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In order to improve the control capability of distributed photovoltaic support, a distributed photovoltaic support consumption method based on energy storage configuration mode and random events is proposed. A networked and constrained parameter analysis model for distributed photovoltaic power supply control was constructed. Based on the direct flexible mode of optical storage, an AC/DC voltage level control model for distributed solar power supply control was constructed. In the operation mode of DC hybrid distribution network, the demand response tracking identification method was used to analyze the uncertain characteristic parameters of distributed solar power supply load, and combined with the planned energy storage capacity parameters, the distributed solar power supply load and photovoltaic output were estimated. By configuring the optimal energy storage capacity, adjusting the power distribution of the microgrid, and integrating the analysis of uncertain factors and random events in the energy storage configuration mode, the design of distributed photovoltaic support consumption has been achieved. The experimental results show that the distributed photovoltaic absorption control using this method has lower load requirements, can effectively reduce the exchange power of the interconnection line, and improve the configuration scale, system reliability, and economy of the photovoltaic energy storage system. [ABSTRACT FROM AUTHOR]

In order to improve the control capability of distributed photovoltaic support, a distributed photovoltaic support consumption method based on energy storage configuration mode and random events is proposed. A networked and constrained parameter analysis model for distributed photovoltaic power supply control was constructed. Based on the direct flexible mode of optical storage, an AC/DC voltage level control model for distributed solar power supply control was constructed. In the operation mode of DC hybrid distribution network, the demand response tracking identification method was used to analyze the uncertain characteristic parameters of distributed solar power supply load, and combined with the planned energy storage capacity parameters, the distributed solar power supply load and photovoltaic output were estimated. By configuring the optimal energy storage capacity, adjusting the power distribution of the microgrid, and integrating the analysis of uncertain factors and random events in the energy storage configuration mode, the design of distributed photovoltaic support consumption has been achieved. The experimental results show that the distributed photovoltaic absorption control using this method has lower load requirements, can effectively reduce the exchange power of the interconnection line, and improve the configuration scale, system reliability, and economy of the photovoltaic energy storage system.

With the high penetration of renewable energy in modern power system, grid-side energy storage can support power system operation as a flexible resource. Evaluating the value of energy storage is a necessary preparation for its capacity sizing. Three value indexes that reflect the value on renewable energy utilization, power system flexibility, and dispatch economy are defined at first. Then, a value evaluation method based on multi-parametric mixed integer linear programming theory is proposed and applied to above indexes. As a result, each index is represented as an analytical piecewise linear function of the power and energy capacity of storage. Finally, the proposed models and method are verified on the Northeast Power Grid data. The simulation results show that proposed method can analytically describe how the value of energy storage is affected by its capacity, along with visualization. The analytical expression contains profound sensitivity information, which reveals the bottleneck of energy storage value and provides insightful reference for energy storage capacity sizing in different application scenarios.

In this work, the one-dimensional (1D) Ni–Co–Se nanowire arrays with rich grain-boundaries were prepared through the solvothermal method and gas-phase selenizaiton. The results showed that the structure and crystallization of the Ni–Co–Se nanowire arrays could be modulated through the optimization of selenizaiton time. The optimal Ni–Co–Se electrode sample displayed an area specific capacitance of 242.6 μ Ah cm−2 at 30 mA cm−2 with a current retention rate of 68.34%. The assembled Ni–Co–Se/Active carbon (AC) electrode-based asymmetric supercapacitor (ASC) showed the area specific capacitances of 329.2 μ Ah cm−2 and 225.8 μ Ah cm−2 at 3 mA cm−2 and 30 mA cm−2, respectively. A 73.33% retention rate of capacitance was observed after 8000 charge/discharge cycles. Besides, the further fabricated all-solid ASC delivered the power densities of 342.94 W kg−1 and 3441.33 W kg−1 at the energy densities of 37.62 Wh kg−1 and 25.81 Wh kg−1, respectively. Those results suggested the potentials of the obtained Ni–Co–Se nanowire arrays as electrode material for the high-performance pseudocapacitors. [ABSTRACT FROM AUTHOR]

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In order to obtain more ideal energy storage capacity planning results, a new stochastic planning method for energy storage capacity of interconnected microgrid was proposed on the basis of considering the optimal power balance and demand response. Under the condition of demand response, based on the operation mode and stochastic theory of networked microgrid, the optimal power balance was taken as the planning goal, and the stochastic planning model of energy storage capacity was established. The particle swarm optimization algorithm was used to solve the stochastic programming model of energy storage capacity, and the optimal stochastic programming scheme of energy storage capacity of interconnected microgrid was obtained. The experimental results show that with the continuous increase of capacitance, the overall balance ability of microgrid becomes stronger. The energy balance index of the proposed method is higher, the rated capacity of energy storage is more stable, and the load of energy storage system is smaller, planning efficiency is higher. The proposed method can better realize the energy storage capacity planning of networked microgrid. [ABSTRACT FROM AUTHOR]

Compared with traditional polyacrylonitrile-based carbon nanofiber materials, cyclized polyacrylonitrile has more excellent toughness and elasticity, which makes it a potential candidate for electrode materials. On the basis of traversing relevant literature at home and abroad, the basic properties and reaction mechanism of cyclized polyacrylonitrile are introduced, while the applications of cyclized polyacrylonitrile in anode and cathode materials are also expounded. Furthermore, the existing problems in the electrode application of cyclic polyacrylonitrile are analyzed, which provides theoretical reference for in-depth research and industrialization development of the promising materials. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we investigated the use of electrocatalysts, PMAc, PMAc-g-CNT, Ni/PMAc, and Ni/PMAc-g-CNT for water splitting and supercapacitor applications. Our results showed that the Ni/PMAc-g-CNT catalyst exhibited superior properties in terms of electrochemical activity, stability, and energy storage capacity. The Tafel slope for OER was found to be 471.25 mV dec−1, which was lower than other catalysts studied. The capacitance value of the Ni/PMAc-g-CNT catalyst was 35.23 F/g at 0.5 A/g current density, which was higher than the Ni/PMAc catalyst. These findings provide a novel and detailed insight into the performance of these catalysts and suggest that the Ni/PMAc-g-CNT catalyst is a promising material for both water splitting and supercapacitor applications. [ABSTRACT FROM AUTHOR]

