High Energy Storage Capability Research Articles

Experimental investigations on the design of a dual-media thermal energy storage with liquid metal

Liquid metals are a promising heat transfer fluid with stability over a wide temperature range and high thermal conductivity. In concentrating solar energy power plants, as well as in the steel processing facilities heat is generated at high temperature level. Many fluids begin to decompose at such high temperatures and gases have poor thermal conductivity, making it difficult to effectively store and extract heat from the source. Liquid metal heat transfer fluids are able to effectively transport energy at a wide range of temperatures (150 ∘C–1000 ∘C). Existing heat transfer fluids, such as molten salts, have a working range between 290 ∘C and 565 ∘C for example. Depending on the metal selected, thermal conductivity can be 30 to 100 times higher than molten salts, but liquid metals have lower energy density. The liquid metal can be paired with a filler material having a higher energy density to develop a system with high energy transport and storage capability. The first lab-scale experiment of thermocline energy storage with liquid metal as a heat transfer fluid and a zirconium silicate filler, called VESPA [Vorversuch EnergieSPeicher Aufbau (ger.), engl. Preliminary test for energy storage setup], was carried out to prove the concept. So far, there are promising, yet only numerical investigations of thermocline energy storage with liquid metal as heat transfer fluid. The storage system under investigation was a dual-media thermocline energy storage system with liquid lead–bismuth eutectic as heat transfer fluid and zirconium silicate as filler material. The experiments were executed at temperatures from 180 ∘C to 380 ∘C, and focused on design aspects of the energy storage system. Different modes of operation of the storage system were investigated, including charging, discharging, and stand-by. Results are presented showing changes in the vertical temperature profile of the energy storage while varying mass flow, inlet temperature, and filler material.

Achieving high energy storage performance in BiFeO3@TiO2 filled PVDF-based composites with opposite double heterojunction via electric field tailoring

Polymer-based dielectric capacitors are well recognized for high energy density and efficiency. However, the energy density is restricted by the deterioration of breakdown strength with excessive addition of inorganic fillers. Herein, an innovative design of the lamellar-structured BiFeO3@TiO2 (BFO@TO) fillers is proposed and a small amount of BFO@TO is added into P(VDF-HFP)/PMMA blended polymer to fabricate BFO@TO-P(VDF-HFP)/PMMA composites, which delivers an outstanding energy density of 19.3 J cm−3 at 549.2 kV mm−1. The filler possesses a BFO/TO/BFO triple-layered structure. Due to the different Fermi level, electrons are injected from TO into BFO to form electron accumulation layer and construct the heterojunction electric fields between TO and BFO layers. Heterojunction electric fields at two interfaces produced by the triple-layered structure are opposite. The opposite double heterojunction can withstand larger external electric field and improve the breakdown strength. Besides, BFO, as a narrow bandgap semiconductor, is easier for electrons and holes to separate, which further widens the width of the built-in electric field and reduces the dielectric breakdown. Electric field distribution simulations intuitively confirm the enhancement of the breakdown strength. The results provide an effective strategy to address the critical issue of improving the breakdown strength for high energy storage capability.

Excellent energy storage properties achieved in PVDF-based composites by designing the lamellar-structured fillers

Polymer-based dielectrics are widely utilized due to the high power density, fast discharging-charging speed and broad operating temperature range. However, suffering from the inherent low energy density, the practical application is restricted. Herein, a novel structure design of lamellar-structured MgO and BiFeO3/MgO (BFO/MgO) fillers is proposed and a series of PVDF-based composites are fabricated. The breakdown strength is significantly improved due to the large heterojunction electric field produced by BFO and MgO. Meanwhile, the large polarization contributes to a high energy storage performance. A high energy density of 9.93 J cm−3 at 409.6 kV mm−1 with energy efficiency of 66% is achieved in 0.9 wt% BFO/MgO-PVDF/PMMA composites. Compared with previous literatures, high energy density is obtained in a relatively low electric field in this work at such trace filling content, which is quite suitable for the long-term electric field application. This work establishes a facile and effective approach for developing the flexible dielectric capacitors with high energy storage capability.

