Effective Storage Capacity Research Articles

Assessing Water Balance Influenced by Conservation Measures for Sustainable High-value Vegetable Cultivation: A Case Study of Battuvagu Watershed in Telangana, India

Rainfed areas are crucial for India’s agriculture, covering 50% of the total farmland and contributing 40% of the country’s food production. In recent years, the adverse effects of climate change have been found to be exacerbating the complex problems in vulnerable rainfed areas. While climate change affects many aspects of the environment, its impact on water resources is often swift and apparent, with far-reaching consequences for ecosystems, human well-being, and sustainable development. In this context, water budgeting at watershed level and its management are crucial towards promotion of climate resilient agriculture in the rainfed ecosystems. Comprehensive assessment of water balance was attempted, estimating the demand from agriculture, domestic and livestock needs and availability of water in terms of groundwater recharge from different sources and effective surface water stored in an agricultural watershed falling in Siddipet district of Telangana state of India. It involved collection of data on population, land use, and estimating irrigation water needs for crops, humans and livestock, followed by inventorying surface storage structures. Further, water inflow, runoff, and groundwater recharge were calculated using standard methods. The water balance was then determined by subtracting total demand from total availability. The study revealed that the water balance improved significantly, shifting from a deficit (-1.18 ha-m) of pre-project phase to a surplus (+67.91 ha-m) during post-watershed development. Thus, this study revealed the effectiveness of soil and water conservation measures taken up as a part of watershed development project in enhancing groundwater recharge and effective surface water storage capacity leading to positive water balance. The study also evaluated the use of groundwater in terms of stage of development in the pre and post project scenarios. The study concluded that there is a need for controlling the over extraction of groundwater through crop diversification especially towards market driven, less water consuming high value vegetable cultivation based on water availability with active people participation along with awareness building, propagation of efficient water application (micro-irrigation) methods, group mode of irrigation, and conjunctive use of surface and groundwater, etc. for long-term water security in the watershed.

Influence characteristic and improvement mechanism of thermal storage performance of Packed-bed thermocline tank based on high-temperature molten salt

Chloride salts and carbonates thermal energy storage (TES) have great application potential in high-temperature concentrated solar power (CSP) plants. However, their thermal storage characteristics, performance improvement mechanism and economic feasibility of application in high-temperature conditions are not clear. In this study, a transient, two-dimensional and axisymmetric model is developed for packed-bed thermocline tanks. The effects of six commonly solid fillers on thermal storage performance of NaCl-KCl-MgCl2 salt and Na2CO3-K2CO3-Li2CO3 salt at an operation temperature of 450–800 °C are simulated. The suggestions for optimizing fillers are provided combined with thermal and economic performance. Results show that high volume heat capacity and low thermal conductivity of fillers play important roles in deferring migration and weakening diffusion of thermocline, thus promoting thermal storage capacity and efficiency of tanks. Concrete and cast iron are suitable fillers for chloride salts and carbonates TES. The concrete tank is suitable for systems with strict cost control and low TES requirements. The iron tank is suitable for systems with high TES and low cost control requirements, which significantly increases effective thermal storage capacity of chloride salts by 222.1 % and considerably reduces TES cost of carbonates by 41.1 %. The results can be beneficial for high-temperature TES system of CSP plants.

