Solid Storage Research Articles

Enhanced hydrogen storage property of MgH2 caused by a BaCrO4 nanocatalyst.

Magnesium hydroxide (MgH2) has a broad application prospect in solid hydrogen storage, but the associated higher dehydrogenation temperature and undesirable cycling capacity limit its large-scale application. In this study, a BaCrO4 nanocatalyst prepared via a wet chemistry method was added to MgH2 to achieve better kinetic and thermodynamic performances. Kinetic tests suggested that the onset hydrogen desorption temperature was decreased for milled MgH2 from 390 °C to below 280 °C after the introduction of a 5 wt% BaCrO4 nanocatalyst and the maximum dehydrogenation amount was up to 6.32 wt%. With regard to hydrogen absorption, MgH2 incorporated with 10 wt% BaCrO4 could fully absorb 5.78 wt% H2 within 10 min at 300 °C and recharge 3.1 wt% H2 at a low temperature of 250 °C. In comparison, the hydrogen uptake amounts for MgH2 under the same conditions were only 3.98 wt% and 1.52 wt%. With regard to hydrogen desorption, 5 wt% BaCrO4-modified MgH2 could discharge 4.25 wt% H2 within 10 min at 325 °C and 4.81 wt% H2 at 300 °C, while MgH2 could not dehydrogenate at 300 °C. Meanwhile, only 5% of the performance decayed for 5 wt% BaCrO4-modified MgH2 during ten cycles. Dehydrogenation E a reduced to 106.75 kJ mol-1 in contrast to 156.55 kJ mol-1 for MgH2. In addition, DFT results verified that the BaCrO4 nanocatalyst reduced the band gap from 2.78 eV to 2.16 eV to improve the thermodynamic property of MgH2 and contributed to the decrease in the dehydrogenation energy barrier from 2.27 eV to 1.54 eV. This work provides an insight into the performance of ternary transition metal nanocatalysts for MgH2 hydrogen storage systems.

Cerium-Organic Framework (CeOF) for hydrogen generation via the hydrolysis of NaBH4

Hydrogen gas has been considered an eco-friendly energy source with a high energy content, making it a suitable energy carrier for several industries. A cerium-organic framework, denoted as CeOF, was synthesized by reacting cerium with a tricarboxylic organic linker using a solvothermal method. The material's characteristics were analyzed using X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier transforms infrared spectroscopy (FT-IR) to confirm its crystallinity, phase purity, elemental composition, chemical bonding, morphology, and thermal stability. CeOF catalysized the release of hydrogen from solid hydrogen storage materials, e.g., sodium borohydride (NaBH4) by the reaction with water via hydrolysis. An examination was carried out to analyze the influence of catalyst loading, NaBH4 weight (0.2–3 wt.%), and reaction temperature. The CeOF catalyst showed a significant hydrogen generation rate (HGR) of 1800 mLH2·gcat-1·min−1, with an activation energy of 58.8 kJ·mol−1. It showed good catalytic recyclability enabling continuous hydrogen production for four cycles without any significant decrease in the material’s performance.

Thermal modeling of solid hydrogen storage in a LaNi5 metal hydrid tank

Thermal modeling of solid hydrogen storage in a LaNi5 metal hydrid tank

Machine learning modelling and optimization for metal hydride hydrogen storage systems

Use of machine learning models for solid state hydrogen storage reactor development.

Interlaced Micro-Fibrous Hard Carbon As Superior Anode for Na-Ion Battery: Insights into the Sodium Storage Mechanism and Solid Electrolyte Interface

Hard carbon has been proved to be a promising negative electrode material for sodium-ion battery (SIBs) application. In this study, we have synthesized carbonaceous anode material by pyrolysis of tissue paper waste at different temperatures ranging from 800° to 1400°C. The tissue paper pyrolyzed at 1400°C has shown highest desodiation capacity of 350 mAhg-1 at 20 mAg-1 with stable cyclic performance and 70% capacity retention after 400 cycles at 200 mAg-1. The morphology, structure and surface chemistry of the cycled hard carbon electrodes were examined by ex-situ FE-SEM, XRD, Raman and XPS. The characterization results obtained reveal the detailed insights of the solid electrolyte interface and sodium storage mechanism of the hard carbon. The parameters of diffusion kinetics were evaluated by Electrochemical Impedance Spectroscopy (EIS) and CV analysis at different sweep rates. The results obtained in the study establish tissue paper waste as a promising precursor material to synthesize carbonaceous anode for SIBs by a simple one-step pyrolysis process.