Stabilized multifunctional phase change materials based on carbonized Cu‐coated melamine foam/reduced graphene oxide framework for multiple energy conversion and storage

AbstractThe leakage of organic phase change materials (OPCMs) at temperatures above their melting point severely limits their large‐scale application. The introduction of porous supports has been identified as an efficient leakage‐proofing method. In this study, a novel carbonized Cu‐coated melamine foam (MF)/reduced graphene oxide (rGO) framework (MF/rGO/Cu‐C) is constructed as a support for fabricating stabilized multifunctional OPCMs. MF serves as the supporting material, while rGO and Cu act as functional reinforcements. As a thermal energy storage material, polyethylene glycol (PEG) is encapsulated into MF/rGO/Cu‐C through a vacuum‐assisted impregnation method to obtain PEG@MF/rGO/Cu‐C composite with excellent comprehensive performance. PEG@MF/rGO/Cu‐C exhibits high phase change enthalpies of 148.3 J g−1 (melting) and 143.9 J g−1 (crystallization), corresponding to a high energy storage capability of 92.7%. Simultaneously, MF/rGO/Cu‐C endues the composite with an enhanced thermal conductivity of 0.4621 W m−1 K−1, which increases by 463% compared to that of PEG@MF. Furthermore, PEG@MF/rGO/Cu‐C displays great light‐to‐thermal and electric‐to‐thermal conversion capabilities, thermal cycle stability, light‐to‐thermal cycle stability, and shape stability, showing promising application prospects in different aspects.

Size effect at discharging process of coconut oil as latent thermal energy storage

Coconut oil is one of the organic PCM materials with high thermal energy storage capability in the form of sensible and latent heat. Ideally, the latent heat storage occurs at a relatively constant temperature associated with phase change transition. Due to relatively low thermal conductivity, the size effect is important to optimize material performance, particularly at the discharging process related to latent heat release. This study will show the simulation results of the size effect in the solidification process of coconut oil by using ANSYS FLUENT. Three plastic balls with radii 2 cm, 3 cm, and 6 cm filled with coconut oil solidified from 308 K to 293 K, and several temperature detectors were placed in the ball to study the heat exchange process. The input parameters of density, heat capacity, thermal conductivity, and viscosity were taken from previous experimental studies. We reported the time evolution of temperature and liquid fraction until the molten coconut oil solidified from different detector positions in each ball.

Numerical Energy Storage Efficiency of MWCNTs-Propylene Glycol by Inducing Thermal Radiations and Combined Convection Effects in the Constitutive Model.

This study examines MWCNTs-PG nanofluid with a uniform dispersion of MWCNTs in PG. It is assumed that both MWCNTs and PG exist thermally in equilibrium and no slip occurs between them. MWCNTs were suspended in PG uniformly and played a significant role. Firstly, the problem is formulated by utilizing empirical correlations, thermophysical attributes, and similarity equations. Then the model is treated numerically along with the coupling of a shooting algorithm. The results against the pertinent flow quantities were plotted and provide a basis for a comprehensive discussion, investigating whether MWCNTs-PG has high thermal storage characteristics under the effects of thermal radiation and combined convection effects. Due to their high energy storage capability, these fluids are reliable for industrial applications.

Nanocrystalline Engineering Induced High Energy Storage Performances of Fatigue-Free Ba2Bi3.9Pr0.1Ti5O18 Ferroelectric Thin Films.

Electrostatic capacitors, though presenting faster rate capability and higher power density, are hindered in applications because of their low energy density. Accordingly, many efforts in electrostatic capacitors, for electronics and electrical power systems, have mainly concentrated on the development of dielectric materials with high-energy density (Ud) and charge-discharge efficiency (η) as well as good stability performances of thermal and fatigue endurance. Herein, we demonstrate that an excellent Ud (∼90 J/cm3) and high η (∼84.2%), as well as outstanding fatigue cycles (1 × 108 st), frequency stability (20-2000 Hz), and a wide temperature range (RT ∼ 160 °C), can be attained in Ba2Bi3.9Pr0.1Ti5O18 (BBPT) ferroelectric thin films via nanocrystalline engineering. It is revealed that nanocrystalline engineering of the BBPT ferroelectric thin films could be controlled via the heat-treatment temperature, which could effectively regulate the breakdown strength and polarization. The enhanced breakdown strength and polarization of the nanocrystalline engineering is further verified through the theoretical phase-field simulations along with experimental results. These results indicate that this is a feasible and scalable route to develop dielectric thin film materials with a high energy storage capability.

