Storage Density Research Articles

Ferroelectric tungsten bronze-based ceramics with high-energy storage performance via weakly coupled relaxor design and grain boundary optimization

A multiscale regulation strategy has been demonstrated for synthetic energy storage enhancement in a tetragonal tungsten bronze structure ferroelectric. Grain refining and second-phase precipitation (perovskite phase) are introduced in the BaSrTiNb2-xTaxO9 ceramics by regulating the composition and sintering process. Disordered polarization and distribution, chemical inhomogeneity, and insulating boundary layers are achieved to provide the fundamental structural origin of the relaxation characteristic, high breakdown strength, and superior energy storage performance. Thus, an ultrahigh energy storage density of 12.2 J cm−3 with an low energy consumption was achieved at an electric field of 950 kV cm−1. This is the highest known energy storage performance in tetragonal tungsten bronze-based ferroelectric. Notably, this ceramic shows remarkable stability over frequency, temperature, and cycling electric fields. This work brings new material candidates and structure design for developing of energy storage capacitors apart from the predominant perovskite ferroelectric ceramics.

Optimized energy storage performances via high-entropy design in KNN-based relaxor ferroelectric ceramics

Dielectric capacitors play an irreplaceable role in complex and integrated electronic systems. However, attaining ultrahigh recoverable energy storage density (Wrec) alongside energy storage efficiency (η) poses a formidable challenge, impeding the advance towards the miniaturization and integration of cutting-edge energy storage devices. In this work, a high-entropy strategy with a viscous polymer process is adopted, bringing about ultrafine grains and polar nanoregions (PNRs) accompanied by enhanced electrical homogeneity and polarization relaxation characteristics. As a result, an ultrahigh Wrec ∼ 7.51 J/cm3 is achieved in a high-entropy KNN-based energy storage ceramic with a high η ∼ 88.4% at 750 kV/cm. Moreover, the ceramic capacitor exhibits a colossal power density reaching approximately 420 MW/cm3 and a discharge energy density of approximately 4.85 J/cm3 at 160 ℃. Impressively, it maintains low variation rates of less than 4% across a broad temperature range from 20 ℃ to 160 ℃. The new approach opens avenues for the design and development of superior dielectric materials used in next-generation high-power pulse devices.

Evaluation of calcium looping CO2 capture and thermochemical energy storage performances of different stabilizers promoted CaO-based composites derived from solid wastes

Calcium looping is considered as an important high-temperature cyclic CO2 capture and concentrated solar energy storage technology. However, the dramatic inactivation of CaO over multiple carbonation-calcination cycles has seriously restricted their practical applications. In this study, a series of metal oxide (i.e. TiO2, MgO, Al2O3 and ZrO2)-stabilized CaO-based materials with high cyclic stability derived from carbide slag were synthesized via a facile and cost-effective approach for simultaneously enhanced CO2 capture and thermochemical energy storage (TCES). The results suggest that CCS-H-TiO2 exhibits high initial CO2 uptake of 0.41 gCO2/gsorbent, superior cyclic stability with an average attenuation of 1.71 %/cycle and remarkably stable energy storage density. CCS-H-Al2O3 shows the best stability with lowest attenuation rate of 9.6 %. Except for CCS-H-MgO, the stabilizers reacted with active calcium to form new phases and used as physical “barrier” and high-TT skeleton to offset the sintering stress, retain the microporous structures, hinder the excessive agglomeration and alleviate sintering.

Design and development of an advanced gas storage device and control method for a novel compressed CO2 energy storage system

Compressed CO2 energy storage (CCES) has advantages over compressed air in energy density and efficiency. Compared to air, CO2 needs to be in a closed-loop cycle in the CCES. The development of CCES is constrained by low-pressure CO2 storage. Storage density can be increased by adsorption without changing pressure. However, the control of the flow rate during adsorption/desorption has rarely been studied experimentally. In this paper, an adsorption tower for CCES is proposed and the regulation of the desorption flow rate is experimentally investigated. Using temperature-swing adsorption, the storage and release can be regulated without reducing the energy storage capacity. During the desorption process, the temperature of the exhaust gas can also be maintained stably. The adsorbent with a volume of 51.81 L was able to release 6121.9 g of CO2 when heated to 200 °C. Under the same pressure conditions, the effective storage density of the tower can reach 118.2 g/L, which is 67.5 times higher than the gaseous density (1.75 g/L, 1 bar, 303 K). The desorption flow rate is linearly related to the forward speed of the front in the adsorption tower. The flow rate can be regulated by controlling the superficial gas velocity and the desorption temperature. This method can match the flow rate of the adsorption tower with the gas consumption of the compressor, providing a novel solution for CCES.

