Search

Hydrogen is emerging as a critical player in transitioning to sustainable and renewable energy systems, serving roles in energy storage, grid balancing, and decarbonization. This paper explores various aspects of hydrogen, including its production through renewable-electricity-driven electrolysis, advanced storage techniques, and incorporation into current energy systems. It highlights primary electrolysis methods like PEM and alkaline, noting their improved efficiency and cost-effectiveness. Various hydrogen storage methods, such as physical, chemical, and advanced porous materials, are examined for their benefits and limitations. The review further explores hydrogen's integration into grid storage systems and microgrids to enhance energy reliability. It discusses hydrogen's application in fuel cells for electricity generation, focusing on technological advancements that improve efficiency and reduce costs. Additionally, the paper underscores hydrogen's crucial role in reducing CO 2 emissions in industrial processes like steel production and its use in residential and commercial energy supply through combined heat and power systems. Economic aspects and supportive policies from regions are analyzed, highlighting the global efforts and policies supporting the potential hydrogen in renewable energy systems. This analysis emphasizes hydrogen's comprehensive role in enhancing renewable energy systems and achieving global sustainability objectives, providing a thorough review of recent progress and challenges. • Identifies PEM and alkaline as efficient electrolysis methods. • Analyzes varied H 2 storage options for mobility and stationarity. • Highlights advancements in H 2 fuel cells for vehicles. • Discusses global policies supporting H 2 integration. • Reviews economic impacts of scaling H 2 infrastructure. [ABSTRACT FROM AUTHOR]

The paper is devoted to the development of a device for protecting facilities with turn-to-turn insulation, namely transformers and wind generators in order to increase the reliability of operation of electrical power systems, renewable energy installations and energy storage systems. The paper presents the results of experimental studies of the parameters of a prototype frequency-dependent device, as well as an assessment of the effectiveness of suppression of high-frequency surge voltages by the proposed device. The results of four groups of measurements are shown, which were compared with each other and with the results of previously showed computer simulations. The high efficiency of the proposed device when influencing the slope and amplitude of short high-frequency transients is shown. It is indicated that the parameters proposed earlier in the simulation allow the device to be used effectively. A brief analysis of alternative methods and means of protection is provided, and the prospects for using the device as protective equipment for wind power plants are also considered. [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carriers (LOHC) can be used as a lossless form of hydrogen storage at ambient conditions. The storage cycle consists of the exothermic hydrogenation of a hydrogen-lean molecule at the start of the transport, usually the hydrogen production site, becoming a hydrogen-rich molecule. This loaded molecule can be transported long distances or be used as long-term storage due to its ability to not lose hydrogen over long periods of time. At the site or time of required hydrogen production, the hydrogen can be released through an endothermic dehydrogenation reaction. LOHCs show similar properties to crude oils, such as petroleum and diesel, allowing easy handling and possibilities of integration with current infrastructure. Using this background, this paper reviews a variety of aspects of the LOHC life cycle, with a focus on currently studied materials. Important factors such as the hydrogenation and dehydrogenation requirements for each material are analysed to determine their ability to be used in current scenarios. Toluene and dibenzyltoluene are attractive options with promising storage attributes, however their dehydrogenation enthalpies remain a problem. The economic feasibility of LOHCs being used as a delivery device were briefly analysed. LOHCs have been shown to be the cheapest option for long distance transport (>200 km), and are cheaper than most at shorter distances in terms of specifically transport costs. The major capital cost of an LOHC delivery chain remains the initial investment for the raw materials and the cost of equipment for performing hydrogenation and dehydrogenation. Finally, some studies in developing the LOHC field were discussed, such as microwave enhancing parts of the process and mixing LOHCs to acquire more advantageous properties. • Efficient hydrogen storage solution for sustainable energy transportation and storage. • Enables safe and cost-effective hydrogen transportation and distribution networks. • Promotes renewable energy integration through versatile and scalable storage capabilities. • Facilitates decarbonization efforts by enabling long-term, stable hydrogen supply chains. [ABSTRACT FROM AUTHOR]

Vanadium Flow Batteries (VFBs) are a stationary energy storage technology, that can play a pivotal role in the integration of renewable sources into the electrical grid, thanks to unique advantages like power and energy independent sizing, no risk of explosion or fire and extremely long operating life. The first part of this paper presents the main features and the basic performance parameters of VFB, which determine their electric, hydraulic, thermal, and aging feature. The latter part outlines the strengths and weaknesses of the technology, the services that it can provide to the grid, and a short economic analysis. After presenting the fundaments of the technology, prospects and trends of VFBs deployment are outlined. Most of the considerations highlighted in this paper are inspired to studies performed on an industrial-size VFB operated at the Electrochemical Energy Storage and Conversion Lab (EESCoLab) at the University of Padua (Italy). [ABSTRACT FROM AUTHOR]

Hydrogen energy storage system (HESS) has excellent potential in high-proportion renewable energy systems due to its high energy density and seasonal storage characteristics. After detailing the volatility of wind speed, irradiance and load, this paper proposes a bi-level optimization model to analyze the economic operation of the wind-photovoltaic-hydrogen hybrid system (WPH-HS). First, the relationship between the source-load output matching and operating conditions of HESS is studied, two evaluation indicators are described, which can be adjusted by wind-solar complementarity on the source side and demand response on the load side. Second, considering the levelized cost of storage (LCOS), the total annual cost (TAC) calculation method of WPH-HS is presented, and this paper provides a new hybrid optimization technology of chaotic search, particle swarm optimization and non-dominated sorting genetic algorithm2. Finally, the system is simulated with the MATLAB software to determine the optimal sizing of components and minimize the LCOS while ensuring the optimal TAC. The simulation results are elaborated in detail. In particular, the added source-load interaction reduces the TAC and LCOS by 7.3% and 10.3%. When two indicators reach 0.03 and 0.1745, the system is economically viable with the LCOS of 0.276 USD/kWh. The hybrid optimization algorithm can achieve better result in fewer iterations. • The cross-season utilization of the hydrogen energy storage system is discussed. • A price bi-level model about the levelized cost of storage and the total annual cost is established. • Evaluation indicators are presented to promote the source-load interaction. • Effects of wind speed, irradiance, and loads are investigated for the levelized cost of storage. • A hybrid optimization algorithm based on three common algorithms is designed. [ABSTRACT FROM AUTHOR]

• Classified sales channels for different quality renewable energy. • Dynamic assessment indicators for the renewable energy's power deviation. • Power curve optimization strategy considers the self-owned battery. • Accurately and timely transmit the peak shaving pressure. • Guarantee the independent decision-making power of new energy stations. By the end of 2023, the installed capacity of renewable energy (RE) in China accounted for 36.0% of the total installed capacity, while the installed capacity of conventional thermal power units had decreased from 64.0% in 2016 to 47.6% in 2023. RE accounts for a higher proportion, leading to a shortage of peak shaving resources (PSR). As a result, the current RE quota system becomes unsustainable. In this paper, RE stations can classify their electricity into high-quality and low-quality parts based on the accuracy of their power curves. High-quality RE will be fully purchased and under stricter assessment, while low-quality RE will compete for clearing in the intraday spot market. Firstly, the article estimates the degree of PSR shortages in different periods based on technical parameters of thermal units, RE forecast information, and load forecast information. Consequently, the PSR supply capacity (PSR supply capacity) can be divided into PSR shortage status and sufficient status. Secondly, a clearing method for low-quality RE in the spot market is designed. The grid can set different PSR supply capacitys for different time periods according to the degree of PSR shortage. The assessment indicator values vary under different PSR supply capacitys. Lastly, based on the classification sales channels, this paper proposes a power curve optimization strategy that considers self-owned battery energy storage (BES). Case studies show that the proposed classification sales channels can effectively decrease the degree of PSR shortage while taking into account the benefits of RE station. The designed PSR supply capacity dividing method can accurately reflect the degree of PSR shortage in real-time, and the proposed power curve optimization strategy can further enhance the economic benefits of RE station. © 2017 Elsevier Inc. All rights reserved. [ABSTRACT FROM AUTHOR]

