Large-scale Energy Storage Technologies Research Articles

The underground performance analysis of compressed air energy storage in aquifers through field testing

Compressed air energy storage in aquifers (CAESA) has been considered a potential large-scale energy storage technology. However, due to the lack of actual field tests, research on the underground processes is still in the stage of theoretical analysis and requires further understanding. In this study, the first kilometer depth compressed air injection-production field test with multiple flat aquifers is controlled. For all three production rates considered, the minimum pressure drop rate can reach 0.9 MPa/h. An actual wellbore-aquifer-coupled numerical model simulated by T2Well/EOS3 is verified using monitoring data. Due to the limitation imposed by the injection rate, air only flows into the top three sandstone aquifers to build air bubbles. During the production stage, air is first produced from the aquifers and then the air stored in the wellbore is gradually extracted due to the weakened air bubble support effect. Finally, an air-water two-phase occurs and the water level rises in the wellbore. Considering a hypothetical long-term cycle, the designed single aquifer scheme has a better underground performance. A concentrated and larger high air saturation domain can support a stable cycle pressure and above 95% underground efficiency. However, the wellhead pressure drops once water coning happens in the wellbore. With an air bubble replenishment scheme in each cycle, it becomes feasible to maintain stable pressure, ensuring a production pressure difference below 0.94 MPa without water production, over a 100-day cycle in the field. The results provide support for future practical engineering applications.

Projected effective energy stored of Zhangshu salt cavern per day in CAES in 2060

As a large-scale energy storage technology, compressed air energy storage (CAES) has the advantages of high efficiency and high reliability. This paper analyzed the feasibility of CAES cavern constructed in salt mine with multi-interlayer in Zhangshu, Jiangxi Province. Salt mine in Zhangshu is a typical bedded rock salt, and a method for calculating the cavern volume in Zhangshu was proposed. Using the proposed volume calculation method, it is expected that the volume of Zhangshu salt caverns can reach 27,840,000 m3 by 2060. By modelling the geomechanics used to calculate its stability. Based on the results of the simulation, the recommended operating pressure is 8.5–11.5 MPa. Finally, If this volume is used for CAES, the cycle pressure is assumed to be 8.5–11.5 MPa, energy storage efficiency of 50 %, the daily effective energy storage is 8.062 × 1014 J. This study will guide the development of the Zhangshu Salt Mine, provide lessons for similar areas and have a positive impact on the energy transition in Jiangxi.

A Review of Capacity Decay Studies of All-vanadium Redox Flow Batteries: Mechanism and State Estimation.

As a promising large-scale energy storage technology, all-vanadium redox flow battery has garnered considerable attention. However, the issue of capacity decay significantly hinders its further development, and thus the problem remains to be systematically sorted out and further explored. This review provides comprehensive insights into the multiple factors contributing to capacity decay, encompassing vanadium cross-over, self-discharge reactions, water molecules migration, gas evolution reactions, and vanadium precipitation. Subsequently, it analyzes the impact of various battery parameters on capacity. Based on this foundation, the article expounds upon the significance of battery internal state estimation technology. Additionally, the review also summarizes domestic and international mathematical models utilized for simulating capacity decay, serving as a valuable reference for future research endeavors. Finally, through the comparison of traditional experimental methods and mathematical modeling methods, this article offers effective guidance for the future development direction of battery state monitoring. This review generally overview the problems related to the capacity attenuation of all-vanadium flow batteries, which is of great significance for understanding the mechanism behind capacity decay and state monitoring technology of all-vanadium redox flow battery.

Surface engineered carbon felt toward highly reversible Fe anode for all-iron flow batteries

Low-cost all-iron flow batteries recently promise a great alternative to conventional flow battery technologies for large-scale energy storage. However, inferior Fe deposition/dissolution reversibility at anode largely impedes further advance of all-iron flow battery in application. Here, we report a surface engineered carbon felt with abundant carbon defects, which realizes highly reversible Fe deposition/dissolution for all-iron flow batteries. By introducing nano-scale pores on carbon fibers via a multistep electrode treatment approach, the modified carbon felt features a high degree of defects and proves effective in promoting Fe/Fe2+ kinetics and improving Fe nucleation and growth morphology, which is beneficial for both uniform Fe deposition and complete Fe dissolution rendering a substantially enhanced reversibility for Fe anode. Theoretical calculations further ascribe the enhanced Fe/Fe2+ reversibility to strong adsorption and intensified hybridization between Fe2+ and carbon defects, while all-iron flow cell tests adopting the modified carbon felt finally demonstrates a high power density of 80 mW cm−2 as well as stable charge–discharge operation over 250 cycles with a Coulombic efficiency of 99 %, which highlights the importance of electrode design in developing stable Fe anode for use in high-performance all-iron flow batteries.