Optimization of a novel liquid carbon dioxide energy storage system by thermodynamic analysis and use of solar energy and liquefied natural gas

Liquid carbon dioxide energy storage with its advantages in terms of geographical constraints and economic performance has garnered significant attention. In this study, a novel liquid carbon dioxide storage system was proposed which utilizes the waste cold energy from LNG and achieves high liquefaction efficiency. By integrating solar energy, net output of the system is increased. The results show that the net output is sensitive to turbine 1 outlet pressure. Round-trip efficiency and energy storage density increases with the rise of the pump outlet pressure first and subsequently exhibits a gradual decline with an inflection point. With the increase in ambient temperature, the system efficiency shows a slight decrease, yet energy storage density shows a significant increase. At basic operating conditions, the system demonstrates energy storage efficiency of 66.64 %, round-trip efficiency of 74.33 %, and energy storage density of 23.51 kWh/m3. In addition, optimization was conducted. Single-objective optimization results show that round-trip efficiency, energy storage density and levelized cost of storage can reach 89.86 %, 25.37 kWh/m3 and 0.1873 $/kWh, respectively. Multi-objective optimization obtained compromise results of round-trip efficiency and levelized cost of storage of 85.33 % and 0.1947 $/kWh when integrated solar energy, showing a 33.77 % increase and a 13.20 % decrease compared to 63.79 % and 0.2243 $/kWh when not integrated solar energy.

Enhanced thermal conductivity of wood-based phase change materials with copper for thermal management and solar-thermal conversion

Polyethylene glycol (PEG) has been regarded as a promising thermal management material for next-generation building materials due to its high energy storage density and phase change performance. However, its practical application has been limited by some issues such as easily leakage and low thermal conductivity. In this work, a high-thermal-conductivity wood-based composite phase change material (Cu-DW/PEG) was fabricated by impregnating copper (Cu) precursor solution and PEG into delignified wood (DW). The incorporation of Cu nanoparticles increased the thermal conductivity of Cu-DW/PEG by 105 % and 64 % compared to pure PEG and DW/PEG composite, respectively. This also endow the Cu-DW/PEG good photo-thermal conversion capability, achieving a conversion efficiency of 76.5 %. Meanwhile, the Cu-DW/PEG exhibits relatively high latent heat (132.93 J/g), good shape stability and thermal cycling stability. Considering these excellent performances, the Cu-DW/PEG is a promising material for thermal management, building energy conservation, and solar thermal harvesting.

Multi-objective optimization and influence degree analysis of the thermally integrated HP-ORC carnot battery based on the orthogonal design method and grey relational analysis

Thermally integrated heat pump (HP)-organic Rankine cycle (ORC) Carnot battery is a promising solution for efficient energy storage and waste heat utilization. Firstly, in order to research the influence degree of the operating parameters on the system performance, single-objective optimization is conducted by the orthogonal design method. Then, multi-objective optimization is conducted by combining the grey relational analysis (GRA) and orthogonal design method to assess the comprehensive performance of the system. The importance order and contribution rates of the operating parameters and the optimal operating combinations are determined. Finally, in order to explore the influence mechanism of the parameters on the system performance, the influence of the parameters on the subsystems and the subsystems on the whole system is quantitatively analyzed. The results show that thermal storage temperature difference, waste heat temperature difference and cold source temperature are the most important parameters affecting the comprehensive performance of the whole system. Under the optimal operating conditions, round-trip efficiency, exergy efficiency, energy storage capacity (ESC), energy storage density (ESD) and levelized cost of storage (LCOS) are 47.05 %, 22.66 %, 1943 kW, 2.90 kWh/m3 and 0.38$/kWh, respectively. Compared to the ORC subsystem, the HP subsystem is more important to round-trip efficiency and exergy efficiency.

