Decrease In Storage Capacity Research Articles

Fabrication of Two-Dimensional Heterostructure Electrodes for Intercalation Batteries Via Cation-Driven Assembly

The cation-driven assembly technique was developed and employed to fabricate two-dimensional (2D) heterostructures of lithium preintercalated bilayered vanadium oxide (δ-LixV2O5·nH2O or LVO) and graphene oxide (GO) nanoflakes. These heterostructures were formed using concentrated lithium chloride solution and annealed under vacuum at 200ºC. The presence of Li+ ions from LiCl enhanced the formation of oxide/carbon heterointerfaces, improving structural and electrochemical stability. Annealing at 200ºC allowed to remove interlayer water excess and partially reduce GO, thus improving electron transport through reduced GO (rGO) nanoflakes. By varying the initial GO concentration, the carbon content in the heterostructures could be adjusted, affecting the electrochemical performance. Scanning transmission electron microscopy (STEM) imaging combined with electron energy-loss spectroscopy (EELS) clearly revealed the formation of LVO/rGO heterointerface with rGO nanoflakes with thicknesses down to the nanometer scale embedded between the nanometer-thick layers of LVO.Electrochemical cycling of the Li+ cation-assembled LVO/rGO heterostructures in Li-ion cells demonstrated enhanced cycling stability and rate performance with increasing rGO content, despite a slight decrease in charge storage capacity. The improved electrochemical stability was attributed to what we have termed the encapsulation effect, which involves the encasing of LVO nanoflakes between the rGO nanoflakes, leading to the suppressed dissolution of LVO in the electrolyte and mitigating the structural distortion of LVO known to be induced by repeated intercalation/deintercalation reactions during electrochemical cycling. Compared to the electrodes prepared by physical mixing of LVO and rGO nanoflakes, the cation assembled LVO/rGO heterostructures showed superior electrochemical stability, highlighting the stabilizing effect of the 2D heterointerface.The versatility of the cation-driven assembly approach was demonstrated by preparing LVO/rGO heterostructures using different assembling cations: Li+, Na+ and K+. The assembling cations influenced the interlayer spacings and structural water content of the resting LVO/rGO heterostructures. STEM/EELS analysis confirmed the formation of a 2D heterointerface between LVO and rGO for all types of the assembling cations used, with the assembling cations trapped in the interlayer regions. Additionally, STEM/EELS identified a V2O3 phase that formed at the LVO/rGO heterointerface and could stabilize the LVO/rGO heterostructures during cycling. Charge storage mechanism analysis indicated that increased interlayer spacings of the BVO phase and the use of assembling cations to define intercalation sites improved ion diffusion and increased capacities during cycling. Li+ and Na+ cation assembled heterostructures exhibited enhanced ion diffusion and charge storage capacities in their respective charge storage systems (Li-ion and Na-ion cells, respectively). Analyses of our results indicate that the choice of cation for heterostructure assembly can modify the final material structure and tailor ion diffusion and charge storage capacity for specific electrochemical systems, offering a versatile approach for utilizing 2D materials in energy storage applications.

Assessment of Siltation Impact and Mitigation Strategies for Sustaining Storage Capacity in Lwanyo Dam, Tanzania

The ongoing generation, transportation, and deposition of silt in the Lwanyo Dam has significantly reduced the storage capacity of the Lwanyo Reservoir, originally constructed to support irrigation and the surrounding ecosystem. The objective of this paper was to assess the extent of siltation in Lwanyo Dam, evaluate its impact on the dam's storage capacity, and propose measures to mitigate silt accumulation. The upstream catchment area, approximately 39.6 km², includes around 128,991 m² allocated for rain-fed crop cultivation and 5.89 km² for pastoral activities. Frequent overtopping of the reservoir has been observed, largely due to siltation reducing its live storage capacity. In the reservoir trial pits were excavated and assessed, and they indicate that average silt layers range in thickness from 0.54 m to 0.98 m per rainy season. The deposited material consists of a silt layer from 0 to 540 mm, followed by an intermediate clay layer from 540 mm to 3100 mm. The impounded silt depth was measured at 1270 mm, with an estimated siltation volume of 58,349.4644 m³. The reservoir's original storage capacity of 210,153 m³ has been reduced by 27.765% due to siltation. The reservoir’s structural design inadequately addresses silt management, lacking both silt flushing tunnels and upstream silt check dams. The analysis indicates that storage capacity decreases by 3.085% annually, and if this linear trend continues without any intervention measures, the dam will lose all storage capacity within 24 years. The study recommends urgent measures to mitigate silt accumulation.