The rapid development of industry has emphasized the importance of phase change materials (PCMs) with a high latent-heat storage capacity and good thermal stability in promoting sustainable energy solutions. However, the inherent low thermal conductivity and poor thermal-cycling stability of PCMs limit their application. In this study, we constructed three-dimensional (3D) hybrid graphene aerogels (GBA) based on synergistic assembly and cross-linking between GO and modified hexagonal boron nitride (h-BN). Highly thermally conductive GBA was utilized as the supporting optimal matrix for encapsulating OD, and further implied that composite matrix n-octadecane (OD)/GBA composite PCMs were further prepared by encapsulating OD within the GBA structure. Due to the highly thermally conductive network of GBA, the latent heat of the composite PCMs improved to 208.3 J/g, with negligible changes after 100 thermal cycles. In addition, the thermal conductivity of the composite PCMs was significantly enhanced to 1.444 W/(m·k), increasing by 738% compared to OD. These results sufficiently confirmed that the novel GBA with a well-defined porous structure served as PCMs with excellent comprehensive performance offer great potential for thermal energy storage applications. [ABSTRACT FROM AUTHOR]

Renewable energy sources are connected to the grid through inverters, resulting in reduced grid inertia and poor stability. Traditional grid-connected inverters do not have the function of voltage and frequency regulation and can no longer adapt to the new development. The virtual synchronous generator (VSG) has the function of voltage and frequency regulation and has more outstanding advantages than the traditional inverter. Based on the principle of the VSG, the relationship between energy storage capacity, frequency response and output power of the VSG is derived, and the relationship between the virtual inertia coefficient, damping coefficient and frequency characteristics of the VSG and output power is revealed. The mathematical model is established and modeled using the Matlab/Simulink simulation software, and the simulation results verify the relationship between energy storage capacity and frequency response and the output power of the VSG.

This paper explores the effect of having a nuclear baseload in a 100% carbon-free electricity system The study analyses numerous scenarios based on different penetrations of conventional nuclear, wind and solar PV power, different levels of overgeneration and different combinations between medium and long duration energy stores (hydrogen and compressed air, respectively) to determine the configuration that achieves the lowest total cost of electricity (TCoE). At their current cost, new baseload nuclear power plants are too expensive. Results indicate the TCoE is minimised when demand is supplied entirely by renewables with no contribution from conventional nuclear. However, small modular reactors may achieve costs of ∼£60/MWh (1.5× current wind cost) in the future. With such costs, supplying ∼80% of the country's electricity demand with nuclear power could minimise the TCoE. In this scenario, wind provides the remaining 20% plus a small percentage of overgeneration (∼2.5%). Hydrogen in underground caverns provides ∼30.5 TWh (81 days) of long-duration energy storage while CAES systems provide 2.8 TWh (∼8 days) of medium-duration storage. This configuration achieves costs of ∼65.8 £/MWh. Batteries (required for short duration imbalances) are not included in the figure. The TCoE achieved will be higher once short duration storage is accounted for. [ABSTRACT FROM AUTHOR]

The temperature dependency of the electrochemical analysis of acetyl ferrocene (AcFc) and iron(III) acetylacetonate ([Fe(acac)3]) has been investigated for non‐aqueous redox flow batteries (NARFBs). AcFc and [Fe(acac)3] were utilized as catholyte and anolyte species, respectively, in an electrochemical cell with a cell voltage of 1.41 V and Coulombic efficiencies >99% for up to 50 total cycles at room temperature (RT, 25 °C). Experiments with a rotating ring disk electrode (RRDE) indicate that the diffusion coefficient reduces with decreasing temperature from 25 °C to 0 °C, yet the overall storage capacity was higher than that of an aqueous redox flow battery (ARFBs). The electrochemical kinetic rate constant (k0) of AcFc was found to be greater than that of [Fe(acac)3]. However, the value of k0 was not affected by the variable temperature. 1H NMR investigations reveal that temperature change during battery trials did not occur in any structural modification. The obtained result demonstrates the suitability of this battery at low temperatures. [ABSTRACT FROM AUTHOR]

Community service has been carried out in Pasuruan, Eastern Java. A hydroponics farming system, run by a group of farmers in Kecamatan Gempol, consumes electric energy provided by a 900 Wp solar power system. The power plant is equipped with two batteries, 12 V 100 Ah, with a Depth of Discharge (DoD) of 80% each, which enables the power system to store the energy of 1920 Wh as a reserve. According to the farmer's report, one of the essential components in the solar power system was damaged twice due to lightning strikes at an adjacent time. Also, the hydroponics system is unable to run all night continuously due to the insufficient capacity of the storage system. Therefore, surge protection devices (SPD) are installed in the solar power plant system to protect crucial components from damage caused by lightning strikes. Furthermore, this activity adds two more batteries to the system that double the energy reserve to extend the operating hours of hydroponics electrical equipment when sunlight is unavailable. The work also created a new hydroponics platform with 126 holes as a part of capacity expansion to meet the market demands. Extra protection against insects is also provided by shielding the hydroponics platforms close to the bushes with the insect net. [ABSTRACT FROM AUTHOR]

We devised a functional form stable composite phase‐change materials (PCMs) to achieve a three‐dimensional (3D) interconnected porous carbon aerogel structure for encapsulating polyethylene glycol (PEG). A novel homogeneity reinforced carbon aerogel with a well‐interconnected porous structure was constructed by combining a flexible carbon resource from biomass guar gum with hard‐brittle carbon from polyimide, to overcome severe shrinkage and poor mechanical performance of traditional carbon aerogel. The supporting carbon aerogel‐encapsulated PEG produced the novel composite PCMs with good structure stability and comprehensive energy storage performance. The results showed that the composite PCMs displayed a well‐defined 3D interconnected structure, and their energy storage capacities were 171.5 and 169.5 J/g, which changed only slightly after 100 thermal cycles, and the composites could maintain the equilibrium temperature at 50.0−58.1 °C for about 760.3 s. The thermal conductivity of the composites could reach 0.62 W m−1 K−1, which effectively enhanced the thermal response rate. And the composite PCMs exhibited good leakage‐proof performance and excellent light–thermal conversion. The compressive strength of the composite PCMs can improve up to 1.602 MPa. Results indicate that this strategy can be efficiently used to develop novel composite PCMs with improved comprehensive thermal performance and high light–thermal conversion. [ABSTRACT FROM AUTHOR]

