of the penstock, the construction of the upper reservoir, placing the pump station and the hydro power plant on the coast and the selection of pump and hydro-turbine models are presented thoroughly. Indicative results are presented from two S-PSS of small and medium size.The study proves that current technology enables the secure use of seawater in PSS. The electricity surplus from Wind Powered Pumped Storage Systems (WP-PSS) can also be exploited in reverse osmosis desalination plants for producing potable water.Seawater can be pumped directly from the sea, thus construction of a lower reservoir is avoided, compensating higher costs arising from the use of corrosion-resistant materials for certain components.
The electrification of the non-interconnected Greek islands is mainly based on Autonomous Power Stations (APSs) that are characterized by considerably high electricity production cost, whilst, in several cases, problems related with power shortage are encountered. At the same time, the contribution of wind energy is significantly restricted due to electrical grid limitations imposed to “secure” the stability of the local network and thus resulting in significant rejected wind energy amounts. On the basis of sensitivity analysis, the present study evaluates the techno-economic viability of a system that incorporates the simultaneous operation of existing and new wind farms (WFs) with pumped storage and hydro turbines, which are able to provide the electrical grid of a remote island with guaranteed energy amounts during the peak load demand hours on a daily basis. The performance of the system is simulated during a selected time period for various system configurations and an attempt is made to localize the optimum solution by calculating various financial indices. Emphasis is given on the conduction of an extensive sensitivity analysis considering three main variables (i.e. produced energy selling price, the percentage of state subsidization and the price of the wind energy surplus bought from the already existing WFs) taking also into account several constraints of the national legislation. Based on the most economically viable (payback period quite less than 10 years) configuration derived (24 MW WFs, 15 MW water pumping system, 13.5 MW hydro turbines), the contribution of renewable energy increases by almost 15% (in absolute terms) compared to current conditions, reaching about 25% of the island’s energy consumption pattern. The proposed analysis may be equally well applied to every remote island possessing remarkable wind potential and appropriate topography.
Since the main problem of continuous energy supply from photovoltaic (PV) power plant is intermittence and inability to provide continuous energy supply, this paper proposes its hybridization with hydro energy, or with pump storage hydroelectric (PSH) as a possible solution. This creates a new type of sustainable hybrid power plant which can work continuously, using solar energy as primary energy source and water for energy storage. The characteristics of the solution as an open thermodynamic system are presented, as well as the basic theoretical settings for its application, i.e. key relationships between power and collector field area of PV power plant and working volume of upper storage. The paper introduces hydrological and hydro-energetic indicators for the hybrid plant description, “artificial rainfall”, as the relationship between the water pumped into the upper water storage of the PSH (artificial water inflow) and collector field area of the PV power plant, as well as hydroenergy potential. The proposed hybrid electric power plant does not emit greenhouse gases, produce waste or significantly exploit water resources while the risks to humans and the environment are far smaller than when using conventional technology. This solution is flexible for implementation and can be applied in various climates, hydrological and physical conditions. It is especially productive in cases of joint use of solar and hydro energy where they naturally complement each other as natural energy sources in the annual working cycle.
Renewable power (photovoltaic, solar thermal or wind) is inherently intermittent and fluctuating. If renewable power has to become a major source of base-load dispatchable power, electricity storage systems of multi-MW capacity and multi-hours duration are indispensable. An overview of the advanced energy storage systems to store electrical energy generated by renewable energy sources is presented along with climatic conditions and supply demand situation of power in Saudi Arabia. Based on the review, battery features needed for the storage of electricity generated from renewable energy sources are: low cost, high efficiency, long cycle life, mature technology, withstand high ambient temperatures, large power and energy capacities and environmentally benign. Although there are various commercially available electrical energy storage systems (EESS), no single storage system meets all the requirements for an ideal EESS. Each EESS has a suitable application range.
