Energy Storage Rate Research Articles

Investigation of Solid-State Batteries for Safer and More Efficient Energy Storage

This research conducts an in-depth quantitative analysis involving 30 participants to optimize solid-state battery electrodes for high-power energy storage applications. The study investigates the intricate relationship between diverse electrode materials and crucial performance metrics, including energy storage capacity, rate capability, and cyclic stability. The findings highlight the pivotal influence of material attributes on electrode behavior, with strong evidence of a positive correlation between conductivity and energy storage capacity. Moreover, the study confirms that smaller particle sizes enhance rate capability, underscoring the significance of material morphology for swift energy exchange. Notably, surface-modified electrodes exhibit enhanced cyclic stability, showcasing the potential of interface engineering for improved long-term performance. The empirical insights gained from this investigation offer valuable guidance for informed material selection and electrode design strategies, not only benefiting high-power energy storage applications but also contributing to broader energy storage technologies. The research outcomes contribute to the advancement of energy storage systems by refining electrode materials and designs, fostering efficiency, sustainability, and technological progress

Strong Ti3 C2 Tx MXene-Based Composite Films Fabricated through Bioinspired Bridging for Flexible Energy Storage Devices.

Flexible energy storage device is one of the most critical components as power source for wearable electronics. The emergence of MXenes, a growing family of 2D nanomaterials, has demonstrated a brand-new possibility for flexible energy storage. However, the fabrication of MXene films with satisfactory mechanical, electrical, and electrochemical reliabilities remains challenging due to the weak interlayer interactions and self-restacking of MXene sheets. Sequential bridging of polydopamine/polyethyleneimine-functionalized (PDA/PEI)-coated MXene sheets to induce synergistically covalent and hydrogen binding connections of MXene-based films is demonstrated here. By interrupting self-hydrogen bonding and π-π stacking interactions, the introduction of long-chain PEI can not only inhibit the massive aggregation of PDA, but also improve the continuity of the interconnection network of PDA/PEI between MXene layers. Hence, the as-prepared MXene/PDA/PEI composite film displays high mechanical strength (≈366MPa) which achieves 12-fold improvement compared with pure MXene film, as well as superior energy storage capability (≈454Fg-1 at 5mVs-1 ) and rate performance of ≈48% at 10000mV s-1 . This modulation of inserted polymer between MXene layers can provide an avenue for assembling high performance MXene films, and can even be extended to the fabrication of other 2D platelets for varied applications.

Numerical analysis of borehole heat exchanger using a single shape-stabilized phase change material in heating and cooling seasons

Borehole heat exchanger (BHE) plays a key role in ground source heat pump (GHSP) and underground thermal energy storage for heating and cooling, which can backfill with phase change material (PCM) to enhance its thermal performance. In this study, a novel PCM-grouted BHE which can run in both heating and cooling seasons by using a single shape-stabilized PCM (SSPCM) is presented and investigated, and the phase change hysteresis (PCH) of SSPCM is detected and applied to achieve the all-seasons run. A heat transfer model considering PCH for U-type BHE was established to evaluate the thermal performance of the novel BHE. And four kinds of backfill materials were concerned and compared to investigate the effect of initial temperature, and pipe spacing on the performance of the BHE and its characteristics of intermittent operation. The results show that octadecane SSPCM with PCH showed the best comprehensive performance in the two seasons with an energy storage rate of 68.9 W/m in heating and 75.9 W/m in cooling, presenting 21.4 % higher than BHE with conventional backfill material. Mean COP during cooling can be improved by 3.61 % when the thermal conductivity increases from 0.5 W/(m·K) to 2 W/(m·K). It also reveals that the selection of PCM for different regions depends on the ground initial temperature.

