Maximum Energy Storage Research Articles

Methods of Increasing the Energy Storage Density of Superconducting Flywheel

This paper presents methods of increasing the energy storage density of flywheel with superconducting magnetic bearing. The working principle of the flywheel energy storage system based on the superconducting magnetic bearing is studied. The circumferential and radial stresses of composite flywheel rotor at high velocity are analyzed. The optimization methods of the thickness distribution of the flywheel rim and the material selection of the flywheel in the multi-layer interference assembly with a certain size are given and used to maximize the energy storage density. Finally, the improved flywheel model is established, and the maximum energy storage density of the flywheel is increased by combining the above methods.

Design of a Self-Expanding Stent Mechanism Enacted by Fluid Pressure Difference

In this study, the design of a metal stent which expands under the influence of a difference in hydraulic pressure is presented. Using the action of existing stents as a reference, the joint of the metal stent model is joined, to lock its own elastic force. The maximum energy storage formula was applied to determine if the joint could withstand the elastic force that is integral to the stent model. Simulations of the stent, under the influence of differences in hydraulic pressure, were performed. During simulation, the fluid pressure, the width of the joint of the stent, the angle of the pipe model, and some other parameters, were changed to determine their impact on the stent joint and to explore the differences.

Optimal state for a Tavis-Cummings quantum battery via the Bethe ansatz method

In this paper, we investigate the effect of different optical field initial states on the performance of the Tavis-Cummings (T-C) quantum battery. In solving the dynamical evolution of the system, we found a fast way to solve the Bethe ansatz equation. We find that the stored energy and the average charging power of the T-C quantum battery are closely related to the probability distribution of the optical field initial state in the number states. We define a quantity called the number-state stored energy. With this prescribed quantity, we only need to know the probability distribution of the optical field initial state in the number states to obtain the stored energy and the average charging power of the T-C quantum battery at any time. We propose an equal probability and equal expected value splitting method by which we can obtain two inequalities, and the two inequalities can be reduced to Jensen's inequalities. By this method, we found the optimal initial state of the optical field. We found that the maximum stored energy and the maximum average charging power of the T-C quantum battery are proportional to the initial average photon number, and the quantum battery can be fully charged when the initial average photon number is large enough. We found two phenomena, which can be described by two empirical inequalities. These two phenomena imply the hypersensitivity of the stored energy of the T-C quantum battery to the number-state cavity field. Finally, we discussed the impact of decoherence on battery performance.

Comparative investigations of sorption/resorption/cascading cycles for long-term thermal energy storage

Long-term thermal energy storage is one of the potential and critical solutions to solve the mismatching between thermal energy supply and demand. Even though single-stage sorption cycle, resorption cycle and multi-stage cascading cycle have been proposed for long-term thermal energy storage, the results are difficult to be utilized for selecting optimal cycles because most of them are investigated under different conditions and their performances are not compared under the same criterion experimentally. Herein, the experimental comparative study of different energy storage cycles is implemented for a wide range of heat source temperature and output temperature. For cycles with CaCl2/expanded nature graphite treated by the sulphuric acid (ENG-TSA) sorption bed as the output side, CaCl2/NH4Cl-NH3 cascading cycle has distinct advantage on effective discharging time. Under the general working conditions with relatively high heat source temperature and low output temperature, CaCl2-NH3 sorption cycle is the optimal choice. For cycles with MnCl2/ENG-TSA sorption bed as the output side, MnCl2-NH3 sorption cycle has the maximum thermal energy storage density, thermal energy storage efficiency and temperature lift of 420 kJ·kg−1, 0.51 and 15.0 °C, respectively, at high heat source temperature of 175 °C. Under the critical conditions such as the heat source temperature lower than 155 °C, MnCl2/CaCl2-NH3 cascading cycle is more suitable and shows optimum adaptability to unsteady heat source. The experimental results exhibit the suitable working range of heat source temperature and output temperature for different cycles, and the guidance is revealed for selecting optimal cycles for different types of low-grade thermal energy.