Electrospun Na3MnTi(PO4)3/C film: A multielectron-reaction and free-standing cathode for sodium-ion batteries

With the continuous advancement of renewable energy sources, sodium-ion batteries are currently regarded as highly promising technologies for large-scale electric energy storage. The compound Na3MnTi(PO4)3 has garnered significant attention owing to its exceptional theoretical capacity, robust structural stability, and abundant availability of resources. Herein, hierarchical carbon-decorated Na3MnTi(PO4)3 nanofibers are synthesized via a feasible electrospinning technique followed by pyrolysis, effectively addressing the issue of poor electronic conductivity in phosphate cathodes. The free-standing Na3MnTi(PO4)3/C electrode serves as a cathode for sodium-ion batteries, exhibiting exceptional electronic conductivity and superior Na+ transport capability. Moreover, it demonstrates an impressive reversible capacity of 171.4 mA h g−1 at 0.2C and exhibits outstanding cyclic stability with a capacity retention of 63.7 % after 6300 cycles at 1C. The full cell, assembled with independent Na3MnTi(PO4)3/C cathode and hard carbon anode, exhibits a reversible capacity of 153.7 mA h g−1 at a current density of 10 mA g−1. The in-situ synthesis of nanomaterial particles within interconnected porous nanocarbon fibers can effectively enhance the materials' poor electronic conductivity, thereby further improving their cyclic stability and Na+ transport kinetics.

A novel array current collector design enabling high energy efficiency liquid metal batteries

Liquid metal battery (LMB) is one of the most competitive large-scale energy storage technologies due to its low-cost, long-lifespan, and high-safety. However, the low energy efficiency of the battery is currently one of the major challenges hindering its application process. The problem of poor wettability of the cathode liquid alloy is exacerbated by the design of the conventional planar structure of the positive collector. And the resulting interfacial mass transfer modes are inefficient. These lead to slow electrode reaction kinetics and large internal polarization. To address this issue, a novel array current collector suitable for LMB was designed here for the first time. The unique structure of the collector greatly increases the effective reaction area at the electrolyte/cathode and the contact area of the cathode/collector, providing more efficient nucleation and growth modes of the products as well as richer ionic mass-transfer channels, thus accelerating the electrode reaction kinetics. Benefiting from the application of the array current collector, the voltage efficiency of Li||Sb-Sn LMBs with a capacity of 20 Ah at 0.5C rate is increased by 4.8 %. Meanwhile, an average voltage efficiency of ∼ 94.7 % and an average energy efficiency of ∼ 92.2 % are achieved at 0.1C, which is the highest efficiency among the most promising LMB systems known to date. These encouraging results provide new directions for the design of high-performance LMBs and further promote the practical process of LMBs.

Power control strategies for modular-gravity energy storage plant

This paper presents the first systematic study on power control strategies for Modular-Gravity Energy Storage (M-GES), a novel, high-performance, large-scale energy storage technology with significant research and application potential. Addressing the current research gap in M-GES power control technology, we propose two corresponding compensation modes and several power control strategies for Hybrid M-GES and M-GES. The effectiveness of these strategies is validated through simulations on the MATLAB/Simulink platform, including tests using sinusoidal power and feasibility verification based on a natural California load curve. Additionally, we analyze the normal and abnormal operating conditions of M-GES. In conclusion, the characteristics of the proposed control strategies are summarized, providing a guideline for further research.