Waste polyvinyl chloride derived latent thermal energy storage composites for waste heat recovery via packed bed system

Latent thermal energy storage (TES) techniques utilizing phase change materials (PCMs) provide a promising way to mitigate the discrepancy between the intermittent nature of solar energy supply and consistent demand for human society. However, the development is hindered by the slow charging/discharging rates of the low thermal conductivity PCMs. Meanwhile, the high value-added utilization of waste plastic is receiving increasing attention as an environmentally sustainable strategy. In this regard, waste polyvinyl chloride (PVC) is recovered as SiC skeletons to obtain green phase change composites (PCCs) for waste heat recovery. After being infiltrated with paraffin wax (OP44E), proposed PCCs demonstrate a high retention ratio of latent heat up to 91.1% and a thermal conductivity of 2.4 W·m−1·K−1, which is benefitted from limited expansion and impurity remove process, respectively. With the elevated thermal conductivity and spectral absorptance, proposed PCCs exhibit superior solar-thermal energy storage rates. Furthermore, numerical simulation of the thermal charging/discharging performance and flow characteristics is carried out for the packed bed TES system. The results reveal a reduction in charging and discharging time by 21% and 41.1% for proposed PCCs, respectively. This work introduces a novel strategy for recycling waste heat via high-performance TES and repurposing waste plastics simultaneously.

Biomimetic optimized vertically aligned annular fins for fast latent heat thermal energy storage

Latent heat thermal energy storage (LHTES) technology has been widely used in balancing energy demand and intermittent energy supply, as well as thermal management in buildings, but suffers from slow heat storage rates. Here, biomimetic topology-optimized vertically aligned annular fins are proposed to accelerate heat storage performance. Taking the maximum average temperature as the optimization objective function, optimized biomimetic fins can shorten the melting time by 45.9% compared with traditional fins as verified by experimental measurements. Such a fast heat storage rate is also superior to that of pitch-varying fins and diameter-varying fins by 18.4% and 23.5%, respectively. Meanwhile, the temperature uniformity is greatly improved by biomimetic fins with a reduction of average temperature difference in phase change materials (PCMs) by 75.3%. The underlying mechanism can be attributed to accelerated melting of PCMs close to the outer bottom boundary due to unique bifurcation structures of topology optimized fins. The fractal dimension of optimized fins is similar to that of leaf vein structures, demonstrating that proposed topology structures are close to Natural’s optimal solutions. This study provides novel biomimetic structures for accelerating thermal energy storage rate and promotes the application of biomimetics in LHTES techniques.

Evaluation and optimisation of hybrid sensible-latent heat thermal energy storage unit with natural stones to enhance heat transfer

Latent heat thermal energy storage improves the utilization efficiency of renewable energy. Phase change materials (PCMs) commonly suffer from low thermal conductivity and many heat transfer enhancement methods have been developed. However, conventional methods need additional material preparation and processing, which increases the cost and makes them less environmentally friendly. In the current study, natural stones are used to enhance the heat transfer of the PCM in a shell-and-tube unit, forming a hybrid sensible-latent heat storage configuration. Namely, stones, which are widely accessible, low-cost and environmentally friendly, not only act as sensible heat storage media but as the thermal enhancer of the PCM. Results indicate that the energy storage rate of cases with 25 mm-sized stones increased by 8.3%–92.6%. The case with a filling height of 72.8 mm is superior owing to the high energy storage rate and large total stored energy. The stone size rarely influences the total stored energy that increases almost linearly with the void fraction, while it affects the energy storage rate significantly. Cases with 20 mm and 40 mm-sized stones generally have a higher storage rate. Finally, the mechanism is analysed.

Experimental and numerical studies of Ca(OH)2/CaO dehydration process in a fixed-bed reactor for thermochemical energy storage

The Ca(OH)2/CaO thermochemical energy storage (TCES) system based on calcium looping has received extensive attention owing to its high energy storage density, prolonged energy storage time, and environmental friendliness. The heat storage process of the Ca(OH)2/CaO TCES system in a mixed heating reactor was evaluated in this study, by employing a combination of direct and indirect heating modes. The dehydration process was studied experimentally, and a numerical model was established and verified based on the experimental results. The dehydration behavior of 500 g of Ca(OH)2 powder was investigated in a fixed-bed reactor with mixed heating. The experimental and simulation results indicated that mixed heating causes combined centripetal and horizontal propulsion. Heat input is the main limiting factor in the heat storage process, because the radial advance of the reaction is hindered by the low thermal conductivity of the solid reactant particles. Heat transmission partitions were added to enhance the performance of the reactor. The performance of the modified reactor was compared with that of a conventional reactor. The radial heat transmission partitions in the modified reactor effectively enhance the energy storage rate and reduce the reaction time by 59.5% compared with the reactor without partitions.