Improved Energy Density and Charge Discharge Efficiency of Polypropylene Capacitor Film Based on Surface Grafting

In this paper, an advanced surface-grafting method is reported to improve the high-temperature performance of biaxially oriented polypropylene (BOPP) membranes. The leakage conductivity of the surface-grafted films decreases by 98% at 85 °C. The decline in the leakage loss contributes to the 99% charge-efficiency at 85 °C. The dielectric constant increases by 7%. The DC breakdown strength grows by 43% at 85 °C. The maximum energy storage density goes up from 1.45 to 2.77 J/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 85 °C. The surface-grafted BOPP film exhibits outstanding energy density and charge-discharge efficiency characteristics. This research provides a theoretical reference for improving the performance of capacitor film based on surface modification.

On the rheological properties of multi-walled carbon nano-polyvinylpyrrolidone/silicon-based shear thickening fluid

Abstract This study examines the rheological properties of shear thickening fluid (STF) enhanced by additives such as multi-walled carbon nanotubes (MWCNTs), polyvinylpyrrolidone (PVP), and nano-silica (SiO2) at different mass fraction ratios. The rheological properties of the liquid (MWCNTs–PVP/SiO2–STF) and the effect of the rheological properties of the STF under different plate spacing of the rheometer were investigated. The optimal mass fraction mixing ratio was also studied. The MWCNTs–PVP/SiO2–STF system with different PVP mass fractions was fabricated using ultrasonic technology and the mechanical stirring method. Then, the steady-state rheological test of the MWCNTs–PVP/SiO2–STF system was carried out with the aid of the rheometer facility. Dynamic rheological and temperature sensitivity tests on the MWCNTs–PVP/SiO2–STF system with 0.1 and 0.15% PVP mass fractions were performed. The rheological test results show that the MWCNTs–PVP/SiO2–STF system has a significant shear thickening effect when the PVP mass fraction is increased from 0 to 0.15%. When the PVP mass fraction is 0.1% and the plate spacing is 1 mm, the system exhibits the best shear thickening performance. This is based on the following facts: the viscosity can be achieved as 216.75 Pa s; the maximum energy storage and energy consumption capabilities can be observed. As a result, PVP can significantly enhance the shear thickening performance of the MWCNTs/SiO2–STF system.

Machine learning and microstructure design of polymer nanocomposites for energy storage application

Film dielectric capacitors have been widely used in high-power electronic equipment. The design of microstructure and the choice of fillers play an important role in nanocomposites' energy storage density. Machine learning methods can classify and summarise the limited data and then explore the promising composite structure. In this work, a dataset has been established, which contained a large amount of data on the maximum energy storage density of nanocomposites. Though using processed visual image information to express the internal information of composite, the prediction accuracy of the prediction models built by three machine learning algorithms increase from 84.1% to 91.9%, 80.9% to 68.9%, 70.6% to 81.6%, respectively. By calculating the branch weight in the random forest prediction model, the influence degree of different descriptors on the energy storage performance of nanocomposites is analysed. A total of 10 groups of composites with different structure and filler amount were prepared in the laboratory, which were used to verify the reliability of prediction models. Finally, the effective filler's structure is explored by three prediction models and some suggestions for the interface design of filler are given.

Ultrahigh energy density of polymer nanocomposites containing electrostatically self-assembled graphene oxide and hydrotalcite nanosheets

In this paper, the nanofiller consisting of graphene oxide (GO) and organically modified hydrotalcite (HT) was fabricated via the electrostatic self-assembly and further reduced and incorporated into the polyimide (PI) matrix to prepare superior nanocomposite films with high energy storage density. It was observed by transmission electron microscopy (TEM) that the insulating HT facesheets were attached well onto the GO film to form a stable sandwich structure. The synthesized ternary nanocomposite film (1.0 rGO@HT/PI) showed high breakdown strength of 175.9 kV/mm and ultra-high dielectric constant at 10 kHz (εr = 35.4), about 10 folds more than pure PI (εr = 3.4), resulting in a maximum energy storage density of 4.84 J/cm3. On account of electrostatic self-assembly, HT nanosheets can efficiently reduce the contact area between graphene oxides and inhibit the formation of conductive networks, thus maintaining a high level of breakdown strength and increasing the energy storage density of the nanocomposite films.

High-capacity and high-power collective charging with spin chargers.