Nanosizing strategy to fabricate uniformly dispersed NiO/Ni/lignin porous carbon composites for high lithium storage

Nickel oxide is considered a promising anode material for lithium-ion batteries. Nevertheless, its performance is hindered by significant volume expansion and low electrical conductivity, particularly at larger particle sizes, which lead to a notable decrease in lithium storage capacity and rate performance. To address these challenges, we introduce a nanocomposite strategy to synthesise nickel oxide and lignin-derived porous carbon composites (LPC/Ni/NiO). Through in situ polymerization, lignin macromolecules form a uniform 3D network with nickel carbonate, which, during the subsequent carbonisation process, results in the formation of nickel oxide within a conductive carbon network. This approach reduces the nickel oxide to nanosize and enhances the composite's electrical conductivity, effectively integrating the buffering framework of porous carbon with the high storage capacity of nickel oxide. As a result, the LPC/Ni/NiO composite exhibited significantly improved lithium storage capacity. Notably, when employed as an anode material in lithium-ion half-cells, the optimized composite maintained an excellent specific capacity of 1065 mAh/g after 100 cycles at a current density of 0.2 A/g. It also shown exceptional rate performance, delivering a specific discharge capacity of 505 mAh/g at a current density of 2 A/g, with stable cycling performance. The electrochemical reaction process was further validated using in ex-situ EIS. This study offers valuable insights into scalable synthesis methods for oxide nanocomposites, highlighting their potential as promising anode materials for lithium-ion batteries.

Excellent work hardening ability in a novel compositionally complex alloy by hierarchical microstructuring

Strength and ductility vary inversely due to a rapid decrease in dislocation storage capacity with the pronounced increase in work hardening rate at the expense of ductility in most conventional and recently designed advanced ductile materials. This limitation can be overcome by creating heterogenous or hierarchical microstructures containing not only presence but also different length scales of twins, bands, phases synergistically. In line of that, here we present Fe44Mn20Cr15Ni7.5Co6Si7.5 (all in at.%) compositionally complex alloy (M-CCA), which showed an exceptional increase in strength and ductility simultaneously as a result of hierarchical microstructuring that forms after conventional thermo-mechanical treatment. The increase in strength-ductility synergy is attributed to the occurrence of hetero-deformation induced (HDI) strengthening in early stage of deformation whereas planar slip assisted hetero-deformation banding, and deformation twinning in later stages of deformation during plastic straining. Hence, hierarchical microstructuring in M-CCA resulted in exceptional work hardening ability which is needed for structural integrity and manufacturing applications under tensile loads to suppress sudden failures during service.

Efficient utilization of cold energy enabled by phase change cold storage brine gels with superior thermophysical properties towards biochemical reagent cold chain

Phase change cold storage, as an emerging cold chain method of maintaining a low-temperature environment and effectively ensuring the quality of biochemical reagents, is extensively utilized because of its benefits of high energy density, low cost, energy conservation and environmentally friendly mode. However, the low thermal conductivity of working medium affects its cold charging/discharging rate and operating efficiency. Meanwhile, the high leakage characteristic in the phase change process leads to a decrease of cold storage capacity and contamination of items. This work proposes the efficient utilization of cold energy enabled by leakage-free phase change cold storage brine gels with extraordinary high thermal conductivity towards biochemical reagent cold chain. Phase change thermal storage gel is prepared by confining brine in the sodium polyacrylate‑calcium alginate network and porous adsorption of expanded graphite. The prepared materials present leak free characteristics and almost 100% mass retention rate. Expanded graphite addition enables the thermal conductivity increase from 0.542 W m−1 K−1 to an extremely high value of 2.766 W m−1 K−1 (an increase of 510%). The enthalpy value of the cold storage brine gel is as high as 144 Jg−1, stably releasing cold at around −24 °C. By regulating the distribution of cold storage working medium, the minimum temperature difference inside the apparatus can be reduced from 6.7 °C to about 1 °C. Finally, performance-enhancing phase change cold storage materials and apparatus in the cold chain of biological reagents is fruitful, effectively providing a long-lasting and uniform low-temperature environment.