Molecular dynamics simulation of carbon dioxide flow in kaolinite pores

In order to estimate the effective storage capacity of carbon dioxide in geological storage, it makes great significance to understand the seepage mechanism of flowing carbon dioxide fluid and its influence on the occurrence state in micropore. In this paper, the molecular simulation method was used to obtain the optimal configuration of kaolinite micropore and carbon dioxide molecules. The molecular dynamics method was used to simulate the flow characteristics of carbon dioxide fluid in kaolinite pores in differential depth of burial under constant pressure drop. The results show that the adsorption capacity of carbon dioxide fluid on the wall of kaolinite decreases with the increase of burial depth, the fluid density in the center of the micropore increases with the increase of burial depth, the diffusion capacity of the fluid changes significantly when the burial depth is greater than 2 km; when a constant differential pressure is applied, the flow of carbon dioxide fluid in the pore conforms to the classical poiseulle flow, the diffusion ability of the fluid increases with the increase of burial depth, nearly doubling, and the slip length also increases with the increase of burial depth; the flow behavior significantly reduces the total amount of carbon dioxide in kaolinite micropore, where the density of the first adsorption layer near the wall decreases by at least 20%, and its effect on fluid is greater than that caused by the increase of burial depth. Therefore, when estimating the effective storage capacity of carbon dioxide in geological storage, the influence of pressure drop and burial depth on the total reduction of geological sequestration should be considered at the same time. The purpose is to provide more detailed theoretical basis for carbon dioxide geological sequestration.

Geomorphic evolution of a tropical river basin in the Deccan Volcanic Province: a critical water supply source to Mumbai metropolitan region (MMR), India

ABSTRACT Reservoir siltation lowers a dam’s effective storage capacity, which is mostly determined by the sediment discharge from soil erosion in the watersheds. The morphometric parameters are significant in determining erosional susceptibility of watersheds. In the present study, morpho-hypsometric aspects of the Surya sub-basin, a major tributary of Vaitarna river, has been considered. This river system and associated dams provide the major source of drinking water supply to the Mumbai Metropolitan Region (MMR). A major part of the river flows through the Deccan Volcanic Province (comprising basalts) and Quaternary alluvial deposits. The seven sub-watersheds (SWs) of Surya sub-basin were analysed using the morphological parameters (linear, areal, and basin shape aspects), along with ratio factors and hypsometric integral (HI) values. The HI values for the SWs range from 0.11 (SW-1) to 0.51 (SW-6) with a HI value of 0.21 for the whole Surya sub-basin. The relatively high HI values of SW-6 (0.51) and SW-7 (0.31) indicate that these SWs are relatively prone to high erosion and sediment discharge resulting in dam siltation, and will be a great threat to livelihood of millions of people in the MMR. Therefore, prioritizing these SWs for proper engineering measures could reduce erosion and improve recharge.

Development and experimental study of a small-scale adsorption cold storage prototype with stable and tunable output for off-grid cooling

Comfort cooling is a growing demand in summer outdoor activities and work. Adsorption cold storage (ACS) can achieve long-term cold storage without insulation measures and release cold without requiring electricity input. However, the challenges, including unstable cooling output and huge volume, hinder its wide applications. In this study, a small-scale silica gel-water ACS prototype for off-grid cooling is developed and experimentally investigated under typical summer conditions. The heat pipe structure is employed in the adsorption bed for heat transfer enhancement and volume reduction. Valve opening control is utilized for cooling output stabilization and adjustment. The experimental results show that the prototype achieves 6.36 h of cooling output with the outlet air temperature of 25 °C and the average cooling power of 107.67 W under the environment conditions of 35 °C and 40 % RH, indicating an effective cold storage capacity of 685 Wh and an operating efficiency of 0.30. Furthermore, the stable output air temperature can be flexibly adjusted from 19 °C to 27 °C while maintaining the inlet air temperature at 35 °C during the discharging process. Notably, the charging environment temperature shows a minimal influence on the cooling output performance. The prototype's design is novel and applicable for portable cooling in outdoor off-grid scenarios.

Monitoring and risk assessment of Taoyuan ponds using an unmanned surface vehicle with multibeam echo sounder, ground-penetrating radar, and electrical resistivity tomography

Ponds are a unique agricultural irrigation method with a long history in the Taoyuan area. However, most of them lack accurate spatial information, such as water depth, water surface area, and effective water storage capacity. In this study, the water depth of pond was measured using an unmanned surface vehicle, which has the advantage of being able to operate in shallow waters and in areas that are inaccessible to manned boats. The results show that it can rapidly provide 3D point cloud and an underwater 50 cm gridded digital elevation model with an accuracy of 6.7 cm, which can be used to identify structural defects at the pond bed and the embankment and to accurately estimate the water surface area and effective water storage capacity. The nests with diameters of 30 to 70 cm dug by male tilapia to attract female tilapia for spawning can also be found. In addition, the ground-penetrating radar and electrical resistivity tomography were carried out to successfully investigate the electricity-related properties of the internal structure of the embankment and the leakage locations of pond. In conjunction with the maintenance experience of the Taoyuan Management Office, a risk reference index was proposed for the safety management.