Quantum battery works as a micro- or nanodevice to store and redistribute energy at the quantum level. Here we propose a spin-charger protocol, in which the battery cells are charged by a finite number of spins through a general Heisenberg XY interaction. Under the isotropic interaction, the spin-charger protocol is endowed with a higher capacity in terms of the maximum stored energy than the conventional protocols, where the battery is charged by a continuous-variable system, e.g., a cavity mode. By tuning the charger size, a tradeoff between the maximum stored energy and the average charging power is found in comparison to the cavity-charger protocol in the Tavis-Cummings model. Quantum advantage of our protocol is manifested by the scaling behavior of the optimal average power with respect to the battery size, in comparing the collective charging scheme to its parallel counterpart. We also discuss the detrimental effect on the charging performance from the anisotropic interaction between the battery and the charger, the nonideal initial states for both of them, and the crosstalk among the charger spins. A strong charger-charger interaction can be used to decouple the battery and the charger. Our findings about the advantages of the spin-charger protocol over the conventional cavity-charger protocols, including the high capacity of energy storage and the superior power law in the collective charging, provide an insight to exploit an efficient quantum battery based on the spin-spin-environment model.

Thermodynamic characterization of Mg‐50 wt% LaNi5 composite hydride for thermochemical energy storage application

AbstractIn the present work, composite material, Mg‐50 wt% LaNi5, is thermodynamically characterized for thermochemical energy storage application, and its mechanism of hydrogen absorption is studied by using Johnson‐Mehl‐Avrami (JMA) equation. Pressure concentration isotherms (PCI) of the composite during hydrogen absorption and desorption are measured at 250°C, 300°C, 350°C, and 375°C. The enthalpy of absorption and enthalpy of desorption are calculated as 62.082 and 66.009 kJ/mol H2. Absorption kinetics is measured at 250°C, 300°C, and 350°C with hydrogen supply pressures of 10, 20, and 30 bar. The activation energies are calculated at different supply pressures using Arrhenius equation. Based on activation energy, the rate‐limiting steps are identified. A thermochemical energy storage method is proposed based on equilibrium pressure‐temperature relation obtained during absorption and desorption. The amount of thermochemical energy stored and recovered per kg of the composite is calculated based on reaction enthalpies and hydrogen concentration. The maximum theoretical thermochemical energy stored and recovered at a temperature of 350°C is calculated as 1452.198 and 1365.804 kJ/kg respectively. The maximum theoretical energy storage efficiency is estimated as 0.94. Hence, the composite, Mg‐50 wt% LaNi5, can be used as thermochemical energy storage material in the temperature range of 250°C‐350°C with a thermochemical energy storage capacity of 0.403 kWh/kg composite.

Experimental investigation on the thermo-hydraulic characteristics and occurrence boundary of geyser in a cryogenic pipe

• The essential characters are summarized for the effective recognition of geyser in cryogenic engineering. • The tank pressure and liquid level have an effective suppression effect on geyser. • The occurrence and transition boundary of geyser is divided by a new dimensionless parameter Ae . • The geyser might occur when Ae is larger than 2, and a strong geyser might occur when Ae is larger than 4. In the present study the thermo-hydraulic characteristics of geyser in the cryogenic fuel transportation pipe of a liquid rocket is experimentally investigated using liquid nitrogen. The typical thermo-hydraulic appearances are characterized and analyzed in the geyser process to effectively recognize the occurrence of geyser in practical engineering. The effect of interfering factors such as heat flux, liquid level and tank ullage pressure on geyser are explored. Moreover, based on the new proposed dimensionless parameter of the maximum energy storage ability ( Ae ), the occurrence boundary of geyser is divided. It could be concluded from the results that a clear periodic pressure and temperature change accompanied by periodic plenty vapor ventilation could serve as an indication for geyser’s occurrence, and the eruption of cryogenic geyser has a similar appearance as that in the geothermal field. It is found that a higher tank ullage pressure and liquid level could reduce the geyser’s intensity, and a violent boiling will occur instead of geyser when the heat flux is extremely high. It is a feasible way to eliminate geyser in the cryogenic pipe by increasing the pressure inside the pipe via increasing the tank ullage pressure or liquid level in the tank. Moreover, it is found that a weak geyser would occur in LN 2 and LO 2 when Ae exceeds 2, and then as Ae being larger than 4, a strong geyser might occur with a noticeable pressure peak.