Managed aquifer recharge in island aquifer under thermal influences on the fresh-saline water interface

Storing and utilizing freshwater in coastal aquifers with managed aquifer recharge (MAR) presents significant challenges, particularly in small island settings where seawater intrusion is a major source of groundwater salinization. Existing studies usually evaluate density-dependent flow under isothermal condition, which neglects the potential impact of temperature on fluid density. To fill the knowledge gap, we performed both laboratory experiments and numerical modeling to investigate the impact of warmer water injection on freshwater storage and extracted water quality for island aquifer. It is found that warmer water (70 °C) injection compromise the “barrier effect” achieved by normal water injection, resulting in a reduced ability to prevent coastal seawater intrusion by, creating an upward hydraulic gradient beneath the injection well. In addition, warm water injection result in a 5 % decrease in freshwater storage capacity for island aquifer. However, by employing a combination of receding tide cycles and intermittent injection-extraction operations, the duration of lowered saline concentration within the extracted water can be extended by approximately 10 % with an 11 % reduction in the overall extracted saline concentration. This study provides valuable insights into the influence of warmer water injection on coastal aquifer quality. The findings from both the laboratory experiments and numerical simulations enhance the understanding of thermal density-dependent dynamics of coastal aquifers, offering valuable guidance for effective freshwater storage and usage in island settings.

Selective Extraction of Lithium from Spent-NMC Battery Cathodes Using Sodium Hydroxide as a Leaching Agent at Elevated Temperatures

Introduction: The demand for lithium-ion batteries (LIBs) is rapidly increasing due to the growth of the electronics and electric vehicle industries. Even though the batteries are rechargeable, their storage capacity decreases, and they eventually end up being wasted. Recycling the spent LIBs is necessary to reduce the environmental impact and utilize the precious metals contained in the waste Methods: The present work focuses on the selective recovery of lithium from the cathodes of spent NMC batteries through the hydrometallurgical process using a sodium hydroxide solution. The leaching process was carried out in 2 M and 4 M NaOH concentrations for 120 minutes at high pressure and at temperatures of 398.15 K, 423.15 K, 448.15 K, and 473.15 K. Experimental results showed that 56.53% of lithium could be recovered with nearly 100% selectivity under the optimum leaching conditions of 473.15 K and 4 M NaOH. The release of lithium ions was due to a combination of sodium adsorption, ion exchange, and impregnation mechanisms. Result: Calculation results showed that the activation energy of the lithium leaching process was 2.1990×104 J/mol, the reaction was endothermic with enthalpy and entropy at standard conditions (298.15 K) of 4.8936×105 J/mol and 1.4421×103 J/mol/K, respectively. Conclusion: The present work also suggested that total lithium recovery can be increased through a series of leaching processes.

Effect of double substitution on hydrogen absorption-desorption properties of Ti2CrV alloy

Doubly substituted Ti2CrV alloy with composition Ti1.5Sc0.3CrVNi0.2 was prepared by arc melting method followed by annealing. The annealed alloy exists in body centred cubic (BCC) structure and shows fast kinetics for hydrogen absorption and desorption at room temperature. BCC phase of the alloy undergoes phase transformation to face centred cubic (FCC) hydride phase with H atoms occupying tetrahedral sites in the lattice, reaching an overall H/M ratio >2.2 (storage capacity ∼ 4 wt%). Storage capacity decreases by 40% in the 2nd cycle and then stabilizes at a value of ∼2.5 wt% for the subsequent 10 cycles. A drastic reduction in hydride desorption temperature upon double substitution (Sc and Ni substitution in Ti2CrV alloy) has been confirmed by DSC studies. Furthermore, the change in isotope effect in doubly substituted Ti2CrV alloy is discussed in light of thermal stabilities of the hydrides and deuterides.

