Reliability Of Storage Systems Research Articles

태양광발전 연계 가정용 배터리 에너지저장장치의 블랙박스 개발

In this paper, a black box, which is provided the reliability and user safety of home battery energy storage system connected with solar energy generation, is developed. In the developed scheme, a status and diagnosis data of battery management system, power conditioning system, solar energy generation and grid is measured. This status and diagnosis data is stored and displayed in the developed black box. In addition, this status and diagnosis data is stored and displayed in a monitoring system and a smart phone of user. A performance evaluation of the developed black box is carried out using emulator of home battery energy storage system connected with solar energy generation. Consequently, the developed black box is proved its superiority of the reliability and user safety.

Advanced Ceramic Li Ion Electrolytes for All-Solid-State Li Ion Batteries

At present, the energy supply around the world comes from fossil fuels and is one of the main causes of greenhouse gas emissions. Attempts have been made to generate electricity using renewable sources, such as wind and solar, but it could be realized through the use of reliable electrochemical storage systems. Batteries can be used in combination with renewable energies to store energy when the demand is low and supply to the grid when demand is high. Among the known secondary batteries, Li ion batteries (LIBs) find applications ranging from small mobile electronics to transportation and even to stationary, grid storage systems. LIBs exhibit the highest power and energy densities over other known batteries. The most frequently used cathodes in LIBs include LiCoO2, LiNi1/3Mn2/3Co1/3O12 and LiFePO4 and graphite is the most popular choice for anode. Typical electrolyte used in the LIB consists of lithium salt (e.g., LiPF6, LiBF4 or LiClO4) dissolved in an organic carbonate such as ethylene carbonate, diethyl carbonate or propylene carbonate. The current LIB research is mainly focused on improving the practical gravimetric and volumetric energy densities by developing advanced Li ion electrolytes and electrodes. Attempts have been made to replace unstable polymer members with high temperature stable and highly conducting ceramic Li ion electrolytes, including Li3N, Li-β-alumina, A-site deficient perovskite-type and garnet-type metal oxides. These solid electrolytes offer the advantages of being safe and compatible with advanced electrode materials, as well as a having a wide temperature range of operation and high Li ion conductivity. In this talk, recent advances in most promising garnet-type Li5La3M2O12 (M = Nb,Ta) oxides will be discussed. Since their discovery as Li ion conductors, there has been an increased interest in the development of garnet-type Li ion electrolytes for all solid-state LIBs. Some of the members of the garnet have been proven to be stable against chemical reaction with Li, as well as electrochemically stable up to 6 V vs. Li/Li+. These attributes, together with the good total Li ion conductivity, make them ideal electrolyte candidates for all solid-state LIBs.

Investigating New Electrode Materials for Better Sodium-Ion Batteries

Currently the extensive use of portable electronic devices have given rise to the high demand for reliable high energy density storage in the form of batteries. Today, lithium-ion batteries (LIBs) are the leading technology as they offer high energy density and relatively long lifetimes.[1] However, safety issues and the rarity of lithium brings about the relatively high cost of these batteries.[2] To address this issue, sodium-ion batteries (SIBs) have been developed as a low cost alternative for LIBs.[2, 3] Sodium’s similar chemistry to lithium enables accessible parallel implementation of LIB technology into SIB and its natural abundance ensures that sodium can be acquired at a much cheaper price compared to lithium.[4, 5] Recent development of sustainable and clean energy sources such as solar and wind has also escalated the need for SIBs.[4, 6] The unstable supply of energy generated from these renewable energy sources makes an efficient and reliable energy storage system crucial to ensure a continuous flow of energy during times where the energy production is poor.[3, 6] Such large scale stationary energy storage systems will be unsuitable for LIBs due to its relatively high cost, however with SIBs this could be realized.[3] Nonetheless, challenges still remain for the development of SIBs. Optimization of electrode materials capable of reversible insertion/extraction of sodium-ions in a safe and economic way under high current density are required in order to produce commercially viable SIBs.[2, 7] Present materials commonly investigated for SIB positive electrodes are metal oxides, phosphates, sulfates and metal-organic frameworks (MOF), while carbon based materials are still a favorable choice as negative electrodes due to its low potential against Na, natural abundance, renewability, and low cost.[3, 4] Despite the fact that the reversible intercalation of sodium-ion into/from graphite is not significant, research has shown that other carbon based materials can be used.[8-10]. Although these electrode materials in SIBs have been studied from an electrochemical perspective, further work is still needed to understand the insertion/extraction mechanism of sodium ions into these materials and more importantly how sodium moves inside these materials. As the structure and chemical environment of materials are closely related to their properties, it is very important to understand the mechanism to be able to design new materials with desired properties. In this study, we use a combination of in-situ X-ray diffraction (XRD), solid state nuclear magnetic resonance (SS-NMR) and quasi-elastic neutron scattering (QENS) to study the mechanism of sodium-ion insertion/extraction in some selected electrode materials. XRD will provide long range ordering of the structure of the material. SS-NMR will provide the local environment of the sodium, and QENS enables insight on the diffusion mechanism of the sodium ions inside the selected materials. The combination of these three techniques will provide a more complete picture of the mechanism of sodium-ion insertion/extraction and movement inside the electrode materials. If these mechanisms can be properly understood, it will be possible to design a safe and reliable SIB which could be an alternative to LIB realizing a cheaper energy storage system for the world. This talk will focus on our first results based on carbon based materials such as carbon nanotubes and graphene. With characterization using XRD and SS-NMR we were able to compare the structure and the chemical environment of the sodium within these carbons after charge and discharge, giving interesting insight on how these materials will behave in a battery.