Constructing high-performance fluoropoly(aryl piperidinium) ion exchange membranes via side-chain engineering for efficient vanadium flow batteries

Vanadium flow batteries (VFBs) have demonstrated significant potential for large-scale energy storage technology. However, the lack of a highly ion-selective and stable ion exchange membrane (IEM) is a major dilemma for developing high-performance VFBs. Herein, we present a new insight to prepare high-performance fluoropoly(aryl piperidinium) IEMs by side-chain engineering modifications. Benefiting from the synergistic effect between the fluorine-containing structure and the functional side chains, distinct microphase-separated structures are formed within the membrane and the prepared IEMs exhibit lower area resistance (0.16–0.41 Ω cm2) compared to Nafion115 (0.57 Ω cm2). The repulsive effect generated by the intrinsic alkaline cation groups inhibits the cross-penetration of vanadium ions, contributing to the ultra-low VO2+ permeability (∼8.63 × 10−9 cm2 min−1, 96 times lower than Nafion115) of the resultant IEMs. Moreover, the unique fluorinated structure effectively suppresses membrane swelling while enabling excellent mechanical and chemical stability. Consequently, the assembled AMPFMP battery achieves excellent efficiency (coulombic efficiency = 99.23% and energy efficiency = 82.15% at a high current density of 200 mA cm−2) and outstanding cycling performance (no significant decay in efficiency during 1000 cycles at 120 mA cm−2), outperforming Nafion 115. These results indicate that the side-chain engineering design of fluorinated IEM provides a valuable strategy for developing efficient and durable VFB diaphragms.

Benzoquinone-Lubricated Intercalation in Manganese Oxide for High-Capacity and High-Rate Aqueous Aluminum-Ion Battery.

Aqueous aluminum-ion batteries are attractive post-lithium battery technologies for large-scale energy storage in virtue of abundant and low-cost Al metal anode offering ultrahigh capacity via a three-electron redox reaction. However, state-of-the-art cathode materials are of low practical capacity, poor rate capability, and inadequate cycle life, substantially impeding their practical use. Here layered manganese oxide that is pre-intercalated with benzoquinone-coordinated aluminum ions (BQ-Alx MnO2 ) as a high-performance cathode material of rechargeable aqueous aluminum-ion batteries is reported. The coordination of benzoquinone with aluminum ions not only extends interlayer spacing of layered MnO2 framework but reduces the effective charge of trivalent aluminum ions to diminish their electrostatic interactions, substantially boosting intercalation/deintercalation kinetics of guest aluminum ions and improving structural reversibility and stability. When coupled with Zn50 Al50 alloy anode in 2m Al(OTf)3 aqueous electrolyte, the BQ-Alx MnO2 exhibits superior rate capability and cycling stability. At 1Ag-1 , the specific capacity of BQ-Alx MnO2 reaches ≈300mAhg-1 and retains ≈90% of the initial value for more than 800 cycles, along with the Coulombic efficiency of as high as ≈99%, outperforming the Alx MnO2 without BQ co-incorporation.

Experimental analysis of packed bed cold energy storage in the liquid air energy storage system

Liquid air energy storage (LAES) is a large-scale energy storage technology with extensive demand and promising application prospects. The packed bed for cold energy storage (CES) is widely applied in LAES due to its safety and environmental friendliness. At present, most of the research on CES is theoretical analysis with symmetric cold energy transfer. Actually, the changes of the temperature field result in asymmetrical energy transfer in the energy storage and release processes, but there are few experimental studies on the dynamic characteristics and parameter influence mechanism. Therefore, a platform is established and experiments with different conditions are conducted. The dynamic characteristics of CES and the corresponding performance of LAES are analyzed. The results show that the thermocline develops until outlet temperature changes, leading to a decrease in the LAES efficiency. Under basic conditions, the energy and exergy efficiencies of CES are 90.3 % and 73.3 %. Selecting materials based on physical properties, reducing the flow rate and temperature range of the fluid can improve the packed bed performance. Furthermore, dynamic characteristics of CES gradually weaken until reaching a stable state after multi-cycle, with energy and exergy efficiencies decreasing by 2.5 % and 8.0 %. The decline in the LAES energy efficiency is 4.7 %.

