Search Results (284)

Modular multilevel converters (MMCs) are widely used in power-conversion applications, including distributed energy storage integration, because of their scalability, high efficiency, and reduced harmonic distortion. Integrating battery storage systems into MMC submodules using dual active bridge (DAB) converters provides electrical isolation and reduces voltage stress, harmonics, and common-mode issues. However, voltage fluctuations due to the battery state of charge can compromise the zero-voltage switching (ZVS) operation of a DAB and increase the reactive power circulation, leading to higher losses and reduced system performance. To address these challenges, this study investigated an active control strategy for submodule voltage regulation in an MMC with DAB-based battery integration. Assuming single-phase-shift modulation, two control strategies were evaluated. The first strategy regulated the DAB voltage on one side to match the battery voltage on the other, scaled by the high-frequency transformer turns ratio, which facilitated the ZVS operation and reduced the reactive power. The second strategy optimized this voltage to minimize the total power-conversion losses. The proposed control strategies improved the efficiency, particularly at low power levels, achieving several percentage points of improvement compared to maintaining a constant voltage. Full article

With the increasing penetration of distributed generation and the diversification of electrical equipment, distribution networks face issues like three-phase unbalance and harmonic currents, while the voltage stability and inertia of the grid-connected system also decrease. A certain amount of energy storage is needed in a Distribution Static Synchronous Compensator (DSTATCOM) to manage power quality and actively support voltage and inertia in the network. This paper first addresses the limitations of traditional $dq0$ compensation algorithms in effectively filtering out negative-sequence twice-frequency components. An improved $dq0$ compensation algorithm is proposed to reduce errors in detecting positive-sequence fundamental current under unbalanced three-phase conditions. Second, considering the impedance ratio characteristics of the distribution network, while reactive power voltage regulation is common, active power regulation is more effective in high-resistance distribution networks. A grid-forming model-based active and reactive power coordinated voltage regulation method is proposed. This method uses synchronous control to establish a virtual three-phase voltage internal electromotive force, forming a comprehensive compensation strategy that combines power quality improvement and active voltage support, exploring the potential of energy storage DSTATCOM applications in distribution networks. Finally, simulation and experimental results demonstrate the effectiveness of the proposed control method. Full article

In this paper, a detailed review of electric vehicle (EV) charging station architectures is first presented, and then an optimal architecture suitable for a large MW-scale EV fast-charging station (EVFS) with multiple fast chargers is proposed and evaluated. The study examines various EVFS architectures, including those currently deployed in commercial sites. Most EVFS implementations use either a common AC-bus or a common DC-bus configuration, with DC-bus architectures being slightly more predominant. The paper analyzes the EV charging and battery energy storage system (BESS) requirements for future large-scale EVFSs and identifies key implementation challenges associated with the full adoption of the common DC-bus approach. To overcome these limitations, a novel multi-zone EVFS architecture is proposed that employs an optimal combination of isolated and non-isolated DC-DC converter topologies while maintaining galvanic isolation for EVs. The system efficiency and total power converter capacity requirements of the proposed architecture are evaluated and compared with those of other EVFS models. A major feature of the proposed design is its multi-zone division and zonal isolation capabilities, which are not present in conventional EVFS architectures. These advantages are demonstrated through a scaled-up model consisting of 156 EV fast chargers. The analysis highlights the superior performance of the proposed multi-zone EVFS architecture in terms of efficiency, total power converter requirements, fault tolerance, and reduced grid impacts, making it the best solution for reliable and scalable MW-scale commercial EVFS systems of the future. Full article

Thermal energy storage technologies are essential for balancing energy demand and supply. There are three main types: sensible heat, latent heat, and thermochemical energy storage. Among them, thermochemical energy storage offers the highest energy density (1–3 GJ/m³) and long-term storage capability. Salt hydrates have attracted attention as energy storage materials due to their low cost, wide availability, and operating temperatures being well-suited for residential and low-temperature applications. This review focuses on the use of salt hydrates in sorption-based thermochemical energy storage systems. It summarizes the current state of knowledge, including screening studies of various salt hydrates, their thermodynamic and operational limitations, advantages, and performance in composite materials. This review also covers recent projects and common reactor designs used in TCES applications. Based on the literature analysis, the most promising salt hydrates for sorption-based TCES systems include SrCl₂, SrBr₂, K₂CO₃, MgSO₄, MgCl₂, and CaCl₂. Despite the high theoretical energy density of many salt hydrates, future work should focus on experimental studies in large-scale reactor systems to better evaluate the practical discharge behavior of the energy storage system beyond theoretical hydration enthalpies or small-scale thermal analyses. Full article