Thermodynamic and Economic Assessment on the Supercritical Compressed Carbon Dioxide Energy Storage System coupled with Solar Thermal Storage

In recent years, renewable energy, particularly solar energy and wind energy, has demonstrated robust growth worldwide. However, the intermittent nature of these energy sources causes significant challenges for the security and reliability of grid, which limits the penetration growth in power market. To enable a higher penetration of renewable energy sources and satisfy the demand for peak shaving and valley filling of the grid, one possibility is to couple them with energy storage systems. In this study, two supercritical compressed carbon dioxide energy storage systems coupled with concentrating solar thermal storage are proposed. One is a simple compression cycle, and the other is a split compression cycle. Both thermodynamic and economic performance have been investigated numerically. The effects of energy storage pressure, heating temperature, thermal oil mass flow rate and split ratio are discussed. The results indicate that under the designed condition, there exists a maximum energy storage efficiency for the simple cycle when the heating temperature is lower than 538.15K. Continuing to increase heating temperature, the efficiency first increases from 64% to 73.9% rapidly as the total pressure ratio rises from 3 to 5. However, the improvement of it will be limited after the pressure ratio exceeds 5. Besides, if the thermal oil mass flow rate rises, the efficiency also has a maximum value, which appears between 150kg/s and 160kg/s. Finally, for the split cycle, there exists an optimal value. And the optimal condition can promote the Dynamic Payback Period and Levelized Cost of Energy to fall about 2 years and 6.1% compared to the simple cycle.

Power Limit Control Strategy for Household Photovoltaic and Energy Storage Inverter

The increased installation capacity of grid-connected household photovoltaic (PV) systems has been witnessed worldwide, and the power grid is facing the challenges of overvoltage during peak power generation and limited frequency regulation performance. With the dual purpose of enhancing the power grid safety and improving the PV utilization rate, the maximum feed-in active power can be regulated by modifying the maximum power point tracking (MPPT) algorithm and battery energy storage (BES) accessibility as control instructions. However, the existing methods not only waste installed PV capacity, but it becomes no longer accessible when the state of charge (SOC) of the BES approaches its upper limit. In response to the above problem, this paper proposes a power limit control strategy to coordinate the MPPT algorithm and the BES accessibility. The proposed strategy directly controls the inverter output current according to the power limit instructions from the electric operation control centers, leading to a bus voltage difference. The difference serves as a control signal for BES and PV. Under a power-limiting scenario, priority is given to power regulation through energy storage to absorb the limited active power. When the SOC of the BES reaches the upper limit of charging, modification of the PV MPPT algorithm facilitates the inverter output power to meet the power limit requirements. To further verify the effectiveness of the proposed power limit control strategy, both simulation and experimental studies are conducted, which consistently indicated a synchronized inverter current with grid voltage and a rapid power response of the power-limiting instruction within 0.2 s. The power limit control strategy not only improves the PV energy utilization but also supports the safe and reliable operation of the power gird in the context of soaring renewable energy penetration.

Low-priced stable SrCl2@SG composite sorbents for low-grade solar heat storage application in open sorption systems