Synthesis of rice husk activated carbon by fermentation osmotic activation method for hydrogen storage at room temperature

In the present study, an innovative method of fermentation osmotic activation was employed to produce activated carbon derived from rice husk. The fermentation procedure dismantles the robust lignin present on the rice husk surface, thereby liberating amorphous SiO2, enhances osmotic activation, and promotes pore development. Following the high-temperature osmosis treatment utilizing a KOH solution, a significant portion of the amorphous SiO2 on the husk's surface is successfully dissolved and removed, leading to the formation of numerous carbon skeletons. This procedure culminates in the production of activated carbon characterized by a high specific surface area and substantial pore volume, attributed to the role of K ions during carbonization. The sample DFRO1-AC exhibited the most effective hydrogen gravimetric storage capacity of 1.21 wt% at room temperature (25 °C) and 80 bar pressure, featuring a BET specific surface area of 2270 m2/g. Compared to other activated carbons used for hydrogen storage, our materials demonstrate superior hydrogen storage capacity and employ renewable agricultural waste, indicating high feasibility and broad application prospects.

Reservoir Static Modelling towards Safe CO2 Storage in Depleted Oil Reservoirs of ‘CRK’ Field, Niger Delta, Nigeria

Geological carbon storage (GCS) is gradually gaining acceptance as the technology of highest repute for the mitigation against greenhouse gas effect. This involves the injection and long-term or permanent storage of carbon dioxide (CO2) in subsurface geological formations. The development of a robust 3D reservoir model then becomes necessary to understand the facies changes and the petrophysical properties distribution of candidate CO2 storage reservoirs. This study attempts the use of static modelling technique to investigate the depleted oil and gas reservoirs of ‘CRK’ field in the Niger Delta sedimentary Basin as a potential CO2 storage site. Using an integrated approach of 3D seismic and a suit of well logs from the study area, two reservoir sands (D10C0 and D6200) were mapped. 3D static modelling of discrete and continuous property distribution of the reservoirs revealed the reservoirs are composed majorly of clean sands with water saturation ranging from 8 to 75%. The average porosity and permeability values are between 20 to 29% and 250 to 890mD respectively. A theoretical storage capacity of 24.85Mt is estimated for the two reservoirs combined, while the median effective storage capacity is 6.22Mt. Comparison of the results obtained in the study with recommended standard values show the reservoirs are suitable for CO2 storage. The property models constructed can serve as primary input for dynamic simulation of the oilfield in future studies.

Operational Mode for Water–Sediment Regulation in Plain-Type Sand-Laden Reservoirs: A Case Study of the Haibowan Reservoir

Excessive sedimentation in sand-laden rivers significantly hinders the normal operation and overall effectiveness of reservoirs. This is observed particularly in plain-type sand-laden reservoirs where weak hydraulic conditions in the reservoir area contribute to sediment deposition. Water–sediment regulation is essential in reducing sedimentation and prolonging the lifespan of such reservoirs. Taking the plain-type reservoir of the primary stream of the Yellow River—Haibowan Reservoir as an example, based on a two-dimensional shallow water equation, a two-dimensional mathematical model of water and sediment in the reservoir area is established, the corresponding boundary conditions are improved, and the reliability of the model is verified. Under the premise of ensuring the flood control safety of the reservoir dam, considering the impact on the power generation of the reservoir and the downstream river, and maintaining the long-term large effective storage capacity of the reservoir as the basic principle, the water–sediment regulation scheme is proposed. A two-dimensional kinetic model of sediment transport and representative water–sediment series are employed to simulate the erosion and sedimentation processes in the reservoir under different schemes. The optimisation and comparison of multiple schemes reveal that the sediment-flushing scheme, which lowers the water level to 1072 m above sea level when the inflow discharge is 1500–2760 m3/s and inflow sediment concentration is 5–10 kg/m3, can yield an effective reservoir capacity of 97 million m3 and an average annual hydropower generation of 389.5 million kWh after 15 years of operation. This scheme outperforms the existing sediment-flushing scheme and is recommended as an optimised approach for water–sediment regulation in reservoirs. The results of this study provide technical support for the application of water–sediment regulation in the Haibowan Reservoir and may be useful in the exploration and management of water–sediment regulation for plain-type reservoirs on sand-laden rivers.

