Large-scale Storage Research Articles

A novel semi-analytical monitoring model for multi-horizontal well system in large-scale underground natural gas storage: Methodology and case study

Carbon neutrality necessitates cleaner and more efficient use of fossil fuels. The storage of substantial amounts of energy in porous subsurfaces, such as underground natural gas storage (UGS), which is regarded the only long-term energy storage solution, is one of the promising technologies. Appropriate monitoring mechanisms are necessary for the security of UGS with a correctly configured injection-withdrawal capacity. In this research, a semi-analytical model of multi-horizontal well systems is presented and used to large-scale underground natural gas storage. The Laplace transform and Stehfest numerical inversion are used in UGS to solve the radial diffusion equation. We used the line source function and the pressure superposition principle to find a solution for a multi-horizontal well system. To illustrate the reliability of the suggested method, a numerical verification was performed. In UGS, pressure behavior at various phases identifies several types of flow regions, including wellbore storage effect stage, skin effect stage, early radial flow stage, linear flow stage, transitional flow stage, and late radial flow stage. Continuous gas injection and withdrawal from offset wells might result in pressure behavior with rising or dropping features when compared to a single well model. The evaluated permeability is 0.68 mD, the well spacing is 502 m, and the initial pressure is 27.28 MPa, according to field data from China's largest Hutubi UGS. The maximum injection and withdrawal capacities for wells with and without interference with wells are 9.46 × 105 and 1.1 × 106 m3/d/MPa, respectively, according to the productivity index. By continually injecting gas from offsetting wells, the target well's potential gas withdrawal capacity is raised by 16.2 %.

Strengthening the metal-support interaction over Pt/SiO2-TiO(OH)2 by defect engineering for efficient dehydrogenation of dodecahydro-N-ethylcarbazole

Liquid organic hydrogen carriers (LOHC) are considered as the promising candidates for large-scale hydrogen storage. The N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NECZ/12H-NECZ) system has received increasing attention due to its excellent comprehensive properties in the hydrogen storage candidates. In this work, the Pt/SiO2-TiO(OH)2 catalysts are synthesized and show good activity, selectivity and stability for 12H-NECZ dehydrogenation reaction. Among them, the 2.5 wt% Pt/SiO2-TiO(OH)2 catalyst shows the best dehydrogenation performance with 5.75 wt% H2 release amount and 98 % selectivity of NECZ. Combined with XRD, HRTEM, ATR-FTIR, XPS and EPR analysis, it is found that the oxygen vacancy concentration in Pt/SiO2-TiO(OH)2 is significantly enhanced due to the formation of Si-O-Ti species compared with Pt/SiO2 and Pt/TiO(OH)2, which strengthens the SMSI (strong metal-supporting interaction) effect between metal Pt and support SiO2-TiO(OH)2. The optimized d-band center of catalyst is beneficial for accelerating the sluggish kinetics of the rate-limiting step of the whole dehydrogenation reaction. Furthermore, compared with the results by replacing SiO2 with Al2O3 or CeO2, it is indicated that the introduction of oxides mainly plays the role of regulating the surface electronic state of TiO(OH)2 and increasing the oxygen vacancy concentration.

All-Liquid Metal Battery

A secondary battery (accumulator) employing molten metals or molten metal alloys as active masses at both electrodes and a molten salt as electrolyte in between is called an all-liquid-metal accumulator battery (LMB). Separation of the electrodes and the liquid electrolyte based on segregation caused by different densities and immiscibility of the materials is a characteristic feature. High coulometric storage capabilities of the molten-metal electrodes combined with the relatively low cell voltage and the high stability of the system and the operational principle yield a secondary battery suitable for grid applications and, in particular, for power-quality management and large-scale stationary storage.