The combination of thermal energy storage (TES) unit and solar air heater is one of the most efficient methods for long-term utilization of solar energy. In this study, a series of stable SrCl 2 @SG composite sorbents were prepared based on silica gel (SG) pellets and strontium chloride hexahydrate (SrCl 2 ·6H 2 O) to store low-grade solar thermal energy for space heating application. Composite characteristics, kinetic hydration/dehydration performance of SG and SrCl 2 @SG sorbents were thoroughly studied. Results demonstrated that the SrCl 2 @SG_10 sorbent has the largest sorption capacity of 0.34 g/g at the temperature of 25 °C and relative humidity (RH) of 90% without any liquid leakage. Additionally, kinetic hydration experiments showed that RH has a great impact on the water sorption performance of the TES materials, while the temperature effect is relatively insignificant. The TES performance of sorbents was further investigated in a laboratory prototype reactor with a multilayer structure, which was designed following an open sorption system concept. 800 g of sorbent pellets were evenly distributed on each layer of the sieve. Maximum instant output power and energy storage density of the SrCl 2 @SG_10 sorbent at 70% RH are 19.7 W and 100 kWh/m 3 respectively. Furthermore, the open TES system still maintains a comparatively high TES performance after fifteen charging/discharging cycles. • Preparation of stabilized SrCl 2 @SG composite sorbent for low-grade thermal energy storage. • Kinetic hydration/dehydration behavior of reversible SrCl 2 ⸱6H 2 O are investigated. • Sorption mechanism of SrCl 2 @SG composite sorbents is proposed. • Thermal energy storage performance of SrCl 2 @SG_10 sorbent is tested in an open sorption system. • SrCl 2 @SG_10 sorbent has discharging efficiency of 58.5% and can be recycled stably.

Conceptual design of LNG regasification process using liquid air energy storage (LAES) and LNG production process using magnetic refrigeration system

This paper presents a theoretical study (conceptual design) aimed at improving the performance of both LNG production and regasification processes. First, a newly process configuration of liquefying natural gas using magnetic refrigerator is developed for a small scale liquefaction process for energy saving purpose. Magnetic refrigeration system has not been utilized for liquefying natural gas up to now. The results show that the new process configuration results in ~74.4% energy savings (SEC 0.0752 kWh/kg) as compared to the SMR-APCI process which has been reported to have the lowest SEC among other small scale LNG processes. The COP of the proposed process has a high value of 6.69. Moreover, a novel process configuration of LNG regasification integrated with Stirling engine and liquid air energy storage (LAES) system is developed for enhanced power production and flexible energy storage options. Stirling engine has not been used for such a system up to now. The results indicate that the proposed LNG-LAES-ST process gives maximum round trip efficiency (192%), exergy efficiency (70.88%) and energy storage capacity (0.4785 kW/kgLNG) when compared to six of the best processes which were recently reported in literature. Two novel processes are modelled by Aspen Hysys and Peng Robinson thermodynamic model.

Ultra-high energy storage density and ultra-wide operating temperature range in Bi2Zn2/3Nb4/3O7 thin film as a novel lead-free capacitor

Capacitor with high energy density, wide operating temperature range, large power density and environmental friendliness is strongly demanded in modern electrical and electronic devices. In this work, Bi2Zn2/3Nb4/3O7 (BZN) thin film as a novel lead-free material with ultra-high energy storage density and ultra-wide operating temperature range, is prepared by magnetron sputtering. Dielectric properties and electric breakdown strength depend on the substrate temperature, resulting in the change of energy storage performance. The dielectric constant and breakdown strength reach respectively 182 and 3.81 MV/cm for the BZN thin film prepared at 700 °C, while the maximum recoverable energy storage density (63.5 J/cm3) at 100 Hz is achieved. Moreover, the BZN thin films possess excellent thermal stability of energy storage properties in an ultra-wide temperature range (-150- 250 °C) and strong fatigue endurance after 1 × 106 charge–discharge cycles. These results reveal that the BZN thin film can be a promising candidate for lead-free energy storage application in equipment working in harsh environment.

Ammoniated salt based solid sorption thermal batteries: A comparative study

Abstract Gas-solid chemisorption pairs of ammonia and halide salts have an edge over other pairs for advanced thermal energy storage batteries due to their abundance, easy availability, cost effectiveness, high sorption capacity, and wide operating temperature range. In the present work, thermodynamic analyses of thermal battery systems are performed for various ammonia-halide salt pairs using measured sorption characteristics. The stored thermal energy can also be upgraded by forming a combination of suitable halide salts. A maximum gravimetric energy storage density of 1664 kJ kg−1 is observed for MnCl2 based thermal battery. The degree of heat upgradation can be as high as 43 °C in case of MnCl2–CaCl2 based resorption thermal battery. The first law efficiency is observed to be as high as 0.42 for CaCl2 based thermal battery. The decrease in first law efficiency due to parasitic mass is observed to be in the range of 26–37 % and 57–66% for different CaCl2 and MnCl2 thermal batteries, respectively. It is possible to recover the stored thermal energy in the form of simultaneous heating and cooling effects by using specific combination of salts which enhances the overall efficiency. First law efficiency as high as 0.92 can be achieved with a CaCl2–NaBr resorption thermal battery delivering simultaneous cooling and heating effects at 10 and 55 °C, respectively, while storing thermal energy at 100 °C.