Energy storage performance of sandwich structure dielectric composite by BNNS/TiO2 Co-doping for the high electric field capacitor

Dielectric capacitors are crucial for power systems and hybrid vehicles. However, the polymer dielectric owns low energy density and cannot meet the demands of high-power and energy storage systems. The synergistic improvement of balance between dielectric constant (εr) and breakdowon field strength (Eb), along with better energy storage performance, is a primary focus of this study. This research employs a high εr of P(VDF-TrFE-CFE) blended with linear PMMA to create a sandwich-structured composite via high-speed electrostatic spinning. Boron Nitride Nanosheets (BNNSs) for insulation and TiO2 for polarization are used as fillers, aiming to achieve polymer-based composite with large energy storage density and minimal energy loss. Results show that the sandwich-structured composite with 0.5 vol.% BNNSs in outer layer and 3 wt.% TiO2 in middle layer achieves the largest Ue of 21.8 J/cm3 at the η of 74 %. This study broadens the application of novel dielectric materials in the fields of energy.

Enhancing chemical heat storage performance of nanocarbon porous particle based MgO/Mg(OH)2 composite by calcination method

The application of MgO/Mg(OH)2 in heat storage technology has been limited due to slow hydration rate and easy agglomeration. In this paper, nanoporous carbon particle (NCP) as a carrier was used to prepare NCP/MgO chemical heat storage composite materials by impregnation and calcination methods, respectively. The microstructure characterization, hydration reaction, and simultaneous thermogravimetric analysis experiments were carried out on the prepared composite materials. The results showed that the internal distribution of MgO in the composite material prepared by calcination method was more uniform, and the particle size of MgO was smaller. Under the conditions of 110 ℃ hydration temperature and 57.8 kPa water vapor partial pressure, the hydration conversion ratio of the composite material prepared by calcination method after 120 min of hydration conversion ratio reached 93 %, which was 17.7 % higher than that of the impregnated composite material and 50 % higher than that of pure MgO. Under the comprehensive influence of specific surface area, pore structure, and active component particle size, compared with pure materials and impregnated composite materials, the dehydration rate of the composite material prepared by calcination method at 300 ℃ was twice that of impregnated method and 6 times that of pure MgO, and the heat storage density reached 1039kJ/kg. After 10 cycles, the heat storage density still maintained an initial state of 95.8 %. Compared with pure materials and impregnated composite materials, NCP/MgO composite materials prepared by calcination method had better heat storage performance and higher cyclic stability.

Effect of stretching orientation on the crystalline structure and energy storage properties of poly(vinylidene fluoride) films

Poly(vinylidene fluoride) (PVDF) with a high content of β phase shows great potential for applications in the pulse energy storage field because of its high dielectric constant and breakdown strength. The stretching process can significantly induce the crystal phase transformation and change the structure of the aggregated state. To deeply investigate the influence mechanism of the fabrication process, solution casting (SC), melt stretching (MS), static biaxial orientation (SBO), and continuous biaxial orientation (CBO) were used to fabricate PVDF films. The essential difference between the four technological routes lies in the different forms of tensile orientation imposed. Stretching perpendicular to the machine direction promotes the transition of the original α phase crystals to the β phase. Stretching orientation can regulate the crystalline phase structure of the film and its applicability. The relative fraction of β phase crystals in the PVDF-CBO film reaches 84.1 %, resulting in a much higher dielectric constant (12.22 @1 kHz) than that of the PVDF-SC film (7.16). The continuous biaxially oriented PVDF exhibited excellent insulation properties with a breakdown strength of 759.21 kV/mm. Meanwhile, the CBO film obtained an energy storage density of 16.76 J/cm3 with a charge-discharge efficiency of 80.13 % at 675 kV/mm. This work is of great scientific significance for the in-depth study of the influence of different film-forming processes on the internal structure of films, ranging from laboratory fabrication to industrialized production.