Evolution of polarization crystallites in 0.92BaTiO3-0.08Bi(Ni0.5Zr0.5)O3 microcrystal-amorphous composite thin film with high energy storage capability and thermal stability

• A new-type microcrystal-amorphous composite films of 0.92BaTiO 3 -0.08Bi(Ni 0.5 Zr 0.5 )O 3 . • Evolution of polarization crystallites in microcrystal-amorphous composite film. • A high energy storage density of 103.7 J cm −3 is obtained at 8.3MV cm −1 . • Excellent dielectric and energy storage stabilities are achieved in a wide range. Thin film capacitors with large energy storage density and high breakdown strength are widely used in modern electronic fields. To solve the problems of interface effect and different polarization mechanism between matrix and fillers in conventional heterogeneous structure composite thin film capacitors, a new-type inorganic microcrystal-amorphous composite film of 0.92BaTiO 3 -0.08Bi(Ni 0.5 Zr 0.5 )O 3 (0.92BT-0.08BNZ) are prepared by sol–gel method. The amorphous matrix improving the breakdown strength is introduced into the film by adjusting preparation technology. Moreover, the nano-scale polar microcrystalline regions (fillers) are introduced and uniformly distributed in the amorphous matrix under various annealing temperatures. Through investigating the influence of different amorphous matrix and microcrystal trend on the dielectric and energy storage properties, it is found that synergistic effect between the polarized microcrystalline regions and the amorphous matrix are optimal at an annealed temperature of 550 ℃. The result shows that a high energy storage density of 103.7 J cm −3 and an efficiency of 88.3% are obtained under the electric field of 8.30MV cm −1 . Simultaneously, the excellent dielectric and energy storage stability is achieved in a wide temperature range of 20–200 °C. Conclusively, this microcrystal-amorphous composite film overcome the low energy storage capability and poor thermal stability of conventional composite films and provide a feasible way for preparing high energy storage performance films.

Research Trend in Rock Salt Structured High Entropy Cathode

Development of lithium-ion rechargeable batteries with high energy storage capability are required in timely manner. Recently, it has been experimentally and computationally proven that oxides with the disordered rock salt structure can be charged and discharged in the Li-ion battery system. In particular, the high entropy disordered rock salt cathode has unique structure property, where both Li-ion and transition metal are randomly located on the cation sites. Such disordering in metal sites can migrate the Li-ion in a percolating way albeit with sluggish kinetics. Therefore, the high entropy disordered rock salt structure has attracted great attention due to its high energy density and stable structure. In this paper, we introduce a simple and effective strategy in the selection of transition metals for high entropy cathodes to achieve desired electrochemical properties.

High energy storage capabilities of CaCu3Ti4O12 for paper-based zinc\u2013air battery

Zinc–air batteries proffer high energy density and cyclic stability at low costs but lack disadvantages like sluggish reactions at the cathode and the formation of by-products at the cathode. To resolve these issues, a new perovskite material, CaCu3Ti4O12 (CCTO), is proposed as an efficacious electrocatalyst for oxygen evolution/reduction reactions to develop zinc–air batteries (ZAB). Synthesis of this material adopted an effective oxalate route, which led to the purity in the electrocatalyst composition. The CCTO material is a proven potential candidate for energy applications because of its high dielectric permittivity (ε) and occupies an improved ORR-OER activity with better onset potential, current density, and stability. The Tafel value for CCTO was obtained out to be 80 mV dec−1. The CCTO perovskite was also evaluated for the zinc–air battery as an air electrode, corresponding to the high specific capacitance of 801 mAh g−1 with the greater cyclic efficiency and minimum variations in both charge/discharge processes. The highest power density (Pmax) measured was 127 mW cm−2. Also, the CCTO based paper battery shows an excellent performance achieving a specific capacity of 614 mAh g−1. The obtained results promise CCTO as a potential and cheap electrocatalyst for energy applications.

Reduced graphene oxide as a charge reservoir of manganese oxide: Interfacial interaction promotes charge storage property of MnOx-based micro-supercapacitors

Reduced graphene oxide (rGO)-based micro-supercapacitors (MSCs) have emerged as a new type of micro-energy storage device. However, the low volumetric energy density of rGO hampers the application of MSCs in miniaturized energy storage devices. Hybridization of pseudocapacitive materials with rGO is a potential approach to increase the energy density of MSCs. Herein, a densely packed hybrid film of birnessite-type manganese oxide (K-MnOx) supported by rGO is developed, and hybrid-film-based MSCs are found to show a high volumetric capacitance (490 F/cm3) that is ∼ 1.2 and 19 times greater than those of rGO and K-MnOx-based MSCs, respectively. A semi-permanent cycle life with capacitance retention of 97% after 10,000 cycles is observed. Moreover, a charge reservoir concept is introduced, which explains the origin of the high pseudocapacitance of the K-MnOx/rGO hybrid in a unique way. It is observed that synergistic interaction among the charge reservoir (rGO) and electron transfer channel (K-MnOx, which becomes conductive at the interface) facilitates the charging and discharging of K ions, with minimum deviation of the Mn oxidation states. This new charge reservoir concept would serve as a stepping stone toward designing novel hybrid devices with high energy storage capabilities.