Many subarctic communities rely entirely on fossil fuels for their energy needs. Solar-assisted ground-coupled heat pumps (SAGCHP) can be a solution to integrate renewable energy sources into their energy portfolios. However, it is currently unknown how such systems could operate in the context of the high North (cold ground, extreme mismatch between insolation and heating need, electricity from diesel). The objective of the paper is to develop a detailed model of a SAGCHP heating a house in Nunavik (Quebec, Canada) in order to gain a better understanding of its potential and limitations. The solar assistance is provided by PVs. Simulations with and without electric storage (batteries) were run. A complex tradeoff between four different modes of operation was obtained depending on the conditions of the system at each time step. For the test case, results show that the ground experiences a weak long-term thermal depletion partly compensated solar energy, but that a significant portion of the PV power production is preferably used by the compressor or stored in batteries rather than stored in the ground as heat. Over ten years, the SAGCHP system reduced fuel consumption respectively by 38.2% (without a battery) and 59.1% (with a battery). [ABSTRACT FROM AUTHOR]

Renewable energy attracts increasing attention from both industry and academia under the context of carbon neutrality. For wind and solar energy, the strong dependence on natural processes results in the imbalance between energy production and real demands. Energy storage technologies, e.g., Compressed Air Energy Storage (CAES), are promising solutions to increase the renewable energy penetration. However, the CAES system is a multi-component structure with multiple energy forms involved in the process subject to high temperature and high-pressure working conditions. The CAES system is a complex process flowsheet consisting of charging and discharging process. The process should be optimized to achieve the best thermodynamic and economic performance. Under the optimal design conditions, it might lead to severe consequences once a failure occurs, e.g., harm to humans, the environment, and assets. Limited attention and scarce available information have been paid to the CAES system risk management yet. Hence, this paper applies the System-Theoretic Process Analysis (STPA), which is a top-down method based on system theory, to identify the CAES system safety hazards. The results are expected to provide a preliminary guideline for practitioners regarding the safety and reliability of the CAES system. As a result, a more reliable CAES system can contribute to a more flexible energy system with more efficient and economic utilization of fluctuating renewable energy. [ABSTRACT FROM AUTHOR]

Green ammonia, a promising zero-carbon energy storage vector, has never been produced using solely tidal stream energy despite its predictable characteristics. Combining tidal stream sites with a phase difference (tidal phasing) facilitates anticorrelation between these sites' power profiles, enabling a more consistent power output. Green ammonia production benefits from a steady and predictable power input. The objective of this paper is to determine if nearby tidal sites have a large enough phase difference (anticorrelation) to reduce the cost of ammonia production. Moreover, producing green ammonia from underutilized or unutilized remote and grid-constrained tidal stream sites may enable viability of these sites. This paper is the first analysis of green ammonia production using solely tidal stream energy and the first analysis of tidal phasing for green fuel production. Two UK case studies are presented in i) the North Channel of the Irish Sea and ii) Orkney. There are tidal sites in each which have a phase difference (e.g. the Mull of Kintyre/Sound of Islay, and Graemsay/North Ronaldsay with correlation coefficients of 0.17 and −0.02 respectively), utilising this phase difference reduces the levelized cost of ammonia by 8% in the Irish Sea and by 12% in Orkney. [ABSTRACT FROM AUTHOR]

C arbon-free microgrids (CFMs) composed of renewable energy and hydrogen energy storage systems (HESS) are a promising solution for low-carbon energy systems. However, when CFMs are off-grid, their reliability is frequently questioned, especially when renewable energy (RE) outputs are extremely low. To reduce the total cost and improve the off-grid reliability, this paper proposes a two-stage robust planning model for CFM with renewable energy and HESS that considers both grid-connected (GC) and short-term (several days) off-grid (OG) statuses. In the GC status, the target is to minimize the system expenses; while in the OG status, the optimization goal is not to lose the important loads in a short period of time considering the worst realization of days. The Nested-C&CG algorithm is employed to solve the robust planning model of CFM. Additionally, a new uncertainty set that takes terrible days into account for RE and loads is presented to make the decision robust. Finally, the numerical analysis based on the case studies shows that the HESS in CFM has the ability to support loads in OG status for a week. And the total cost of the CFM using HESS and batteries can be reduced by 11.83% compared with that using only batteries. In addition, the planning results with robust optimization can guarantee that all the important loads are satisfied. [ABSTRACT FROM AUTHOR]

The present review paper aims to shed lights on the concept of fully green energy system which includes both the source of energy and the storage system. The objective is to propose an energy label "Green to Green" (G2G) that identifies systems involving simultaneously green source and green storage, as an efficient solution to achieve a significant reduction in the dangerous level of pollution that most countries have reached today. Green sources include mainly renewable energy systems such as solar, wind, geothermal and wave energy systems. In its turns green storage includes pumped hydroelectric, flywheel, hydrogen and compressed air. Moreover, and as a case investigation on G2G concept, the paper reviews the main solar-hydrogen coupling systems, that are categorized within four categories parabolic trough-hydrogen, solar tower-hydrogen, photovoltaic-hydrogen and solar chimney-hydrogen. • Green to Green (G2G) is presented as a label to promote pollution-free systems. • Green storage includes Hydrogen, flywheel, compressed air and pumped hydro. • As a case study on (G2G) concept, the paper highlights solar – hydrogen coupling. [ABSTRACT FROM AUTHOR]

The exploitation and utilisation of solar energy is challenging because of both diurnal and seasonal variation. Seasonal thermal energy storage is a prominent solution to solve the problem of seasonal variation of solar production. This paper investigates both the optimal design and energy management of a renewable energy plant with seasonal thermal energy storage. As a case study, the thermal, cooling and electrical energy demands of a university campus during one year are considered. Three scenarios, characterized by a different available area (20,555 m2, area covered at present; 50,000 m2, potentially available area by exploiting the entire rooftop and parking area; unlimited area) for solar thermal collectors and photovoltaic panels are investigated. In the first two scenarios, the exploitation of solar energy allows a primary energy saving of 31% and 57%, respectively compared to the use of a conventional plant. The seasonal storage reaches an overall efficiency (thus considering both charging and discharging) up to 84%. Finally, the analysis of the third scenario shows that the feasibility of meeting the energy demands by only exploiting solar energy is technically challenging because a large area equal to about 100,293 m2 is needed for solar thermal collectors and photovoltaic panels. [ABSTRACT FROM AUTHOR]

One crucial requirement for power systems is the necessity to enhance flexibility, enabling the seamless integration of a substantial amount of renewable energy generation. While flexibility holds significance in current power systems, the escalating penetration of renewable energy resources emphasizes an ongoing and growing need for flexibility in the future, given the intermittent nature of these energy sources. To address the crucial aspects of decarbonization for sustainable development and recognizing decentralization as a strategy for grid development, this research concentrates on flexibility in the context of microgrids. Diverging from many existing review papers that explore flexibility in the broader power system context, this study pioneers an investigation from the local energy system's perspective, introducing a novel classification of flexibility resources. The exploration begins with elucidating various concepts and definitions of flexibility. Subsequently, flexibility resources available to microgrids are systematically categorized based on the operation modes. A comprehensive review of conducted research follows, highlighting diverse categories and emphasizing primary flexibility resources. Special attention is given to recent concepts such as power-to-gas/hydrogen conversion, using electrolyzers as flexible loads for (green) hydrogen production, and various storage devices, as they offer flexibility during both off-grid and grid-connected operation modes in microgrids. Furthermore, a comparative analysis is undertaken, detailing the objective function(s) and flexibility resources employed in different research studies. To quantify flexibility, the latest metrics are categorized and explained. The study concludes by presenting suggestions for future research directions and summarizing key findings. [Display omitted] • Reviewing the concept of flexibility from the point of view of microgrids. • Novel classification for flexibility resources based on microgrids operating modes. • Special attention to recent technologies such as power-to-gas/hydrogen. • A comparative analysis, detailing the objective function(s) and flexibility resources. • Categorization and explanation of the latest flexibility metrics and their application. [ABSTRACT FROM AUTHOR]