High energy storage performance in SrZrO3-modified quaternary relaxor ferroelectric ceramics

Lead-free relaxor ferroelectric ceramics have attracted much attention in pulse power systems owing to their excellent energy storage performance and environmentally friendly characteristics. However, it is challenging to simultaneously achieve high energy storage density and efficiency in ferroelectric ceramics for practical applications. Herein, a novel optimization strategy is designed by introducing a linear dielectric SrZrO3 (SZ) with wide bandgap (Eg) into the BaTiO3-Bi0.5Na0.5TiO3-NaNbO3 (BT-BNT-NN) to form quaternary ceramics, disrupting long-range ferroelectric ordering and constructing weakly coupled polar nanoregions (PNRs). As a result, the recoverable energy density (Wrec) and energy storage efficiency (η) are simultaneously improved in (1-x) (BT-BNT-NN)-xSZ ceramics. At an electric field of 530 kV/cm, a Wrec of 3.37 J/cm3 and an η of 82.5 % were optimally achieved at x = 0.16 due to the formation of slim P-E loops, delayed polarization saturation, and ultra-high breakdown field strength (Eb), where the improvement of Eb is attributed to the reduction of porosity and the increase of Eg. Furthermore, the as-fabricated samples also exhibit excellent frequency and temperature stability. This study provides an effective method for developing high-performance dielectric capacitors for energy storage applications.

Adsorption‐Based Thermal Energy Storage Using Zeolites for Mobile Heat Transfer

ABSTRACTThe utilization of the water–zeolite pair as an adsorbate–adsorbent system has garnered significant attention in the realm of thermochemical energy storage, offering great potential for various applications. Despite promising results in laboratory settings, widespread implementation of this technology has yet to be realized. Recent advancements in mobile thermal energy storage (m‐TES) employing thermochemical materials have opened new avenues for enhancing the practicality and cost‐effectiveness of solar thermal energy harnessing and waste heat recovery. This experimental study investigates the feasibility of storing thermal energy in zeolites, charged externally to the heat recovery reactor, and discusses the potential applications of externally charged zeolites for m‐TES over short distances, shedding light on their practicality and significance in advancing the field of mobile thermal energy storage. Our findings reveal that zeolites charged at 200°C and subsequently stored outside the discharging unit exhibit an impressive energy storage density (ESD) exceeding 110 kWhth/m3 under conditions of 0.45 m/s air velocity and 60% relative humidity during zeolite discharging. These ESD values are comparable to previously reported figures in the literature. Moreover, ESD values of 30.6 kWhth/m3 were achieved by charging zeolite beads contained within packed transportable tubes constructed from stainless‐steel mesh.

Investigation of a novel combined ab- and ad- sorption based thermal energy storage and upgrade system

This paper presents a novel sorption-based cycle combining energy storage with energy upgrade to store low-grade heat for long periods and transform it on demand to usable energy at elevated temperatures. The system consists of an ammonia-water absorption system coupled to a resorption thermal transformer using manganese chloride and calcium chloride as the working pair with an ammonia absorbate. The absorption and adsorption systems are charged by separating the constituent sorbent-sorbate pairs, and they remain separated during the transition season. The discharge consists of a two-stage sorption process between the two systems. This work presents a transient thermodynamic model and analysis of the two-stage sorption system. For a typical solar thermal energy input of 106 °C during charging, and ambient temperatures of 5 °C and 25 °C in the winter and summer, respectively, the system is capable of discharging at an average elevated temperature of 62 °C with an energy storage efficiency of 27 %. This system is capable of simultaneously producing heat at a lower temperature by varying the mass flow rate through the high-temperature salt. The energy storage density of the combined system under different conditions is between 71 and 185 kJ kg−1. In comparison with other conventional single-stage thermal energy storage systems, this combination of absorption and adsorption-based storage provides a higher coefficient of performance for a comparable temperature output.