Evaluation of PCM thermophysical properties on a compressed air energy storage system integrated with packed-bed latent thermal energy storage

Compressed air energy storage (CAES) is a promising large-scale energy storage technology to mitigate the fluctuations and intermittence of renewable energies. The application of latent thermal energy storage (LTES) using phase change materials (PCM) to recover compressed waste heat can further improve the energy storage density and round-trip efficiency of CAES. However, there are very few guidelines of PCM selection for a CAES system. In view of the challenge, this study first conducts orthogonal experiments to analyze the effects of the thermophysical properties of PCMs on the performance of the packed-bed LTES and CAES system. Then a PCM selection procedure for CAES is developed based on the orthogonal experiment design and TOPSIS method. The results of range analysis indicate that each thermophysical property of PCM has quite different relative importance to the performance indicators of the CAES system. From the aspect of packed-bed LTES, the density (40.8 %) and latent heat (32.8 %) of PCMs are the top two impact factors for the heat storage rate, while the melting temperature (45.7 %) and thermal conductivity (22.4 %) are the top two impact factors for the residual heat. From the aspect of the CAES system, the density (31.9 %) and melting temperature (24.4 %) are the top two impact factors for the round-trip efficiency, while the density (42.2 %) and latent heat (35.2 %) rank the top two impact factors for the air storage capacity.

A Review on Conventional to Bipolar Design of Anode Less All Solid-State Batteries

Large-scale energy storage technologies are becoming more and more necessary for the effective use of clean and sustainable energy sources. Solid-state lithium batteries (SSLBs) based on non- or less flammable...

Research on Design Parameters of Pumped Storage Power Station Based on Different Geographical Locations

Energy storage technology plays an extremely crucial role in the transition of the current social energy structure to renewable energy. Energy storage technology with high efficiency, safety and long storage period has become the key to breaking through the limitations of renewable energy utilization. As one of the most widely used large-scale energy storage technologies, pumped storage hydropower (PSH) has the advantages of high efficiency and large energy storage capacity. It has good development potential in countries with abundant water resources, but there are also problems such as high initial investment, high cost, construction. The cycle is long and largely limited by geographical conditions. This paper analyzes the parameters of PSH station in different geographical locations, compares their differences based on the cost per unit of electricity of the whole life cycle, explores the relationship between the location of pumped storage power plants and the cost of power per unit of electricity, and provides a basis for promoting the development of this technology. Provide effective technical support for development.

Towards Low Cost and Long Duration Iron-Air Flow Batteries

The electrification of the energy economy necessitates the development of low cost and large scale energy storage technologies that can integrate intermittent renewables (e.g. solar and wind). Among the various technological options (e.g. lithium ion batteries, vanadium redox flow batteries), metal-air batteries are promising alternatives owing to their high energy density, safety, and use of abundant raw materials. Moreover, when combined with the principles of redox flow batteries, mass transfer is enhanced, which results in a more uniform metal deposition and a reduction in the metal electrode passivation [2]. Furthermore, metal-air flow batteries could enable decoupling of power and energy, while retaining the scalability advantages of redox flow batteries. Additionally, they are more compact than conventional redox flow batteries since only one electrolyte tank is needed.Several metal-air flow battery systems have been investigated such as vanadium-air [3], lithium-air [4] and zinc-air batteries [5]. However, they suffer from limitations which challenge their scalability. Specifically, vanadium is costly and only available in certain regions, lithium requires the use of organic solvents which compromises the battery safety, and zinc forms dendrites leading to a lower performance and safety issues. In this context, iron-based batteries are a promising alternative due to their high specific capacity, low cost, large availability, safety, non-toxicity, and recyclability. Compared to zinc, iron is also less prone to dendrite formation during cycling in aqueous electrolytes since iron deposition kinetics is slower[6]. Despite these advantages, the performance of the iron anode is limited by electrode degradation during cycling due to phase transformations, hydrogen evolution, and low utilization of the activate material [6], which motivates fundamental research to advance the performance and durability of the system.In this poster presentation, we will discuss the main goals of our new project FAIR-RFB [7]. Our overall aim is to develop a low cost and durable iron-air flow battery system and, to this goal, we will investigate, (i) the role of porous electrode microstructure in defining the performance of iron-air flow batteries, (ii) the influence of electrode surface properties in determining transport phenomena, kinetics, selectivity and durability, and (iii) new electrochemical reactor architectures for high power iron-air redox flow batteries.