Effect of metal foam with two-dimensional porosity gradient on melting behavior in a rectangular cavity

The thermal performance of the latent heat thermal energy storage unit (LHTESU) can be effectively promoted by metal foam. In the present work, a new structure of metal foam with a two-dimensional porosity gradient (MFTDPG) is proposed to further accelerate the melting process inside the rectangular cavity. The MFTDPG is obtained by placing the metal foam with small porosity near the left wall and the bottom wall. With consideration of natural convection, the melting behavior under different parameters is numerically analyzed, including the direction of the porosity gradient, the temperature of the left wall, and the aspect ratio of the rectangular cavity. The results show that the structure of metal foam with vertical porosity gradient (MFVPG) and horizontal porosity gradient (MFHPG) can reduce the total melting time by 7.65% and 3.37% respectively. The MFTDPG can shorten the total melting time by 12.07% compared with the structure with uniform porosity. Furthermore, the MFTDPG can achieve the shortest melting time and the maximum thermal energy storage rate (TESR) with different wall temperatures and aspect ratios. For example, when the aspect ratio is 2.5, the total melting time of MFTDPG is reduced by 24.35%, and TESR is increased by 25.88%.

Effect of Zr:Sn ratio in the PBLZST ceramic thick films on the energy storage characteristics

Pb0.91Ba0.06La0.02(Zr0.95−xSnxTi0.05)O3 (PBLZST, x = 0.325, 0.35, 0.375, 0.4) thick films are prepared by solid-state reaction method and flow-casting method. Trace Ba2+ content is introduced to PLZST which is effective in narrowing the hysteresis loop, lowering the Curie temperature point, and improving the fatigue characteristics. Besides that, Zr:Sn ratios are adjusted to study its influence on the material’s energy storage characteristics. PBLZST ceramics with different Zr:Sn ratios are all in tetragonal perovskite structure. The increase of Sn4+ content promotes miniaturization of crystal grain and contributes to stability of antiferroelectric phase, together with enhances the phase transition field strength and breakdown field strength of PBLZST ceramics. The PBLZST ceramic has high energy storage efficiency, which is more than 80%. The maximum effective energy storage density of PBLZST ceramics at 1.94 J/cm3 is obtained when x = 0.35, and their energy storage efficiency is 81.9%, which confirms that they are the potential materials in the pulse energy storage components.

Nonlocal dual-phase-lagging thermoelastic damping in rectangular and circular micro/nanoplate resonators

Accurately estimating thermoelastic damping (TED) is of significance for the design of micro/nano-resonators with high quality factor. This work aims at providing new investigation of TED with considering the non-Fourier heat conduction (NFHC) effect and the size-dependent effects in the thermal and mechanical fields. Analytical models of TED in rectangular and circular micro/nanoplate resonators are firstly developed in the theoretical frameworks of nonlocal dual-phase-lagging (DPL) model and the modified couple stress (MCS) model. The governing equation of coupled thermoelasticity is modeled by adopting the nonlocal DPL theory, and the solution of dilatation temperature is solved by utilizing the trial-function method. The energy-definition approach is used to obtain TED expressions, in which the maximum stored energy includes the classical elastic potential energy and the MCS potential energy. Two representative materials involving the semiconductor silicon and the metal gold with typical thermal and mechanical length parameters and DPL times are selected in simulation. The influences of material intrinsic parameters on TED spectra, which include the DPL times, the MCS length parameter, and the nonlocal thermal length parameter referring to the mean free path, are investigated. TED spectra obtained by the classical models are also plotted for comparison. The results indicate that TED in micro/nanoplate resonators depends significantly on the DPL-NFHC effect and the nonlocal thermal size-dependent effect. Moreover, TED can be reduced by the MCS size-dependent effect resulting in improving the quality factor.