Calcium hydroxide and porous silicon-impregnated silicon carbide-based composites for thermochemical energy storage

Thermal energy storage has a prospect for large-scale storage of renewable energy. Thermochemical energy storage using reversible gas–solid reactions can store thermal energy for unlimited periods with high energy density. Calcium hydroxide (Ca(OH)2), which is abundant and environmentally friendly, is one of the most promising materials for thermochemical energy storage systems. However, pure Ca(OH)2 powder has poor power density and bulk stability owing to its low thermal conductivity, volume change, and agglomeration over dehydration–rehydration cycles. Practical composites that can simultaneously overcome these problems have not been reported yet. This study combines Ca(OH)2 with ceramic foam and honeycomb structures of silicon-impregnated silicon carbide (Si–SiC) and demonstrates the improved power density and bulk stability of the resulting composites. The Si–SiC foam composite, loaded in a laboratory-scale fixed-bed reactor, exhibits a thermal discharging power density of 0.71 MW mbed−3, which is 1.6 times that of the pure Ca(OH)2 powder. In addition, the foam composite reduces the volume change by 80% and does not form centimeter-scale agglomerates even after 15 cycles, unlike the pure powder. The results suggest that embedding solid storage materials into thermally conductive open-cell foams can simultaneously enhance power density and bulk stability.

Characteristics and Formation Mechanism of Multiscale Storage Spaces in Ancient Deep Tight Reservoirs: Examples from the Cambrian Yurtus Formation in the Northern Tarim Basin, China

AbstractUnder the background of complicated diagenetic fluids, high-temperature pressure in superimposed basin, the pore-forming and pore-preserving effects of deep tight reservoirs are complex, and the formation mechanism of high-quality reservoirs has always been the core issue. With the discovery of oil and gas in ultradeep drilling in Tarim Basin, the most unconventional tight reservoir of Lower Cambrian Yuertus Formation in Tabei area began to receive attention. Based on the research of typical field outcrops in Tabei area, the lithofacies, reservoir space differences, and reservoir formation mechanism are systematically analyzed. (1) The stratum has undergone complex multistage diagenetic fluid transformation, and the rock types are diverse with great differences; siliceous rock and dolomite are the main rock types, often in thin-medium layered distribution. (2) After long-term deep burial transformation, siliceous rock and dolomite can still retain a large number of effective storage spaces; hydrothermal dissolution pores, organic acid dissolution pores, atmospheric freshwater dissolution pores, and intercrystalline pores are the main pore types, which provide main storage spaces. Multiscale pores are developed in siliceous rock and dolomite, with good connectivity and good pore structure. (3) The large-scale storage spaces mainly come from the effective maintenance of primary pores, organic matter, and hydrothermal dissolution. The siliceous minerals and dolomite have stable properties and strong resistance to compaction and can effectively maintain the early pores. (4) The large-scale reservoir space was formed in the early diagenetic stage; the pressure-solution and cementation are the two most important diagenetic processes for reducing storage spaces; however, under the pore-forming and pore-preserving effects of early silicification and dolomitization, various types of dissolution, and oil charging, the tight lithology can still maintain effective storage spaces. The related research has important theoretical and practical significance for studying the formation mechanism of tight reservoirs in deep ancient strata and predicting high-quality reservoirs.

The what , The from , and The to : The Migration Games in Deduplicated Systems

Deduplication reduces the size of the data stored in large-scale storage systems by replacing duplicate data blocks with references to their unique copies. This creates dependencies between files that contain similar content and complicates the management of data in the system. In this article, we address the problem of data migration, in which files are remapped between different volumes as a result of system expansion or maintenance. The challenge of determining which files and blocks to migrate has been studied extensively for systems without deduplication. In the context of deduplicated storage, however, only simplified migration scenarios have been considered. In this article, we formulate the general migration problem for deduplicated systems as an optimization problem whose objective is to minimize the system’s size while ensuring that the storage load is evenly distributed between the system’s volumes and that the network traffic required for the migration does not exceed its allocation. We then present three algorithms for generating effective migration plans, each based on a different approach and representing a different trade-off between computation time and migration efficiency. Our greedy algorithm provides modest space savings but is appealing thanks to its exceptionally short runtime. Its results can be improved by using larger system representations. Our theoretically optimal algorithm formulates the migration problem as an integer linear programming (ILP) instance. Its migration plans consistently result in smaller and more balanced systems than those of the greedy approach, although its runtime is long and, as a result, the theoretical optimum is not always found. Our clustering algorithm enjoys the best of both worlds: its migration plans are comparable to those generated by the ILP-based algorithm, but its runtime is shorter, sometimes by an order of magnitude. It can be further accelerated at a modest cost in the quality of its results.

