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Climate change motivated by human activities constitutes one of the main challenges of this century. To cut carbon emissions in order to mitigate carbon's dangerous effects, the current energy generation mix should be shifted to renewable sources. The main drawback of these technologies is their intermittency, which will require energy storage systems to be fully integrated into the generation mix, allowing them to be more controllable. In recent years, great progress to develop an effective and economically feasible energy storage systems, particularly motivated by the recent rise of demand for electric transportation, has been made. Lithium-ion (Li-ion) battery prices have fallen near 90% over the past decade, making possible the affordability of electric vehicles and transforming the economics of renewable energy. In this work, a study on storage capacity demand previously presented as conference paper is expanded, including a deep analysis of the Spanish generation mix, the evaluation of the energy storage requirements for different low-carbon and carbon-free scenarios in Mainland Spain, and the calculation of the CO2 emissions' reduction and the associated storage costs. [ABSTRACT FROM AUTHOR]

Considering the broad range of applications, efficient retrieval and storing electrical energy methods are still challenging. Besides the load variations, the ever‐increasing intermittent renewable energy penetration into the grid system has witnessed the system complexities. In off‐grid applications, energy storage can balance electricity consumption and electricity generation to avoid voltage and frequency deviations. This research paper focuses on the energy management of an off‐grid climate refuge system used for hot and arid locations with a system comparison for two routes of different storage techniques, namely flywheels and a lithium‐ion battery. The proposed system can generate its power from photovoltaics and provide cooling and other auxiliaries through vapor compression cycle and water misting units with an operation of about 16 hours (ie, from 7:00 am to 11:00 pm) on the weekdays and 12 hours on the weekends. A comparison of levelized costs is conducted for the evaluation using HOMER software. The annual energy production by solar photovoltaics for the proposed system is 20 MWh, and the annual consumption is 16 MWh. The photovoltaic‐battery storage system has shown the lowest cost of electricity, corresponding to 0.761 $/kWh, and net present cost of $66 238 and is optimum in all sensitivity analysis cases. [ABSTRACT FROM AUTHOR]

Electrical energy becomes necessary for human being. Generation of electrical energy mostly depends on fossils fuel, they are limited in nature and also responsible for environmental pollution. Renewable energy resources provides a better alternative for future,In comparison to conventional energy resources economical aspect is a major issue of renewable energy sources with the feasibility and efficiency. These limitations are tried to overcome by deployment hybrid renewable energy resources. There are certain criteria to analyze and implement the sized, optimized and cost efficient system. This paper focus on hybrid energy systems based on solar photovoltaic (PV) and wind resources. This paper shed lights on various parameters of economic feasibility, sizing strategies with logical advancements to enhance their utilization, future prospects, and their arrangement. Strategies to develop an effective storage system is also presented here.A brief review on developments in optimization techniques, reliability index and cost analyzing techniques for hybrid renewable energy systems are also presented. [ABSTRACT FROM AUTHOR]

Unit Commitment (UC) is an optimization problem used to determine the operation schedule of the generating units at every hour interval with varying loads and generations under different generational, environmental and technical constraints. With the significant increase of Renewable Energy Sources (RES) integration into the power networks, effects posed by these system changes to the UC are actively being studied and investigated by global researchers and operation engineers. To this end, this paper firstly provides a literature survey of UC concept, objectives and constraints. Different UC models developed for addressing RES impacts are also reviewed. Moreover, many algorithms have been proposed in the past few decades to optimize the UC problem. This work explores the necessity for alternative optimization approaches for UC solution. In doing that, the work uncovers the advantages and disadvantages of the existing methodologies so that future algorithms could be designed in retaining the advantages of the existing methodologies while avoiding the presented weaknesses. In addition, installation of energy storage devices to balance the fluctuation in power generation and their associated impacts on UC models are reviewed. The contents of this paper provide ready-to-refer and ready-to-use information for the researchers working in the field of UC. [ABSTRACT FROM AUTHOR]