The hydrogen (H₂) economy is seen as a crucial pathway for decarbonizing the energy system, with green H₂—i.e., obtained from water electrolysis supplied by renewable energy—playing a key role as an energy carrier in this transition. The growing interest in H₂ comes from its versatility, which means that H₂ can serve as a raw material or energy source, and various technologies allow it to be produced from a wide range of resources. Environmental impacts of H₂ production have primarily focused on greenhouse gas (GHG) emissions, despite other environmental aspects being equally relevant in the context of a sustainable energy transition. In this context, Life Cycle Assessment (LCA) studies of H₂ supply chains have become more common. This paper aims to compile and analyze discrepancies and convergences among recent reported values from 42 scientific studies related to different H₂ production pathways. Technologies related to H₂ transportation, storage and use were not investigated in this study. Three environmental indicators were considered: Global Warming Potential (GWP), Energy Performance (EP), and Water Consumption (WF), from an LCA perspective. The review showed that H₂ based on wind, photovoltaic and biomass energy sources are a promising option since it provides lower GWP, and higher EP compared to conventional fossil H₂ pathways. However, WF can be higher for H₂ derived from biomass. LCA boundaries and methodological choices have a great influence on the environmental indicators assessed in this paper which leads to great variability in WF results as well as GWP variation due credits given to avoid GHG emissions in upstream process. In the case of EI, the inclusion of energy embodied in renewable energy systems demonstrates great influence of upstream phase for electrolytic H₂ based on wind and photovoltaic electricity. Full article

Nowadays, the rise of DC loads along with distributed energy resources (DERs) and energy storage systems (ESSs) have led to a growing interest in using direct current (DC) microgrid systems. Conventional droop control methods face significant limitations when applied to parallel-connected distributed generation (DG) units, particularly in achieving balanced power sharing and minimizing voltage deviations. To overcome this issue, an enhanced power sharing control method is proposed in this paper to address load sharing in parallel-connected DG units based DC microgrids, considering unmatched line impedance and load variation. The enhanced control method aims to achieve balanced load power sharing and voltage control through the use of a Luenberger observer to estimate the Point of Common Coupling (PCC) bus voltage and accordingly estimate the voltage deviation. The proposed method compensates for the effects of unmatched line impedances and dynamic load variations, enabling accurate power sharing and precise DC bus voltage regulation. Various scenarios are studied to evaluate the performance of the proposed method under different operating conditions including system and load parameters variations. Finally, the performance of the proposed control method was validated through real-time simulation using OPAL-RT target, and compared with conventional droop control approaches. Full article

Ionic liquids (ILs) have attracted increasing attention due to their unique physicochemical properties. Among them, 1-Methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl)imide, emerges as an ideal candidate for fundamental studies in electrochemical applications. This work aims to deepen the understanding of its conductivity performance, and potential interaction with added metal salts, providing insight into its applicability in advanced energy storage systems. Firstly, binary mixtures with ethylene carbonate have been prepared to improve the transport properties and select the optimal concentration of both components. Subsequently, lithium salt was added to design the adequate electrolyte. The thermal and electrochemical characterisation of these mixtures was performed by differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and Broad Band Dielectric Spectroscopy (BBDS). The results reveal a wide liquid range for the ternary systems studied, extending below −80 °C and above 120 °C. Additionally, they exhibit notably high conductivity values at room temperature (ranging from 0.2 S·m⁻¹ for the most concentrated to 0.70 S·m⁻¹ for the lowest concentrated), which highlights their suitability for advanced electrochemical applications, including but not limited to batteries. This extended liquid phase mitigates, or potentially eliminates, some of the most common issues associated with current electrolytes, such as undesired crystallisation at low temperatures. In this paper, a new promising electrolyte, consisting of a ternary mixture obtained by adding lithium salt to the eutectic composition of [C₃C₁Pyrr][TFSI] and ethyl carbonate is proposed. Full article