A series of polyurethane/graphene oxide (PU/GO) solid–solid phase change materials (SSPCMs) were synthesized by using GO as a light-absorbing filler and polyethylene glycol (PEG) as a phase change matrix. The effects of PEG content on the energy storage capacity, thermal stability and photo–thermal conversion performance of PU were investigated. The results show that the form-stability of PU/GO decreases while the phase change enthalpy and photo–thermal conversion efficiency of PU/GO increases with the increasing PEG content. The introduction of a very low content of GO can maintain comparable energy storage density and greatly improve light absorption by reasonably modulating the soft segment contents. The PU/GO composite with 92 wt% PEG has a phase change enthalpy of 138.12 J/g and a high photo–thermal conversion efficiency (87.6%). The composite solid–solid PCMs have great potential for effective energy storage and solar energy utilization. [ABSTRACT FROM AUTHOR]

Shape-memory polymers (SMPs) show great potential in various emerging applications, such as artificial muscles, soft actuators, and biomedical devices, owing to their unique shape recovery-induced contraction force. However, the factors influencing this force remain unclear. Herein, we designed a simple polymer blending system using a series of tetra-branched poly(ε-caprolactone)-based SMPs with long and short branch-chain lengths that demonstrate decreased crystallinity and increased crosslinking density gradients. The resultant polymer blends possessed mechanical properties manipulable across a wide range in accordance with the crystallinity gradient, such as stretchability (50.5–1419.5%) and toughness (0.62–130.4 MJ m−3), while maintaining excellent shape-memory properties. The experimental results show that crosslinking density affected the shape recovery force, which correlates to the SMPs' energy storage capacity. Such a polymer blending system could provide new insights on how crystallinity and crosslinking density affect macroscopic thermal and mechanical properties as well as the shape recovery force of SMP networks, improving design capability for future applications. [ABSTRACT FROM AUTHOR]

The rapid development of industry has emphasized the importance of phase change materials (PCMs) with a high latent-heat storage capacity and good thermal stability in promoting sustainable energy solutions. However, the inherent low thermal conductivity and poor thermal-cycling stability of PCMs limit their application. In this study, we constructed three-dimensional (3D) hybrid graphene aerogels (GBA) based on synergistic assembly and cross-linking between GO and modified hexagonal boron nitride (h-BN). Highly thermally conductive GBA was utilized as the supporting optimal matrix for encapsulating OD, and further implied that composite matrix n-octadecane (OD)/GBA composite PCMs were further prepared by encapsulating OD within the GBA structure. Due to the highly thermally conductive network of GBA, the latent heat of the composite PCMs improved to 208.3 J/g, with negligible changes after 100 thermal cycles. In addition, the thermal conductivity of the composite PCMs was significantly enhanced to 1.444 W/(m·k), increasing by 738% compared to OD. These results sufficiently confirmed that the novel GBA with a well-defined porous structure served as PCMs with excellent comprehensive performance offer great potential for thermal energy storage applications.

The electrothermal breakdown of high‐temperature dielectric materials has received increasing attention. However, the theoretical characterization of quantitative relationship between breakdown strength and temperature has been a challenge. Herein, a theory termed energy storage capacity has been developed to generate and understand the nature of this quantitative relationship. This theory defines a limit value of stored energy associated with the material breakdown, including electric energy and the equivalent heat energy. Then, a parameter‐free theoretical model of temperature‐dependent breakdown strength of materials is developed, which takes into account the effects of dielectric constant and melting point. This non‐fitting model, without the need to carry out any destructive experiments and data fitting, is validated with excellent agreement between the predicted and measured values of both polymers and ceramics, monolithic and multilayered polymer/ceramic composites. It is shown that the failure of large classes of substances, including ceramics and polymers under heat and electrical force or mechanical force can be accurately modeled using the concept of the temperature independent limit value of the stored energy. This should become the new insight and entry point for the development of quantitative characterization of temperature‐dependent physical and mechanical properties of materials. [ABSTRACT FROM AUTHOR]

This paper comprehensively evaluates the PV power smoothing control method using the spline function. As a result of the verification, it is shown that the ESS capacity can be reduced while maintaining the smoothing effect by PV power smoothing control with energy control and limiting fluctuation rate control. Based on the charging/discharging power of the ESS and the operating conditions of the ESS, the section time that achieves both improvement of the smoothing effect and reduction of the ESS capacity is determined to be 1500 s. Then, the rated capacity of the ESS for a rated power of 1.75MW PV system is 1128 kWh. This is 49.6% of the rated capacity of the ESS, which is required in the PV power smoothing control method with fluctuation rate control. As a result of comparing the proposed method and the moving average method, the proposed method improved the smoothing effect by 49.8% compared to the moving average method. [ABSTRACT FROM AUTHOR]

As a large-scale energy storage technology, compressed air energy storage (CAES) has the advantages of high efficiency and high reliability. This paper analyzed the feasibility of CAES cavern constructed in salt mine with multi-interlayer in Zhangshu, Jiangxi Province. Salt mine in Zhangshu is a typical bedded rock salt, and a method for calculating the cavern volume in Zhangshu was proposed. Using the proposed volume calculation method, it is expected that the volume of Zhangshu salt caverns can reach 27,840,000 m3 by 2060. By modelling the geomechanics used to calculate its stability. Based on the results of the simulation, the recommended operating pressure is 8.5–11.5 MPa. Finally, If this volume is used for CAES, the cycle pressure is assumed to be 8.5–11.5 MPa, energy storage efficiency of 50 %, the daily effective energy storage is 8.062 × 1014 J. This study will guide the development of the Zhangshu Salt Mine, provide lessons for similar areas and have a positive impact on the energy transition in Jiangxi. • A method for calculating the volume of salt caverns in the Zhangshu is proposed. • The recommended pressure range for CAES in Zhangshu is 8.5–11.5 MPa. [ABSTRACT FROM AUTHOR]