Numerical investigation of an amalgamation of two phase change materials thermal energy storage system

In the last three decades, many researchers have published their findings on the storage of thermal energy using various phase transition materials (both organic and non-organic). One of their goals was to have a higher heat storage capacity with a shorter heat charging cycle for thermal energy storage. This study looked into a floating capsule thermal energy storage system (TESS). A number of spherical capsules filled with beeswax were placed in a paraffin-filled cylindrical shell. With heat transfer fluid flowing through three hexagonal tubes arranged at 120° inside the TESS core, the two phase change materials (beeswax with a thermal conductivity of 0.25 W/mK and paraffin with a thermal conductivity of 0.23 W/mK) were charged and discharged. For the proposed TESS, a mathematical model was created and utilised to forecast thermal energy storage capacity and charging/discharge times for various configurations. In TESS, a 70–30% mixture of the two PCMs results in a 21.5 percent increase in heat storage capacity when beeswax alone is used, and an 8.4 percent decrease in storage capacity when paraffin alone is used. For a heat storage capacity of 7300 kJ, the model estimates charging and discharging times of around 2.6 and 3.2 hours, respectively.

Experimental Investigation of Injection and Production Cycles for Limestone Reservoirs via Micro-CT: Implications for Underground Gas Storage

Global demand for underground gas storage (UGS) is steadily increasing, with the limestone-based UGS system situated in the Sichuan Basin of China gathering considerable interest in recent years. However, studies focusing on the fundamental mechanisms of the injection-production process in these systems are limited. Moreover, existing studies utilizing physical experimental methods frequently fall short in effectively visualizing micro-flow or incorporating real core samples from the reservoir. To address these gaps, we performed a coreflood experiment, integrating micro-Computed Tomography (CT) scanning to investigate mechanisms of fluid flow and storage capacity during the injection and production cycles in limestone reservoirs. Our approach involved utilizing core plugs with artificially engraved fracture-vuggy structures, which mimic the characteristics of the reservoir. Micro-CT scans were performed to visualize the microscopic changes in fractured-vuggy structures and the distribution of irreducible water during each cycle. This study reveals that increased cycles correspondingly affect gas storage capacity, particularly by expanding it in relative larger vuggy structures while reducing it in finer fissure network structures. The amount of irreducible water decreases after injection-production cycles, likely being expelled alongside the extracted dry gas. This plays a critical role in expanding the storage capacity in larger vuggy systems. Conversely, there is a decrease in storage capacity within fissure network systems, as the irreducible water is replaced by gas. This leads to a reduction in the opening force of the fine conduit. The dense matrix has a very limited effect on the flow mechanism and its influence on storage capacity. Overall, these findings offer practical insights for optimizing injection and production strategies in limestone UGS systems within the Sichuan Basin, contributing to a deeper understanding and efficient utilization of this vital infrastructure.

Proposal design and thermodynamic analysis of a coal-fired sCO2 power system integrated with thermal energy storage

It is essential to develop supercritical carbon dioxide (sCO2) power systems integrated with thermal energy storage (TES) to achieve efficient and flexible operation of thermal power plants. This study proposes a novel integrated configuration of the sCO2 coal-fired power system and TES. The extracted sCO2 from the high-pressure turbine inlet is utilized as the source of the stored heat, and the extracted heat is used for storage, work, and recovery in steps to decrease the feasible lowest power load ratio. While in the discharging process, the stored energy is used to heat the branched sCO2 to increase the output power. Thermodynamic models for both design and off-design conditions are developed, and the multi-parameter optimization is carried out by genetic algorithm aiming at the highest energy efficiency. The energy conversion characteristics of the heat storage/release process are obtained, and the impacts of variations in the sCO2 extraction ratio and the initial temperature of the molten salt on the performance are analyzed. The results indicate that the adjustable power load range of the integrated system widens with an increase in the sCO2 extraction ratio. When the extraction ratio reaches its maximum value of 0.2749, the minimum power load of the charging process can reduce from 30 % of the rated load to 10.47 %, and the load of the discharging process can increase from 75 % of the rated load to 88.20 %, thus enhancing the operational flexibility. At this point, the round-trip efficiency of the TES system is 67.56 %, which is mainly limited by the performance of the charging process, especially the throttling loss of the turbine. Furthermore, as the temperature of the molten salt cold tank increases, the heat storage capacity decreases, while the minimum power load of the unit increases, thereby reducing the system's flexibility.