High energy density and energy efficiency in AgNbO3-based multilayer ceramic capacitors induced by coexisted antiferroelectric and paraelectric phases

AgNbO3-based lead-free antiferroelectric materials have been attracted increasing attention due to their excellent energy storage performance. But most of the AgNbO3-based ceramics still suffer from low energy efficiency. Herein, coexisted antiferroelectric phase and paraelectric phase are realized in La-doped AgNbO3-based multilayer ceramic capacitors at room temperature, which resulted in slim polarization-electric field loops with hysteresis-free and high breakdown strength over 1000 kV/cm. Both the hysteresis-free polarization-electric field loops and high breakdown strength are beneficial for the energy storage density and energy efficiency. In (Ag0.64La0.12)NbO3 multilayer ceramic capacitors, a high breakdown strength of 1060 kV/cm was attained, which contributes to a recoverable energy storage density (Wrec) of 9.1 J/cm3 and an energy efficiency (η) of 95.8%. Furthermore, the Wrec and η remains above 7.5 J/cm3 and above 83% in the temperature range of 30 °C to 130 °C under 1000 kV/cm, and remains above 4.8 J/cm3 and above 91% in the frequency range of 1 to 100 Hz under 700 kV/cm. This work provides a feasible method for preparing AgNbO3-based ceramics with high energy storage performance.

Self-acceleration effect of Mn/Ce-modified carbide slag in CO2 absorption for CaO/CaCO3 energy storage

Carbide slag, a solid waste from the chlor-alkali industry, can be used for CO2 capture and energy storage. Herein, the cyclic reaction activity of Mn/Ce-modified carbide slag under energy storage conditions was studied. The Mn/Ce-modified carbide slag shows energy storage density over 2100 kJ/kg and CO2 absorption capacity of 0.52 g CO2/g sorbent after 30 cycles. Notably, both carbonation and calcination rates are accelerated with the number of cycles. This self-acceleration effect is related to the evolution of oxygen vacancy concentration and texture structure of Mn/Ce-modified carbide slag during the cycles. In the cycles, CaMnO3 in the Mn/Ce-modified carbide slag reacts with the formed CaCO3 in the carbonation stage to produce more Ca2MnO4. The formation of Ca2MnO4 increases oxygen vacancies in the Mn/Ce-modified carbide slag, significantly enhancing its CO2 adsorption capacity. Thus, the release of the increased CO2 in the calcination stage generates more pores in the 10–100 nm diameter range in the modified carbide slag, facilitating rapid carbonation. Thus, the Mn/Ce-modified carbide slag exhibits good prospect for CaO/CaCO3 thermochemical energy storage.

High energy storage performance in Mg modified BaTiO3 films with superparaelectric behavior

In this work, by doping the B-site of BaTiO3 with Mg elements, we have prepared BaMgxTi1-xO3-x(BMxT) films with superparaelectric behaviors. The microstructures, polarization behaviors, breakdown strength, leakage current density, and energy storage performance are investigated systematically of the BMxT films. The breakdown strength of the film reaches 7.5MV/cm when x = 0.18, at the same time, excellent energy storage density (67.7J/cm3) and energy storage efficiency (94.9%) are obtained, which is attributed to the doping of the acceptor element Mg. By doping Mg with a lower chemical valence state to form defect dipoles in the lattice, the breakdown strength and polarization properties of the film are improved while reducing the crystallinity of the film, forming a hysteresis loop with superparaelectric properties. This work provides a feasible route to design superparaelectric materials with simple compositions for high-performance capacitive energy-storage.

Thermally driven MnCl2[sbnd]NH4Cl resorption cycle for seasonal thermal management of urban buildings

The frequency of extreme weather conditions caused by global greenhouse gas emissions has led to a significant increase in energy consumption for refrigeration and heating supply in urban buildings. However, conventional sensible and latent heat storage technologies hold low thermal energy storage density and short-term energy storage capabilities. Additionally, electrically driven compression refrigeration with non-negligible global warming potential (GWP) is unsuited to high ambient temperatures in summer. We propose an advanced strategy, adopting the MnCl2NH4Cl resorption cycle to achieve efficient desorption refrigeration of NH4Cl and resorption heating supply of MnCl2 under seasonal conditions. Experimental results have demonstrated that our proof-of-concept system can output 70 °C heat with a thermal energy storage density of 166.2 kJ·kg−1, providing continuous heating for 30.5 min under the winter ambient temperature of 10 °C. Moreover, COPref remained at 0.589 for continuous indoor refrigeration lasting 58.5 min under summer ambient and refrigeration temperatures of around 30 °C and 2 °C, respectively. This exceptional adaptability to ambient temperatures enables efficient adjustment of urban building comfort. Our work presents a promising zero-carbon pathway for replacing conventional fossil fuels employed in the thermal management of urban buildings with solar energy.