Renewable energy sources, such as wind and solar, can reduce environmental pollution and promote the transformation of the energy structure. However, the intermittency and uncertainty of new energy sources such as wind and photovoltaics pose challenges to large-scale grid integration. Effective utilization of intermittent energy sources requires large-scale energy storage facilities. Salt rock is recognized as an excellent medium for underground large-scale energy storage with a wide range of applications. This paper identifies the potential of salt caverns to be used for large-scale energy storage by analyzing the distribution of wind and solar energy resources in China, taking into account the grid-connected infrastructure of the Chinese power grid and the geographic location of salt mines. The overlapping areas are identified for utilization in compressed air energy storage and hydrogen storage. Through meticulous categorization and analysis of the factors influencing salt cavern underground storage site selection, the AHP-EWM method is introduced to establish an objective hierarchy model for a comprehensive evaluation system of salt cavern underground storage site selection. The comprehensive planning of China's 20 major salt mines is conducted, and the research findings hold significant reference value for facilitating the low-carbon energy transition in China. • The ways which salt mines can be used for renewable energy peaking are summarized. • Renewable energy religions combined with grid-connected infrastructure and salt mines in China were studied. • Objective hierarchical modeling of subsurface salt cavern siting was developed using a combinatorial assignment method. • Energy Storage Planning for 20 Major Salt Mines in China. [ABSTRACT FROM AUTHOR]

[Display omitted] • PCM energy storage and PV/T coupled multi-source heat pump systems were combined. • The thermal performance, energy efficiency, and economy of the system were analyzed. • The performance of paraffin C17 and water as energy storage materials were compared. • The performance of six low-temperature PCMs applied to the system were analyzed. • Compared to the existing system, it saves 56 % of energy and 27.7 % of operating costs. To improve the application of renewable energy in the heating zone, as well as to address the limitations of air and water source heat pump. The study presents a PV/T (photovoltaic/thermal) coupled air–water source heat pump system integrated with phase change energy storage. A theoretical analytical model and TRNSYS simulation model of the system were developed to evaluate the thermal performance, energy efficiency and economics of the system. The performance of phase change energy storage was compared with that of water storage, and the effect of different phase change materials on the system characteristics. The results show that the coupled system achieves a seasonal performance factor of 2.3, a 56 % reduction in energy consumption, and a 27.7 % reduction in operating costs compared to a conventional gas boiler system. Comparative analysis with the water storage system showed that the system equipped with phase change materials performed well in terms of energy consumption, operating costs and heating stability. In addition, the density of the phase change material has a biased effect on the overall performance of the system. This paper can provide a reference value for the study of renewable energy heating systems in cold zone. [ABSTRACT FROM AUTHOR]

The integration of 5G base station (5G BS) clusters and edge data services introduces novel digital loads (NDLs) into the distribution system (DS), significantly impacting the interactive coordination of 5G-DS. This paper proposes an expansion planning model of 5G and DS considering source-network-load-storage coordination. Here, renewable energy resources (RESs), 5G BS clusters, edge data centers (EDCs), and DS source-network-load-storage are coordinately planned. The dynamic service access of 5G BS cluster are formulated to capture the coupled nature and inherent flexibility of 5G services. Considering the flexible processing of EDCs, a detailed categorization is conducted based on data service type, leveraging the synergies between cloud and edge computing to achieve flexible data load distribution. The original expansion planning model is reformulated as a mixed integer linear programming (MILP) problem to facilitate its computational solution. Simulation results from case studies on Portugal 54 node network over individual expansion planning and 5G static-access are performed to validate the effective and superior performances of the proposed method. Simulations results show that the system cost can be reduced by at most 15% with a higher operational flexibility. [Display omitted] • An expansion planning model of 5G and DS considering source-network-load-storage coordination is proposed. • NDLs from 5G BS clusters and EDCs are introduced to accommodate the RESs. • Dynamic access services of 5G BS clusters are formulated to leverage their flexibility. • Synergies of cloud and edge computing in EDCs are captured to facilitate source-network-load- storage coordination. [ABSTRACT FROM AUTHOR]

Local energy sharing (LES) is a concept that enables sharing between distribution system participants such as consumers, producers, and prosumers at the local level in a transparent and cooperative manner. It can improve local supply-demand balancing, reduce voltage deviations, and improve social welfare. However, the feasibility of such an approach is highly dependent on the regulatory framework and implementation requires investment in an adequate information and communication infrastructure. This paper examines components for the implementation of LES within energy communities in the EU, with a focus on price-forming methods that can be integrated into a net-billing system and adopted for different regulatory set-ups. Further, a method for the assessment of impacts on market participants is provided. The approach is applied for the assessment of the opportunities for LES in the city of Križevci, considering local generation, flexibility options, and real-life regulatory requirements. It is shown that LES under appropriate regulatory provisions can be an effective market-based mechanism for stimulating local generation and flexibility activation, and that way support decarbonization and local self-sufficiency. All members can benefit from participating in the energy community, but the distribution of the benefits notably depends on the applied LES price-forming method. On the other hand, subject to regulatory setup, the trade-offs are reflected on reduced revenues for market participants that generate income based on transmission fees, taxes, and/or surcharges. • Components for local energy sharing (LES) implementation within energy communities. • Framework for feasibility evaluation of LES under different regulatory set-ups. • MILP LES market-clearing model with energy sharing compensation price method. • LES price-forming methods integrated into a net-billing system. • Simulation of LES as a market with a local energy sharing coordinator. [ABSTRACT FROM AUTHOR]

The Philippines is exploring different alternative sources of energy to make the country less dependent on imported fossil fuels and to reduce significantly the country's CO 2 emissions. Given the abundance of renewable energy potential in the country, green hydrogen from renewables is a promising fuel because it can be utilized as an energy carrier and can provide a source of clean and sustainable energy with no emissions. This paper aims to review the prospects and challenges for the potential use of green hydrogen in several production and utilization pathways in the Philippines. The study identified green hydrogen production routes from available renewable energy sources in the country, including geothermal, hydropower, wind, solar, biomass, and ocean. Opportunities for several utilization pathways include transportation, industry, utility, and energy storage. From the analysis, this study proposes a roadmap for a green hydrogen economy in the country by 2050, divided into three phases: I–green hydrogen as industrial feedstock, II–green hydrogen as fuel cell technology, and III–commercialization of green hydrogen. On the other hand, the analysis identified several challenges, including technical, economic, and social aspects, as well as the corresponding policy implications for the realization of a green hydrogen economy that can be applied in the Philippines and other developing countries. • A green hydrogen economy could be feasible in the Philippines. • Renewable energy potential from geothermal, hydropower, wind, solar, biomass, and ocean for green hydrogen production. • Utilization pathways for transport, industry, utility, and energy storage. • The hydrogen economy faces challenges from technical, economic, and social perspectives. • Green hydrogen economy can be achieved by transforming the energy and other sectors to 100% renewables. [ABSTRACT FROM AUTHOR]