Angkutan Sedimen Total Saluran Pembawa Embung Rawasari menggunakan Metode Empiris dan Software HEC-RAS 6.0

The need for water will continue to increase, while the availability of water is limited; therefore, the provision of water must be pursued both by the government and independently. Rawasari Reservoir is one of the reservoirs in Tarakan City with a relatively stable volume and an effective storage capacity of 112,982 m3. The water source of Rawasari Reservoir comes from a channel that is a tributary experiencing sedimentation due to the sedimentation process. Based on this, the research team was interested in calculating sediment transport in the conveyance channel of Rawasari Reservoir using both empirical methods and the HEC-RAS 6.0 software. The methods used in this research are empirical using the Engelund Hansen and Laursen equations, as well as the use of HEC-RAS 6.0 software. Based on the analysis results, the sediment transport rate in the conveyance channel of Rawasari Reservoir calculated using the empirical method at STA 0+025 is 1,6427 x 10-9 ton/s for the Engelund Hansen method and 2,9898 x 10-9 ton/s for the Laursen method. The simulation of sediment transport in the bed of the conveyance channel of Rawasari Reservoir using the HEC-RAS 6.0 sediment transport model at STA 0+025 is 4,61x10-5 ton/s with the Engelund Hansen sediment transport function and 0,000306 ton/s using the Laursen sediment transport function.

Underground Hydrogen Storage in the Bunter Sandstone Formation in the North German Basin: Capacity Assessment and Geochemical Modeling

With planned hydrogen import terminals and production sites along the North and Baltic Seas, the German coast is likely to become the center of the hydrogen economy. Underground hydrogen storage in the sedimentary reservoirs of the region, particularly in the Bunter Sandstone Formation, could provide the required storage capacity for the future hydrogen economy due to its widespread occurrence and proven sealing system. Herein, the storage capacity is assessed using a probabilistic volume approach and possible reactions between the Bunter Sandstone and hydrogen based on geochemical simulations with PHREEQC are determined. This assessment gives an effective storage capacity of 0.84–4.14 PWh in the saline aquifers of the Bunter Sandstone, of which 0.52–2.57 PWh could be stored onshore. If production from currently operating fields are to cease, additional capacities of between 89.43 and 285.53 TWh could be found in its hydrocarbon fields. Mineralogical reactions are shown to be restricted to redox reactions, which do not affect the formation integrity of siliciclastic reservoirs. As a result, pore storage facilities in the Bunter Sandstone could provide an important storage option for the hydrogen economy, but will require further investigations in the lab and in the field.