LDM

With the explosive growth in data volume, the I/O bottleneck has become an increasingly daunting challenge for big data analytics. Economic forces, driven by the desire to introduce flash-based Solid-State Drives (SSDs) into the high-end storage market, have resulted in hybrid storage systems in the cloud. However, a single flash-based SSD cannot satisfy the performance, reliability, and capacity requirements of enterprise or HPC storage systems in the cloud. While an array of SSDs organized in a RAID structure, such as RAID5, provides the potential for high storage capacity and bandwidth, reliability and performance problems will likely result from the parity update operations. In this article, we propose a Log Disk Mirroring scheme (LDM) to improve the performance and reliability of SSD-based disk arrays. LDM is a hybrid disk array architecture that consists of several SSDs and two hard disk drives (HDDs). In an LDM array, the two HDDs are mirrored as a write buffer that temporally absorbs the small write requests. The small and random write data are written on the mirroring buffer by using the logging technique that sequentially appends new data. The small write data are merged and destaged to the SSD-based disk array during the system idle periods. Our prototype implementation of the LDM array and the performance evaluations show that the LDM array significantly outperforms the pure SSD-based disk arrays by a factor of 20.4 on average, and outperforms HPDA by a factor of 5.0 on average. The reliability analysis shows that the MTTDL of the LDM array is 2.7 times and 1.7 times better than that of pure SSD-based disk arrays and HPDA disk arrays.

Does RAID Improve Lifetime of SSD Arrays?

Parity protection at the system level is typically employed to compose reliable storage systems. However, careful consideration is required when SSD-based systems employ parity protection. First, additional writes are required for parity updates. Second, parity consumes space on the device, which results in write amplification from less efficient garbage collection at higher space utilization. This article analyzes the effectiveness of SSD-based RAID and discusses the potential benefits and drawbacks in terms of reliability. A Markov model is presented to estimate the lifetime of SSD-based RAID systems in different environments. In a small array, our results show that parity protection provides benefit only with considerably low space utilizations and low data access rates. However, in a large system, RAID improves data lifetime even when we take write amplification into account.