A Multi-objective Control Strategy of the Energy Storage System in Distribution Networks with a High Proportion of Renewable Energy

With the development of battery technology and power electronic technology, battery-based energy storage has been widely used in Peak Shaving and Valley Filling frequency and voltage regulation for the power system with a high proportion of renewable energy integration. However, the existing control strategies of the energy storage system (ESS) mostly take peak shaving and valley filling frequency and voltage regulation as a single control objective, causing the rest capacity of the energy storage in the single control working period to be wasted, which significantly reduces the utilization rate and economic benefits of energy storage. How to improve the utilization rate and economic benefits of the ESS while enhancing the support performance of ESS has not received much attention. This paper proposes a multi-objective control strategy of ESS to maximize energy storage’s benefit and ensure the distribution network’s safe and stable operation. First of all, this paper combines the auxiliary compensation benefits of the price system of distributed energy storage power stations and proposes a comprehensive index that comprehensively considers the economy of the ESS and the stable operation of the distribution network to support the evaluation needs of multi-objective control of energy storage. On this basis, this paper predetermines the multi-layer judgment logic for ESS operation control under different operating conditions, divides the ESS into different operating conditions according to the control objectives, and proposes a multi-objective control strategy based on variable droop coefficients. It effectively utilizes the idle capacity of the ESS and achieves an optimized control of energy storage that takes into account both technology and economy. The simulation verification based on the energy storage model built in Matlab/Simulink is conducted to validate the effectiveness of the proposed ESS multi-objective control strategy.

Experimental study of the heat transfer during the ice formation of TiO2 water-nanofluid around a helical coil CTES system

Attending to the increasing energy consumption, the interest in Cooling Thermal Energy Storage (CTES) has grown since its application might enhance the performance of refrigeration systems by storing thermal energy at low temperatures via ice-making. CTES is essential in many applications, including central air conditioning in buildings, high-powered electronic cooling applications, waste heat recovery, and food processing, to correct the imbalance in electrical power between daytime demand and nighttime abundance. Regarding air conditioning, CTES releases cool energy through ice melting to support the primary chilling equipment throughout the day, regarded as the peak period. Following this path, this work contributes to the existing bench-scale results in the literature by performing a comparative analysis of the thermal performance of CTES systems operating with water and a 0.19 vol.% TiO2 water-based nanofluid as phase change material (PCM). The bench scale CTES system is an insulated rectangular-shaped tank filled with 36 liters of PCM flooding a helical coil. Since a water/alcohol mixture was the coolant, the temperature of the helical coil allowed ice to grow around itself. The CTES with 0.19 vol.% TiO2 nanofluid results in an 11.1% larger amount of ice and a faster charging process (10.6%). Moreover, the heat transfer process observed on the CTES system operating with the nanofluid has improved the system’s maximum energy storage rate by 17.18%. Analyzing the heat transfer process by computing the involved thermal resistances has allowed explaining the observed improvements. Based on this thermal analysis, we have identified that TiO2 nanoparticles mainly affect the natural convection between the ice layer and the liquid phase of the PCM by increasing the convective heat transfer coefficient.

Optimization of capsule diameters in cascade packed-bed thermal energy storage tank with radial porosity oscillations based on genetic algorithm

The packed-bed thermal energy storage system (PBTES) has broad application prospects in renewable energy, such as for solar, hydraulics, biomass, and geothermal. This study varied the capsule diameter arrangement of the PBTES using a genetic algorithm (GA) to optimize the thermal performance of the cascaded three-layer PBTES during charging. When considering the oscillatory distribution of the radial porosity, the thermal energy storage (TES) rate density was used as an objective function to evaluate the system’s thermal performance. The TES rate density of PBTES was calculated for more than 4000 capsule diameter arrangements. The results indicate that the tank-to-capsule diameter ratio significantly affects the radial porosity distribution, velocity, and temperature distribution of PBTES. The optimal capsule diameter arrangement in the range of 15 mm ≤d≤ 40 mm was obtained as d1 = 15.58 mm, d2 = 21.78 mm, and d3 = 27.68 mm. Compared with the original model, the optimal model’s charging time was reduced by 33.90%, the TES rate density improved by 37.07%, and the cost per unit of heat storage increased by 92.41%. The results show that the GA is a powerful tool for optimizing PBTES structures.