Magnesium based multi-metallic hybrids with soot for hydrogen storage

Magnesium hydride is one of the most sought-after materials for solid state hydrogen storage due to its low cost and high gravimetric capacity (7.6 wt% hydrogen). However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties. It is seen that the hybrid absorbs ∼6.2 wt% hydrogen at a plateau pressure of ∼2 bar at 300 °C and exhibits fast kinetics with ∼6.6 wt% hydrogen absorption within ∼30 min at 300 °C and 20 bar hydrogen pressure. The role of Mg2Ni as a catalyst as well as hydrogen absorbing medium provides an effect akin to ‘hydrogen pump’, thus enhancing the rate of hydrogen absorption. Presence of carbon in various forms such as aciniform, carbonaceous microgel and cenospheres (derived from soot) plays a vital role by providing channels for diffusion of hydrogen through the hybrid. The ARB technique provides an inexpensive and scalable method of synthesis of Mg based hybrids with large number of interfaces and high amount of strain leading to enhanced hydrogen storage properties.

Storage performance of a novel array metal hydride hydrogen storage reactor based on PCM thermal management

Metal hydrides (MH) are an attractive option for solid hydrogen storage with the large thermal effects of their hydrogen absorption and desorption processes when used in reactors. Phase-change materials (PCM) have been used as thermal management media in the MH reactor. To further improve the performance of the reactor, this study proposed a novel PCM-based MH reactor with array layouts, aiming to construct a heat transfer interface with a high specific surface area. A mathematical model was constructed to elucidate the phenomenon of heat transmission and absorption reaction. It was found that an increase in the number of array units significantly increased the heat transfer area but had a limited impact on enhancing the absorption rate and heat transfer. Nevertheless, the array reactor with seven units had a significant 1.0 times increase in the absorption rate compared to the traditional reactor with only one array unit. Furthermore, the enhancement of thermal conductivity in MH/PCM and the elevation of hydrogen supply pressure have the potential to accelerate the reaction rate and heat transfer during absorption. The enhanced absorption pressure not only enhances the driving force of the reaction directly but also amplifies the temperature difference in heat transfer between PCM and MH. Consequently, this leads to a further improvement in heat transfer and reaction efficiency.

A novel fin efficiency concept to optimize solid state hydrogen storage reactor

The process of heat-driven mass transfer involved in hydrogen storage within metal hydrides (MHs) demands implementing a heat transfer system (HTS) to facilitate faster hydrogen charging and discharging. One effective method to enhance heat transfer is utilizing an HTS equipped with fins and a cooling tube. Among the crucial factors for optimizing the reactor, fin efficiency (FE) plays a vital role, although it has not been explored in unsteady processes like the present one. This study introduces a novel FE technique to optimize fins in a conventional longitudinal finned tube MH reactor based on LaNi5. Due to the intricacies of the problem, making analytical estimation of FE challenging, the authors turned to the concept of reverse engineering. This approach utilizes simulated data's temporal temperature profiles to calculate the FE. The number of fins is varied from 4 to 12 while keeping the total fin weight constant. Heat transfer performance improved as the number of fins increased, but the FE deteriorated from 0.89 to 0.56 due to the reduction in fin thickness. A performance index (PI) that considers the number of fins is introduced to assess the overall performance. Its values are 0.58, 0.79, 0.96, 1.05, and 1.1 for configurations with 4, 6, 8, 10, and 12 fins, respectively. The configuration with 8 fins is deemed optimal because further increasing the number of fins led to only marginal improvements in PI value. Subsequent optimization of fin shape, precisely radial tapering, had a minimal impact on heat transfer performance. Finally, the desorption behavior was examined for the optimal configuration with 8 fins of constant thickness.

Retrofit of a coal-fired power plant with a rock bed thermal energy storage

Power production accounts for about one-fifth of the global final energy consumption and over one-third of all energy-related CO2 emissions. Low-cost, large-scale thermal energy storages are considered as solutions for the decarbonization of fossil-fired power plants by their conversion into power-to-heat-to-power systems, so-called thermal storage power plants. This paper investigates the retrofit of a Chilean coal-fired power plant with an innovative solid media storage from a techno-economic perspective. Selecting a storage capacity of 5.27 GWhth, corresponding to 8 h of discharge, and increasing the inlet steam generator temperature from 590 to 650 °C lead to the highest annual round-trip efficiency of 34.9% and to up to 3.4% lower levelized cost of electricity. Minimum levelized cost of electricity as low as 88.1 €/MWh is attained and considered as close to competitiveness with well-established molten salt storage systems. A sensitivity analysis shows that assuming even five times lower storage costs, initially the strongest driver of capital expenditure, only meant 4% lower levelized costs of electricity on average. On the other hand, the design of electricity purchase for charging, for example with green power purchase agreements, turns out to be the key lever to a successful implementation.