Impact of operation parameters and lambda input signal during lambda-dithering of three-way catalysts for low-temperature performance enhancement

A synthetic exhaust gas bench was dynamically operated to investigate the impact of temperature, amplitude, split cycle, mean lambda, gas hourly space velocity, and oxygen storage capacity on average pollutant conversion and product selectivity of three-way catalysts in periodic operation. As temperature and amplitude increase and oxygen storage capacity decreases, the optimal frequency for maximum pollutant conversion increases. This is consistent with faster desorption of CO and O2 from the catalyst, yielding free surface sites. Regarding the formation of secondary products, the optimal frequency for maximum pollutant conversion does not always correspond to minimal N2O and NH3 emissions. The split cycle variation reveals the enhancement of C3H8 and NO conversion after both lean-rich and rich-lean switches and C3H6 and CO conversion after rich-lean switches at the optimal frequency. As periodic operation does not affect existing engine settings or operating conditions, it is a cost-effective control strategy for meeting future emission limits.

Microstructure and gas-solid hydrogen storage properties of La1-xCexY2Ni10.95Mn0.45 (x = 0 – 0.75) alloys

RE-Y-Ni-based superlattice alloys have been studied for their high hydrogen storage capacity and excellent activation properties. However, their practical applications in gas-solid hydrogen storage devices are limited by their low hydrogen absorption/desorption platform pressure and the occurrence of a double platform phenomenon. In this study, we investigated the phase structure and gas-solid hydrogen storage properties of La1−xCexY2Ni10.95Mn0.45 (x = 0, 0.15, 0.30, 0.45, 0.60, 0.75) alloys. As the Ce content increases, the content of Ce2Ni7 phase and the platform pressure also increase, while the hydrogen storage capacity and hydrogen desorption enthalpy decrease. When the Ce content increases to 0.45, the Gd2Co7 phase disappears and the LaNi5 phase appears, the hydrogen absorption/desorption platform of the alloy changes from a double platform to a single platform. However, the increase in Ce content leads to a higher amount of residual hydrogen during the dehydrogenation process, attributed to the increased content of the Ce2Ni7 phase. The La0.55Ce0.45Y2Ni10.95Mn0.45 alloy exhibits a hydrogen absorption capacity of 1.61 wt%, with a capacity retention of 97.89% after 100 cycles, and achieves a hydrogen desorption platform pressure of 0.23 MPa. These results indicate that this alloy demonstrates the best overall hydrogen storage performance, characterized by high platform pressure and hydrogen storage capacity.

Numerical analysis of temperature effect on CO2 storage capacity and CH4 production capacity during the CO2-ECBM process

Temperature is a key factor affecting the CO2 injection efficiency and CH4 production efficiency, so it is of great significance to clarify the evolution diagram of temperature change during the CO2-ECBM process. In this study, the crushed soft coal seam with low permeability in Huainan coalfield was taken as the research object. Firstly, the fully coupled mathematical models of CO2-ECBM process were constructed, and the influence of temperature field on CO2-ECBM process was emphasized. Secondly, the evolution law of CO2-ECBM process at different time was revealed. Then, the effects of injection temperature and initial temperature on the CO2-ECBM process were analyzed. Finally, the evolution mechanism of reservoir temperature during the CO2-ECBM process was illustrated, and the effect of temperature on temperature field of CO2-ECBM process was further illustrated. The results show that the longer the displacement time, the CH4 concentration gradually decreased, and the CO2 concentration gradually increased. The area where the temperature changes are more concentrated focuses on the vicinity of CO2 injection well, which are mainly determined by the dominant reaction of adsorption and desorption reactions of binary gas. Reservoir temperature and permeability are positively and negatively correlated with injection temperature, respectively. Both CO2 storage capacity and CH4 production capacity increase with the increase of injection temperature, and the sensitivity of CO2 storage capacity to temperature was greater than that of CH4 production capacity. With the increase of displacement time and injection volume, the effective displacement radius increases, but the increment of influencing radius gradually decreases. The lower the initial temperature of coal reservoir, the larger the influencing radius, and which increases with the increase of displacement time. CO2 storage capacity and CH4 production capacity decrease with the increase of initial temperature. Young's modulus and Poisson's ratio can effectively change the reservoir strength. CO2 storage capacity and CH4 production capacity decrease with the increase of Young's modulus, and increase with the increase of Poisson's ratio. This study can support the engineering landing of CO2-ECBM technology in crushed soft coal seam with low permeability, and promote the realization of China's “Dual Carbon” strategic goal.