Thermal control performance evaluation of a phase change material-based heat sink for the electronic device suffering transient heat flux shock

To solve the instantaneous thermal shock of electronic devices suffering transient heat flux, a phase change material-based heat sink is designed. The thermal control performance on the maximum temperature, phase change material liquid volume fraction, energy storage rate of the phase change material, natural convection heat transfer between the system and surrounding air, and temperature control efficiency is studied. Results show that in comparison to the heat sink without phase change material, the maximum temperature of the phase change material-based heat sink can be reduced by approximately 10 K. When the phase change material is filling outside the fins, optimum thermal performance can be achieved. For these three PCM and fin combinations, an outstanding temperature control efficiency can be achieved by the fin outside filling scheme, which is about 19%. The temperature control ability is restrained as the electrical device is situated at an angle with a vertical direction. As the orientation increases from 0° to 30°, 60°, and 90°, the average flow velocity decreases by 7.12%, 50.6%, and 75.7%, respectively. In addition, when the dimensionless phase change material filling size is 0.3, a relatively excellent heat transfer performance can be achieved.

Evolution Model of Coal Failure Using Energy Dissipation under Cyclic Loading/Unloading

The damage and fracture of coal is accompanied by a complex energy conversion process, and these different stages of energy evolution are closely related to coal failure. In this paper, an evolution model describing the behavior of coal failure was proposed using the energy dissipation under cyclic loading/unloading. The energy growth pattern and energy consumption characteristics of the coal fracture were analyzed under cyclic loading/unloading. An evolution model of the energy behavior of coal fracture was established. The damage variables of energy dissipation were defined, and a theoretical model was established. The parameters included the relationship between the energy state, damage state, and strength state according to the uniaxial cyclic loading/unloading test. The results show that there are energy excitation and inhibition effects in the process of coal fracture; that is, the accumulation rate and level of energy are affected by the energy storage state, and the energy storage rate changes in the mode of “low promotion and high inhibition”. The abrupt increase in dissipated energy can be regarded as the precursor of coal fracture. Based on the analysis of the characteristics of the damage and failure state and dissipated energy, the discriminant equation for the stability of the coal energy state was constructed; it is a meaningful discovery for predicting and evaluating coal failure.

Energy storage and milk chilling performance of metal oxide nanofluids

The commencement of the cold-chain from the milk production points in smallholder and unorganized dairying in developing nations is still an unmet need. In the present study, an attempt was made to develop nanofluid based phase change materials (n-PCMs), using Al2O3, CuO and TiO2 nanoparticles (at 0.00%, 0.50% and 1.00%) for efficient storage of thermal energy and its subsequent utilization in rapid chilling of milk. Thermal conductivity of the n-PCMs was enhanced up to 29.49% as compared to the base fluid (water) and exhibited the supercooling reduction by 53.74%. Slight reductions in the specific and latent heats were observed (maximum at 1.00% level of nanoparticles) in the range of 0.10–0.25 and 0.4–0.8 kJ/kg, respectively. The n-PCMs capsuled inside a spherical module exhibited energy storage and milk chilling rate augmentations up to 31.97% and 39.11%, respectively. Temperature mapping of n-PCMs along the central vertical points (viz., upper, middle and lower) inside the spherical capsule exhibited the distinct trends during the pre and post phase-transition regimes, which were primarily driven by the buoyancy and natural convections. The study demonstrated the feasibility of developing the energy efficient passive chillers for rapid chilling of milk under the field conditions.