Renewables around the globe, provide fuel diversification, energy security and produce little or no emissions during the electricity generation. The unavailability of rotating masses prohibits on-grid renewable energy generation systems from providing inertia during a frequency disruption. This would be extremely unsettling and impactful when the proportion of energy in the grid due to renewables is high. India currently, has a 28.04% share of on-grid renewable energy. The grid infrastructure systems of India would face severe challenges when the share of on-grid renewables leaps past 50% in the future. Thus, this paper primarily addresses the repercussions of increasing share of on-grid renewables in terms of inertia and frequency response in India. The energy scenario of 2040 in India under 80% proliferation of on-grid renewables has been well reviewed in this paper. The novelty of this paper is the narrative literature review of the Indian Electricity Grid Code (IEGC) on frequency response which is unique and exclusive to this manuscript. It demonstrates the current strategies prevalent in the grid system of India towards frequency response and inertia support. This paper also explains the diverse control strategies and energy storage technologies required for adoption with the on-grid renewables in India for frequency response. The other novelty in this paper is the insight about the inertia lost due to an on-grid 100-kW p solar photovoltaic system to explain the readers about the impact when the integration is hundreds to thousands of kilowatts. • Share of renewables in the Indian grid network is 28.04% (113.226 GW) as of 2022. • India aspires to achieve 54% share of on-grid renewables by 2030 and 80% by 2040. • Indian Electricity Grid Code indicates need for expansion in active power reserves. • India requires diverse control strategies and energy storages for inertia support. • On-grid 100-kW p solar photovoltaic system loses inertia of 100-kW for 4.44 s. [ABSTRACT FROM AUTHOR]

This paper focuses on a review of the state of the art of future power grids, where new and modern technologies will be integrated into the power distribution grid, and will become the future key players for electricity generation, transmission, and distribution. The current power grids are undergoing an unprecedented transformation from the original design, changing the way how energy has been produced, delivered, and consumed over the past century. This new energy era includes the integration of renewable sources such as wind and solar, supported by the distributed or community energy storage, to power distribution grids through innovative high-frequency magnetic links and power-electronic converters. The use of emission free transportation, such as electric vehicles, and energy efficient technologies, such as superconducting generators and storage systems, are also rapidly emerging and will be integrated into the power grids in the foreseeable future. However, it is necessary to reconsider the current paradigms of system analysis and plan with a focus on how to achieve the most flexible, efficient, and reliable power grid for the future––the one that enables operation in a domain which is very different than the current one to deliver the services to consumers at an affordable cost. [ABSTRACT FROM AUTHOR]

Renewable Energy Sources have been growing rapidly over the last few years. The spreading of renewables has become stronger due to the increased air pollution, which is largely believed to be irreversible for the environment. On the other hand, the penetration of renewable energy technologies causes major problems to the stability of the grid. Along with the fluctuations of the renewable energy technologies production, storage is important for power and voltage smoothing. Energy storage is also important for energy management, frequency regulation, peak shaving, load leveling, seasonal storage and standby generation during a fault. Thus, storage technologies have gained an increased attention and have become more than a necessity nowadays. This paper presents an up to date comprehensive overview of energy storage technologies. It incorporates characteristics and functionalities of each storage technology, as well as their advantages and disadvantages compared with other storage technologies. Comparison tables with several characteristics of each storage method are included, while different applications of energy storage technologies are described as well. Finally, several hybrid energy storage applications are analyzed and different combinations of energy storage technologies are reviewed. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen is a flexible energy carrier that can be produced in various ways and support a variety of applications including industrial processes, energy storage and electricity production, and can serve as an alternative transportation fuel. Hydrogen can be integrated in multiple energy sectors and has the potential to increase overall energy system flexibility, improve energy security, and reduce environmental impact. In this paper, the interactions between fuel cell electric vehicles (FCEVs), hydrogen production facilities, and the electric power grid are explored. The flexibility of hydrogen production systems can create synergistic opportunities to better integrate renewable sources into the electricity system. To quantify this potential, we project the hourly system-wide balancing challenges in California out to 2025 as more renewables are deployed and electricity demand continues to grow. Passenger FCEV adoption and refueling behavior are modeled in detail to spatially and temporally resolve the hydrogen demand. We then quantify the system-wide balancing benefits of controlling hydrogen production from water electrolysis to mitigate renewable intermittency, without compromising the mobility needs of FCEV drivers. Finally, a control algorithm that can achieve different objectives, including peak shaving, valley filling, and ramping mitigation is proposed. Our results show that oversizing electrolyzers can provide considerable benefits to mitigate renewable intermittency, while also supporting the deployment of hydrogen vehicles to help decarbonize the transportation sector. Highlights • Interactions between FCEVs and electric power systems are studied. • FCEV powertrain, adoption and refueling behavior are modeled. • Two controllers are designed to mitigate California “Duck Curve” problems. • Controllable H 2 production systems can facilitate renewable energy deployment. [ABSTRACT FROM AUTHOR]