Hydrogen energy storage systems (HydESS) and their integration with renewable energy sources into the grid have the greatest potential for energy production and storage while controlling grid demand to enhance energy sustainability. This paper presents a bibliometric analysis based on a comprehensive review of the highly cited articles on HydESS to provide a detailed insight into future directions and applications. The study was carried out by using the Scopus database search engine to look for filtered keywords in the HydESS and related research. It can be demonstrated that the HydESS literature expanded rapidly from 2016 to 2021 compared to 2011 to 2015. It is found that 89.17% of published articles explained control and test systems-based methods, whereas 10.83% of publications discuss review assessments. Our analysis of highly cited articles on HydESS highlights several aspects, such as methods and systems, issues, difficulties, and challenges to establishing current constraints and research gaps. This evaluation can enhance operational performance, environmental friendliness, energy savings, uninterrupted power supply service, cost benefits, on-site generation, and adaptability. It would be beneficial for technology development and the growth of the hydESS industry. This study may act as a guideline not only for academics in determining the line of research and generating additional discoveries, but also for the government in formulating financial strategies. • Top-cited hydrogen energy storage system articles are reviewed under specific conditions. • Hydrogen storage integrated grids have the potential for energy sustainability. • A historical overview of hydrogen storage was analyzed using the Scopus database. • This survey has exhibited a developing hydrogen storage and renewable energy fields of research. • Bibliometric analysis was used to identify potential future research directions. [ABSTRACT FROM AUTHOR]

Electrical Energy Storage (EES) technologies have received considerable attention over the last decade because of the need to reduce greenhouse gas emission through the integration of renewable energy sources. Renewable sources have an intermittent power output to the electrical grid, thus EES represents a strategic solution in balancing electrical grids and enables the decarbonisation of the energy sector. Cryogenic Energy Storage (CES) is a novel method of EES falling within the thermo-mechanical category. It is based on storing liquid cryogenic fluids after their liquefaction from an initially gaseous state. A particular form of CES, Liquid Air Energy Storage (LAES), has gained growing attention respect to other cryogens. The current state of LAES is still at the development and demonstration stage since no commercial or pre-commercial plants have been built. This technology has been developed in different ways throughout its history (from 1977), and, to the best of our knowledge, no review paper has been published so far about the CES topic. Therefore, the present paper intends to provide a clear picture of the CES/LAES virtues in the literature as well as the challenges associated to the system to be commercially viable. For this purpose, this review includes: an investigation of the properties of cryogens and different CES processes as well as the main ways the system could be combined to other facilities to further enhance the energy efficiency, in particular the combination to a refrigerated warehouse with cold energy recovery from the cryogen evaporation. [ABSTRACT FROM AUTHOR]

• A comprehensive operational cost function was established based on the deep peak shaving characteristics of thermal generators. • The impacts of different combinations of renewable energy penetration on the power system operation were analyzed. • The effect of energy storage deployment on improving flexibility in high penetration renewable energy systems were analyzed. Higher proportions of renewable energy are one of the most prominent features of future power systems. However, renewable energy, such as wind and PV power generation, is subject to inherent variability and uncertainty, which leads to fluctuations in electrical production and necessities flexibility enhancement to ensure sufficient adjustable resources responding to such fluctuations. This paper proposes to enhance the flexibility of renewable-penetrated power systems by coordinating energy storage deployment and deep peak regulation of existing thermal generators. First, the growing flexibility requirement in the presence of variable renewable energy is discussed and quantified using proposed indices. Then, we analyze the characteristics of thermal generators providing deep peak regulation, and establish a comprehensive operation cost function including coal consumption, wear-and-tear consumption, and oil consumption of thermal generators. On this basis, we propose a flexibility enhancement method coordinating battery energy storage capacity optimization and deep peak regulation of thermal generators, which aims at minimizing the total investment and operation costs while satisfying operating constraints on representative days. Extensive case studies on a modified IEEE-RST 24 system verified the proposed flexibility enhancement method under different scenarios. [ABSTRACT FROM AUTHOR]

As renewable energy becomes more prevalent in the power grid, energy storage systems (ESSs) are playing an ever-increasingly crucial role in mitigating short-term supply–demand imbalances. However, the operation and control of ESS are not straightforward, given the ever-changing electricity prices in the market environment and the stochastic and intermittent nature of renewable energy generations, which respond to real-time load variations. In this paper, we propose a deep reinforcement learning (DRL) approach to address the electricity arbitrage problem associated with optimal ESS management. First, we analyze the structure of the optimal offline ESS control problem using the mixed-integer linear programming (MILP) formulation. This formulation identifies optimal control actions to absorb excess renewable energy and perform price arbitrage strategies. To tackle the uncertainties inherent in the prediction data, we then recast the online ESS control problem into a Markov Decision Process (MDP) framework and develop the DRL approach, which involves integrating the optimal offline control solution obtained from the training data into the training process and introducing noise to the state transitions. Unlike typical offline DRL training over a long time interval, we employ the Deep Deterministic Policy Gradient (DDPG) and Proximal Policy Optimization (PPO) algorithms with smaller neural networks training over a short time interval. Numerical studies demonstrate the promising potential of the proposed DRL-enabled approach for achieving better online control performance than the model predictive control (MPC) method under different price errors. This highlights the sample efficiency and robustness of our DRL approaches in managing ESS for electricity arbitrage. • Incorporate optimal strategy as prior knowledge by revising the DRL reward. • Employ small neural networks to efficiently train samples and update models. • Utilize noise to enhance error tolerance and reduce distribution shifts' impact. [ABSTRACT FROM AUTHOR]

To increase the share of electricity generation from renewable energies for both grid-connected and off-grid communities, storage systems are needed to compensate for their intermittent nature. Compressed air energy storage (CAES) processes are of increasing interest. They are now characterized as large-scale, long-lifetime and cost-effective energy storage systems. Compressed Carbon Dioxide Energy Storage (CCES) systems are based on the same technology but operate with CO 2 as working fluid. They allow liquid storage under non-extreme temperature conditions. A literature review of this new technology was conducted. The difference between the systems lies in the presence or absence of an external heat source, the thermodynamic state of the stored CO 2 , and the means of heat recovery and utilization. To better understand the wide variety of configurations, they have been classified according to the external heat use and the storage location (underground or aboveground). As there is no dynamic model for liquid storages, one is presented in this paper and bring new challenges that have to be considered in future researches. Also, experimental studies are lacking to validate the CCES behaviour and some components like turbomachines and thermal storages. • Providing an overview of current CCES studies and configurations. • Comprehensive comparison of different CCES categories. • A simplified dynamic model is presented. • CCES is a promising energy storage for renewable energies development. • Pointing out the issues and future needed investigations. [ABSTRACT FROM AUTHOR]

In order to alleviate the resource depletion as well as achieve decarbonization, developing renewable energy system is a feasible solution. This paper establishes a wind-photovoltaic-battery-thermal energy storage hybrid power system, and investigates its multi-objective planning-operation co-optimization. The hybrid system utilizes the cost-effectiveness of thermal energy storage and flexibility of battery to jointly tackle the intermittency of renewable energy. A novel coordinated operation strategy based on the operation threshold of power block is proposed, and the planning-operation co-optimization model considers the minimization of net present cost and loss of power supply probability to determine the optimal operation threshold and sizing decision variables. The co-optimization problem is solved by a proposed multi-objective evolutionary algorithm with decision-making (MOEA-DM), which introduces the preference information of decision-maker to guide the evolution towards preferred region. Furthermore, the uncertainties and losses of wind power are captured by a data-driven forecast model. Finally, the results of case study show that: (1) the data-driven model performs higher accuracy in wind power forecast compared to commonly-used physical models; (2) The proposed MOEA-DM has better convergence, diversity and robustness performance in decision-maker's preferred region compared to widely-used Non-dominated Sorting Genetic Algorithm-Ⅱ (NSGA-Ⅱ); (3) Hybrid battery-thermal energy storage system achieves better economy and reliability through the optimal coordinated operation strategy compared to either single energy storage under different test conditions. [ABSTRACT FROM AUTHOR]