UV-Vis Spectroscopic Monitoring of state-of-Charge in Vanadium Flow Batteries

There is considerable interest in flow batteries for storing energy from non-dispatchable power sources such as solar, wind and ocean energy and for other large and medium scale energy storage applications. Vanadium flow batteries (VFB), also known as vanadium redox flow batteries (VRFB or VRB), are particularly attractive because, in addition to having long cycle life, they are essentially immune to cross-contamination problems due to mass transfer across the membrane that can limit the service life of the electrolyte in other systems. Accurate monitoring of state of charge (SoC) is intrinsically important for the reliability of energy storage systems, particularly large systems in critical applications. Furthermore, independent monitoring of the SoC of both electrolytes is important for effective operation of flow battery technology. For example, in a VFB, transfer of vanadium ions across the membrane and side reactions such as hydrogen formation at the negative electrode can cause the battery to become unbalanced (e.g. more VV on the positive side than VIIon the negative), and balancing by overcharging is not practical because it can lead to significant degradation of the carbon at the positive electrode. The principal active species in a VFB are vanadyl (VO2+) and pervanadyl (VO2 +) ions (i.e. VIV and VV) in the positive electrolyte (catholyte) and V3+ and V2+ in the negative electrolyte (anolyte), typically in H2SO4 solutions. These solutions are highly colored: the vanadium species all have strong absorbance spectra in the visible region. Thus, as we have previously suggested,1,2 ultraviolet-visible (UV-Vis) spectroscopy offers an attractive method of independently measuring the SoC of both electrolytes. Spectroscopic monitoring of SoC is independent of electrochemistry and offers the possibility of performing in-situ analysis. Because the absorbance of VII-VIII mixtures is a linear combination of that of the constituents, it is straightforward to implement UV-Vis spectroscopic monitoring of the SoC of the anolyte. However, at the concentrations typically used in a VFB, the absorbance of VIV-VV electrolytes is high and is a very non-linear function of the mole fraction of VIV and of overall vanadium concentration.1-5 Because of this, it was previously suggested in the literature that UV-Vis spectroscopic monitoring of VFB catholytes is not feasible. We have shown4,5 that the non-linear absorbance behavior of the catholyte can be quantitatively explained by the formation of a strongly absorbing 1:1 mixed-valence complex, V2O3 3+, in equilibrium with VO2+ and VO2 +. A model of the spectra based on this equilibrium, using an excess absorbance parameter p to quantify the effect of V2O3 3+ formation together with the extinction coefficients of VO2+ and VO2 +, shows excellent quantitative agreement with experiment and comprehensively explains the spectroscopic behaviour. In this paper, we present results for the UV-Vis spectroscopy of VFB catholytes over a range of concentrations and extend our model to analyse electrolytes with different concentrations of total vanadium. We measured and analysed the ultraviolet-visible spectra of catholytes for vanadium flow batteries (VFBs) for a range of VIV:VV ratios and vanadium concentrations. The results showed that p varies weakly with the vanadium concentration C and we quantified this variation relative to a reference concentration C r in terms of a single parameter M that is independent of the choice of C r. We generated standard spectra of p (at a reference concentration of 1 mol dm-3) and of the extinction coefficients of VO2+ and VO2 +. The spectrum of any catholyte may be simulated using the measured value of M in a governing equation which expresses the absorbance, at any wavelength λ, of catholyte with any VIV mole fraction f and any total vanadium concentration C in terms of these standard spectral parameters. The precision of the simulation was verified against experimental spectra of an independent set of VIV-VVmixtures. We constructed calibration curves for SoC using the governing equation and the standard spectral parameters. Values of SoC determined from the measured absorbance of independent VIV-VV mixtures using these calibration curves were in good agreement with the corresponding values determined from the concentrations of the parent solutions. Based on these results, we extended our experiments to in-situmonitoring of SoC by UV-Vis spectroscopy. We will discuss our results with particular emphasis on the behavior of the positive electrolyte. 1. X. Gao, et al., ECS Trans., 45, 25 (2013). 2. D.N. Buckley, et al, European Patent EP 13195315 (2013). 3. P. Blanc, et al, Inorg. Chem., 21, 2923 (1982). 4. D.N. Buckley, et al, J. Electrochem. Soc., 161, A524 (2014). 5. C. Petchsingh, et al, J. Electrochem. Soc. 163, A5068 (2016) Figure 1

Immovable food storage facilities, knowledge, and landscape in non-sedentary societies: Perspectives from northern Michigan