Solar hydrogen for high capacity, dispatchable, long-distance energy transmission – A case study for injection in the Greenstream natural gas pipeline

This paper presents the results of techno-economic modelling for hydrogen production from a photovoltaic battery electrolyser system (PBES) for injection into a natural gas transmission line. Mellitah in Libya, connected to Gela in Italy by the Greenstream subsea gas transmission line, is selected as the location for a case study. The PBES includes photovoltaic (PV) arrays, battery, electrolyser, hydrogen compressor, and large-scale hydrogen storage to maintain constant hydrogen volume fraction in the pipeline. Two PBES configurations with different large-scale storage methods are evaluated: PBESC with compressed hydrogen stored in buried pipes, and PBESL with liquefied hydrogen stored in spherical tanks. Simulated hourly PV electricity generation is used to calculate the specific hourly capacity factor of a hypothetical PV array in Mellitah. This capacity factor is then used with different PV sizes for sizing the PBES. The levelised cost of delivered hydrogen (LCOHD) is used as the key techno-economic parameter to optimise the size of the PBES by equipment sizing. The costs of all equipment, except the PV array and batteries, are made to be a function of electrolyser size. The equipment sizes are deemed optimal if PBES meets hydrogen demand at the minimum LCOHD. The techno-economic performance of the PBES is evaluated for four scenarios of fixed and constant hydrogen volume fraction targets in the pipeline: 5%, 10%, 15%, and 20%. The PBES can produce up to 106 kilotonnes of hydrogen per year to meet the 20% target at an LCOHD of 3.69 €/kg for compressed hydrogen storage (PBESC) and 2.81 €/kg for liquid hydrogen storage (PBESL). Storing liquid hydrogen at large-scale is significantly cheaper than gaseous hydrogen, even with the inclusion of a significantly larger PV array that is required to supply additional electrcitiy for liquefaction.

Transient behavior and thermodynamic analysis of Brayton-like pumped-thermal electricity storage based on packed-bed latent heat/cold stores

Pumped-thermal electricity storage has the advantages of high energy storage density, no geographical restrictions and low costs, making it the most promising large-scale electricity storage technology. In this paper, a numerical model of the Brayton-like pumped-thermal electricity storage based on packed-bed latent heat/cold stores is established and a recuperator is added between the hot store and the expander. The rated power of the system is 150 kW and the charging/discharging time is 4 h. The dimensionless analysis is applied to the energy storage units including transient temperature, charging/discharging time as well as axial position. Moreover, based on the finite element method, an extensive thermodynamic analysis is carried out in MATLAB. It is concluded that compared with the non-recuperated system, the total input power of the recuperated system can be reduced by 18.1 kW in the charge duration and the energy density of the system using PCMs instead of sensible heat storage materials can be improved from 202.4 kWh/m3 to 267.4 kWh/m3. The roundtrip efficiency of the system could reach 0.55. In addition, detailed exergy flow and exergy loss of each component are studied. It is found that the total exergy loss of the recuperated system is 52.27 kW, a 22.4 % decrease compared to that of the non-recuperated system and the compressor has the largest exergy loss, accounting for 36 % of the total loss, which can be ameliorated by improving the level of industrial manufacturing in the future.

Analytical model for transient pressure analysis in a horizontal well intercepting with multiple faults in karst carbonate reservoirs