Kinetic characteristics of methane hydrate formation under the synergistic effect of electric field and Hexadecyl trimethyl ammonium Bromide

Exploring hydrate formation methods with high gas storage capacity and high formation rate will be of great significance to the large-scale application of hydrate storage and transportation technology. The synergistic promotion of electric field and surfactant is an effective solution. In this work, the effects of sinusoidal alternating electric field and surfactant Hexadecyl trimethyl ammonium Bromide (CTAB) on the kinetics of methane hydrate generation were investigated. Methane hydrate formation kinetics experiments were conducted at different CTAB concentrations (0, 200, 500, 800 ppm) and voltages (0, 100, 500, 1000, 1500, 2000V) under the condition of 7 MPa and 275.15 K. The results showed that the synergistic effect of electric field and CTAB could effectively shorten the induction time of methane hydrate formation, greatly increase the formation rate, and improve the mobility of the generated hydrate. The downside was a slight decrease in gas storage capacity. A series of microscopic tests demonstrated that the introduction of electric field and CTAB did not change the crystal type of methane hydrate. This study was expected to provide new insights for rapid preparation of hydrates.

Two centuries of changes - revision of the hydrography of the Biebrza Valley, its transformation and probable ecohydrological challenges

Human-induced changes in hydrography have led to serious changes in the hydrological and ecological condition of ecosystems, including habitat fragmentation and reduction of water in the landscape. The aim of this study was to assess the transformation of the hydrographic network in the Biebrza National Park (BbNP) over the XIX-XXI centuries and to analyze its probable ecohydrological challenges. The analysis of changes in the hydrographic network was based on a spatial comparison of hydrographic network elements on the basis of spatial sources. As a result of both natural and human-induced processes, there have been significant changes to elements of the hydrographic network of the BbNP. The length, area and sinuosity of the rivers in the BbNP area have decreased significantly in the XIX-XXI centuries, in contrast to the length of the canals dug in the XIX century - their length increased. On average, river channelization reduced channel water storage capacity by 49%. In other cases the average decrease of storage capacity of the channel was about 14%. As a result of drainage works in the XIX century, the network of drainage ditches was established in the BbNP, which was significantly extended (more than 6 times) in the XXI century. A comprehensive analysis of hydrographic changes, their causes and possible consequences is necessary to understand the dynamics of river networks. It also makes it possible to predict the future ecohydrological response of rivers to anthropogenic influences and climate change, thus helping to establish appropriate management and ecohydrological restoration of aquatic ecosystems.

Tailoring hydrogenation and anti-oxidation properties of titanium - iron - chromium alloys by regulating zirconium content at room temperature

The effects of Fe substitution by Zr on the microstructure, hydrogen storage properties and oxidation resistance of the TiFe0.85-xCr0.15Zrx (x = 0, 0.05, 0.10, 0.15) alloys are studied in this work. It is shown that all the alloys are consisted of TiFe phase, MgZn2-type phase and minor Ti phase. The introduction of Zr causes no change for the TiFe main phase. All the alloys absorb hydrogen directly under mild conditions without any activation process. As Zr content increases, the maximum hydrogen storage capacity of the first hydrogenation increases while the reversible hydrogen storage capacity decreases. The marked change of the first hydrogenation properties may be due to the formation of the bright phase (MgZn2-type phase). The decrease of the reversible hydrogen storage capacity is due to the formation of the stable hydrides Cr2ZrH3 and TiH2, which start to decompose at around 700 °C. During the air exposure test, the alloys with higher Zr content show good oxidation resistance. For the PCT measurement, the alloys with higher Zr show lower hydrogen absorption and desorption platform pressure, which means more stable hydrides are formed during the first hydrogenation. Moreover, the rate limiting step model of the first and fifth hydrogenation processes of all the alloys has also been investigated in detail.