Physical food storage in immovable facilities, typically categorized as large-scale storage, is used as a scarcity mitigation strategy by some small-scale, relatively low density, non-sedentary hunter–gatherer (and low-level horticulturalist) societies. When mobile societies rely on immovable food storage facilities, they face particular technological and landscape placement challenges that must be navigated to reduce the risks of facility failure and realize scarcity mediation. We explore how the materiality and spatial positioning of immovable food storage facilities themselves can encode knowledge necessary for these facilities to form a reliable food storage system. We suggest immovable food storage facilities be understood as emplaced features, that is, as features whose placement in the landscape is the result of, but also subsequently the producer of, socioecological knowledge. We explore these ideas through a case study in the northern Great Lakes region. During the Late Precontact period (ca. AD 1000/1100–1600), socioeconomic shifts pushed communities into increasingly spatially and seasonally restricted annual mobility rounds. The region’s relatively low density, egalitarian, non-sedentary hunter–gatherer–fisher and low-level horticulturalist societies turned to physical food storage in immovable facilities, in the form of subterranean cache pits, to circumvent the risks posed by socioecological variability. Exploring one inland lake landscape in detail, we find cache pit storage facilities were purposefully planned and built in ways that successfully navigated the technological and landscape placement challenges of immovable food storage in this specific setting. We found the enduring presence and use of these immovable food storage facilities in the landscape encoded and transmitted knowledge about sustaining successful food storage across spatially and temporally dispersed groups. Cache pits were emplaced features that served to enhance community well-being in the increasingly restricted socioeconomic context of Late Precontact.

Primary control provided by large-scale battery energy storage systems or fossil power plants in Germany and related environmental impacts

Increasing renewable energy generation influences the reliability of electric power grids. Thus, there is a demand for new technical units providing ancillary services. Non-dispatchable renewable energy sources can be balanced by energy storage devices. By large-scale battery energy storage systems (BESSs) grid efficiency and reliability as well as power quality can be increased. A further characteristic of BESSs is the ability to respond rapidly and precisely to frequency deviations, making them technical ideal candidates for primary control provision (PCP).In this paper environmental impacts of PCP by novel Li-ion BESSs are compared to impacts of PCP by state-of-the-art coal power plants (CPPs) using a Life Cycle Assessment (LCA) approach and considering German control market conditions. The coal power plant stock is characterized by varying properties. Thus, different scenarios of CPP operation are analyzed by varying sensitive parameters like efficiency loss and required must-run capacity. Finally, PCP by BESSs and CPPs are compared in terms of environmental performance. The more must-run electricity generation is attributable to PCP of CPPs, the higher are the environmental impacts of these CPPs. This leads to a better relative environmental performance of BESSs in most scenarios. Contrary, comparative or even better environmental performance of CPPs compared to state-of-the-art BESSs can solely be achieved if power plants without load restrictions for provision of primary control and with extreme low efficiency losses caused by PCP are applied. Consequently, the results of this paper indicate that BESSs are a promising option to reduce environmental impacts of primary control provision.

Near-optimal tape transport control with feedback of velocity and tension

Abstract: With the increasing recording areal density and volumetric density targeted by magnetic tapes, high-performance tape transport is of fundamental importance to achieve the required reliability in tape storage systems. In this paper, the time-varying characteristics of tape transport are taken into account to design a velocity and tension feedback control system using p-type controllers that depend on the longitudinal tape position. Analytical expressions are given for the controller gains, for which all transfer functions become essentially independent of longitudinal position. Experimental results are presented for a tape system where feedback of tension is provided by a tension sensing roller.

A novel solid–gas thermochemical multilevel sorption thermal battery for cascaded solar thermal energy storage

An innovative solid–gas thermochemical multilevel sorption thermal battery is developed for cascaded solar thermal energy storage to enhance the versatility and working reliability of solar heat storage system by widening the working temperature range. Solar thermal energy can be stored in the form of bond energy of sorption potential at different cascaded temperatures resulting from solid–gas thermochemical multilevel sorption processes. The operating principle and working performance of the thermochemical multilevel sorption thermal battery for energy storage is described and analyzed. Thermodynamic analysis showed that the proposed thermochemical multilevel sorption thermal battery has the potential capacity for meeting the challenge of solar heat storage during the random variation of low and high solar insolation with time by using cascaded thermal energy storage technology. An energy density higher than 1200kJ/kg of reactant can be attained from the advanced energy storage system. The promising method can enhance the versatility and working reliability of solar heat storage due to its distinct advantages of high energy density and a wide range of solar collection temperature when compared with conventional heat storage methods. It has potential applications for energy management of renewable energy utilization and waste heat recovery in large-scale industrial processes.