In recent years, the Shunbei karst-carbonate reservoirs becomes a huge productivity oilfield, which produced over one million tonnes crude oil annually. However, there are difficulties in understanding production contribution of each fault-karst branch in reservoirs, which significantly impacts the efficient development. Multibranched fault-karst reservoirs in the Shunbei have an obvious tree-shaped geostructure, in which the natural fractures and eroded cave develop along multiple large-scale faults. The existing models for pressure transient analysis (PTA) were mainly established for fracture-cave reservoirs only with single fault, which cannot be applicable to characterize the multibranched fault-karst reservoir. To fill this gap, a novel analytical PTA model for horizontal commingled production well in the multibranched fault-karst reservoir was established to describe pressure response and identify flow regimes. First, our model includes the Darcy flow with the fluid compressibility effect in fracture region, and the large-scale vertical storage flow in cave region as well as the horizontal laminar flow in the horizontal wellbore. Then, the accuracy of this PTA model is verified by comparing it with the existing single branch fault-karst pressure model. Further, we applied the model to analyze the Shunbei oilfield case data. Last, the effect of boundary type, fluid compressibility effect, fracture physical properties, and cave spatial distribution on the pressure response are discussed in detail. The sensitivity analysis results show (a) the cave storage flow regime exhibits an obvious unit-slope-line on pressure derivative curve, at the time the skin transient flow constitutes a V-shape characteristic. (b) The number of fracture-cave branches can be directly obtained by counting the number of V-shaped appearances on the pressure derivative curve. (c) The fluid compressibility effect leads to an upward trend on the pressure and its derivative, reservoir engineers should be cautious to explain that characteristic as a closed boundary effect. (d) The cave volume and cave position control the timing of the V-shape occurring. As the cave volume increases, the linear flow regime lasts longer and the V-shaped feature becomes apparent. With the cave distance and cave depth increasing, the V-shape characteristic comes later. This work can provide technical support for accurate characterization of multibranched fault-karst reservoirs, and give a type curve analysis method for rapidly diagnosing the spatial location of each karst cavity by analyzing bottom-hole pressure.

Thermal performance investigation of large-scale latent heat storage for heat supply

This work conducts a thermal performance investigation on an industrial-scale low-temperature latent heat storage unit based on thermal behavior identification and parametric analysis of the storage unit. The thermal performance of thermal power-driven and heat transfer fluid temperature-driven charges and discharges are investigated. Two groups of parametric analyses are conducted to reveal the effects of different operating conditions and heat transfer structures on the power rate and thermal efficiency of the storage unit. Two practical application scenarios including a space heating system and a domestic hot water supply system using the storage unit are designed and simulated. The results show that the charging/discharging thermal power and charging/discharging efficiency are always inversely correlated. Using densified fin structures can effectively improve the charging rate and discharging efficiency of the storage unit at specific operating conditions. In addition, a single storage unit with a storage capacity around 100 kWh can meet a 16-h heating demand of space heating with a base heating load of 30 W m−2 and a minimum heating temperature of 40 °C for an area of 195.7 m2,and can provide 2500 L of domestic hot water above 45 °C for the daily use of 25 residents within 6 h.

Semi-analytical modeling of large-scale water tank for seasonal thermal storage applications

Buildings consume large amount of energy for cooling in summer and heating in winter. A renewable energy-based district heating using seasonal thermal storage can better serve for a lower carbon space heating for buildings. The research objective is to propose a first semi-analytical model of large-scale water tank storage as an efficient and flexible tool for further development of TES. A new idea of “three-zone method” is proposed for detailed heat and mass flow inside water storage with least increase in computational burden and better capture of internal non-uniform thermal distribution. All three modes of charging, discharging and standby are modeled separately with high flexibility. A modified finite cylindrical source model for TES was proposed, for the first time, for transient heat transfer in the ground, which is inspired by analytical model of ground source heat pump. A complete comparison was made between the new semi-analytical model and validated reference data, which shows a good match in temperature profile in different locations. This study will pave a way for a further systematical study on seasonal thermal storage.

A Scalable Open-Source Framework for Machine Learning-Based Image Collection, Annotation and Classification: A Case Study for Automatic Fish Species Identification