This paper investigates the melting behaviour of phase change material (PCM) in a vertical thermal energy storage system with provision of thin rectangular fins of uniform and variable lengths on the heat transfer tube surfaces. The selected PCM and heat transfer fluid (HTF) are paraffin wax and water, respectively. The HTF is passed through the helically coiled copper tube of 10 mm diameter to melt the PCM. The time required to complete the melting of PCM in the system with fins is found to be five hours, whereas for the system without fins it is five hours and forty minutes, for the same conditions of constant water temperature of about 70°C and flow rate of 0.02 kg/s. HTF tube with fins is observed to be more effective with a 13.33% faster rate of melting when compared to that of the HTF tube without fins. Such a fast charging process will be helpful in storing maximum energy within a short period/duration of time shorter duration in for solar thermal and heat recovery applications during lean production times. ©2020. CBIORE-IJRED. All rights reserved

Except for pumped storage, other existing electric energy storage technologies are difficult to achieve large-capacity energy storage and not easy to simultaneously meet the requirements in terms of site selection, cost, efficiency, and response. For this end, this paper combines the advantages of maglev technology and vacuum technology, proposes a new type of mechanical large-capacity energy storage technology which is vacuum pipeline maglev energy storage. Based on the idea of vacuum pipeline maglev energy storage technology, we have constructed a case system of vacuum pipeline magnetic maglev energy storage technology. The key technical parameters of the energy storage system, such as the maglev train's weight ratio and speed per hour, the mode of levitation and guidance, the car-track structure, the type and size of the vacuum pipeline, the type of the motor, the process of charging with acceleration, the process of no-load with uniform-speed and the process of generating electricity with deceleration were studied. On this basis, the energy storage capacity and cost of the vacuum pipeline maglev energy storage system were obtained through analysis. By comparing the energy storage capacity and cost of Fengning Pumped Storage Power Station in China, the advantages of vacuum pipeline maglev energy storage technology in economy and technology were verified. Finally, based on the technical characteristics of the vacuum pipeline maglev energy storage system, we analyzed its broad applications in renewable energy power consumption, optimization and upgrade of distribution network structure, urban emergency power supply and pulse power supply.

A series of polyurethane/graphene oxide (PU/GO) solid–solid phase change materials (SSPCMs) were synthesized by using GO as a light-absorbing filler and polyethylene glycol (PEG) as a phase change matrix. The effects of PEG content on the energy storage capacity, thermal stability and photo–thermal conversion performance of PU were investigated. The results show that the form-stability of PU/GO decreases while the phase change enthalpy and photo–thermal conversion efficiency of PU/GO increases with the increasing PEG content. The introduction of a very low content of GO can maintain comparable energy storage density and greatly improve light absorption by reasonably modulating the soft segment contents. The PU/GO composite with 92 wt% PEG has a phase change enthalpy of 138.12 J/g and a high photo–thermal conversion efficiency (87.6%). The composite solid–solid PCMs have great potential for effective energy storage and solar energy utilization.

Shape-memory polymers (SMPs) show great potential in various emerging applications, such as artificial muscles, soft actuators, and biomedical devices, owing to their unique shape recovery-induced contraction force. However, the factors influencing this force remain unclear. Herein, we designed a simple polymer blending system using a series of tetra-branched poly(ε-caprolactone)-based SMPs with long and short branch-chain lengths that demonstrate decreased crystallinity and increased crosslinking density gradients. The resultant polymer blends possessed mechanical properties manipulable across a wide range in accordance with the crystallinity gradient, such as stretchability (50.5–1419.5%) and toughness (0.62–130.4 MJ m−3), while maintaining excellent shape-memory properties. The experimental results show that crosslinking density affected the shape recovery force, which correlates to the SMPs’ energy storage capacity. Such a polymer blending system could provide new insights on how crystallinity and crosslinking density affect macroscopic thermal and mechanical properties as well as the shape recovery force of SMP networks, improving design capability for future applications.

This paper explores how the requirement for energy storage capacity will grow as the penetration of renewables increases. The UK's electric grid is used as a case study. The paper aims to provide insight on what is the most economical solution to decarbonize the electric supply. A two-dimensional study varying the penetrations of wind and solar PV is carried out to identify the most appropriate generation mix for the country. The study is based on 9 years of demand and generation data with a 1hr resolution. It discusses the risk of underestimating the storage capacity needed, by failing to capture the inter-annual variability of renewables and analyzes the economic trade-off between over-generation (curtailment) and storage capacity. It also aims to determine the percentage of over-generation that minimizes the total cost of electricity. Results suggest that the UK could need a storage capacity of approximately 43 TWh to decarbonize its electricity supply. This figure considers a generation mix of 84% wind +16% solar PV, a roundtrip storage efficiency of 70%, and 15% of curtailment. Based on current costs of bulk energy storage technologies, this storage capacity translates into an investment of ∼£165.3 billion or approximately 7% of the country's GDP. • The UK will need 43 TWh of storage for a 100% renewable penetration with 15% curtailment. • If no overgeneration is allowed; storage increases to reduces to 116.5 TWh. • The generation mix has a very strong impact on the storage capacity required. • The optimum mix for the UK is a wind penetration of 84% and a solar PV penetration of 16%. • Considering current costs, a 100% renewable supply would have a LCOE of 80.2 £/MWh. [ABSTRACT FROM AUTHOR]