Compressed air energy storage (CAES) systems offer significant potential as large-scale physical energy storage technologies. Given the increasing global emphasis on carbon reduction strategies and the rapid growth of renewable energy sources, CAES has garnered considerable attention. However, the optimal design of CAES systems presents challenges due to the intricate coupling of multiple parameters, complex physical processes, and highly variable operating conditions. This paper comprehensively reviews three key aspects related to CAES optimal design. Firstly, it examines system analysis and optimization methodologies. Secondly, it investigates the off-design characteristics of CAES systems. Lastly, it explores system design methodologies specifically addressing off-design operations. Notably, the corresponding-point methodology (CPM) is proposed as a means to provide clearer guidance for system improvements. Future research should aim to combine CPM with traditional methods to establish more efficient and intuitive system optimization approaches. Furthermore, the exploration of active off-design regulation strategies, including the integration of various adjustment methods and multistage combined regulation for CAES systems experiencing wide load fluctuations, requires further investigation. Novel CAES configurations that enable efficient off-design conditions should also be explored, despite the inherent complexities associated with regulation and control. Finally, a coupled design methodology based on off-design operation data and probabilistic-load factor analysis is presented. This paper provides valuable insights and guidance for the optimal design and study of CAES systems. • CPM combined with traditional methods is needed to improve CAES round-trip efficiency • Not high temperature/pressure but "corresponding" is key factor to high round-trip efficiency • Multiple regulations and new system structure are needed for wide-load operation • Design methodology addressing complex off-design operations needs further improvement [ABSTRACT FROM AUTHOR]

To cope with the uncertainty of electric vehicles(EVs) and renewable energy in VPP, this paper proposes a two-stage robust optimal scheduling method for VPP considering the controllability of electric vehicle group (EVG). Highlights of the work in this paper are presented below: • The study found that the controlled capacity of EVG varies significantly, and the resulting operational benefits obtained by VPP vary significantly. It is recommended that operators should minimise the management of EVG in Category III status and increase the dispatch of EVs in Category I and II status in order to improve the controlled capacity of EVG and obtain more operational benefits. • Increasing the ESS capacity within a certain range can increase the revenue of the VPP, but the optimal capacity of the ESS should be configured is not the same when the controlled capacity of EVG varies. Further analysis reveals that when the total number of EVs and the nominal parameters of the system are constant, the VPP system shown in the paper can find the optimal ESS capacity for obtaining stable gains regardless of the number of EVs of each type. • When the forecast deviation coefficient is large, the day-ahead dispatching scheme for VPP developed by the two-stage robust optimization method has the highest total benefit and the strongest ability to resist fluctuations in WPP and PV output compared to other methods, with obvious advantages. To cope with the uncertainty of electric vehicles and renewable energy in virtual power plant(VPP), this paper proposes a two-stage robust optimal scheduling method for VPP considering the controllability of electric vehicle group (EVG). Firstly, the calculation method of the controlled capacity of EVG is given based on Minkowski's addition idea. Then a two-stage robust optimization model of min-max-min structure considering the controlled capability of EVG is developed, which involves the operational constraints and coordinated control of EVG, energy storage systems, convention gas turbine units, and distributed power sources. Finally, the model is solved based on the column and constraint generation(C&CG) algorithm. The results show that fully exploiting the controlled capabilities of EVG can help VPP optimize scheduling schemes and improve the economics of operation. [ABSTRACT FROM AUTHOR]

The potential role of hydrogen as a tool for the decarbonization of the energy sector is widely recognized. In this paper, a comprehensive analysis of the marginal utility of increasing the hydrogen penetration on the energy and environmental performances of a multi-energy system is developed to assess its potential. A distributed energy system satisfying the energy requirements for an existing building is chosen as test case, assumed as representative of a wide set of applications. Starting from real energy consumption profiles, representative scenarios and optimized design configurations are defined using a methodology that takes into account uncertainties both in demand and renewable production profiles and in techno-economic parameters assumptions. For each multi energy system configuration, an optimal dispatch control strategy is achieved through a mixed-integer linear programming method to maximize the building self-independence from the grid. Results show how an increase of hydrogen technologies penetration allows a reduction of the specific carbon footprint of the system down to 100 grCO 2 /kWh while increasing the system resilience up to 85%. Detailed information about the marginal effect of H 2 technologies on resilience, carbon footprint, and fossil energy savings are presented and can be used for extensions to similar applications. • Resilience up to 85% is achieved through hydrogen integrated multi-energy system. • Specific carbon footprint is reduced up to 100grCO 2 /kWh. • Uncertainties are accounted through a coupled clustering-Montecarlo approach. • Hydrogen seasonal storage is crucial for decarbonization of the energy system. [ABSTRACT FROM AUTHOR]

The combined operation of renewable energy and pumped storage unit (PSU) has become an important researching tendency in rural electrification, for handling the variable characteristics of power as well as load demand, particularly in standalone applications. Recently, adjustable-speed pumped storage unit (ASU) has been developed as an evolutionary version of fixed-speed pumped storage unit (FSU) due to its adjustable power in pumping mode, larger output range and higher efficiency in generating mode, but presents an increased capital outlay in terms of equipment. Therefore, it is a meaningful topic to appraise the economic benefit of using ASU as energy storage device for the hybrid system, which has rarely been studied quantitatively. In this paper, a scheduling model composed of a photovoltaic generator, a wind turbine, a diesel generator and a PSU, is presented and the technical features of two different PSUs are analysed. The main purpose of the proposed model is to highlight the potential of the ASU to reduce the operation cost for the developed hybrid system. The simulations have been carried out using Cplex called by Matlab. Two scenarios are investigated, including a summer and a winter case. The results show that using the ASU for the developed hybrid system, 46.7% fuel can be saved on a summer day and 11.24% fuel saving can be achieved on a winter day compared to the case where the FSU is used as the energy storage device. [ABSTRACT FROM AUTHOR]

This paper is a critical review of selected real-world energy storage systems based on hydrogen, ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics, control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible, they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes, hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However, there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally, it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with short-term energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system. Therefore, control systems and energy management strategies are important factors to achieve optimal results, both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems, new hybrid energy systems could be tailored to fit each situation and to reduce energy losses. • Review of 15 projects that use hydrogen as energy storage in a power system. • Hydrogen is one of very few alternatives for long-term electricity storage. • Hydrogen storage should in most cases be combined with battery storage. • Power-to-gas-to-power for hydrogen still has a low energy efficiency (15–40%). • Intermittent in-flow of energy and high costs are big challenges for these systems. [ABSTRACT FROM AUTHOR]

Over the past years, hydrogen has been identified as the most promising carrier of clean energy. In a world that aims to replace fossil fuels to mitigate greenhouse emissions and address other environmental concerns, hydrogen generation technologies have become a main player in the energy mix. Since hydrogen is the main working medium in fuel cells and hydrogen-based energy storage systems, integrating these systems with other renewable energy systems is becoming very feasible. For example, the coupling of wind or solar systems hydrogen fuel cells as secondary energy sources is proven to enhance grid stability and secure the reliable energy supply for all times. The current demand for clean energy is unprecedented, and it seems that hydrogen can meet such demand only when produced and stored in large quantities. This paper presents an overview of the main hydrogen production and storage technologies, along with their challenges. They are presented to help identify technologies that have sufficient potential for large-scale energy applications that rely on hydrogen. Producing hydrogen from water and fossil fuels and storing it in underground formations are the best large-scale production and storage technologies. However, the local conditions of a specific region play a key role in determining the most suited production and storage methods, and there might be a need to combine multiple strategies together to allow a significant large-scale production and storage of hydrogen. • Large-scale production and storage of hydrogen are presented. • Renewable hydrogen is summarized. • Non-renewable hydrogen is discussed. • Natural underground hydrogen storage is presented. [ABSTRACT FROM AUTHOR]