Study on the thermal storage performance of high-temperature molten salt spheres packed bed using different heat transfer fluids

The high-temperature packed bed latent heat thermal energy storage system (PBLHTES) system is regarded as the key to the efficient operation of concentrating solar power (CSP) system. The heat transfer and storage materials determine the thermal performance of the thermal energy storage (TES) system. In this study, a discrete scheme for the PBLHTES system has been programmed, and a one-dimensional non-equilibrium model has been established. The numerical results are in good agreement with the experimental findings of the references. Originally, the effects of different fluids' thermodynamic characteristics on thermal performance are studied. Three widely used heat transfer fluids for high temperature working conditions, namely mixed nitrate salt, mixed chloride salt, and thermal oil, are applied for the established packed bed system, respectively. Then, three systems are numerically simulated, and sensitivity analyses of the Reynolds number, Stefan number, and sphere diameter are performed. According to the results, raising the Reynolds and Stefan numbers improves the energy storage rate but leads to an increase in heat transfer temperature difference and a decrease in exergy efficiency. Increasing Stefan number enhances the thermal storage capacity of three systems but causes irreversible loss. Differently, increasing the particle diameter not only extends the thermal storage time and increases the heat transfer temperature difference in all three systems but also decreases the energy storage rate and exergy efficiency. Furthermore, the decreasing slope of exergy efficiency with an increase in Reynolds and Stefan numbers is slowing down in systems 1 and 2 but growing in system 3. With the increase in sphere diameter, the decline slope is decreasing in all three systems. Overall, it is critical to choose the suitable HTF in a traditional or novel PBLHTES system to optimize thermal storage performance.

A comparative study of melting behavior of phase change material with direct fluid contact and container inclination

Finding a low-cost method to improve the heat transfer rate in thermal energy storage (TES) is essential in the modern world. In the current research, the comparison of inclined systems, which are among the inexpensive methods, with the new combined system employing the auxiliary fluid of water is discussed. Oleic acid is selected as an unsolvable PCM in water to reuse chosen materials at the end of the melting process in more TES cycles. In the combined system, the density difference between water and PCM is utilized to enhance the melting rate of PCM by placing water on the top of PCM to make direct contact. Therefore, water, which has a heavier density than PCM, takes the place of the melted PCM at the bottom of the enclosure during the melting of PCM. At first, the inclined system is examined at seven different inclination angles to identify the energy storage rate. A mathematical model is formulated using the water-PCM system's continuity, momentum, and energy equations. Then, the melting process of the combined system is studied to compare the energy storage rate of combined and inclined systems. Comparing the combined system with the optimal case of inclined systems, the average fluid velocity is 5.44 times higher, which shows the improvement of convection. It was found that the energy storage rate of the combined system (0.299136 kW/kg) is 1.85 times higher than the inclined system (0.161983 kW/kg at the inclination of 30°). As a result, the comprehensive study of the combined system is essential in future research to replace expensive methods.

Critical Review of Ca(OH)2/CaO Thermochemical Energy Storage Materials

Thermal energy storage is an essential technology for improving the utilization rate of solar energy and the energy efficiency of industrial processes. Heat storage and release by the dehydration and rehydration of Ca(OH)2 are hot topics in thermochemical heat storage. Previous studies have described different methods for improving the thermodynamic, kinetic, and structural stability of Ca(OH)2 to improve energy storage density, energy storage rate, and cycle stability, respectively. Here, the mechanisms and effects of different techniques on the performance improvement of Ca(OH)2 and some common problems were reviewed. Specific problems were also clarified based on the characteristics of different technologies. Finally, suggestions for the future development of Ca(OH)2 heat storage materials were provided.