The utilization of affordable and cost-effective storage materials is a crucial factor in the development of such systems. In this study, the influence of coil pitch, inlet fluid temperature and hot fluid velocity on sand based thermal energy storage (TES) unit is investigated, using experimental results and theoretical models. The experimental segment of this study focuses on measuring the thermophysical properties of two sand samples obtained from different locations within the United Arab Emirates. A conjugated heat transfer model is developed to predict TES using the experimentally measured sand properties. A regression model utilizing response surface methodology (RSM) approach is developed to represent the energy stored per kilogram of sand as a function of the input factors. Furthermore, an optimization algorithm is employed to determine the optimal values of input factors that maximize the energy storage density. The results reveal that the three factors (fluid inlet temperature, velocity, and number of coil turns) significantly affect the stored thermal energy. The RSM analysis illustrates that maintaining high levels of both inlet temperature and fluid velocity maximizes the energy stored. Similarly, keeping inlet temperature and coil turns at the high level maximizes the energy stored. The optimized sand energy storage unit mass reaches 6.348 kJ/kg after an 8-h charging period, with an associated pressure drop of 71.4 Pa for the currently designed unit. • Elemental and thermal characterization of two common sand types in the UAE are measured. • Conjugate heat transfer model is developed to predict the TES capacity of a sand-based unit. • The RSM is employed to analyze key factors that impact the storage capacity of the proposed sand unit. • Fluid inlet temperature, velocity, and coil turns are significantly affecting the stored thermal energy. [ABSTRACT FROM AUTHOR]

To support long-term energy storage capacity planning, this study proposes a non-linear multi-objective planning model for provincial energy storage capacity (ESC) and technology selection in China. The model aims to minimize the load peak-to-valley difference after peak-shaving and valley-filling. We consider six existing mainstream energy storage technologies: pumped hydro storage (PHS), compressed air energy storage (CAES), super-capacitors (SC), lithium-ion batteries, lead-acid batteries, and vanadium redox flow batteries (VRB). The optimized results show that 1) the accumulated ESC in China could increase at an average annual rate of 14.4–17.6% in 2020–2035, reaching 271.1–409.7 GW in 2035 at a total cost of 34.9–41.6 trillion yuan. 2) With favorable technical development levels and application prospects, lithium-ion batteries will be the dominant technology in 2035 in all scenarios. SC has the fastest growth rate among the six technologies in most scenarios because of its flexible location and long lifetime. 3) In the BAU scenario, Xinjiang, Inner Mongolia, Hebei, Ningxia, and Qinghai are the provinces with the largest ESC in 2035 while the four municipalities of Chongqing, Beijing, Tianjin, and Shanghai, as well as Tibet, have the smallest. This layout depends on the differences in the installed capacity of renewable energy in the provinces. • A multi-objective model for optimizing energy storage capacity and technology selection. • Six energy storage technologies are considered for China's 31 provinces in seven scenarios. • Accumulated energy storage capacity will reach 271.1 GW-409.7 GW in 2035. • Inner Mongolia, Qinghai, and Xinjiang are the provinces with the largest capacity in 2035. • Lithium-ion batteries gradually dominates in all energy storage technologies. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) have displayed superior performance compared to other types of rechargeable batteries. However, the depleting lithium mineral reserve might be the most discouraging setback for the LIBs technological advancements. Alternative materials are thus desirable to salvage these limitations. Herein, we have investigated using first-principles DFT simulations the role of polypyrrole, PP functionalization in improving the anodic performance of boron nitride nanosheet, BNNS-based lithium-ion batteries and extended the same to sodium, beryllium, and magnesium ion batteries. The HOMO-LUMO energy states were stabilized by the PP functional unit, resulting in a significantly reduced energy gap of the BNNS by 45%, improved electronic properties, and cell reaction kinetics. The cell voltage, ΔEcell was predicted to improve upon functionalization with PP, especially for Li-ion (from 1.55 to 2.06 V) and Na-ion (from 1.03 to 1.37 V), the trend of which revealed the influence of the size and the charge on the metal ions in promoting the energy efficiency of the batteries. The present study provides an insight into the role of conducting polymers in improving the energy efficiency of metal-ion batteries and could pave the way for the effective design of highly efficient energy storage materials.

This study focuses on the preparation, thermophysical and rheological characterization of phase change material nanoemulsions as latent functionally thermal fluids. Aqueous dispersions with fine droplets of cetyl alcohol (with a melting temperature at ~321 K) were prepared by means of a solvent-assisted method, combining ultrasonication with non-ionic and anionic emulsifiers. Eicosyl alcohol (melting at ~337 K) and hydrophobic silica nanoparticles were tested as nucleating agents. Droplet size studies through time and after freeze–thaw cycles confirmed the good stability of formulated nanoemulsions. Phase change analyses proved the effectiveness of eicosyl alcohol to reduce subcooling to a few Kelvin. Although phase change material emulsions exhibited thermal conductivities much larger than bulk cetyl alcohol (at least 60% higher when droplets are solid), reductions in this property reached 15% when compared to water. Samples mainly showed desirable Newtonian behavior (or slight shear thinning viscosities) and modifications in density around melting transition were lower than 1.2%. In the case of phase change material nanoemulsions with 8 wt.% content of dispersed phase, enhancements in the energy storage capacity overcome 20% (considering an operational temperature interval of 10 K around solid–liquid phase change). Formulated dispersions also showed good thermal reliability throughout 200 solidification–melting cycles.

Energy storage will be required over a wide range of discharge durations in future zero-emission grids, from milliseconds to months. No single technology is well suited for the complete range. Using 9 years of UK data, this paper explores how to combine different energy storage technologies to minimize the total cost of electricity (TCoE) in a 100% renewable-based grid. Hydrogen, compressed air energy storage (CAES) and Li-ion batteries are considered short-, medium-, and long-duration energy stores, respectively. This paper analyzes different system configurations to find the one leading to the lowest overall cost. Results suggest that the UK will need a storage capacity of ~66.6 TWh to decarbonize its grid. This figure considers a mix of 85% wind + 15% solar-photovoltaics, and 15% over-generation. The optimum distribution of the storage capacity is: 55.3 TWh in hydrogen, 11.1 TWh in CAES and 168 GWh in Li-ion batteries. More than 60% of all energy emerging from storage comes from medium-duration stores. Based on current costs, the storage capacity required represents an investment of ~£172.6 billion, or approximately 8% of the country’s GDP. With this optimum system configuration, a TCoE of ~75.6 £/MWh is attained.