Experimental and Numerical Study of Electrolyte Mixing in the Tanks of Vanadium Redox Flow Batteries: Insights from Conventional and 3D-Printed Tanks

Vanadium redox flow batteries (VRFBs) are a promising technology for large-scale grid energy storage. Despite extensive research on the electrochemical and fluid dynamic phenomena in the cells or stacks [1, 2], the impact of electrolyte flow and mixing in the tanks has received much less attention. Previous research has shown that the cell potential and battery capacity may substantially differ from those predicted under the perfect mixing assumption [3] (i.e., continuous stirred-tank reactor). Recent numerical simulations have detected the formation of segregated zones within the tanks that cause inhomogeneous electrolyte utilization and significant capacity decay [4]. The authors have confirmed these results by means of transient laminar numerical simulations [5] and experimental testing of an industrial VRFB system [6]. However, these first attempts should be carefully extended, using a well-controlled lab-scale system, so that the effects of the different components can be independently studied.In this study, we investigate the effect of electrolyte mixing on VRFB response using a medium-size lab-scale system. Two experimental campaigns were conducted to explore i) the impact of flow rate and applied current on the predicted fluid behavior, and ii) the performance of 3D-printed tanks designed for improving electrolyte mixing with reduced dead recirculation zones. In both campaigns, the transient response of the system was investigated to assess the effect of electrolyte mixing on battery performance. The experimental results were also compared with numerical simulations, which showed good agreement with the experimental data.This work makes a novel contribution to the field by using 3D-printed tanks to investigate the impact of electrolyte mixing on RFB performance. The results extend previous research on this topic and provide insights into the design of RFBs for improved energy storage. Specifically, the use of 3D-printed tanks could be a promising approach to address the issue of inhomogeneous electrolyte exploitation in RFBs. The findings of this study could serve in the design of RFBs for large-scale grid energy storage and facilitate the adoption of this technology as a sustainable energy storage solution.

Describing the permeability of permanganate co-ions in a CEM with varying supporting electrolyte concentrations

Redox flow batteries (RFBs), a promising technology for large-scale power grid energy storage, utilize a membrane separator to facilitate an ionic current while preventing mixing of the anolyte and catholyte solutions. The anolyte and catholyte of an RFB each contain an electroactive species, and usually an additional supporting electrolyte to charge balance the anode and cathode redox reactions and reduce overall ohmic losses. This study investigates the impact of the supporting electrolyte concentration and composition on Nafion’s transport properties using permanganate as the permeant. The permanganate concentration was kept constant at 0.1m, while sodium chloride and sodium hydroxide were both studied as supporting electrolytes. The sodium chloride concentration was varied from 0.1m to 4.0m, while the sodium hydroxide concentration was varied from 0.1m to 10m. The permanganate permeability, water sorption coefficient, and salt sorption coefficients were measured for Nafion, with a peak permeability being observed at a supporting electrolyte concentration of 1m for both electrolytes. A framework to describe the observed behavior was derived using first principles to determine the transport coefficients under these conditions. It was found that at low concentrations, the permanganate permeability is controlled by Donnan exclusion and salt sorption, while at high concentrations it is controlled by salt diffusion and osmotic deswelling.

Development of Iron Fluoride Based Nanocomposite Materials to Enable High Performance Aluminium-Ion Batteries