A novel attempt to enhance the heat transfer rate of thermal energy storage using multitemperature phase change materials through experimental and numerical modelling

This work aims to develop the numerical model for the three-stage phase transition of multi-level phase change materials (PCMs) and present the comparative performance analysis between single PCM and multi-temperature PCM thermal energy storage (TES) systems. The performance of the thermal energy storage system was conducted by the implementation of multiple phase change materials (PCMs) which are arranged following the temperature profile of the heat transfer fluid. The proposed TES system has two models; the first is fully packed with single PCM – Erythritol TES, and the second is packed with multi-temperature PCMs, namely acetanilide in the first half of the tank and 1-Naphthol in the second half of the tank. The experiments are conducted to validate the numerical model values and observed that the results are in close agreement with each other and the percentage variation is within 3–5%. The results show that using multi-temperature PCMs provides better performance than single-PCM systems. Based on the results, the performance of the TES system can be enhanced with multi-level PCMs rather than choosing high-conductivity materials in the system, which lead to considerable potential in saving energy loss and an economical way of designing the efficient TES system.

Comprehensive thermal energy storage analysis of ceramic foam-enhanced molten salt in a shell-and-tube unit

Ceramic foam can be used to enhance the energy storage efficiency of molten salt for high-temperature solar thermal applications. However, its performance in a shell-and-tube unit is not fully understood. In this study, the energy storage performance of ceramic foam-enhanced molten salt in a shell-and-tube unit is investigated. The effects of ceramic foam configurations such as the filling height, porosity and outer diameter are studied. The results show that when the ceramic foam reaches the inner tube, the enhancement performance is remarkable, while it is insignificant in the case of below the inner tube. Although the total stored energy of the full foam-filled case is decreased by 13.6% compared to the no foam-filled case, the energy storage rate is improved by 54.9%. The variation of energy storage rate with porosity is generally regular. Ceramic foam with a small outer diameter has great enhancement performance; as the outer diameter increases, the difference in the enhancement gets less remarkable. The three factors are compared through a normalised effective porosity and the ceramic foam with varying outer diameters shows the best performance including the shortest melting time, the largest total stored energy and the highest energy storage rate. It is attributed that the ceramic foam surrounds the tube completely and concentrates around the tube, so its performance of conducting the heat of the tube is the best. The corrosion resistance of ceramic foams and the cost advantage make it a suitable thermal enhancer for molten salt in high-temperature solar thermal energy storage applications.

Sea urchin skeleton-inspired triply periodic foams for fast latent heat storage

The latent heat storage technology has been widely applied in various thermal management fields, but its extensive deployment is limited due to the poor thermal conductivity of phase change material. Here, inspired by the microstructure and functions of sea urchin skeleton, four different metal foam skeletons based on triply periodic minimal surface (TPMS) are introduced to enhance latent heat thermal energy storage performances, which are evaluated by both experiment and numerical simulation. The metal foam-PCM (MFPCM) based on the Primitive structure has the fastest thermal energy storage rate with melting time prominently reduced by 20% compared to the traditional structure (Lattice). The underlying mechanism can be attributed to a more continuous and compact internal structure of TPMS compared with traditional MFPCM by thermal resistance analysis. In addition, the effect of gradient porosity is investigated as well, and the positive gradient in porosity has the fastest melting rate. The present study provides a new idea to design high-performance MFPCM and promotes the application of bionics in accelerating latent heat thermal energy storage.

Numerical Simulation on the Hydrogen Storage Performance of Magnesium Hydrogen Storage Reactors.

Magnesium hydride (MH) is one of the most promising hydrogen storage materials. Under the hydrogen storage process, it will emit a large amount of heat, which limits the efficiency of the hydrogen storage reaction. In this paper, the hydrogen storage performance of the magnesium hydrogen storage reactor (MHSR) and the effect of structural parameters were studied by numerical simulation. The effect of different operating conditions on the hydrogen storage performance of the MHSR is analyzed. The volume energy storage rate (VESR) was taken as the comprehensive evaluation index (CEI). The results show that fins and heat exchange tubes can improve the heat transfer performance of the MHSR. Increasing fin thickness can reduce hydrogen storage time, but increasing fin spacing is the opposite. With the increase of fin thickness and fin spacing, VESR increases first and then decreases. With the increase of inlet temperature, the hydrogen storage time decreases first and then increases. When the inlet velocity is more than 5 m/s, the hydrogen storage time basically stays at 900 s. By optimizing the operating conditions, the hydrogen storage time can be shortened by 57.8%.