The planning and design of an electric power system, including high-voltage direct-current transmission, is a complex optimization problem. The optimization must integrate and model the engineering requirements and limitations of the generation, while simultaneously balancing the system electric load at all times. The problem is made more difficult with the introduction of variable generators, such as wind and solar photovoltaics. In the present paper, we introduce two comprehensive linear programming techniques to solve these problems. Linear programming is intentionally chosen to keep the problems tractable in terms of time and computational resources. The first is an optimization that minimizes the deviation from the electric load requirements. The procedure includes variable generators, conventional generators, transmission, and storage, along with their most salient engineering requirements. In addition, the optimization includes some basic electric power system requirements. The second optimization is one that minimizes the overall system costs per annum while taking into consideration all the aspects of the first optimization. We discuss the benefits and disadvantages of the proposed approaches. We show that the cost optimization, although computationally more expensive, is superior in terms of optimizing a real-world electric power system. The present paper shows that linear programming techniques can represent an electrical power system from a high-level without undue complication brought on by moving to mixed integer or nonlinear programming. In addition, the optimizations can be implemented in the future in planning tools. [ABSTRACT FROM AUTHOR]

We use the model DIETER, introduced in a companion paper, to analyze the role of power storage in systems with high shares of variable renewable energy sources. The model captures multiple system values of power storage related to arbitrage, capacity, and reserve provision. We apply the model to a greenfield setting that is loosely calibrated to the German power system, but may be considered as a more generic case of a thermal power system with increasing shares of variable renewables. In a baseline scenario, we find that power storage requirements remain moderate up to a renewable share of around 80%, as other options on both the supply and demand side may also offer flexibility at low cost. Yet storage plays an important role in the provision of reserves. If the renewable share further increases to 100%, the need for power storage grows substantially. As long-run parameter assumptions are highly uncertain, we carry out a range of sensitivity analyses. As a general finding, storage requirements strongly depend on the costs and availabilities of other flexibility options, particularly regarding flexible power generation from biomass. We conclude that power storage becomes an increasingly important element of a transition toward a fully renewable-based power system, and gains further relevance if other potential sources of flexibility are limited. [ABSTRACT FROM AUTHOR]

Electric energy generation from renewable energy sources is generally non-dispatchable due to its intrinsic volatility. Therefore, its integration into electricity markets and in power system operation is often based on volatility-compensating energy storage systems. Scheduling and control of this kind of coupled systems is usually based on hierarchical control and optimization. On the upper level, one solves an optimization problem to compute a dispatch schedule and a coherent allocation of energy reserves. On the lower level, one performs online adjustments of the dispatch schedule using, for example, model predictive control. In the present paper, we propose a formulation of the upper level optimization based on data-driven probabilistic forecasts of the power and energy output of the uncontrollable loads and generators dependent on renewable energy sources. Specifically, relying on probabilistic forecasts of both power and energy profiles of the uncertain demand/generation, we propose a novel framework to ensure the online feasibility of the dispatch schedule with a given security level. The efficacy of the proposed scheme is illustrated by simulations based on real household production and consumption data. [ABSTRACT FROM AUTHOR]

Energy storage is more important today than ever. It has a key role in storing intermittent electricity from renewable sources – wind, solar and waves – enabling the decarbonisation of the electricity sector. Liquid air energy storage (LAES) is a novel technology for grid scale energy storage in the form of liquid air with the potential to overcome the drawbacks of pumped-hydro and compressed air storage. In this paper we address the performance of next generation LAES standalone plants. Starting our experience with LAES pilot plant at Birmingham (UK), we developed for the first time a validated model to address the dynamic performance of LAES. The model allows us to understand the relationship between component and system level performance through dynamic modelling. We found that the temporary storage of cold thermal energy streams using packed beds improves efficiency of LAES by ∼50%. However, due to dynamic cycling charge/discharge, packed beds can bring an undesired 25% increase in the energy expenditure needed to liquefy air. In summary, this work points outs that (a) dynamics of LAES should not be neglected; (b) novel design for cold thermal storage are needed and (c) linking component and system level performance is crucial for energy storage. [ABSTRACT FROM AUTHOR]