This paper is an Editorial for the special issue (SI) of Energy Reviews (RSER) dedicated to the 10th International Conference on Sustainable Energy and Environmental Protection SEEP, held in Bled-Slovenia. During the conference more than 300 papers were presented, around 25% of these papers were accepted for this special issue. Papers discussed different topics related to renewable energy, energy storage systems and some environmental issues related to transportation. During this conference Prof Olabi presented a keynote talk on the relation between circular economy and renewable energy, case studies about implementing this concept in Scotland were included in his presentation. This editorial will give a short description on the relation between circular economy and renewable energy, then it will be followed by addressing the accepted papers in this special issue. [ABSTRACT FROM AUTHOR]

Abstract In recent years, providing green and reliable energy supply to islands has appeared in the strategic plans of many countries. This paper introduces three representative island microgrids that have been built and are operating in the East China Sea. Key technologies of the island microgrids are discussed, including the analysis of island resources and load, selection of energy storage, control strategies, and energy management systems. Through analyzing their operation data for one year, this paper demonstrates the impacts of the three microgrids from the perspectives of technology, economics, and sustainability. Summarizing the experiences and insights gained from their construction and operation, this paper provides references for the future development of island microgrid projects. Highlights • Three representative island microgrids in the East China Sea are demonstrated. • Key technologies such as control technology and energy management for island microgrids are studied. • Renewable energy penetration is discussed for the design and operation of island microgrids. • The operation data for a year of the three island microgrids are analyzed from various aspects. • Experiences and insights gained from the construction and operation are presented. [ABSTRACT FROM AUTHOR]

The aim of this paper is to present options to make low-carbon footprint large-scale desalination a reality on arid islands with weak electrical grids. Through these options, the goal is to reconfigure on-grid wind energy/desalination systems for large- and medium-scale water production. In this context, it is proposed to use lithium-ion batteries for stationary energy storage together with management strategies aimed at avoiding the wind energy/desalination systems having to consume energy from the conventional grid they are connected to. The control strategy is based on ensuring that the power provided by the wind farm and batteries remains in synchrony with the power demand of the desalination plant throughout the system's useful life. The interannual variation of wind energy is considered when sizing the renewable energy system and processes for its estimation are proposed. The case study is centred on the Canary Archipelago, a region that is especially vulnerable to the impacts of climate change, but which enjoys exceptional characteristics for the exploitation of wind energy. The results obtained show the optimal wind farm and energy storage system capacities of the analysed configurations. The approach presented allows a low-carbon operational footprint. If the control strategy were to be put into practice today, the current grid restrictions and a life cycle assessment of the system carried out in a societal context that continues to be fossil fuel dependent indicate a potential reduction of 77.4% of the footprint. However, the remaining 22.6% could be eliminated in the future when the manufacturing processes of wind turbines, batteries and desalination plants receive the benefits of carbon-neutral societies. [Display omitted] • A method for achieving large-scale, low-carbon desalination is presented. • Optimal wind farm and storage capacities for the system are determined. • The method offers substantial CO2 emission reduction potential. • Using climate ERA5 reanalysis data, enhances robustness by addressing wind variability. • Proposed adjustments enhance adaptability to technological advances and future scenarios. [ABSTRACT FROM AUTHOR]

Future energy system will feature in a high-share of renewable energies (REs), which poses huge challenges to obtain full utilization of renewable power generation. To solve the problem, this paper presents a joint-operation two-stage mixed integer linear programming model to coordinate the power system and train transportation system by optimizing the logistics of mobile batteries and real-time charge/discharge in cities. The full/empty batteries are transported through the train transportation system between the load side and the renewable energy station, which improves renewable energy penetration, economics, and mobilities. The first-stage model deals with the preliminary logistic optimization of batteries including routes, time and capacities of transportation, and the second-stage model optimizes real-time schedule of charge/discharge of batteries. The aim of the proposed model is to minimize the transportation cost, maximize the utilization rate of renewable energy in an energy system and smooth the daily load curve. The proposed model considers technical constraints such as railway transportation capacity, load demand satisfaction and renewable energy consumption in the power system. The optimal logistics plan and real-time charging and discharging plan can be obtained for both full and empty battery transportation. The validity of the method is verified with real data from Northeast China and Northern China, including railway routes, renewable energy output, and load profiles. The results show that the renewable energy penetration rate increases from 84.4% to 95.3% in Northeast China and from 42.7% to 78.2% in Northern China under the 2050 scenario with the proposed method. The peak-to-valley difference in the daily load curve decreases by 84% and 100% in Northeast China and Northern China, respectively. Meanwhile, the case study shows that the costs of battery transportation decrease from 0.398 CNY/kWh and 0.377 CNY/kWh to 0.252 CNY/kWh and 0.254 CNY/kWh when energy density of battery increases from 0.170 kWh/kg to 0.250 kWh/kg. This indicates that mobile energy storage has great economics. Moreover, renewable energy penetration rate is increased and peak-to-valley difference of daily load curve is decreased with no additional transmission lines. The model moves renewable energy from renewable energy power plants to end users. [Display omitted] • MESS aims to solve uneven spatio-temporal distribution of renewable energy and load. • A framework for joint operation of power system and transportation system is proposed. • The model is validated based on real data from Northeast and North China. [ABSTRACT FROM AUTHOR]

The concept of shared energy storage in power generation side has received significant interest due to its potential to enhance the flexibility of multiple renewable energy stations and optimize the use of energy storage resources. However, the lack of a well-set operational framework and a cost-sharing model has hindered its widespread implementation and large-scale development. This paper introduces three distinct cost-sharing methods, namely the uniform allocation method, the predictive weighted allocation method, and the dynamic weighted allocation method, which are laterly applied to develop a combined operational and cost distribution model. The objective is to improve the efficiency of the power generation system by incorporating shared energy storage assistance and allocating the associated costs based on the use of various renewable energy stations. Furthermore, the viability of the suggested operational framework for shared energy storage and the methods for allocating costs are confirmed through numerical simulation. The findings indicate that the uniform allocation method represents the most straightforward approach for distributing costs evenly. In contrast, the second model introduces a cost allocation method that addresses the issue of fairness by considering the predicted generation level of each renewable energy plant. However, the third model takes into account the actual generation level of the plants when determining their respective costs. Sensitivity analysis is further conducted to offer valuable insights into cost-saving policies for four representative regions in China. The proposed operation and cost-sharing model is anticipated to serve as a useful reference for the widespread implementation of shared energy storage in power generation side. • Design three cost-sharing methods to allocate costs among various entities. • Formulate a combined operational and cost allocation model. • Optimize operational and cost allocation strategies for various entities. • Reduce total costs by up to 36% through the dynamic weighted allocation method. [ABSTRACT FROM AUTHOR]

Large-scale renewable integration presents an effective way to decarbonize power grids, but carries increased risk of supply shortfalls owing to its volatility and uncertainty. Storage is a promising option to improve the generation adequacy of renewable. Thus, capacity credit assessment of renewable and storage is crucial in ensuring adequate generation capacity to meet loads. However, efficiently and accurately assessing capacity credit of these resources is challenging due to temporal dependencies in the operational time series (net loads and conventional generation units) and the need for extensive operation simulations. This paper develops a comprehensive multi-time-scale assessment framework integrating analytical and simulation methods to calculate the capacity credit of renewable and storage, thus capturing temporal features of these time series. Then, an interval-based strategy is proposed to simulate system operations, incorporating demand response in key scenarios. Furthermore, partitioning around medoids clustering and parallel computing techniques are employed to greatly accelerate the numerous operations for capacity credit assessment. The proposed method is validated using the RTS-79 system and a provincial real-world power grid in China. The results indicate that the developed framework can achieve efficient and refined capacity credit assessment and thus evaluate the impact of storage on the capacity credit. • Propose a novel method to quantify temporal features of operational time series for capacity credit (CC) assessment. • Develop a multi-time-scale CC assessment framework with an interval-based strategy to capture temporal features. • Utilize partitioning around medoids clustering and parallel computing to greatly enhance calculation efficiency. [ABSTRACT FROM AUTHOR]