Enhanced low‐field energy storage performance in Nd3+‐doped (Bi0.40K0.2Na0.2Sr0.2)TiO3 high‐entropy ceramics

AbstractThe burgeoning requirement for compact electronic devices has intensified research into lead‐free dielectric ceramics that offer superior recoverable energy storage density and efficiency at low electric fields. In this study, we report the synthesis of Nd3+‐doped (Bi0.4K0.2Na0.2Sr0.2)TiO3 perovskite ceramics via the solid‐state reaction technique. The synthesized ceramics adopted a tetragonal crystal structure. As the concentration of Nd3+ ions increased, both the maximum dielectric constant (εm) and its corresponding temperature (Tm) decrease. The incorporation of Nd3+ ions perturbed the long‐range ferroelectric order, leading to diminished maximum polarization (Pm) and remanent polarization (Pr). The ceramics achieved optimal properties with 12 mol% Nd3+ doping, showcasing a significant recoverable energy storage density of 1.50 J/cm3 at a low electric field of 140 kV/cm, along with an exceptional storage efficiency of 94.6%. This research not only highlights a promising candidate for dielectric materials in low electric field applications but also introduces an innovative approach to enhance energy storage performance.

Achieving high energy storage density and charge-discharge performance via high-energy ball milling combined with two-step sintering

In this study, the microstructure, ferroelectricity, energy storage density, and charge-discharge characteristics of 0.95(K0.5Na0.5)NbO3-0.05Ba(Zn1/3Nb2/3) (0.95KNN-0.05BZN) ceramic, fabricated by combining two-step sintering with high-energy ball milling, were investigated. The two-step sintering technique enabled a wide sintering temperature range of 1020–1120 °C for the ceramic. Accordingly, under optimal sintering conditions, the ceramic exhibited high relative density (98.1 %) and nanoscale grain size (<90 nm). The samples also displayed excellent pulse power performance at room temperature with a high recoverable energy storage density (Wrec) of 3.1 J/cm3, along with the following charge-discharge parameters: current density (CD), power density (PD), and discharge time (t0.9) reached 1821.7 cm−3, 227.7 MW/cm3, and 36.8 ns, respectively. The ceramic also obtained robust frequency stability (10–1000 Hz), good temperature stability (30–130 °C), and outstanding fatigue resistance (105 cycles), indicating its potential application in improved pulse capacitor materials.

Achieving ultra-high energy storage performance in simple systems through minimal element substitution

Dielectric capacitors are essential components of modern advanced electronic devices and power systems based on their ultra-fast charging and discharging speeds and supreme power densities. Nevertheless, how to comprehensively boost their energy storage density and storage efficiency is still an insurmountable challenge. Here, we report a simple micro-chemical polarizability modulation strategy that enables SrTiO3-based dielectric materials to achieve excellent energy storage properties. The energy density and energy efficiency are increased to as high as 76 J∙cm−3 and 72 % from 0.4 J∙cm−3 and 46.7 % of pure STO, respectively, which is the largest value in micro-substitution (less than 3 %). Our results show that the introduction of trace amounts of elements with high ionic polarizabilities (Mn, V) facilitates the increase of chemical disorder and the formation of stable and highly dynamic polar nanoregions (PNRs), which reduces the hysteresis of the polarization switching and improves the polarization at the breakdown field strength, synergistically fostering the energy storage performance. The results of X-ray photoelectron spectroscopy and scanning electron microscopy reveal that the micro-substitution of Mn and V promote the reduction of oxygen vacancies and grain size, improving the breakdown resistance and stability of the capacitor. This present approach is expected to be widely used in the development of high-performance dielectrics.