Polyphenylene sulfide scaffold based flexible supercapacitor electrode with competitive areal capacitance and flame-retardant behavior

Flexible supercapacitor electrode has been strongly developed as next-generation wearable energy storage electronics in the last decades. The state-of-the-art performance always requires the implantation of compelling energy-storage stuff and flexible scaffolds. However, the inflammable nature of such supercapacitors gives rise to safety issues, and it is a challenge to maintain high energy storage capability and flame-retardant behavior synergistically. Herein, we use a paper-making technique to engineer polyphenylene sulfide (PPS) ultrafine fibers and multi-walled carbon nanotubes (MWCNT), followed by the deposition of in-situ polymerization polypyrrole (PPy). This highly porous electrode exhibits a high areal capacitance of ~1650 mF cm−2 at a current density of 1 mA cm−2, and > 93% of capacitance retention after 5000 charging-discharging cycles at a current density of 20 mA cm−2. Notably, PPS/MWCNT/PPy electrode features noninflammability and zero generation of dense fume in the open flame. Also, the areal capacitance of the electrode remains more than 50% after 0.5 h annealing at 200 °C. This work delivers a new PPS scaffold-based supercapacitor electrode-manufacturing system directing at high energy-storage capability and harsh-environment adaptability.

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

Two-Dimensional Metal–Organic Frameworks with Unique Oriented Layers for Oxygen Reduction Reaction: Tailoring the Activity through Exposed Crystal Facets

Reinforced Via the Insulative Boric Oxide in the Batio3 Amorphous Glass Composite Thin Film with High Energy Storage Capability and Stability

Reinforced Via the Insulative Boric Oxide in the Batio3 Amorphous Glass Composite Thin Film with High Energy Storage Capability and Stability

High-peak-power orthogonally-polarized dual-wavelength Nd:YLF/BaWO<sub>4 </sub>Raman laser

Orthogonally-polarized dual-wavelength laser has significant practical applications in various fields, such as precision metrology, terahertz radiation generation, differential radar, spectral analysis. The Nd:YLF crystal has two orthogonally-polarized emission peaks with comparable emission cross sections, high-energy storage capability and relatively weak thermal lens effect. Owing to these properties, it has been recognized as a suitable gain medium for generating orthogonally-polarized dual-wavelength laser. In this paper, the Nd:YLF crystal with low doping concentration is employed as a laser gain medium to produce 1047 nm and 1053 nm dual-wavelength fundamental lasers with orthogonal polarizations, and the risk of thermal cracking of Nd:YLF crystal is reduced by appropriately increasing the pump spots. Using the intracavity Raman frequency shift in BaWO<sub>4</sub> crystal, orthogonally-polarized dual-wavelength Raman lasers at 1159.9 nm and 1167.1 nm are achieved to have high peak power. Under the total incident pump power of 40 W and a pulse repetition rate of 5 kHz, the maximum dual-wavelength Raman output power is obtained to be 2.67 W. The corresponding total optical conversion efficiency is 6.7%. For 1159.9 nm and 1167.1 nm Raman laser, their maximum average output power values are 1.31 W and 1.36 W, respectively. Their narrowest pulse widths are 1.50 ns and 1.53 ns, and the corresponding peak power values are as high as 174.7 kW and 177.8 kW, respectively. The results show that the problem of thermal cracking of Nd:YLF crystal at high pump power can be solved by reducing the doping concentration and increasing the pump spot. The Nd:YLF/BaWO<sub>4</sub> is a promising crystal combination for realizing orthogonally-polarized dual-wavelength Raman laser.

Recent Progress and Future Prospects on All-Organic Polymer Dielectrics for Energy Storage Capacitors.

With the development of advanced electronic devices and electric power systems, polymer-based dielectric film capacitors with high energy storage capability have become particularly important. Compared with polymer nanocomposites with widespread attention, all-organic polymers are fundamental and have been proven to be more effective choices in the process of scalable, continuous, and large-scale industrial production, leading to many dielectric and energy storage applications. In the past decade, efforts have intensified in this field with great progress in newly discovered dielectric polymers, fundamental production technologies, and extension toward emerging computational strategies. This review summarizes the recent progress in the field of energy storage based on conventional as well as heat-resistant all-organic polymer materials with the focus on strategies to enhance the dielectric properties and energy storage performances. The key parameters of all-organic polymers, such as dielectric constant, dielectric loss, breakdown strength, energy density, and charge-discharge efficiency, have been thoroughly studied. In addition, the applications of computer-aided calculation including density functional theory, machine learning, and materials genome in rational design and performance prediction of polymer dielectrics are reviewed in detail. Based on a comprehensive understanding of recent developments, guidelines and prospects for the future development of all-organic polymer materials with dielectric and energy storage applications are proposed.