Residential communities are increasingly adopting renewable energy sources (RES) to minimize energy consumption costs. However, these RES are weather-dependent and uncertain, posing challenges to ensuring reliable operations. Addressing the uncertainties in power supply management becomes a critical research question. Energy storage systems play a crucial role in providing battery-powered supply for residential loads under uncertain conditions. The operation of microgrids is directly influenced by uncertainties. This paper proposes data-driven-based net load uncertainty quantification fusion mechanisms for cloud-based energy storage management with renewable energy integration. Firstly, a fusion model is developed using SVR, LSTM, and CNN-GRU algorithms to estimate day-ahead load and PV power forecasting errors. After that, two mechanisms are proposed to determine the day-ahead net load error. In the first mechanism, the net load error is directly forecasted, while in the second mechanism, it is derived from the forecast errors of load and PV power. The net error analysis is conducted with a statistical mean and standard deviation, resulting in different uncertainty-bound confidence intervals around the forecasted value. Subsequently, the cloud energy storage system operation cost is calculated with the best uncertainty quantification mechanism for two different case studies. This approach allows for better management of uncertainties in energy storage systems and enables more informed decision-making under varying conditions. • Learning-based fusion algorithm for net load forecasting. • Develop uncertainty mechanism for uncertainty quantification. • Economic assessment of cloud energy storage. [ABSTRACT FROM AUTHOR]

• The state-of-the-art research advances in power system restoration with large renewable penetration are reviewed from different system levels, i.e., transmission system, distribution system, and coordinated transmission and distribution system. • The methods of handling renewable power uncertainty during system restoration are summarized. • The laboratory validations and practical applications of the renewable power system restoration strategies are reviewed. • Promising research directions for renewable system restoration are provided, including uncertainty handling, artificial intelligence techniques, transient stability issues, cyber-physical interlinking, and multi-energy coupling. The catastrophic blackout events and ever-increasing penetration of renewable power generation highlight an advanced restoration strategy to effectively and reliably employ renewable power generation to contribute to renewable power system restoration. This paper reviews the research advances of power system restoration involving large renewable penetration, and the methods of handling renewable power uncertainty during restoration are also summarized. First, the transmission system restoration processes are divided into three sequential stages: a) black-start, b) network reconfiguration and c) load restoration, and the research advances of these three restoration stages involving large renewable generation are presented. Then, the distribution system restoration assisted by multiple flexible resources, such as renewable distributed generators, remotely-controlled switches, energy storage systems, and soft open points, are reviewed with emerging techniques, including micro-grids, multi-agent systems, repair crews, and mobile power sources. Furthermore, with the growing activeness and flexibility of the distribution system, the coordinated transmission and distribution system restoration and their information interactions are also discussed. Finally, for practical applications, the laboratory validations of restoration strategies using realistic power grid data, real-world restoration strategies, decision support systems, and field tests of black-start procedures are introduced to complete this literature review. Effectively deploying renewable power sources can significantly improve the power system restoration efficiency, and their inherent uncertainty should be carefully handled. Moreover, promising research trends are provided to improve the power system restoration with large renewable penetration. [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]

This paper compares different strategies to transform the heating sector into a future 100% renewable energy solution. It focuses on the consequences for infrastructures in terms of grids and storage across the electricity, gas and heating sectors. The hypothesis is that these consequences are rarely taken into proper consideration, even though the costs are significant and differ substantially between the alternative pathways. While the smart grid scenarios are based on electricity as an energy carrier, the “smart energy systems” approach is based on a cross-sectoral use of all grids. Using Denmark as a case, this paper shows how the current gas and district heating grids each have twice the capacity of the electricity distribution grid. Moreover, the existing gas and thermal storage capacities are substantially higher and the additional future capacities are more affordable than within the electricity sector. The conclusion is that the “smart grid” pathway requires a 2–4 times expansion of the electricity grid and significant investments in electricity storage capacities, while the “smart energy systems” pathway can be implemented with relatively few investments in affordable minor expansions of existing grids and storage capacities. [ABSTRACT FROM AUTHOR]

Energy demands, environmental impacts of energy conversion, and the depletion of fossil fuels are constant topics of discussion in the energy industry. Renewable energy technologies have been proposed for many years to address these concerns. However, the transformation from traditional methods of power generation, usually based on fossil fuels, to power generation based on renewable resources presents many challenges associated with emerging, or less established, technologies. This paper examines the role of renewable energy in the U.S. and its potential to meet current and future energy needs in a way that is technically and economically sound. Renewable energy technologies, ranging from well-developed and established to new and emerging technologies, are presented in terms of their technical potential, current state of the technology, potential for further growth, and economic potential. While renewable energy sources are abundant across the U.S., issues of dispatchability, variability, scalability, energy storage, geographic limitations, and investment costs are critical in determining future progress. The analysis in this paper can be used to guide the integration of renewable energy systems toward becoming a larger share of energy production. [ABSTRACT FROM AUTHOR]

Electricity powered vehicles/Electric vehicles using renewable energy are becoming more and more popular, since they have become an effective way to solve energy shortage, and environmental pollution. Battery electric vehicles with zero emission characteristics are being developed on a large scale. With the scale of electric vehicles, electric vehicles with controllable load and vehicle-to-grid functions can optimize the use of renewable energy in the grid. This puts forward the higher request to the battery performance. The energy density of the batteries and renewable energy conversion efficiency have greatly also affected the application of electric vehicles. This paper presents an overview of the research for improving lithium-ion battery energy storage density, safety, and renewable energy conversion efficiency. It is discussed that is the application of the integration technology, new power semiconductors and multi-speed transmissions in improving the electromechanical energy conversion efficiency, and the issues and challenges of increasing battery energy density. In order to improve the safety, it is analyzed how to improve the estimation accuracy and temperature control performance of the battery management system. As the demand for fast charging and renewable energy of electric vehicles increases, the latest developments and technical challenges of on-board rapid charging technology are introduced. • We present an overview on energy storage density and energy conversion efficiency of electricity powered vehicles. • Methods to increase the energy storage density of electricity powered vehicles are proposed. • Efficient inverter and multi-speed transmission improving renewable energy conversion efficiency are discussed. • The integration improves the energy efficiency of electricity powered vehicles. • Integrated fast charging and coordinated charging for renewable energy are discussed. [ABSTRACT FROM AUTHOR]

Facilitated by advanced information and communication technologies (ICTs), local energy trading develops rapidly, playing an important role in the energy supply chain. Thus, it is essential to develop local trading models and strategies that can benefit participants, not only stimulating local balancing but also promoting renewable penetration. This paper proposes a new local energy trading decision-making model for suppliers by using the Cournot Oligopoly game, considering the uncertainty costs of renewable energy. Four types of representative energy providers are modelled, traditional thermal generation, wind power, photovoltaic (PV) power, and electricity storage. The revenue of these technologies is extensively formulated according to their operation cost, investment cost, and income from selling energy. The uncertainty cost of renewable generation is integrated into the trading, modelled as a penalty for potential energy shortage that is derived from output probability distribution function (PDF). This trading model is formulated as a non-cooperative Cournot oligopoly game to enable energy suppliers to maximize their profits through local trading considering price. The response of the customer to energy price variations, i.e. demand elasticity, is also included in the model. A unique Nash equilibrium (NE) and optimum strategies are derived by the proposed Optimal-Generation-Plan (OGP) Algorithm. As demonstrated in a typical local market, the proposed approach can effectively model and resolve multiple suppliers' competition in local energy trading. It can work as a vehicle to facilitate the trading between various generation technologies and customers, realising local balancing and benefiting all market participants with enhanced revenue and reduced energy bills. • A non-cooperative trading model in local market by Cournot Oligopoly game. • Business models for four typical energy providers to formulate their behaviours. • A penalty for renewables to deal with their uncertainties issue in energy trading. • A OGP algorithm to find the optimal trading strategies to maximize their revenues. [ABSTRACT FROM AUTHOR]