This paper investigates the melting behaviour of phase change material (PCM) in a vertical thermal energy storage system with provision of thin rectangular fins of uniform and variable lengths on the heat transfer tube surfaces. The selected PCM and heat transfer fluid (HTF) are paraffin wax and water, respectively. The HTF is passed through the helically coiled copper tube of 10 mm diameter to melt the PCM. The time required to complete the melting of PCM in the system with fins is found to be five hours, whereas for the system without fins it is five hours and forty minutes, for the same conditions of constant water temperature of about 70°C and flow rate of 0.02 kg/s. HTF tube with fins is observed to be more effective with a 13.33% faster rate of melting when compared to that of the HTF tube without fins. Such a fast charging process will be helpful in storing maximum energy within a short period/duration of time shorter duration in for solar thermal and heat recovery applications during lean production times. [ABSTRACT FROM AUTHOR]

In residential microgrids, an energy storage system (ESS) can mitigate the intermittence and uncertainty of renewable energy generation, which plays an important role in balancing power generation and load consumption. Distributed energy storage (DES) is a common form of ESS. However, the high investment cost and fixed energy storage capacity limit their application in residential areas. This study proposes an improved service mechanism based on an alternative form of DES, cloud energy storage (CES). The energy transaction service is added in traditional CES service mechanism to enhance the power interaction between users. In addition, the pricing scheme of CES service fee is formulated, which is calculated based on the battery life loss caused by charging/discharging behaviour during the service period. This study considers that CES can improve energy storage utilisation and meet the energy storage requirements of users at a lower cost than DES. Finally, the CES service decisions are solved by the solver LINGO, including charging/discharging power decisions and energy trading decisions of users. Simulation results show that users' electricity costs are further reduced under the improved CES model. The rationality and economic feasibility of the improved CES model are demonstrated. [ABSTRACT FROM AUTHOR]

Solid-phase thermophysical properties of solar salt (a mixture of NaNO3 and KNO3) influence the performance of sensible heat and latent heat thermal energy storage systems. Solar salt's lower thermal conductivity imparts kinetic limitation during the discharge cycle and hence its thermal conductivity needs to be enhanced. This work is aimed at studying the influence of MWCNT incorporation on the improvement of solid-phase thermophysical properties of solar salt. Accordingly, experiments were carried out to study the influence of method of MWCNT-solar salt preparation, MWCNT concentration and temperature on solid-phase specific heat and thermal conductivity. Our results reveal that 0.5 wt% MWCNT-solar salt composite prepared by ultrasonication and milling for an appropriate time lead to 18.3% enhancement in the solid-phase thermal conductivity and 18% enhancement in the solid-phase specific heat. In addition, the total energy storage capacity over the temperature range of 50–270 °C (including solid–liquid phase change) is amplified by 11.5%. These results augur well for deployment of the MWCNT-solar salt composite in the thermal energy storage system as a storage medium. Research highlights: MWCNT-solar salt composites prepared and characterized. Solid-phase thermal conductivity and specific heat enhanced with addition of MWCNT. α-KNO3–β-KNO3 transition affected by addition of MWCNT @ 0.5 wt%. Thermal conductivity enhancement influenced by reduced α-KNO3–β-KNO3 transition. Solar salt nanoparticles in composites augment solid-phase specific heat. [ABSTRACT FROM AUTHOR]

[Display omitted] • g-C 3 N 4 /VO 2 (B) cathodes were synthesized via hydrothermal method. • XRD confirmed monoclinic crystal phase of the VO 2 (B) nanowires. • Hybrid cathodes showed capacity of 779 mAh/g for rechargeable Li-ion batteries. • Hybrid electrodes have ∼1.2 and ∼2.2 folds higher capacity than individual electrodes. Owing to energy density, powder density, and eco-friendliness, Li-ion batteries (LIBs) are increasingly used in transportable electronic devices and electric vehicles. Monoclinic VO 2 (B) has been broadly used as a cathode owing to its abundance, affordability, high capacity, and multiple oxidation states, but it's low repeatability and slow kinetics have restricted its practical applications. To mitigate these shortcomings, novel 1D/2D VO 2 (B) nanowire/g-C 3 N 4 hybrid architecture cathode materials were synthesized via hydrothermal method, and its electrochemical activity (i.e., repeatability constancy and rate capability) for LIBs was investigated. X-ray diffraction experiments confirmed that VO 2 (B) exhibited a monoclinic crystal phase. SEM images revealed that the g-C 3 N 4 and VO 2 (B) presented sheet-like morphologies and comprised nanowires of uniform thickness, respectively. Electrochemical experiments revealed that the hybrid architectures showed a capacity of 779 mAh/g, and VO 2 (601.4 mAh/g) and g-C 3 N 4 (340.6 mAh/g) at 0.1 C current density. The remarkable electrochemical activity of the materials was attributed to their distinctive structures, excellent electronic conductivity associated with g-C 3 N 4 sheets, small transport distances for Li+ ions, and fast charge transmission owing to the presence of VO 2 (B) nanowires attached to g-C 3 N 4 sheets. Consequently, distinct VO 2 (B) nanowire/g-C 3 N 4 hybrid architectures delivered suitable electrode performance to facilitate the design of high-power LIBs and these hybrid composites can serve as suitable cathode materials for rechargeable LIBs. [ABSTRACT FROM AUTHOR]