High-capacity hydrogen storage in lithium decorated penta-BN2: A first-principles study

The development of solid hydrogen storage materials is an important part of the large-scale application of hydrogen energy. The gravimetric density of hydrogen storage materials and modified metal atoms agglomeration are the key research issues in two-dimensional hydrogen storage materials. Based on first-principles calculations, lithium-modified penta-BN2(P-BN2) is developed as a new hydrogen storage material. The geometric and electronic structures of lithium-modified P-BN2 (Li-P-BN2) have been calculated. P-BN2 has strong binding ability to lithium metal atoms, preventing the formation of lithium metal clusters, and the material has a strong stability. Twenty-eight hydrogen molecules can be stably adsorbed by the Li-P-BN2 system, and the theoretical storage gravimetric density of hydrogen is 13.27 wt%. Ab initio molecular dynamics (AIMD) shows that the material has a useable capacity of 8.95 wt% at 300 K. The mean desorption temperature is 437.13 K. The excellent hydrogen adsorption capacity and high gravimetric density of Li-P-BN2 may make it a promising hydrogen storage material.

A Model of Integration between a CSP System and a PV Solar Field Sharing a Solid Particles Two-Tanks Thermal Storage

The integration of a CSP tower system with a PV solar field, sharing a thermal energy storage, is modeled and discussed. The tower system uses a new-design solid particle fluidized bed receiver integrated with a thermal storage, where hot particles are directly collected to store daily energy for overnight production of electricity. The PV solar field is aimed to supply the daily energy demand; when there is a surplus of PV energy production, the electric energy is converted to heat and accumulated in the thermal storage too. The integration of the two energy systems is modeled, building efficiency functions for all the sub-components of the integrated plant (heliostat field, receiver, storage, power block, PV field). Yearly simulations are performed for two different locations, Spain and Australia, obtaining that a system with a peak power of 10 MWe CSP + 15 MWe PV can supply—with a limited curtailment—a fraction of more than 60% (respectively, 62% and 68%) of a realistic electric load with a peak demand around 10 MW, to be compared with the 45/47% of the same load obtained adopting a PV-only system with the same overall peak power. In the integrated system, PV directly supplies 40/41% of the load, the remaining 23/28% being produced by the power block (mainly fed by the CSP).

Simulation study on a novel solid–gas coupling hydrogen storage method for photovoltaic hydrogen production systems

Compressed hydrogen storage in photovoltaic hydrogen production systems faces several challenges, including limitations in storage volume, compression energy consumption and safety concerns. To improve the comprehensive hydrogen storage performance, this study develops a novel solid–gas coupling hydrogen storage method that combines metal hydride and phase change material (MH-PCM). Firstly, a vertical MH-PCM solid storage model considering the natural convection effect is proposed and investigated. Building upon this model, the solid–gas coupling hydrogen storage is constructed and integrated into the photovoltaic hydrogen production system to evaluate its comprehensive storage performance. Results reveal that considering natural convection leads to an approximately 12.7 % increase in the average storage rate, but is also accompanied by an uneven storage process. To address this unevenness and further enhance the storage rate, it's advisable to focus on structural optimization at the bottom of the tank. Additionally, improving the PCM thermal conductivity and hydrogen inlet pressure (to approximately 1 MPa) are also proven effective strategies. The proposed solid–gas coupling hydrogen storage demonstrates comprehensive advantages, particularly compact size and reduced energy consumption. Furthermore, appropriately increasing the coupling ratio between solid and gaseous capacities can achieve the even smaller storage volume. These findings can provide valuable theoretical and engineering guidance for implementing such hydrogen production and storage systems.

Electrochemical-energy- exergy analysis of reversible solid oxide cell-based small-scale stand-alone energy storage system

The present renewable energy systems should shift towards more storage-based systems due to their inherent intermittency. This study examines the electrochemical, energy, and exergy performances of a Reversible Solid Oxide Cell (ReSOC) based stand-alone energy storage system “with a pressurized gas tank”. The system operates in the fuel cell mode (SOFC) for power generation and electrolysis cell mode (SOEC) for syngas production. The exergy analysis gives a detailed insight into the irreversibility points in both system operation modes. The ReSOC system model is based on a validated ReSOC stack electrochemical model and system components’ mass-energy balance model. The power extraction level in the ReSOC stack was shown to determine the thermal management required through the electrochemical analysis. The energy analysis resulted in a system roundtrip efficiency of 51 % at the considered operating conditions. In addition, the highest points of exergy loss/destruction are the exhaust air (SOFC: 32 %, SOEC: 34 %), ReSOC stack (SOFC: 25 %, SOEC: 28 %), and pressure regulation valve (SOFC: 11 %, SOEC: 17 %). The results also show that the SOEC mode performed better than the SOFC mode in the energy and exergy analyses. This study may be used as a basis for stand-alone system performance improvement leading to higher efficiency.