Developing grid-scale energy storage is important for the penetration of intermittent renewable energies such as wind and solar, but remains one of the biggest challenges in the field of electrochemical energy storage [1]. The application of mature lithium-ion batteries (LIBs) to grid energy storage is controversial due to the limited Li resources and geographical distribution, high cost of materials (e.g., Co, Li), limited lifetime, and safety concerns [2]. Rechargeable aluminium ion batteries (AIBs), which normally utilises aluminium (Al) metal as anode, are one of the most promising battery technologies for future large-scale energy storage, due to the high theoretical volumetric capacity (8046 mAh cm−3), high safety, and low cost and high abundance of aluminium (the third most abundant metal in the earth crust) [3].AIBs have achieved long cycle life (>7500 cycles) when using graphite and graphene as cathode materials [4-5]. Nevertheless, the reported graphite-based cathodes have intrinsically low storage capacities (60–200 mAh g-1) due to the intercalation mechanism of the solvated ions rather than the multivalent Al3+ transformation. Extensive efforts have been made to develop new cathode materials to promote the specific/volumetric capacity of AIBs, including transition metal oxides [6], sulfides [7], selenides [8] and others. These AIBs based on non-graphite cathodes usually demonstrate either low discharge voltage, or high initial capacity but significant capacity decay and poor cycle life. To further improve the performance of AIBs, new cathode materials with high storage capacity and long cycle life needs to be developed.In this paper, we report the development of a nanoscale FeF3@expaned graphite (EG) composite as a novel conversion-type cathode material for AIBs [9]. AIB coin cells were assembled using high-purity Al foil as the anode, the ionic liquid [EMIm]Cl/AlCl3 as the electrolyte, and the FeF3@EG composite as cathode. The conversion reaction between the Al3+ ions and FeF3 through transferring three electrons for per Al3+ ion reacted could boost the storage capacity of AIBs. A single-wall carbon nanotube-modified separator was introduced into the system, to significantly restrict the shuttle effect of the intermediate product of FeF3. The assembled AIBs exhibited a satisfactory reversible specific capacity of 266 mAh g-1 at a current density of 60 mA g-1 after 200 cycles, and a good Coulombic efficiency approaching 100% after 400 cycles at a current density of 100 mA g-1 [9]. Ex-situ X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) have been applied to explore the energy storage mechanism of FeF3 in AIBs for the first time [9].To further overcome the corrosion issue of ionic liquid, a gel polymer electrolyte (GPE) has been successfully synthesised via an innovative method where no solvent or initiator was utilised in the polymerisation process. The application of GPE significantly reduced the corrosivity and enhances the moisture sensitivity of EMIC ionic liquid, as well as improving the reversible ability of the AIBs. The FeF3@EG-based AIB with 0.8g-EMIC-gel electrolyte exhibits a reversible capacity of 204.5 mAh g-1after 1000 cycles at a current density of 100 mA g-1 and stable rate performance for 600 cycles with a Coulombic efficiency of approximately 95%.This work provides unprecedented insight into novel conversion type cathode materials for AIBs. The findings in this work can serve as guidance for the successful design of low cost and high discharge capacity AIBs for large-scale energy storage and are also meaningful for the fundamental understanding of the metal fluorides cathodes for AIBs.

Multi-{Physics, Phase, Scale} Computational Modeling of Interface-Coupled Problems in Redox Flow Battery Design

Motivated by an urgent need to deploy large-scale energy storage technologies to integrate intermittent renewables, redox flow batteries (RFBs) are gaining prominent attention due to their interesting features including higher durability and power-energy decoupling. RFBs are rechargeable electrochemical systems in which an electrolyte solution containing dissolved or suspended active species is stored in external tanks and pumped through the electrochemical stack - consisting of flow fields, porous electrodes, and membranes - where the active species undergo electrochemical reactions to charge/discharge the battery. However, large-scale deployment of RFBs has feasibility issues regarding costs and efficiency, which can be tackled by tuning their multi-scale design parameters [1].Developing a coupled multi-scale computational model for RFBs can facilitate our understanding of the interplay between intricate phenomena occurring at several length and time scales (depicted schematically in the figure), ranging from transport phenomena, i.e., mass, charge, momentum, and heat, on the cell level (macro and meso scales) to microstructure effects and wettability behavior on the pore-scale (micro and nano scales). Furthermore, the modeling framework should capture the reaction kinetics and multi-phase chemistry of emerging flow battery concepts (e.g. metal-air) including plating and stripping reactions [2].In this research, we are developing a multi-{physics, phase, scale} model for the optimization of next-generation RFBs in the cell-, electrode-, and pore-scale. The model includes free fluid flow (representing flow field channels) over a porous medium (porous electrode) and solves the transport mechanisms over the entire computational domain with a focus on the electrolyte-electrode interface. The model is developed using finite element/volume methods combined with pore network modeling techniques, implemented using various open-source modeling frameworks including OpenFOAM [3], FEniCS [4], and OpenPNM [5].In this presentation, I will first discuss the structure of the modeling framework including the continuum transport models, the pore network model, and the employed numerical schemes. Then, I will present the coupling between continuum and porous medium models. Finally, I will highlight some initial results focused on the efficiency of the coupling of the electrolyte fluid transport with the porous medium and pore network representation of the electrode [6]. We hope that the developed model can be a functional tool to assess and optimize RFB materials and operating conditions and can be broadly adopted to model emerging flow battery chemistries. References K. Chakrabarti et al., Sustainable Energy & Fuels. 4, 5433–5468 (2020).Hein et al., ACS Applied Energy Materials. 3, 8519–8531 (2020).G. Weller et al., Computers in Physics. 12, 620 (1998).Alnæs et al., Archive of Numerical Software, in press, doi:10.11588/ANS.2015.100.20553.Gostick et al., Computing in Science & Engineering. 18, 60–74 (2016).van der Heijden et al., Journal of The Electrochemical Society. 169, 040505 (2022). Figure 1