The building-integrated PV/T technologies have garnered significant attention due to their considerable potential in low-carbon and zero-energy buildings. To gain deeper insights into the practical application of this technology, a comprehensive study was conducted on a rural building integrated with PV/T walls for demonstration purposes. A novel simulation approach, coupling the numerical models of the PV/T walls with the building energy software, was proposed and experimentally validated. Based on the validated simulation approach, this study investigated the comprehensive performance of the demo building and explored the optimal capacity of the energy storage system (ESS). The main findings are as follows: (1) The proposed simulation approach could accurately predict the energy behaviors of the multi-room building integrated PV/T wall. (2) The demo building with the optimized EES yielded 1355.32 kWh of clean electricity and 455.3 kWh of heat gain for water heating, while reducing cooling and heating loads by 5% and 12%, respectively. (3) The optimal azimuth for the building in the studied region was 45°, and the total energy benefits of the building decreased by 28.5% with an increase in dust density from 0 g/m2 to 10 g/m2. • A rural multi-room building was used to study the performance of the PV/T wall application. • A novel simulation approach was proposed for modeling the building integrated PV/T walls. • The energy storage configuration was analyzed and optimized in terms of 3E performance. • The sensitivity of the energy benefits to building orientation and dust deposition was analyzed. [ABSTRACT FROM AUTHOR]

In this work, the one-dimensional (1D) Ni-Co-Se nanowire arrays with rich grain-boundaries were prepared through the solvothermal method and gas-phase selenizaiton. The results showed that the structure and crystallization of the Ni-Co-Se nanowire arrays could be modulated through the optimization of selenizaiton time. The optimal Ni-Co-Se electrode sample displayed an area specific capacitance of 242.6 μ Ah cm -2 at 30 mA cm -2 with a current retention rate of 68.34%. The assembled Ni-Co-Se/Active carbon (AC) electrode-based asymmetric supercapacitor (ASC) showed the area specific capacitances of 329.2 μ Ah cm -2 and 225.8 μ Ah cm -2 at 3 mA cm -2 and 30 mA cm -2 , respectively. A 73.33% retention rate of capacitance was observed after 8000 charge/discharge cycles. Besides, the further fabricated all-solid ASC delivered the power densities of 342.94 W kg -1 and 3441.33 W kg -1 at the energy densities of 37.62 Wh kg -1 and 25.81 Wh kg -1 , respectively. Those results suggested the potentials of the obtained Ni-Co-Se nanowire arrays as electrode material for the high-performance pseudocapacitors., (© 2023 IOP Publishing Ltd.)

• Compression springs are the best for energy storage capacity per mass. • Spiral springs are the best for energy storage capacity per enclosed volume. • Parallelization of springs is beneficial for energy storage capacity. • Compression springs are the best choice when parallelization of springs is done. • Case study shows that parallelization is especially useful for mass reduction. The key component in compliant actuators is the elastic element, typically a spring. Nevertheless, different types of springs have different characteristics in terms of size, weight, maximum allowable force, maximum allowable torque and maximum allowable deflection. It is however very important to compare them on these requirements, since each application has other demands. In this paper, the energy storage capacity of different types of compliant elements are calculated using scaling laws in order to easily derive the maximum achievable energy capacity for a certain arrangement. These scaling laws are given as a function of the structural parameters and are validated with catalog data of spring manufacturers and distributors such as Alcomex, Lesjöfors and Century Spring. As such, different types of compliant elements can be compared in an easy way. To fully exploit the capabilities of compliant elements, these scaling laws are used to verify the effect of spring parallelization on mass and/or enclosed volume, which is interesting regarding redundant compliant actuation. From theoretical calculations and a case study, it follows that parallelization is beneficial, especially for mass reduction. [ABSTRACT FROM AUTHOR]

Highlights • Method for accurately measuring enthalpy of metal oxides for thermochemistry. • Catalysts enable accurate solution calorimetry data for metal oxides in strong acids. • Facilitates accurate computation of energy storage potentials of novel metal oxides. • Distinguishes energy stored as sensible heat from that as reaction energy. • Results shown for novel magnesium-manganese oxide energy storage material. Abstract Transition metal oxide compounds have been demonstrated to be promising candidates for thermochemical processes, particularly energy storage. A calorimetric method for measuring enthalpy of these materials is developed in this work. A combination of drop calorimetry and acid-solution calorimetry is used to measure the total enthalpy and standard enthalpy of formation of these materials for compounds that form at high temperatures (≥ 1000 °C) after undergoing thermal reduction. These measurements are used to compute the energy storage potential of these materials for a specified set of redox cycle operating temperatures. The construction and calibration of appropriate calorimeter devices are described. A novel approach to performing acid-solution calorimetry is introduced by including tin (II) chloride as a reducing agent for enhancing the dissolution rate of these compounds sufficiently so that acid-solution calorimetry can be implemented accurately. The general procedure is presented and applied to three variations of magnesium-manganese oxide materials for a redox cycle operating under an oxygen partial pressure of 0.2 atm between 1000 and 1500 °C. Using this method, the total energies stored by magnesium-manganese oxides of molar ratios Mn/Mg of 2/1, 1/1, and 2/3 were found to be 924 ± 56.7, 1029 ± 57.0, and 1070 ± 64.2 kJ kg−1, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • The capability of B 3 O 3 monolayer as an anode in non-lithium ion batteries using first-principles calculations. • The energy storage capacities of B 3 O 3 for K+, Ca2+, and Al3+ are above 790.00 mAh g−1, respectively. • Metal ion migration on the B 3 O 3 monolayer is fast with low energy barriers. The rapid development of high-capacity anodes for non-lithium ion batteries (NLIBs) has attracted significant attention in the scientific community towards removing fossil fuels. Herein, first-principles calculations based on density functional theory (DFT) were utilized to look into the applicability of the hexagonal boron oxide (B 3 O 3) monolayer as an anode material for non-lithium ion (K+, Ca2+, and Al3+) batteries. The K+, Ca2+, and Al3+ ions are preferentially adsorbed on the large hollow site of B 3 O 3 monolayer with binding energies of −53.77, −170.55, and −620.85 kcal mol−1, respectively. It was found the adsorption energies generally decrease by increasing the metal ion concentration. The theoretical storage capacities were predicted to be 790.33, 1185.50, and 1778.25 mAh g−1 for K+, Ca2+, and Al3+ ions, respectively. Furthermore, the diffusion energy barrier of a single metal ion was very low (0.22/0.39, 0.12/0.35, and 0.17/0.05 eV for K+, Ca2+, and Al3+ ions, respectively). The findings suggested that the B 3 O 3 monolayer can be used in designing high-performance boron-containing nanostructures for NLIBs. [ABSTRACT FROM AUTHOR]