With the rapid growth of renewable energy generation capacity, integrating thermal power units and renewable energy units at the point of common coupling (PCC) as a coupling system (CS) can significantly enhance the operational reliability and economic efficiency of modern power systems. To better reflect the coordinated operational capability of thermal power units with molten salt thermal storage retrofit (TPUMSTSR) in multi-coupling system (MCS) scheduling, this study proposes a multi-stage optimization-based dispatch method for MCSs. First, rapid load variation (RLV) technology and thermal storage retrofitting are combined to establish a thermal power unit operation model incorporating molten salt thermal storage (MSTS) retrofits under RLVs. Based on this, a three-stage economic dispatch optimization method is proposed to maximize the daily comprehensive generation revenue of MCSs while dynamically allocating peak regulation (PR) revenue costs across different time periods to relax and simplify nonlinear objectives and constraints in the optimization process. Finally, a simulation study is conducted on an MCS in northeast China. The results demonstrate that the proposed flexibility retrofit scheme and optimization algorithm enable a more coordinated and economically efficient dispatch strategy. Full article

The urgent need for climate change mitigation has increased the focus on reducing embodied carbon and energy, particularly in the construction sector. Utilizing sustainably sourced mass timber products provides a low-carbon alternative to traditional concrete and steel structural systems in buildings. These carbon impacts can be quantified by evaluating the total environmental impact of a building, from material extraction and product manufacturing to construction, operation, and demolition. This study evaluated the environmental impacts of a 14-storey mass timber–steel hybrid building in Madison, USA, through a Whole-Building Life Cycle Assessment (WBLCA) using the Tally LCA tool integrated with Autodesk Revit. The hybrid design was compared to full mass timber, full steel, and post-tensioned concrete structures, which are common structural systems for high-rise buildings, enabling meaningful comparisons of their environmental performance. The results showed that the full mass timber design had the lowest global warming potential (GWP), reducing emissions by 16% compared to the concrete structure. The hybrid design achieved a 14% reduction, with both timber-based systems demonstrating about 30% lower non-renewable energy use. In addition, they provided significant biogenic carbon storage during the building’s lifespan. However, the mass timber and hybrid systems showed higher impacts in categories such as acidification, eutrophication, ozone depletion, and smog formation. Full article

The two-tank molten salt thermal storage system is the most common storage solution in concentrated solar power (CSP) plants. Solar salt (60% NaNO₃ + 40% KNO₃) is the most widely used energy storage material in solar thermal plants. In solar tower technology, where the molten salts must operate at temperatures ranging from 290 °C to 565 °C, several issues related to tank failures have emerged in recent years, with some of these failures attributed to the welding process. The welding process of joints in 316L stainless steel (ASS) probes exposed to a moving flow of a binary mixture containing 60% NaNO₃ and 40% KNO₃ (solar salt) is analysed. The results were evaluated using scanning electron microscopy (SEM) at 120, 500, 1000, 1500, and 2300 h of exposure. It was identified that arc mechanical oscillations significantly improve the microstructural properties and geometrical characteristics of welded joints, reducing structural defects and improving corrosion resistance. The technique promotes uniform thermal distribution, refined dendrite morphology, and homogeneous alloying element distribution, resulting in lower mass loss in high-temperature molten salt environments. Additionally, oscillation welding optimises the bead geometry, with reduced wetting angles and controlled penetration, making it ideal for high-precision industrial applications and extreme environments, such as molten salt thermal storage systems. Full article