Composition optimization and hydrogen storage properties of Ti–V–Mn–Fe alloys

Ti–V-based hydrogen storage alloys have garnered interest owing to their salient advantages of reversible hydrogen absorption/desorption at room temperature and excellent kinetic properties. However, the complicated smelting technology of high-purity V metal renders expensive prices, hampering their large-scale production and application. Herein, to overcome this hurdle, abundant and inexpensive Mn and Fe are added to obtain Ti–V–Mn–Fe hydrogen storage alloys. The novel alloy compositions were obtained using a uniform design method. The hydrogen absorption/desorption behaviors of alloys prepared using arc melting technology were analyzed in detail. Systematic investigations show that the activation, kinetics, and thermodynamic properties of alloys are closely correlated with the Ti/(Mn + Fe) ratios. The designed alloy compositions have a multiphase structure with a body-centered cubic (BCC) main phase. The lattice parameters of the BCC phase increase with increasing Ti/(Mn + Fe) ratio, and the large lattice parameters of alloys are beneficial to facilitate the diffusion of hydrogen atoms, resulting in fast kinetics. A reasonable Ti/(Mn + Fe) ratio positively affects the hydrogen storage properties. Among them, the Ti40V40Mn2Fe18 alloy with Ti/(Mn + Fe) = 2 achieved a hydrogen absorption capacity of 3.472 wt% at 298 K and an effective reversible hydrogen storage capacity of 1.485 wt% above 0.1 MPa at 363 K. This study provides a novel insight for designing Ti–V-based alloy compositions via the uniform design method.

Critical drawdown pressure prediction for sanding production of underground gas storage in a depleted reservoir in China

AbstractSanding production of the underground gas storage (UGS) in the depleted reservoir will cause the decline of effective storage capacity, and the erosion of well string and auxiliary equipment, and other engineering problems. A deep understanding of the sanding production contributes to maintaining the injection and production capacity of gas storage and the long‐term safety of the UGS. In this paper, core samples of five main sedimentary microfacies were drilled from the UGS in middle China. The mechanical properties with different conditions of the moisture content in multi‐cycling injection–production process were tested. The critical drawdown pressure (CDP) calculation methods for the UGS were established based on the stress analysis near the wellbore and the Mogi–Coulomb criterion. Adopting the finite element method simulation on the geological model of the target UGS, the geo‐stress of the formation was calculated by inversed analysis and validated based on the Kaiser effect of rock. Then, the CDP of two target wells of the UGS were investigated. The effects of the water moisture and the cycling times of the injection–production process on the CDP were also analyzed. The geo‐stress distribution shows that the horizontal maximum principal stress ranges from 53 to 68 MPa, and the horizontal minimum principal stress is 46–58 MPa in the target reservoir section, and the vertical minimum principal stress is 69–77 MPa in the target reservoir. The calculated CDP changed with the types of the sedimentary microfacies in the range of [6.27, 8.77] MPa, in which the CDP of the mixed mud and sand flat sedimentary facies was the lowest. The weakness of the CDP with the increasing of the moisture content and the cycling times were analyzed quantitively.

The improved analytical stochastic model of infiltration trenches for stormwater quantity control

As one of the infiltration-based low-impact development (LID) measures, infiltration trenches are widely used to reduce runoff and improve water quality. The conventional analytical stochastic approach developed for use in the hydrologic design of infiltration trenches often overestimates the trench's runoff reduction performance when the infiltration rate at the bottom of the trench exceeds some high level or when the size of the trench is smaller than some threshold level. Furthermore, the appropriateness of using kernel density estimation (KDE) for rainfall event separation and frequency analysis has not been examined yet in the actual hydrologic design of LIDs. To overcome these deficiencies, an improved analytical stochastic model (ASM) was developed in this study incorporating the KDE-based rainfall event characterization and a modified formula for estimating the effective storage capacity of trenches. The calibration, verification and application of the improved ASM were systematically presented and their results were discussed. The accuracy of the improved ASM were verified by comparing the analytical results against the corresponding continuous simulation results. A large number of design cases in nine provincial capital cities of China were analyzed using the improved ASM and considering the effects of soil types, trench's storage reservoir depth, area ratio, and climate conditions. The improved ASM of infiltration trenches is useful for quickly and accurately assessing their water quantity control performances. The results indicated that the accuracy of improved ASM improved by up to 71 % in terms of R-square among the 9 study areas compared to conventional ASM. The improved ASM can be used to directly and quickly calculate the useful hydrologic performance indices for a given trench size, soil condition, area ratio and local climate condition, it can thus provide scientific guidance for the Sponge City construction in China and sustainable urban stormwater management.