Citizen science platforms, social media and smart phone applications enable the collection of large amounts of georeferenced images. This provides a huge opportunity in biodiversity and ecological research, but also creates challenges for efficient data handling and processing. Recreational and small-scale fisheries is one of the fields that could be revolutionised by efficient, widely accessible and machine learning-based processing of georeferenced images. Most non-commercial inland and coastal fisheries are considered data poor and are rarely assessed, yet they provide multiple societal benefits and can have substantial ecological impacts. Given that large quantities of georeferenced fish images are being collected by fishers every day, artificial intelligence (AI) and computer vision applications offer a great opportunity to automate their analyses by providing species identification, and potentially also fish size estimation. This would deliver data needed for fisheries management and fisher engagement. To date, however, many AI image analysis applications in fisheries are focused on the commercial sector, limited to specific species or settings, and are not publicly available. In addition, using AI and computer vision tools often requires a strong background in programming. In this study, we aim to facilitate broader use of computer vision tools in fisheries and ecological research by compiling an open-source user friendly and modular framework for large-scale image storage, handling, annotation and automatic classification, using cost- and labour-efficient methodologies. The tool is based on TensorFlow Lite Model Maker library, and includes data augmentation and transfer learning techniques applied to different convolutional neural network models. We demonstrate the potential application of this framework using a small example dataset of fish images taken through a recreational fishing smartphone application. The framework presented here can be used to develop region-specific species identification models, which could potentially be combined into a larger hierarchical model.

Assessment of maize and beans storage insect pest in major grain markets, Morogoro-Tanzania

Post-harvest losses for maize and beans are common storage challenges affecting Tanzania's smallholder and large-scale farmers' storage facilities. Consequently, this leads to a reduction of over 50% of harvested grain qualitatively and quantitively per year. Therefore, this experimental study was conducted at the entomological laboratory of the Sokoine University of Agriculture Tanzania, where the research was aimed to assess different common storage insect pests of beans and maize at Morogoro major markets (i.e., Kihonda, Mazimbu and Morogoro Central Market) with similar storage conditions in Morogoro municipality. The complete block design (CBD) with three experimental replications was used. Where locations (Kihonda, Mazimbu and Central market) markets were considered as experimental treatments. The results obtained show that there were no significant differences in number of insect pests (such as maize weevils and bean bruchids) identified between the Kihonda and Central markets (P > 0.05). However, there is a significant difference (P< 0.05) between Mazimbu and other markets regarding the number of insect pest multiplication resulting from the storage condition of those grains in a particular market. Nevertheless, continuous winnowing of stored grains was observed to significantly intensify the infestation of the storage pest in maize and common beans. Therefore, alternatively, to reduce insect pest infestation to maize and common beans in storage facilities, it is important to avoid constant winnowing of stored grains.

Controlling the electrochemical hydrogen generation and storage in graphene oxide by in-situ Raman spectroscopy

Hydrogen, generated from water splitting, is postulated as one of the most promising alternatives to fossil fuels. In this context, direct hydrogen generation by electrolysis and fixation to graphene oxide in an aqueous suspension could overcome storage and distribution problems of gaseous hydrogen. This study presents time-resolved determination of the electrochemical hydrogenation of GO by in-situ Raman spectroscopy, simultaneous to original functional groups elimination. Hydrogenation is found favoured by dynamic modulation of the electrochemical environment compared to fixed applied potentials, with a 160% increase of C–H bond formation. Epoxide groups suppression and generated hydroxide groups point at these epoxide groups being one of the key sites where hydrogenation was possible. FTIR revealed characteristic symmetric and asymmetric stretching vibrations of C–H bonds in CH 2 and CH 3 groups. This shows that hydrogenation is significantly also occurring in defective sites and edges of the graphene basal plane, rather than H-Csp 3 groups as graphane. We also determined a −0.05 V RHE reduction starting potential in alkaline electrolytes and a 150 mV cathodic delay in acid electrolytes. The identified key parameters role, together with observed diverse C-H x groups formation, points at future research directions for large-scale hydrogen storage in graphene.

Preparation and characterization of fire-extinguishing efficiency of novel gel-protein foam for liquid pool fires

The re-ignition of large-scale storage tank fires poses one of the greatest challenges in firefighting and it is thus of practical importance to develop efficient fire extinguishing agents to suppress and control liquid pool fires. In this study, a novel gel-protein foam was prepared. The microstructure, foamability, stability and water retention capacity of the gel-protein foam were analyzed systematically to identify three best formulations, which were then used to assess their fire extinguishing and burnback performance against a commercial film-forming fluoroprotein foam (FFFP). The experimental results indicated that the gel-protein foam with the best fire extinguishing efficiency is the one with a SA/CaCl2 ratio of 9:1 and a concentration of 0.1 wt%. The average size and water loss ratio are 126.46 μm and 30.6%, respectively, compared to 273.24 μm and 44.1% for FFFP. The fire extinguishing tests also confirmed that this gel-protein foam has the best cooling and burnback performance. Its 90% burnback time is 454s, a 54.42% increase that of FFFP, because it can float stably on the fuel surface to reduce the hazard of re-ignition. This work provides important data and guidance in further development of gel foams for extinguishing oil storage tank fires.