Stability of Alizarin for Aqueous Organic Redox Flow Batteries

The intermittent nature of renewable energy sources like solar and wind requires suitable large-scale energy storage technologies to properly respond supply and demand of energy. Aqueous organic redox flow batteries (AORFBs) have demonstrated great potential to revolutionize grid-scale energy storage as a result of their low-cost, safety and ability to separate energy and power1. However, most of the organic compounds suffer from lack of sufficient long-term stability.Alizarin (1,2-dihydroxyanthraquinone) is a low-cost, nontoxic, and industrially accessible dye which could potentially be used as an affordable redox-active negative electrolye (negolyte)2. Here, we present an in-depth investigation on the long-term cycling stability of Alizarin. Furthermore, we implement an aggressive cycling conditions to investigate the degradation of the cycled negolyte within just a single day, achieving an equivalent capacity fade percentage as electrolyte cycled for over two weeks3. The capacity fade of alizarin was partially mitigated by the employment of a SOC restriction strategy which was able to decrease the capacity fade rate by more than 60 %.4 Capacity fade measured via cycling is corroborated by ex situ chemical analysis methods.

A thermo-hydro-mechanical damage model for lined rock cavern for compressed air energy storage

Large-scale compressed air energy storage (CAES) technology is regarded as an effective way to alleviate the instability of electricity generated from renewable sources such as wind and solar power, which involves the expensive construction of underground caverns to store highly pressurized and high-temperature compressed air. This study documents mechanical behavior and gas permeability of granite under temperature-pressure synchronous cyclic loading, and the response of the surrounding rock to Thermo-Hydro-Mechanical-Damage (THMD) evolution. Firstly, physical experiments were conducted to examine mechanical property and gas permeability evolutions of granite due to temperature-pressure synchronous cyclic loading. Based on these experiments, equations describing the damage evolution of granite were deduced. Subsequently, using these equations in combination with a thermo-hydro-mechanical coupled model of porous media with two-phase fluid flow, a sophisticated computational routine for the thermo-hydro-mechanical-damage analysis of underground gas storage caverns was developed. Lastly, numerical simulations were conducted to study heat transfer, two-phase seepage, and mechanical response of a CAES cavern under operating conditions. Under low to medium pressure and high-temperature synchronous cyclic loading, granite exhibited a significant variation in elastic modulus and compressive strength. Also, its permeability showed a substantial increase due to damage evolution. After two months of operation, prominent heat transfer was observed in the surrounding rock, particularly in the region extending to approximately 10 m from the inner surface of the cavern, exceeding the range of gas leakage diffusion within the cavern. The plastic zone of surrounding rock is distributed above the cavern's roof and below its bottom. Moreover, areas with higher damage are concentrated in the surrounding rock near the cavern's side walls. These findings contributed to our understanding of the behavior of granite in the context of CAES technology and provided valuable insights for the design and operation of gas storage caverns. The development of the THMD model offered a valuable tool for investigating stress and deformation characteristics of the lining and surrounding rock in CAES plants.