Hybrid Minimum Pearson and Euclidean Distance Detection

The reliability of mass storage systems, such as optical data recording and non-volatile memory (Flash), is seriously hampered by uncertainty of the actual value of the offset (drift) or gain (amplitude) of the retrieved signal. The recently introduced minimum Pearson distance detection is immune to unknown offset or gain, but this virtue comes at the cost of a lessened noise margin at nominal channel conditions. We will present a novel hybrid detection method, where we combine the outputs of the minimum Euclidean distance and Pearson distance detectors so that we may trade detection robustness versus noise margin. We will compute the error performance of hybrid detection in the presence of unknown channel mismatch and additive noise.

Reliable transformerless battery energy storage systems based on cascade dual‐boost/buck converters

In this study, the cascade dual-boost/buck half-bridge and full-bridge bidirectional ac–dc converters are proposed for grid-tie transformerless battery energy storage systems (BESSs). The proposed converter contains the advantages of the traditional cascade H-bridge (CHB) converter. However, compared with CHB converter, there is no shoot-through issue in the proposed converter, which is more reliable for BESS. In addition, a unified control scheme is proposed for active-power control and individual state-of-charge-balancing control of BESS, which is very modular and easy to implement. At the end, a laboratory BESS is constructed and tested combining a cascade two-unit dual-boost/buck half-bridge converter with nine lead–acid series-connected battery units. Experimental results obtained from the laboratory system verified the feasibility and effectiveness of the proposed BESS and unified control scheme.

Design optimization and optimal control of grid-connected and standalone nearly/net zero energy buildings

Abstract Nearly/net zero energy buildings (nZEBs) have attracted increasing attention particularly when high and complex performance is required in terms of energy-saving, indoor thermal comfort, environmental friendliness and grid-friendliness. However, there is no exact approach at present for the design and control of buildings to achieve the nearly/net zero energy target. This is mainly due to the complex interplay of energy production/consumption/storage systems as well as the automatically and manually controlled systems/elements in the highly integrated buildings. This paper therefore presents a comprehensive review on the issues related to the design and control of these buildings, i.e. the effects of climate/site on design, design optimization methods, uncertainty and sensitivity analysis for robust design and system reliability, efficient and optimal control of high efficient generation systems and energy storage systems for alleviating/shifting the peak load, model predictive control for fast responses to smart grid, and adoption of advanced smart technologies. An outline of the progress of nZEBs is presented by summarizing the internationally known nZEBs identified including 30 case studies on the design strategies applied and the actual building performance. This review could also support the future development of methods that address the design and control of buildings with a holistic view.

Structure and Surface Chemistry Optimization of Graphite Electrodes for High-Voltage Dual-Intercalation Batteries

Existing standalone grid-level power systems rely on inefficient operation of diesel generators or expensive traditional battery technologies. Dual-intercalation batteries, which rely on high-voltage ion insertion into both cathodes and anodes, offer a promising electrical energy storage alternative. The respective 372 mAh/g and 90 mAh/g capacitances for cation and anion intercalation offer grid-level charge storage densities, implementation of affordable and available materials, and simpler disposal procedures for optimized and reliable energy storage systems[1]. Despite several expected advantages, the 5.2 V intercalation process currently exhibits low first-cycle efficiencies and limited charge/discharge rates. Possible causes can be likely attributed to a poor solid-electrolyte interface (SEI) and the large anion diameters, increasing inefficiencies from long intercalation pathways. Furthermore, theoretical predictions limit cathode stage 1 intercalation to one anion per 24 carbons (compared to one cation per 6 carbons for stage 1 anode intercalation), inherently limiting the system’s energy density. To maximize capacitance and long-term cyclabilities, the carbon structure and surface chemistry of both the cathode and anode materials must be optimized for the specific electrolyte and be appropriately matched with respective properties of the opposite electrode material. To accomplish this goal, we subjected spherical, core-shell, and stacked graphite structures to 1100 – 1800 °C vacuum annealing, impact milling, 570 °C air oxidation, C2F6 plasma discharge, and high-temperature treatments using melamine and H2. These procedures defunctionalized surfaces [2], altered defects in the sp2 lattice, or selectively grafted C=O, C-F, C-Nx, and C-H groups, respectively. Following electrochemical cycling between 4.0 and 5.2 V in 2.0 m LiPF6 in fluoroethylene carbonate (FEC), ethylmethycarbonate (EMC) electrolytes and a tris(hexafluoro-iso-propyl)phosphate (HFiP) additive, we observed different effects of specific surface chemistries on anode and cathode capacities and first-cycle efficiencies. In particular, we observe positive influences of hydrogenated anode surfaces and improved performances for oxidized cathodes. Similar modifications of spherical and layered graphite electrodes yielded asymmetric efficiencies and long-duration cyclabilities, indicating divergent influences of functionalities on specific intercalated ions. Matching the appropriate surface groups for anode and cathode dual-graphite batteries, we observe improvements in coulombic efficiencies and long-term cyclabilities. Our findings offer fundamental insights into the dual-intercalation process and provide pathways for optimization of these all-carbon, environmentally friendly energy storage systems [3] for grid-level applications. 1. Read, J. A.; Cresce, A. V.; Ervin, M. H.; Xu, K., Dual-graphite chemistry enabled by a high voltage electrolyte. Energy & Environmental Science 2014, 7(2), 617-620. 2. Dyatkin, B.; Gogotsi, Y., Effects of Structural Disorder and Surface Chemistry on Electric Conductivity and Capacitance of Porous Carbon Electrodes. Faraday Discussions 2014, 172. 3. Dyatkin, B.; Presser, V.; Heon, M.; Lukatskaya, M. R.; Beidaghi, M.; Gogotsi, Y., Development of a Green Supercapacitor Composed Entirely of Environmentally Friendly Materials. ChemSusChem 2013, 6 (12), 2269–2280. Figure 1