Energy storage systems (ESSs) play a very important role in recent years. Flywheel is one of the oldest storage energy devices and it has several benefits. Flywheel Energy Storage System (FESS) can be applied from very small micro-satellites to huge power networks. A comprehensive review of FESS for hybrid vehicle, railway, wind power system, hybrid power generation system, power network, marine, space and other applications are presented in this paper. There are three main devices in FESS, including machine, bearing, and Power Electronic Interface (PEI). Furthermore, advantages and disadvantages all of them have been presented. In addition a brief review of new and conventional power electronic converters used in FESS, have been discussed. Finally, practical ways to develop this technology in the future are presented. [ABSTRACT FROM AUTHOR]

As numerous generation side assets, such as the generating units and the plant equipments, in the Smart Grid system have already aged, well planned maintenance and operational scheduling is needed to maintain their expected longevity. Forced outages and short-notice/temporary maintenance of thermal units should also be considered as likely events. Backup energy sources are required to replace the generating units during the maintenance period. Using conventional storage devices for this purpose is feasible, but costly. Electric vehicles and plug-in hybrid electric vehicles, with vehicle-to-grid capability, referred to as “gridable vehicles”, are a useful choice as storage devices for the same. Second life batteries, disassembled from gridable vehicles after passing their automotive life, are another candidate for this purpose from the economic perspective. A system model that aggregates gridable vehicles and second life batteries together in an intelligent way to provide such backup energy can reduce significant storage costs. Such a system model is presented in this paper for a Smart Grid environment. Our simulation results suggest that using gridable vehicles and second life batteries together can save up to 70% of conventional storage energy costs and recover capital costs for the second life batteries in only 1.5 years. [ABSTRACT FROM AUTHOR]

Abstract: This paper attempts to review and discuss the status and future prospects of renewable energy in Oman. Renewable energy sources like solar, wind, hydro, geothermal, and biomass have been revised. The electricity shortages and the challenges to overcome the increase in electrical demands for the near future have been discussed. The investigations found that solar, shore-wind and geothermal could play an important role in the future of renewable energy in country. Also, it is found that there is need to investigate the potential of offshore-wind, biomass, and hydro (tide, wave and ocean thermal energy). The appearance and weight of renewable energy in the higher education programs and the Oman commitment toward renewable energy have been discussed. The paper finishes with some conclusions and recommendations. [Copyright &y& Elsevier]

Abstract: Portugal is a country with an energy system highly dependent on oil and gas imports. Imports of oil and gas accounted for 85% of the country’s requirements in 2005 and 86% in 2006. Meanwhile, the share of renewable energy sources (RES) in the total primary energy consumption was only 14% in 2006. When focusing only on electricity production, the situation is somewhat better. The share of RES in gross electricity production varies between 20% and 35% and is dependent on the hydropower production in wet and dry years. This paper presents, on a national scale, Portugal’s energy system planning and technical solutions for achieving 100% RES electricity production. Planning was based on hourly energy balance and use of H2RES software. The H2RES model provides the ability to integrate various types of storages into energy systems in order to increase penetration of the intermittent renewable energy sources or to achieve a 100% renewable island, region or country. The paper also represents a stepping-stone for studies offering wider possibilities in matching and satisfying electricity supply in Portugal with potential renewable energy sources. Special attention has been given to intermittent sources such as wind, solar and ocean waves that can be coupled to appropriate energy storage systems charged with surplus amounts of produced electricity. The storage systems also decrease installed power requirements for generating units. Consequently, these storages will assist in avoiding unnecessary rejection of renewable potential and reaching a sufficient security of energy supply. [ABSTRACT FROM AUTHOR]

This paper presents a new active/reactive power closed-loop control system for a hybrid renewable energy generation system used for single-phase residential/commercial applications. The proposed active/reactive control method includes a hybrid estimator, which is able to quickly and accurately estimate the active/reactive power values. The proposed control system enables the hybrid renewable energy generation system to be able to perform real-time grid interconnection services such as active voltage regulation, active power control, and fault ride-through. Simulation and experimental results demonstrate the superior performance of the proposed closed-loop control system. [ABSTRACT FROM PUBLISHER]