Design and testing of automatic downpipe equipment for deep grain piles

China is a large grain storage country, and at this stage, the effective storage capacity of the country has exceeded 900 million tonnes. Grain is subject to localized high temperatures, pests, and other abnormalities during storage. Therefore, regular quality checks need to be carried out on the grain, and cuttings are the first step in carrying out grain quality checks. The current domestic cutting equipment suffers from low cutting efficiency and high manual labor intensity, so the need to develop new cutting equipment is imminent. In response to the current problems with domestic cuttings equipment, this work has developed a deep grain pile automatic down tube equipment, which is driven by compressed air and is capable of completing cuttings within a ten-meter depth range in grain silos. Compared with traditional cutting equipment, this equipment greatly improves the efficiency of cutting samples, reduces manual labor intensity, provides new ideas for the development of automation of cutting equipment, and has a broad market.

Assessment of CO2 mineral storage potential in the terrestrial basalts of China

Basalts contain a lot of carbon-fixing minerals which can achieve the fast mineral trapping of CO2. Based on the CO2 mineral trapping mechanism, an evaluation method for CO2 storage capacity in basalts was established, which considers two injection scenarios including direct CO2 injection and carbonated water injection. Then the geological conditions of terrestrial basalts in China were assessed. The range of CO2 mineral storage capacity in basalts at different probabilities was calculated by Monte Carlo simulation. The results show that the total theoretical mineral storage capacity of CO2 in the terrestrial basalts of China is 39792.05–54325.44 Gt with an average of 46948.36 Gt (P50). The effective mineral storage capacities for direct CO2 injection and carbonated water injection are 607.79–1121.44 Gt (P50 = 847.95 Gt) and 201.13–303.85Gt (P50 = 249.50 Gt), respectively. The corresponding effective storage coefficients at P50 are 0.0181 and 5.31 × 10-3, respectively. Carbonated water injection is advised for prior use, which can achieve CO2 mineral trapping more rapidly. The effective storage capacity is usually much larger than the CO2 emissions in the same region except for the eastern region, but their distributions are not well matched, needing a comprehensive source-sink optimization. The screening and classification of basalts in China should also be strengthened in the future to promote the utilization of CO2 mineral storage capacity and the implementation of demonstration projects.

Screening, classification, capacity estimation and reservoir modelling of potential CO2 geological storage sites in the NW Adriatic Sea, Italy

In Italy, the central-northern Apennines and Adriatic Sea domains have been identified as potential CO2 storage areas. Although capacity estimates have been undertaken at a regional scale, more detailed research is required to reduce uncertainty. The present study helps address this gap by conducting a detailed screening of a representative area in the north-western Adriatic Sea for suitable CCS sites, using an extensive dataset composed of both public and private seismic and borehole data. Work included selecting suitable sites based on proposed selection criteria, calculating their theoretical and effective storage capacities applying a probabilistic approach, and then performing dynamic flow modelling on one of the selected sites that is representative of fractured carbonate reservoirs. Based on the screening results, a total of 21 out of 38 structures were selected as having the required characteristics suitable for CO2 storage. As expected, the clastic rock reservoirs have the greatest potential capacity, although some fractured carbonate reservoirs did yield important volumes due to their dual porosity / permeability characteristics. Modelling of one such site highlighted the complex interplay between primary and secondary porosity / permeability on plume migration and capacity estimation. Our results highlight the need to integrate analytical calculations with dynamic simulations for more detailed, site-specific studies to improve the estimates of CO2 storage capacity.