Solid state hydrogen storage: Decoding the path through machine learning

We present a machine learning (ML) framework HEART (HydrogEn storAge propeRty predicTor) for identifying suitable families of metal alloys for hydrogen storage under ambient conditions. Our framework includes two ML models that predict the hydrogen storage capacity (HYST) and the enthalpy of hydride formation (THOR) of multi-component metal alloys. We demonstrate that a chemically diverse set of features effectively describes the hydrogen storage properties of the alloys. In HYST, we use absorption temperature as a feature which improved H2wt% prediction significantly. For out-of-the-bag samples, HYST predicted H2wt% with R2 score of 0.81 and mean absolute error (MAE) of 0.45 wt% whereas R2 score is 0.89 and MAE is 4.53 kJ/molH2 for THOR. These models are further employed to predict H2wt% and ΔH for ∼ 6.4 million multi-component metal alloys. We have identified 6480 compositions with superior storage properties (H2wt% > 2.5 at room temperature and ΔH < 60 kJ/molH2). We have also discussed in detail the interesting trends picked up by these models like temperature dependent variation in the rate of hydrogenation and alloying effect on H2wt% and ΔH in different families of alloys. Importantly certain elements like Al, Si, Sc, Cr, and Mn when mixed in small fractions with hydriding elements like Mg, Ti, V etc. systematically reduce ΔH without significantly compromising the storage capacity. Further upon increasing the number of elements in the alloy i.e from binary to ternary to quaternary, the number of compositions with lower enthalpies also increases. From the 6.4 million compositions, we have reported new alloy families having potential for hydrogen storage at room temperature. Finally, we demonstrate that HEART has the potential to scan vast chemical spaces by narrowing down potential materials for hydrogen storage.

Analysis of a hybrid heat and underwater compressed air energy storage system used at coastal areas

Offshore wind power has achieved a storage interest in recent years due to the advantages such as high wind speed, constant wind direction, rich wind energy resources and sufficient annual utilization hours. It has been widely recognized that the underwater compressed air energy storage is one of the most competitive technologies to be integrated into the offshore wind farms. However, the economics of the underwater gas storage device is the main obstacle when this type of energy storage is arranged in shallow-water areas. A hybrid heat and underwater compressed air energy storage system is thus suggested to be integrated with the fluctuating renewable energies. This necessitates the use of electrically heated solid thermal energy storage to provide greater flexibility. Both the system thermodynamics and economics are examined under the premise of constant or varying power input. Results demonstrate that the system behavior is strongly dependent on the water depth at 0–100 m. The combined efficiency and net present value are 44.4% and 67.41 million dollars for a 10 MW hybrid energy storage system as the water depth is 100 m, while they are 29.9% and 40.39 million dollars for the standalone system. The system integrating with the solid thermal energy storage is verified to be a much more valuable technology to manage offshore renewable powers. Furthermore, it indicates that the underwater pipe with a larger diameter is favorable to improve system performance.

Simplicity is the ultimate sophistication: One-step forming for thermosensitive solid–solid phase change thermal energy harvesting, storage, and utilization

In light of the growing recognition of low-carbon initiatives, renewable energy is gradually assuming a dominant role within the energy framework. Phase change materials can enhance the efficiency of renewable energy utilization by energy peak shaving and time shifting. However, leakage and inherent rigidity signify that a significant amount of energy input is required for scale-up applications of phase change materials to enhance shape stability and processability during industrial installation. In conventional enhancement strategies, high-quality encapsulation means more intricate processes and higher energy consumption. Here we propose a simplified thermally-initiated encapsulation and molding strategy, which involves grafting the phase change materials onto thermosetting polymer backbones by covalently integrated, to construct self-supported phase change materials with complex three-dimensional geometry. The encapsulation process is macroscopically manifested as a transformation from solid-liquid to solid–solid phase change. Therefore, by imposing restrictions on liquid materials, any ultra-high-precision complex structure can be molded, and mechanical properties are imparted through curing to achieve shape stability, ultimately enables the integration of phase change material encapsulation and casting. The complete process requires no curing agents or organic solvents, and no pollution emissions, making it highly maneuverable and environmentally friendly. Furthermore, we demonstrate the universal high value applications of new materials in different fields. In the ancient thermotherapy experiment, the sample exhibited sustained heat release for 8 min. In the advanced chip cooling simulation, the chip exhibits superior heat dissipation performance, as evidenced by its operating temperature being 50 °C lower than that of natural cooling within 20 min. It confirms the remarkable potential of phase change materials constructed through this approach for thermal energy applications.