As the demand for sustainable and resilient energy systems grows, providing planners with effective tools for microgrid design becomes increasingly important. This research addresses the need for such tools by introducing a new method for distributed energy resource sizing in microgrid capacity planning. The planning process begins with a comprehensive assessment of the required capacity based on a given set of power load requirements. Rather than providing a single solution, as is common in related works, the sizing method introduced in this paper efficiently identifies a wide range of microgrid design options that satisfy the stated power needs. The benefit of this multi-solution approach is that it allows decision makers to consider vastly different possibilities, such as varying levels of renewables and battery storage, and weigh trade-offs between these potential designs before selecting one or more solutions for further detailed design planning. The proposed method is constructed as a three-step heuristic search procedure: (1) an exhaustive search identifies an initial set of candidate solutions; (2) a global binary search builds a diverse set of microgrid design options; and (3) a local linear search refines those options. A computational experiment is presented to demonstrate the method’s effectiveness at identifying diverse solutions sets and its computational tractability. The results show that increasing the number of capacity levels considered per distributed energy resource from 11 to 41 increases the size and diversity of the microgrid design set; however, further increasing the number of capacity levels beyond that point is not beneficial. The method presented is implemented and released in Microgrid Planner, an open source software platform. Full article

Electric vehicles (EVs) play a crucial role in addressing the energy crisis and mitigating the greenhouse effect. Lithium-ion batteries are the primary energy storage medium for EVs due to their numerous advantages. State of health (SOH) is a critical parameter for managing the health of lithium-ion batteries, and accurate SOH estimation forms the foundation of battery management systems (BMS), ensuring the safe operation of EVs. Data-driven deep learning techniques are attracting significant attention because of their strong ability to model complex nonlinear relationships, which makes them highly suitable for SOH estimation in lithium-ion batteries. This paper provides a comprehensive introduction to the common deep learning techniques used for SOH estimation of lithium-ion batteries, with a focus on model architectures. It systematically reviews the application of various deep learning algorithms in SOH estimation in recent years. Building on this, the paper offers a detailed comparison of these deep learning methods and discusses the current challenges and future directions in this field, with the aim of providing an extensive review of the role of deep learning in SOH estimation. Full article

In this article, a comprehensive review of electrical microgrids is presented, emphasizing their increasing importance in the context of renewable energy integration. Microgrids, capable of operating in both grid-connected and standalone modes, offer significant potential for providing energy solutions to rural and remote communities. However, the inclusion of diverse energy sources, energy storage systems (ESSs), and varying load demands introduces challenges in control and optimization. This review focuses on hybrid microgrids, analyzing their operational scenarios and exploring various optimization strategies and control approaches for efficient energy management. By synthesizing recent advancements and highlighting key trends, this article provides a detailed understanding of the current state and future directions in hybrid microgrid systems. Full article

In recent years, with the continuous growth of energy demand and the large-scale deployment of renewable energy sources, the power system’s need for high-capacity power transmission and energy storage systems has increased significantly. In this context, the integration of modular multilevel converters (MMCs) with energy storage (ES) systems has led to the development of the MMC with embedded energy storage systems (ES-MMC), which combines the advantages of both the MMC and the ES system. Over the past few years, research on ES-MMC-related technological issues has emerged rapidly. On this foundation, this paper provides an overview of the ES-MMC in terms of electrical topology, steady-state control strategies, common applications, and the challenges it faces. First, the advantages of various ES interfaces are analyzed, and a comparison on the techno-economic feasibility of different submodules with embedded energy storage is conducted. Then, the main control strategies of distributed ES-MMC are examined from several perspectives. Finally, the paper discusses the advantages of the ES-MMC over traditional solutions in various application scenarios and explores possible future research directions. The final analysis establishes ES-MMC’s advantages over traditional solutions in various application scenarios and explores its potential research prospects. Full article

The use of pumps in water distribution networks is very useful when there is a need for additional pressure head. However, the functioning of pumps can be influenced by the presence of private storage tanks in the network, which alters the way the users draw water due to their compensation ability. This condition is very common in areas affected by the historical scarcity of water resources or intermittent supply (Mediterranean Area, Arabian Peninsula, etc.). This paper studies the effects of private tanks on the performance of pumps in a network model, considering different retention times and evaluating possible effects on background leakages. A sample network and two real water distribution networks in the UAE will be analyzed. The results show that low retention time (i.e., 12 h) leads to a decrease in pump running time, thus lowering the energy consumption and carbon footprint, which gives a sustainable solution. These results, therefore, suggest that considering the presence of private storage tanks for the pump design in network models is of crucial economic importance, as well as for efficient designs and sustainable water distribution systems. Full article