The limitation of energy storage capacity in vanadium redox flow battery impedes further commercialization of the battery. The concept proposed in this study is to overcome the limit by using nanofluidic electrolytes. Multi-walled carbon nanotubes (MWCNTs) are chosen to disperse in electrolytes due to their high surfaces to volume ratio. Nanofluid electrolytes with three electrolyte weight percent MWCNT (0.05, 0.1, 0.2 wt%) were tested and compared with the pristine electrolyte. Half-cell test with cyclic voltammetry has shown that electrochemical reaction performance is proportional to the content of MWCNT in nanofluidic electrolytes. The redox reaction of nanofluidic electrolytes are enhanced by the increased electrochemical activity and reversibility in addition to the lower polarization effect. Meanwhile, single-cell test reveals that the optimum weight percent of nanofluidic electrolytes is 0.1% of MWCNT because the electrolyte containing 0.2% of MWCNT induces the unwanted precipitation at the electrodes during the electrochemical reaction. After completion of 62 charge/discharge cyclings, nanofluidic electrolyte with 0.1% MWCNT retains specific discharge capacity of 31.7 Ah L −1 while pristine electrolyte does 26.0 Ah L −1 . This corresponds to 22% enhancement of energy storage by using the nanofluidic electrolytes. We conclude that nanofluidic electrolytes can considerably improve the energy storage capacity with optimized content of MWCNT. [ABSTRACT FROM AUTHOR]

Thermochemical systems offer high energy densities and the possibility of long-term storage for the promotion of renewable energy utilization. In particular, CaO/CaCO 3 is a very promising system in the field of thermochemical energy storage due to its high energy density, widespread availability and low cost. However, this system makes stringent demands on the performance of CaO/CaCO 3 energy storage, including the high reactivity and robust cycling stability. In this study, thermodynamics, kinetics and cycling stability of SiO 2 -doped CaCO 3 are investigated by thermogravimetric analysis and differential scanning calorimetry. The obtained results show that SiO 2 has a slightly negative effect on heat storage capacity, but the amount of released heat is increased, and the specific heat capacity is improved by 20% due to the high thermal conductivity of SiO 2 . Additionally, samples with an optimal mass ratio of 5% SiO 2 show a decrease in the activation energy by approximately 40 kJ/mol because an increase in SiO 2 surface coverage (>10 wt.%) leads to a reduction in the calcination conversion. Moreover, the cycling stability of SiO 2 -doped CaCO 3 is enhanced by 28% with an attenuation ratio of 0.85% per cycle, especially at 700 °C, which is ascribed to the faster CO 2 diffusion at higher carbonation temperature. [ABSTRACT FROM AUTHOR]

This paper presents a theoretical study of the acoustic performance of different Helmholtz resonator (HR) array configurations. A dual HR consisting of two HRs connected in series (neck-cavity-neck-cavity) could be considered as a serial HR array. Two HRs mounted on the same cross-section of the duct constitute a parallel HR array. A lined HR array is composed of two HRs installed on the longitudinal direction of the duct. Since HR is reactive silencer without energy consumption, the energy storage capacity ( C TL ) of HR arrays could be defined as the area under transmission loss curve. The transfer matrix method is developed to conduct the investigation. The predicted theoretical results fit well with the Finite Element Method (FEM) simulation results. The results indicate that the installation methods have significant effects on transmission loss curves. However, the C TL of the dual HR equals the C TL of each single component HR mounted on the duct in despite of the dual HR having two HRs. The C TL of the parallel HR array is equivalent to the C TL of the lined HR array, which is twice the C TL of the dual HR. The C TL should therefore be considered as one of the main acoustic characteristics of a HR or an array and be taken into consideration in noise control optimization and HR design. [ABSTRACT FROM AUTHOR]

In this report, flexible cross-linked polyarylene ether nitrile/functionalized barium titanate(CPEN/F-BaTiO3) dielectrics films with high permittivitywere prepared and characterized. The effects of both the F-BaTiO3 and matrix curing on the mechanical, thermal and dielectric properties of the CPEN/F-BaTiO3 dielectric films were investigated in detail. Compared to pristine BaTiO3, the surface modified BaTiO3 particles effectively improved their dispersibility and interfacial adhesion in the polymer matrix. Moreover, the introduction of F-BaTiO3 particles enhanced dielectric properties of the composites, with a relatively high permittivity of 15.2 and a quite low loss tangent of 0.022 (1 kHz) when particle contents of 40 wt % were utilized. In addition, the cyano (-CN) groups of functional layer also can serve as potential sites for cross-linking with polyarylene ether nitrile terminated phthalonitrile (PEN-Ph) matrix and make it transform from thermoplastic to thermosetting. Comparing with the pure PEN-ph film, the latter results indicated that the formation of cross-linked network in the polymer-based system resulted in increased tensile strength by ~67%, improved glass transition temperature (Tg) by ~190 °C. More importantly, the CPEN/F-BaTiO3 composite films filled with 30 wt % F-BaTiO3 particles showed greater energy density by nearly 190% when compared to pure CPEN film. These findings enable broader applications of PEN-based composites in high-performance electronics and energy storage devices materials used at high temperature. [ABSTRACT FROM AUTHOR]

• Thermo-economic evaluation is performed for sub-ambient thermally integrated PTES. • Efficiency up to 99% is achievable by sacrificing the storage capacity and cost. • Cold-storage medium flowrate affects the storage capacity, cost, and power output. • Continuous high flowrate external heat source can reduce the LCOS up to 0.17 $/kWh. • Proposed technology performs comparably to others without geographical limitations. Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a "cold TI-PTES" system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration. [ABSTRACT FROM AUTHOR]