Modelling VOC levels in a new office building using passive sampling, humidity, temperature, and ventilation measurements

New buildings often have high initial concentrations of VOCs that, although not necessarily harmful, may be disturbing and cause discomfort among occupants. In new buildings, running the ventilation system continuously and at full rate during the first year is common practice to reduce VOC levels. However, the drawback of such an arbitrary strategy is the risk of over-ventilating with unnecessary heat losses as a consequence. In this article, a new approach, a VOC-passport, is developed where early measurements of VOCs together with a calculation model are used to find an optimized ventilation strategy. The proposed calculation model is tested on two newly built office rooms where VOCs were measured using passive samplers, together with temperature, humidity and ventilation rates, and it shows good agreement with measurements. An example of how a daily ventilation schedule may look like if optimized with the prosed model is presented. The example illustrates that in buildings where VOC levels are allowed to increase periodically, VOC levels can be kept at acceptable levels during occupancy hours if the effective storage capacity is known. The proposed method has a potential to improve the indoor air quality in new buildings without compromising energy efficiency.

Research on the feasibility of storage and estimation model of storage capacity of CO2 in fissures of coal mine old goaf

The concept of the carbon cycle in the old goaf of a coal mine based on CO2 utilization and storage was put forward adhering to the principle of low-carbon development, utilization of space resources in old goafs, and associated gas resources development. Firstly, the evolution characteristics of overburden fissures in the goaf of the case was studied using a two-dimensional physical similarity simulation test, the sealing performance of the caprocks after stabilization was analyzed, and the fissures were counted and classified. Then, the process of gaseous CO2 injection in the connected fissure was simulated by Ansys Fluent software, and the migration law and distribution characteristics of CO2 under the condition of gaseous CO2 injection were analyzed. Finally, the estimation models of free CO2 storage capacity in the old goaf were constructed considering the proportion of connected fissure and the effectiveness of CO2 injection. The CO2 storage capacity in the old goaf of the case coal mine was estimated. The results showed that a caprock group of “hard-thickness low-permeability hard-thickness” was formed after the caprock-fissures system in the goaf of the case tended to be stable vertically. The connected fissure, occlude cracks, and micro-fractures in the goaf accounted for 85.5%, 8.5%, and 6% of the total fissures, respectively. Gaseous CO2 first migrated to the bottom of the connected fissure after CO2 was injected into the goaf, then spread horizontally along the bottom of the connected fissure after reaching the bottom, and finally spread longitudinally after filling the bottom of the entire connected fissure. The theoretical and effective storage capacities of free CO2 at normal temperature and pressure in the old goaf of the case were 9757 and 7477 t, respectively. The effective storage capacity of free CO2 at normal temperature and pressure in the old goaf after all minefield mined was 193404 t. The research can provide some reference for the coal mining industry to help the goal of “carbon peaking and carbon neutrality”.

Effect of V content on hydrogen storage properties and cyclic durability of V–Ti–Cr–Fe alloys

Vanadium-based body-centered-cubic (BCC) alloys are ideal hydrogen storage media because of their high reversible hydrogen capacities at moderate conditions. However, the rapid capacity decay in hydrogen ab-/desorption cycles prevents their practical application. In this work, V-based BCC alloys with three different V contents (V20Ti38Cr41.4Fe0.6, V40Ti28.5Cr30.1Fe1.4, V60Ti19Cr19Fe2, named as V20, V40, V60) were prepared by arc melting, and their microstructures and hydrogen ab-/desorption properties were investigated systematically. XRD results show that there is a number of C15-Laves phase presence in V20, which does not appear in V40 and V60. Meanwhile, the lattice constant of the BCC phase clearly decreases as the V content rises. These differences result in a hydrogen storage capacity of only 1.82 wt% for V20 alloy, but 2.13 wt% for V40 and 2.14 wt% for V60, and an increment in hydrogen ab-/desorption plateau pressure. The V40 and V60 alloys are chosen in de-/hydrogenation cycle test owing to higher effective storage capacities, and the results show that the V60 alloy has better cycle durability. According to the microstructural analysis of the two alloys during the cycles, the micro-strain accumulates, the cell volume expands, the particles pulverizes and the defects increase during the cycles, which eventually lead to the attenuation of the hydrogen storage capacity. The increment of the V content obviously improves the elastic properties of the alloy, which further diminishes the micro-strain accumulation, cell volume expansion, particle pulverization and defect increase, eventually resulting in a higher capacity retention and better cyclic durability.