Insular electricity grids are considered to have a more fragile structure than the mainland ones due to several factors such as the lower inertia because of lower number of generation facilities connected to the system, absence or insufficient interconnection with the main grid, etc. The recent trend of integrating large portions of environmentally sustainable power generation units that have a significantly volatile nature in the generation mix (such as wind and solar energy conversion systems) within this fragile structure, poses profound challenges that need deeper and specific analysis. This study aims to provide an overview of insular power system structures and operational requirements, especially under increasing penetration of renewable energy sources. Firstly, a general evaluation of insular power systems is presented. Then, potential challenges are thoroughly discussed together with opportunities to tackle them. Future technological developments, as well as innovative applications are also given special attention. Hence, this paper contributes to the scarce literature regarding insular power systems by providing a critical overview of issues regarding their operation and possible solutions. [ABSTRACT FROM AUTHOR]

The share of the renewable energy sources (RES) in the global electricity market is substantially increasing as a result of the commitment of many countries to increase the contribution of the RES to their energy mix. However, the integration of RES in the electricity grid increases the complexity of the grid management due to the variability and the intermittent nature of these energy sources. Energy storage solutions such as batteries offer either short-term storage that is not sufficient or longer period storage that is significantly expensive. This paper introduces an energy management approach which can be applied in the case of power and desalinated water generation. The approach is based on mathematical optimization model which accounts for random variations in demands and energy supply. The approach allows using desalination plants as a deferrable load to mitigate for the variability of the renewable energy supply and water and/or electricity demands. A mathematical linear programming model is developed to show the applicability of this idea and its effectiveness in reducing the impact of the uncertainty in the environment. The model is solved for the real world case of Saudi Arabia. The optimal solution accounts for random variations in the renewable energy supply and water and/or electricity demands while minimizing the total costs for generating water and power. [ABSTRACT FROM AUTHOR]

A major challenge that needs to be addressed in systems that generate power using renewable energy sources (RES) is the stochastic behaviour of both solar and wind energy. This problem can be overcome by using hybrid systems that combine power generation units and storage media of diverse functionalities under an integrated scheme. Such system often involve photovoltaic panels and wind turbines to generate power that meets the demands of a targeted application. The intermittent nature of RES require the incorporation of batteries to store excess energy and release it under environmental condition variations. Also the systems include a controller, a converter, an inverter, a fuel cell assembly, an electrolyser and a unit for hydrogen storage. Whereas batteries are only able to serve short-term and limited power demands, hydrogen is emerging as an alternative, long-term and flexible energy storage medium that requires a rich infrastructure, to be integrated within hybrid power generation systems. All these problems are significant barriers on the way towards real market and will be disscused in this paper taking into account two possible scenario. [ABSTRACT FROM AUTHOR]

Abstract: The intermittent nature of wind energy poses questions on how electricity production can match the demand. The present paper analyses possible ways of achieving this goal when a large share of the energy is provided by wind. The study considers a certain share of wind energy as a target to be reached, and analyses different avenues for reaching such a target. The possible role of electricity energy storage, wind curtailment and transmission grid reinforcement is highlighted and discussed. The results show that above a certain percentage of electricity produced by wind, electricity storage becomes an economical option for integrating wind energy by reducing wind curtailments. Also, the synergy of storage and grid interconnections is highlighted. [Copyright &y& Elsevier]

A new low cost high power density photovoltaic power conditioning system (PV PCS) with an energy storage system is proposed in this paper. Its high power density and cost effectiveness can be achieved through the unification of the maximum power point tracker and the battery charger/discharger. Despite the reduced power stage, the proposed system can achieve the same performance in terms of maximum power point tracking and battery charging/discharging as the conventional system. When a utility power failure happens, the proposed system cannot perform maximum power point tracking at the UPS mode. However, the predetermined battery voltage near the maximum power point of the PV array can effectively generate a reasonable PV power even at the UPS mode. Therefore, it features a simpler structure, less mass, lower cost, and fewer devices. Finally, to confirm the operation, validity, and features of the proposed system, a theoretical analysis and experimental results from a single phase AC 220Vrms/1 .5kw prototype are presented. [ABSTRACT FROM AUTHOR]