Preparation of corn straw-based carbon by “carbonization-KOH activation” two-step method: Gas–solid product characteristics, activation mechanism and hydrogen storage potential

Making excellent carbon-based hydrogen adsorbents requires thoroughly understanding the two-step activation method's reaction mechanism. This research examined the properties of gases and solids with high KOH/biochar ratios (4:1), various carbonization temperatures (400–600 °C), and activation temperatures (700–900 °C). The potential of biochar for hydrogen storage was further examined. These results demonstrate the division of the KOH activation process into four temperature-dependent reaction stages. The emission of CH4, CO, and H2 in various temperature ranges can be significantly influenced by the degree of carbonization and activation temperature. The outcome of activation is primarily determined by the volatile content and reactivity of carbon precursors. Biochar produced at 400 °C for carbonization and 900 °C for activation has a specific surface area (SSA) of 3567.33 m2/g. The oxygen concentration of H-400 decreases as the activation temperature rises, whereas the oxygen-containing structure can be built by raising the carbonization level. The hydrogen storage capacity of biochar was 2.49 wt.% at −196 °C and 1 bar, and increased to 5.51 wt.% at 50 bar, while it is 0.43 wt.% at 50 bar and room temperature. These findings can provide a novel strategy for developing carbon-based hydrogen storage materials.

Effect of structural characteristics on the transport characteristics of solid particles in the thermal storage and release system of circulating fluidized bed

Coal-fired power generation stands as the most economically viable modulating power source in present-day China. It holds the potential to offer prospective solutions to the challenges posed by the rapid expansion of intermittent, unpredictable, and unstable renewable energy sources. Solid particle thermal storage technology emerges as an effective means to enhance the flexibility of coal-fired circulating fluidized bed power units. To attain an optimized structure for the solid particle thermal storage and release system in circulating fluidized bed units, experimental research was conducted on a 0.1 MWth circulating fluidized bed test platform. This study delved into the impact of ash storage bin geometries and the shapes of their feed-discharge valves on the control properties of solid particle transportation. The experimental outcomes reveal that employing inverted m-shaped valve and dual U-shaped valves for feed control, alongside U-shaped valves and N-shaped valves for discharge control, both enable efficient and rapid storage and release of solid particles within the circulating fluidized bed. Under similar air distribution conditions, the inverted m-shaped valve exhibits lower conveying energy consumption than the dual U-shaped valves, while the N-shaped valve excels in control characteristics over the U-shaped valve. Furthermore, the inverted m-shaped valve and the N-shaped valve demonstrate optimal overflow port heights, and the ash storage bin exhibits an optimum height-to-diameter ratio.

Design of the LIMELIGHT Test Rig for Component Testing for High-Temperature Thermal Energy Storage with Liquid Metals

Thermal energy storage systems for high temperatures &gt;600 °C are currently mainly based on solid storage materials that are thermally charged and discharged by a gaseous heat transfer fluid. Usually, these systems benefit from low storage material costs but suffer from moderate heat transfer rates from the gas to the storage medium. Therefore, at the Karlsruhe Liquid Metal Laboratory, liquid metals are investigated as alternative heat transfer fluids for such heat storage systems, making use of the broad temperature range, in which the metals are in a liquid state, and their efficient heat transport capabilities. In this work, the design and construction of a high-temperature test rig using liquid lead is presented. The goal of the experiments is to demonstrate the operability of a pump, valves and measurement equipment at 700 °C in a challenging corrosive environment. Based on material pre-tests in stagnant lead at 700 °C, which are also shown in this study, aluminizing and pre-oxidation of the pipes and components are applied for enhanced corrosion protection.

The investigation of a fuzzy-internal mode PID-based temperature control system for solid state electric storage heaters

It is a fuzzy internal mode PID temperature control system designed for solid electric storage heating systems with high inertia, hysteresis, and nonlinearity. Experimental results demonstrate that the control strategy has a high level of model adaptability and anti-interference capability for the changing operating conditions of solid-storage boilers, that the system overshoot is steadily controlled within 5% and that hysteresis cannot adversely affect the stability of the control system, that the control accuracy of water supply temperature can reach ± 1∘C, and that the control quality is superior to traditional PID strategies.