The fluctuation and intermittence of renewable energies are raising concerns about the economical scheduling and the security operation of power system. The shift from traditional fossil energies to renewable energies causes the shortage in rotational inertia and affects the frequency stability of power system. One of the promising solutions is to construct a certain number of energy storage facilities with virtual inertia in suitable places for improving stability, which simulates the characteristics of traditional generators through specific controls over the converters of energy storages. While transient issues about the optimal allocation of energy storages have not been well addressed. From the perspective of system inertia support, the system state-space model is firstly established in this paper. Then the guidance of allocating energy storages optimally is provided via ℋ 2 -norm calculation and projected gradient derivation. Moreover, for the purpose of evaluating system disturbances more precisely, an appropriate method for equivalenting the disturbance strength of nodes is proposed, the advantages of which are later examined in comparative simulations. The contribution of this paper is verified through the time-domain simulations of the New England 39-bus system together with the illustration and comparative analysis of the optimal results. • Construct the guidance of allocating energy storages optimally for inertia support. • Propose a method for equivalenting node disturbance and its transmission mechanism. • The proposed method can improve both transient performance and allocation costs. [ABSTRACT FROM AUTHOR]

A user-on-demand power source based on renewable energy requires storage devices to balance power sources and power demands because of the fluctuation of power sources like solar cells or wind power generators. The role of the control system is defined as two different tasks: allowing a power-flow imbalance between demand and power sources; and balancing the power flow inside the system. Since this control is complicated, many control methods using precise calculation of the power balance have been proposed. An analogue-like distributed control method - named "modified DC-bus signalling" - for controlling a renewable-energy power source without the need for a central processing unit is proposed. The modified DC bus signalling method discussed in this paper is composed of a DC-bus line connected with a battery, water-splitting electrochemical cell, and a fuel cell for hydrogen-energy storage via converters. The proposed control method was demonstrated to be able to control step-like and random changes in input and output power. The battery compensated high-frequency fluctuations in power demand, and the electrochemical cell and fuel cell handled the remaining low-frequency ones, which were matched to their response speeds. • The energy storage system to keep the demand and supply balance of electric power. • Modified DC-bus signaling control for battery and hydrogen storage. • The battery is for fast response and hydrogen storage is for slow and large energy change. • The energy compensation observed even at the step-like change of demand and supply. [ABSTRACT FROM AUTHOR]

Decarbonization of the energy sector calls for new energy sources and power-system operation paradigms. In this context, consumers can partake in system operation as loads and generators by leveraging own resources, such as rooftop photovoltaics (PVs). These prosumers can be gathered into energy communities (ECs) and operated in a centralized manner to exploit eventual synergies optimally. The ECs are usually connected to a distribution network and thus interact with the distribution grid operator (DSO), complicating the scheduling strategies under agent interactions. Moreover, the DSO can thus manage his own resources such as distributed generators or medium-scale storage systems. The operation becomes more complex due to multi-source uncertainties in ECs and DSO. This paper addresses this issue by developing a novel bi-level energy management framework for the robust optimal coordination of ECs and DSO against uncertainties. In this framework, the upper-level agents provide the information by solving the designed optimization problems for the EC operation, sending it to the lower-level agents to facilitate the optimal scheduling of distributed assets. In particular, a novel robust reformulation of the lower level problem is proposed, to handle with uncertainties in renewable generation, demands, and energy prices fixed by the local retailer. The resulting formulation is mixed-integer-linear programming that is efficiently manageable by common solvers. Simulation results on the standard IEEE 33-bus distribution system with six connected ECs and various distributed assets (e.g., renewable generators and storage systems) demonstrate the effectiveness and robustness of the proposed framework. The results also evidence the vital role of storage systems in maximizing the DSO's profits while reducing the ECs' operating costs. [ABSTRACT FROM AUTHOR]

Building a multi-energy complementary power generation system is a viable way to encourage the use of renewable energy and decarbonize power generation. However, the intermittent nature of renewable power generation, such as photovoltaic and wind power, has prompted concerns regarding power grid stability. To balance such fluctuations, energy storage systems or other flexible power generation technologies should be integrated. In this paper, the peak regulation ability of integrated solar combined-cycle has been enhanced via employing a gas/oil exchanger between the top and bottom cycle. When integrating high penetration intermittent renewable energy, an appropriate operational strategy towards high-quality steady power output regulation is proposed. Dynamic performance analysis of the system, coupled characteristic of heat and mass transfer between subsystems have been highlighted. The case study demonstrates that fluctuations of the multi-energy complementary system power output can be controlled below 0.3 MW without renewable energy curtailment, even though wind-PV power generation fluctuates from 0.3 MW to 26.1 MW with variations per second reaching −2.8/3.7 MW. Furthermore, the system's levelized cost of electricity is down to 0.0512 $/kWh, which is cost-competitive with conventional power generation technologies. • Combination of integrated solar combined cycle with wind and PV power plant. • Power stability of system with high penetration intermittent energy. • Novel system configuration and operation strategy. • Deviations from target power output below 0.3 MW per second. [ABSTRACT FROM AUTHOR]

In 100% renewable energy systems, the requirements for flexibility will be greater than for traditional carbon-based energy systems. New technologies and system setups are needed to provide flexibility for balancing the system. Implementing electricity storages in the energy system could provide parts of the required flexible demand and production, though most of these storage solutions have been shown to have relatively high costs. So-called Carnot batteries have been shown to have a relatively lower cost than traditional batteries, but at a reduced electric efficiency. This paper investigates to what extent large-scale integration of Carnot batteries has a role in the transition to and the operation of 100% renewable energy systems. By implementing Carnot batteries in a 100% renewable energy scenario for Denmark, the energy system effects are identified. The results indicate that the potential economic benefit could be as high as 60.5–66.2 EUR/MWh e discharged, not including costs related to investment as well as operation and maintenance of the Carnot batteries. Thus, large-scale integration of Carnot batteries must perform below this economic threshold to be economic relevant. Existing concepts for stand-alone Carnot batteries are not able to achieve these costs today, therefore solutions for cost reductions should be investigated. • Electricity storages could provide parts of future required system flexibility. • Most of these storage solutions have been shown to have relatively high costs. • Carnot batteries have a relatively lower costs but at reduced electric efficiency. • Large-scale integration of Carnot batteries is tested in a renewable energy system. • Carnot battery concepts should aim for a cost lower than 60.5–66.2 EUR/MWh e. [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]

This paper deals with an optimal battery energy storage capacity for the smart grid operation. Distributed renewable generator and conventional thermal generator are considered as the power generation sources for the smart grid. Usually, a battery energy storage system (BESS) is used to satisfy the transmission constraints but installation cost of battery energy storage is very high. Sometimes, it is not possible to install a large capacity of the BESS. On the other hand, the competition of the electricity market has been increased due to the deregulation and liberalization of the power market. Therefore, the power companies are required to reduce the generation cost in order to maximize the profit. In this paper, a thermal units commitment program considers the demand response system to satisfy the transmission constraints. The BESS capacity can be reduced by the demand response system. The electric vehicle (EV) and heat pump (HP) in the smart house are considered as the controllable loads of the demand side. The effectiveness of the proposed method is validated by extensive simulation results which ensure the reduction of BESS capacity and power generation cost, and satisfy the transmission constraints. [ABSTRACT FROM AUTHOR]