Abstract: With the growing amount of decentralized power production the design and operation of the grid has to be reconsidered. New problems include the two-way flow of electricity and maintaining the power balance given the increased amount of uncertain and fluctuating renewable energy sources like wind and solar that deliver electricity to the grid. Solution directions are the development of smart grids, demand side management, virtual power plants and storage of electricity. These are directions that, rightly so, are already attracting a lot of attention and R&D funding. In this paper critical issues are identified and specified. However, we will also explore new solution directions based on an integrative approach as proposed by the Dutch Royal Academy of Science foresight committee on renewable energy conversions. These alternative solutions include flexible coproduction and local production of chemicals and fuel that can also fulfill a storage function. [Copyright &y& Elsevier]

In this paper, a control scheme is proposed for a three-phase isolated photovoltaic (PV)-diesel microgrid without energy-storage element. The scheme aims to: track maximum power from the PVA, regulate the load voltage, compensate the load unbalance viewed by the diesel generator, and to control the diesel-engine speed. The first three tasks are achieved by controlling the pulse width modulation inverter interfacing the PV array to the system. The fourth is realized by a modified fuzzy logic controller of the diesel engine. The obstacles encountered on operating the system under certain probable loading conditions are addressed. Two different operation strategies are proposed to provide high-quality power under all loading scenarios, and to achieve the targets of the control scheme. The system operation is investigated under a variety of conditions to prove the aptness of the proposed techniques. [ABSTRACT FROM PUBLISHER]

Abstract: Renewable energy sources (RES) are mainly used in the electrical sector. Electricity is not a storable commodity. Hence it is necessary to produce the requested quantity and distribute it through the system in such a way as to ensure that electricity supply and demand are always evenly balanced. This constraint is actually the main problem related to the penetration of new renewables (wind and photovoltaic power) in the context of complex energy systems. Moreover the design of optimal energy resource mixes in climate change mitigation actions is a challenge faced in many places. The paper analyzes the problem of new renewable energy sources penetration. The case of Italian scenario is considered as a meaningful reference due to the characteristic size and the complexity of the same. The various energy scenarios are evaluated with the aid of a multipurpose software taking into account the interconnections between the different energetic uses. In particular it is shown how the penetration of new renewable energy sources is limited at an upper level by technological considerations and it will be more sustainable if an integration of the various energy uses (thermal, mobility and electrical) will be considered. A series of optimized scenarios are developed. In each case the maximum RES penetration feasible with the constraints was defined. Then analysis is applied to an energy system model of Italy showing how an integrated development of CHP and electric mobility can aid a further integration of wind and photovoltaic energy power. Finally the primary energy consumption saving possible in case of consistent penetration of intermittent renewables and CHP was identified. [ABSTRACT FROM AUTHOR]

Abstract: The recently released report of the International Energy Outlook (IEO2009) projects an increase of 44% in the world energy demand from 2006 to 2030, and 77% rise in the net electricity generation worldwide in the same period. However, threatening in the said report is that 80% of the total generation in 2030 would be produced from fossil fuels. This global dependence on fossil fuels is dangerous to our environment in terms of their emissions unless specific policies and measures are put in place. Nevertheless, recent research reveals that a reduction in the emissions of these gases is possible with widespread adoption of distributed generation (DG) technologies that feed on renewable energy sources, in the generation of electric power. This paper gives a detailed overview of distributed energy resources technologies, and also discusses the devastating impacts of the conventional power plants feeding on fossil fuels to our environment. The study finally justifies how DG technologies could substantially reduce greenhouse gas emissions when fully adopted; hence, reducing the public concerns over human health risks caused by the conventional method of electricity generation. [Copyright &y& Elsevier]

Abstract: Hydrogen is an energy carrier which can be used for the storage of intermittent and renewable energy sources. In this paper, the general characteristics of an integrated and automated hydrogen-based auxiliary power unit (APU) are presented. A PEM water electrolyzer (production capacity ranging from zero up to 1Nm3 H2/h), which can be powered by a panel of photovoltaic cells, is used to produce hydrogen at day hours. Hydrogen is dried and stored in hydride reservoir tanks (the storage capacity of individual reservoirs is 1Nm3 H2). Then hydrogen is used for the co-generation of heat and electricity at night hours using a PEM fuel cell (1kW maximum output power). The main electrochemical and technological features of the overall system are presented. This kind of APU can potentially be used as an electric power source for domestic applications, for the production of electricity on remote sites or as a mobile hydrogen refuelling station for transport applications in urban areas. [Copyright &y& Elsevier]