Pressure transient analysis of horizontal wells in multibranched fault-karst carbonate reservoirs: Model and application in SHB oilfield

Current flow models for fault-karst reservoirs are mostly described as a single fault formation, which cannot be applied in recent-developed multibranched fault-karst reservoirs. This paper established a novel analytical model to investigate pressure response behavior of a horizontal well in multibranched fault-karst reservoirs. The model is able to describe the influence of the physical properties and spatial structure of fracture-cave system on pressure transient response. The flow model considers different flow behaviors in each region, which includes Darcy flow (gravity included) in fault-fracture, large-scale storage flow in karst-cave, and Poiseuille-law-based horizontal laminar flow in the horizontal wellbore, respectively. These assumptions enable the model to match complex situations in multibranched fault-karst reservoirs. Then, the model was retrograded to compare with a single fault-karst reservoir model to verify its accuracy. Further, the solutions were graphed on log-log plots, and we discussed the effect of fluids mobility, formation storability, and structure characteristics (e.g., length, angle, depth, distance) of fracture-cave branches on transient pressure responses. Results show that (a) the number of fracture-cave branches in a reservoir can be directly observed by counting the number of V-shaped appearances on the pressure derivative curve. (b) The exact shut-in time when V-shape appears is affected by volume and distance between two neighboring fracture-cave branches. (c)The characteristics of the V-shape are affected by fluid mobility, formation storability, and length of fracture region. (d) The slope of the pressure derivative curve in the boundary-dominated flow regime can be used to evaluate the gravity effect. (e) The pressure response behavior exhibits a near-well effect when a horizontal well commingled production in the multibranched fault-karst reservoir. Finally, we applied our model and resulting observations to analyze pressure build-up data tested from SHB Oilfield, which demonstrated a workflow to identify the number of fault-karst branches and also to estimate reservoir properties.

Evaluation of cubic, PC-SAFT, and GERG2008 equations of state for accurate calculations of thermophysical properties of hydrogen-blend mixtures

Hydrogen (H2) is a clean fuel and key enabler of energy transition into green renewable sources and a method of achieving net-zero emissions by 2050. Underground H2 storage (UHS) is a prominent method offering a permanent solution for a low-carbon economy to meet the global energy demand. However, UHS is a complex procedure where containment security, pore-scale scattering, and large-scale storage capacity can be influenced by H2 contamination due to mixing with cushion gases and reservoir fluids. The literature lacks comprehensive investigations of existing thermodynamic models in calculating the accurate transport properties of H2-blend mixtures essential to the efficient design of various H2 storage processes. This work benchmarks cubic equations of state (EoSs), namely Peng–Robinson (PR) and Soave Redlich–Kwong (SRK) and their modifications by Boston–Mathias (PR-BM) and Schwartzentruber–Renon (SR-RK), for their reliability in predicting the thermophysical properties of binary and ternary H2-blend mixtures, including CH4, C2H6, C3H8, H2S, H2O, CO2, CO, and N2, in addition to Helmholtz-energy-based EoSs (i.e., PC-SAFT and GERG2008). The benchmarked models are regressed against the experimental data for vapor–liquid equilibrium (VLE) that covers a wide range of pressures (0.01 to 101 MPa), temperatures (92 K to 367 K), and mole fractions (0.001 to 0.90) of H2. The novelty of this work is in benchmarking and optimizing the parameters of the mentioned EoSs to study VLE envelopes, densities, and other critical transport properties, such as heat capacity and the Joule–Thomson coefficient of H2 mixtures in a wide range of associated conditions. The results highlight the significant effect of the temperature-dependent binary interaction parameters on the calculations of thermophysical properties. The SR-RK EoS demonstrated the highest agreement with VLE data among the cubic EoSs with a low root mean square error and absolute average deviation. The PC-SAFT VLE models demonstrated results comparable to the SR-RK. The sensitivity analysis highlighted the high influence of impurity on changing the thermophysical behavior of H2-blend streams during the H2 storage process.