Study on thermal energy storage properties of bio-based n-dodecanoic acid/fly ash as a novel shape-stabilized phase change material

In the present study, a novel BSPCM was prepared with the n-dodecanoic acid (or) LA phase change material, which was vacuum impregnated into the porous FA pebbles. The surface morphology of the BSPCM has confirmed the presence of the lauric acid in the porous supporting matrix. The XRD analysis of the BSPCM revealed that the crystalline nature of the PCM was unaltered after impregnation. The surface structure study verified the chemical compatibility between the PCM and supporting material. The DSC results showed that, BSPCM has exhibited a good latent heat of fusion of 68.93 kJ/kg with high thermal energy storage capability of 97.62%. The BSPCM was thermally stable up to 150 °C and showed good leakage stability up to 85 °C. Thermal reliability of the BSPCM performed for 1000 thermal cycles revealed excellent thermal reliability index of 96.76%. Further, thermal conductivity of BSPCM was found to be 0.1702 W/mK, which was attributed to the effective impregnation of the PCM into the fly ash pebbles. In total, the developed BSPCM can be a viable candidate for achieving passive thermal energy storage in buildings.

Demonstration of a compact, multi-joule, diode-pumped Tm:YLF laser.

We report the demonstration of a diode-pumped Tm:YLF laser operating at 1.88 µm that produces pulse energies up to 3.88 J in 20 ns. The compact system consists of a Q-switched cavity-dumped oscillator generating 18 mJ pulses, which are then amplified in a four-pass power amplifier. Energies up to 38.1 J were obtained with long-pulse amplifier operation. These results illustrate the high energy storage and extraction capabilities of diode-pumped Tm:YLF, opening the path to high peak and average power mid-infrared solid-state lasers.

Melting and solidification characteristics of cylindrical encapsulated phase change materials

Thermal energy storage using encapsulated phase change materials (EPCM) has been attracting the attention of researchers in solar energy applications due to their high energy storage capabilities. However, the melting characteristics of EPCMs are affected by many parameters. In this study, experimental and CFD model were used to investigate the parameters influencing the melting and solidification characteristics of a cylindrical EPCM. The developed CFD model was validated with the experimental model's results and with experimental data from the literature. The CFD model is used to investigate the effect of changing the PCM type, heat transfer fluid (HTF) temperatures, HTF flowrates, number of fins and solidification temperatures. Lauric acid and paraffin wax at HTF temperature ranging from 55 to 73 °C and flowrates from 0.064 to 0.323 kg/s are compared. Then the number of fins from 4 to 12 were inserted inside the capsule and compared with the case without fins at the same amount of PCM. The solidification is simulated at HTF temperature from 20-35 °C. Results revealed that increasing the HTF flow rate by five times decreases the melting times of lauric acid and paraffin wax by 30% and 22%, respectively. The total energy stored in paraffin wax is much higher compared with that in lauric acid under the same HTF conditions. Furthermore, increasing the number of internal fins in the capsules to 12 enhances the melting time by 41% of paraffin wax at an HTF mass flow rate of 0.3238 kg/s and temperature of 73 °C. The presence of fins effectively enhances the solidification and melting time of lauric acid and paraffin wax.

Cobalt-iron oxide nanotubes decorated with polyaniline as advanced cathode hosts for Li-S batteries

Lithium-sulfur (Li-S) batteries are generally considered as potential candidates for sustainable energy storage systems owing to low cost and high theoretical energy storage capability. However, the actual implementation of sulfur cathode in Li-S batteries is seriously hampered by the undesirable shuttle effect of lithium polysulfides (LiPS), inferior electroconductibility of S/Li2S and huge volume change during lithiation/delithiation process. Herein, the CoFe2O4 nanotubes decorated with polyaniline (PANI) are rationally designed and fabricated as efficient sulfur hosts to handle these challenges. Specifically, both CoFe2O4 and PANI components possess strong chemical affinity to the soluble intermediate LiPS. Meanwhile, from the perspective of structural superiority, the internal void space of nanotubes can effectively accommodate active sulfur particles and tolerate the large volume change upon cycling. Besides, the conductive polymer of PANI can greatly improve the cathode conductivity and facilitate the electron transfer for active materials. More importantly, the S/CoFe2O4@PANI electrode achieves excellent cycling performance with superior initial capacity of 864.1 mAh g−1 and good reversible capacity retention with 582.6 mAh g−1 even after 500 cycles at 2 C rate.