Electricity plays a crucial role in the well-being of humans and is a determining factor of the economic development of a country. Electricity issues have encouraged researchers to focus on improving power availability and quality along with reliability. This pursuit has increasingly raised the intention to integrate renewable energy (RE) into power systems to curb the problem of energy deficiency. However, intermittency in the sources of RE supply coupled with fluctuating changes in demand with respect to time has induced high risk in maintaining system reliability in terms of providing adequate supply to consumers. Whilst an energy storage system (ESS) is not another source of electricity, it is proven to be effective and viable in solving the aforementioned issues. Thus, this paper comprehensively reviews the development of ESS technologies and discusses the benefits and real-life applications of these technologies. The concept of reliability in power systems is also explored to provide an improved understanding of this study. Lastly, notable studies that have addressed the reliability impact of ESSs on power systems are discussed. This review paper therefore is expected to provide a critical analysis of ESS developments, as well as recognize their research gaps in terms of reliability studies in modern RE-integrated power networks. [ABSTRACT FROM AUTHOR]

Compressed air energy storage (CAES) is an established and evolving technology for providing large-scale, long-term electricity storage that can aid electrical power systems achieve the goal of decarbonisation. CAES facilities often utilise large underground storage caverns to ensure high capacity systems. This results in the need of locations with suitable geological features to develop a CAES plant. This paper examines recent and ongoing large-scale CAES projects and presents candidate methods of storing high pressure air using underground features. An assessment of the overall potential for CAES in India is presented by examining its geological features and locations with the greatest potential for CAES plants are determined. This is combined with an analysis of the renewable electricity generation potential in India to identify candidate areas for renewable generation and CAES integrated systems. Up to 1.05% of Indian land area is deemed suitable for CAES plant development and if fully utilised would be sufficient to meet the energy storage needs of India, however, practically a very small fraction of the total suitable land that could be developed so other competing energy storage technologies should be considered. Conversely, the UK possesses a very good potential for CAES, enough to greatly exceed necessary energy storage, owing to the abundance of salt beds not present in India. For CAES to garner serious consideration in India, aquifer storage based CAES needs to be demonstrated. • A comparative assessment of the Indian and UK potential for CAES. • Methodology for linking CAES suitable regions and renewable electricity generation. • Comprehensive review of all major large-scale CAES projects. • Economic and geographic problems have led to the failure of many CAES projects. [ABSTRACT FROM AUTHOR]

This paper presents a case study of using hydrogen for large-scale long-term storage application to support the current electricity generation mix of South Australia state in Australia, which primarily includes gas, wind and solar. For this purpose two cases of battery energy storage and hybrid battery-hydrogen storage systems to support solar and wind energy inputs were compared from a techno-economical point of view. Hybrid battery-hydrogen storage system was found to be more cost competitive with unit cost of electricity at $0.626/kWh (US dollar) compared to battery-only energy storage systems with a $2.68/kWh unit cost of electricity. This research also found that the excess stored hydrogen can be further utilised to generate extra electricity. Further utilisation of generated electricity can be incorporated to meet the load demand by either decreasing the base load supply from gas in the present scenario or exporting it to neighbouring states to enhance economic viability of the system. The use of excess stored hydrogen to generate extra electricity further reduced the cost to $0.494/kWh. [ABSTRACT FROM AUTHOR]

While wind farms have no inherent storage to supply power in calm conditions, this paper demonstrates that large tidal turbine farms in channels have short-term energy storage. This storage lies in the inertia of the oscillating flow and can be used to exceed the previously published upper limit for power production by currents in a tidal channel, while simultaneously maintaining stronger currents. Inertial storage exploits the ability of large farms to manipulate the phase of the oscillating currents by varying the farm's drag coefficient. This work shows that by optimizing how a large farm's drag coefficient varies during the tidal cycle it is possible to have some flexibility about when power is produced. This flexibility can be used in many ways, e.g. producing more power, or to better meet short predictable peaks in demand. This flexibility also allows trading total power production off against meeting peak demand, or mitigating the flow speed reduction owing to power extraction. The effectiveness of inertial storage is governed by the frictional time scale relative to either the duration of a half tidal cycle or the duration of a peak in power demand, thus has greater benefits in larger channels. [ABSTRACT FROM AUTHOR]