Understanding the acceleration effect of manganese and cerium doping on the hydration of CaO in CaO/Ca(OH)2 heat storage by density function theory

CaO/Ca(OH)2 heat storage system is one of the most promising candidates for large-scale thermochemical heat storage at temperature of 300–600 °C. In this work, the CaO/Ca(OH)2 heat storage performances of the Ce- and Mn-doped CaO were investigated and the mechanisms of promoting hydration by Ce and Mn doping were determined via density functional theory (DFT) calculations. The Mn-doped CaO exhibits the higher hydration conversion than CaO and Ce-doped CaO. The structural parameters, partial density of states, electron differential densities and energy barriers during hydration stage on the CaO, Ce- and Mn-doped CaO surfaces were compared to clarify the effects of Ce and Mn on hydration of CaO. The results show the detailed hydration reaction pathways on the CaO, Ce- and Mn-doped CaO surfaces. During the H2O adsorption stage, H2O on the Ce-doped CaO surface approaches the Ca atom first, while H2O on the Mn-doped CaO surface approaches the Os atom first. The adsorption energy for Ce- and Mn-doped CaO are −1.612 and −0.896 eV, respectively, which are higher than that for CaO. The doping of Ce and Mn accelerates the H2O adsorption on the CaO surface. The Mn doping causes the 84.3 % reduction in the energy barrier for hydration of CaO and the reduction by Mn doping is larger than that by Ce doping. Thus, Mn-doped CaO exhibits the higher hydration reactivity and hydration conversion than CaO and Ce-doped CaO. The DFT calculations determined the promotion mechanism of Ce and Mn doping on the hydration of CaO in CaO/Ca(OH)2 heat storage.

Development of multilayer interacted characteristic melting region for large-scale horizontal latent heat storage investigation

The development of thermal energy storage (TES) technology has aroused extensive attentions due to its considerable energy-saving benefits. In the current work, the strategy of multilayer interacted characteristic melting region (MCR) was established to characterize large-scale horizontal latent heat thermal energy storage (LHTES). Based on the shell-and-tube configuration, the influence of multilayer interaction was numerically investigated and the single-tube approach was found to be inapplicable to characterize the melting performance of horizontal LHTES devices. Furthermore, the characterization strategy with MCR was applied to reexamine typical eccentric design and quite different rules were concluded. The melting performance of cases with intersection angles ranging from 60° to 120° and the tube eccentricity ranging from 0 to 0.6 were established and compared. For the design of eccentric side fins, horizontally spreading heat transfer structures was found to be a better choice, which extended the area dominated by the natural convection above the tubes. The full melting time of the case with the intersection angle of 90° was reduced by 2.9 % and 6.2 % compared with the case with intersection angles of 60° and 120°, respectively. The eccentric tube arrangement was found to have negative influence on the melting performance for large-scale horizontal LHTES devices. The full melting time of the case with the fin-tubes eccentricity of 0.6 was increased by 23.3 % compared with the concentric design.

Hydrogen-brine mixture PVT data for reservoir simulation of hydrogen storage in deep saline aquifers

An accurate assessment of hydrogen storage mechanisms in an aquifer storage project requires detailed flow and transport modeling. The equation-of-state (EOS) based compositional phase equilibrium approaches make these models computationally expensive. This paper proposes using the black-oil simulation approach for the specific case of hydrogen storage in saline aquifers to reduce the computational burden of the flow simulations. We present a simple and efficient algorithm for converting hydrogen-brine phase equilibrium compositional data obtained from the Redlich and Kwong EOS into black-oil PVT data. The algorithm accurately predicts the hydrogen-brine transport properties required for the black-oil flow simulations of underground hydrogen storage. Numerical simulations for a simple cyclic hydrogen injection-production case reveal that the black-oil simulations are at least one order of magnitude faster than the compositional ones without loss of accuracy. These results support applying the black-oil PVT model and the simulation approach for numerical simulations of large-scale hydrogen storage in deep saline aquifers.