Thermo-economic assessment of sub-ambient temperature pumped-thermal electricity storage integrated with external heat sources

Thermally integrated pumped-thermal electricity storage (TI-PTES) offers the opportunity to store electricity as thermal exergy at a large scale, and existing studies are primarily focused on TI-PTES systems based on high-temperature thermal energy storage. This paper presents a thermo-economic analysis of a “cold TI-PTES” system which converts electricity into cold energy using a vapor compression refrigeration (VCR) unit and stores it at sub-ambient temperatures during the charging process, and generates electricity by using an organic Rankine cycle (ORC) working between the sub-ambient temperature and an external low-grade heat source during the discharging process. The effects of key parameters, i.e., mass flowrate and temperature of the storage medium, ORC evaporation temperature, component efficiencies, and pinch-point temperature differences, on the system performance are evaluated based on a whole-system thermo-economic model. The results reveal that the roundtrip efficiency and levelized cost of storage (LCOS) of the system increases while the electrical energy storage capacity decreases as the temperatures of the two cold storage tanks approach each other. When the temperature of the cold storage tank 1 rises from 1 °C to 8 °C while the cold storage tank 2 remains as 13 °C, there is an increase of 25% and 20% in the roundtrip efficiency and LCOS respectively while the energy storage capacity decreases by 69%. A roundtrip efficiency of 0.74 and LCOS of 0.32 $/kWh are achieved with a heat source temperature of 85 °C, using a mass flowrate and temperature of the cold storage medium of 50 kg/s and 1 °C. Furthermore, any change in cold storage medium mass flowrate changes both electrical energy storage capacity and power output by the same proportions. With a continuous high-flowrate external heat source, the LCOS can be as low as 0.17 $/kWh. By providing sufficient heat from an external heat source, the proposed system possesses a high potential for medium-to-large scale energy storage with a unique hybrid nature for electricity storage and thermal integration.

Paraffin-Multilayer Graphene Composite for Thermal Management in Electronics

Multilayer graphene-paraffin composites with different contents of graphene (0-10 wt.%) were prepared using an ultra-high shear mixer. The aim is to improve the heat transfer in paraffin wax, which will lead to more-efficient thermal buffering in electronic applications. The multi-layer graphenes obtained by supercritical fluid exfoliation of graphite in alcohol were investigated by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Interesting morphological features were found to be related to the intercalation of paraffins between the multilayer graphene flakes. Thermal properties were also investigated in terms of phase change transition temperatures, latent heat by differential scanning calorimetry and thermal conductivity. It was found that the addition of graphene resulted in a slight decrease in energy storage capacity but a 150% improvement in thermal conductivity at the highest graphene loading level. This phase-change material is then used as a thermal heat sink for an embedded electronic processor. The temperature of the processor during the execution of a pre-defined programme was used as a performance indicator. The use of materials with multilayer graphene contents of more than 5 wt.% was found to reduce the processor operating temperature by up to 20%. This indicates that the use of such composite materials can significantly improve the performance of processors.

Energy–Water–Carbon Nexus Study for the Optimal Design of Integrated Energy–Water Systems Considering Process Losses

Integrated energy–water systems have been explored using different process integration techniques considering the energy–water–carbon nexus to minimize the carbon footprint, e.g., pinch analysis techniques (power cascade table, water cascade table, and energy planning pinch diagram). However, the power and water losses while considering the energy–water–carbon nexus have not been explored in detail in the previous works. This work focuses on the modifications of the existing pinch analysis methods for energy–water–carbon nexus study while considering power and water losses, for an optimized energy–water system. Power and water losses should not be neglected in the analysis as they have a significant impact on the carbon emissions and overall capacities of energy and water. The effect of losses on energy storage capacity, outsourced electricity, water supply volume and water storage capacity were evaluated on an industrial case study. Results from the case study demonstrate that, while considering power losses during power allocation can lower storage capacity, it tends to raise the needed outsourced electricity supply. As water supply volume tends to increase, the water storage capacity tends to decline when losses are considered. The results were compared to the data without losses, and it was observed that the storage capacity of energy decreases by 4% while outsourced energy increases by 6%. Water supply volume increases by 20% but water storage capacity decreases by 13.7%. The emissions from energy system remains same while from the water system the emissions rise significantly by 20%. It is expected that consumers that takes power and water losses into account will produce more realistic and reliable energy, water, and carbon reduction targets and prevent under-sizing issues in designing integrated energy–water systems.