HeMatch: A redundancy layout placement scheme for erasure-coded storages in practical heterogeneous failure patterns

Erasure codes are widely used in storage systems for providing data reliability due to the advantage of high storage efficiency, while the access efficiency becomes the main shortcoming because of the extra data retrieve and decoding for accessing unavailable data. Most existing work designs erasure codes based on the ideal failure pattern where all storage nodes fail at the same rate. However in practice, the physical storage nodes fail at different rates due to the heterogeneous hardware, topologies and application behaviors. In this paper, we consider the heterogeneous failure pattern and analyze how the failure pattern impacts the overall access efficiency and reliability of erasure-coded storage systems. We propose HeMatch, a redundancy layout placement scheme in practical heterogeneous failure pattern for erasure-coded storage access efficiency. Specifically, we first study how the heterogeneous failure pattern impacts the access efficiency and propose a general model based on the Tanner graph to evaluate and predict the access efficiency in specific failure pattern and redundancy layout. Then, we propose the redundancy layout placement scheme, which matches the redundancy layout with the physical storage nodes in practical heterogeneous failure patterns based on the evaluation and prediction from our model. The experimental results demonstrate that the model we propose accurately evaluates the access efficiency, and HeMatch saves unavailable data access cost by up to 20% and improves the system reliability as well.

Study on Thermal-fluid Effect of Thermal Energy Storage Tank Design in Solar Energy Applications

The growth of technologies in energy storage has urged new proficiencies and application areas. Energy storage technologies can be varied from an electric battery to a flywheel that can results in deliverable power based on the application. These variations are a challenge to design a reliable and efficient energy storage system. The purpose of this paper is to study the thermal-fluid effect of thermal energy storage (TES) tank design. A three-dimensional modelling of TES tank was carried out using commercial computational fluid dynamics (CFD) code by differentiate the heat source temperature and heat transfer fluid (HTF) velocity. The results predict the thermal-fluid behaviour of TES tank. Since the HTF used is water, the expected outcome of the outlet temperature is in the range of 40 to 60 °C.The outlet temperature of the TES tank is compared with the experimental data. It can conclude the TES tank thermal-fluid behaviour is affected by heat source temperature and velocity HTF. The results can be further used to design dependable TES system for green energy application

Rebuttal to “Beyond MTTDL: A Closed-Form RAID-6 Reliability Equation”

A recent article on the reliability of RAID-6 storage systems overlooks certain relevant prior work published in the past 20 years and concludes that the widely used mean time to data loss (MTTDL) metric does not provide accurate results. In this note, we refute this position by invoking uncited relevant prior work and demonstrating that the MTTDL remains a useful metric.

Marching-Based Wear-Leveling for PCM-Based Storage Systems

Improving the performance of storage systems without losing the reliability and sanity/integrity of file systems is a major issue in storage system designs. In contrast to existing storage architectures, we consider a PCM-based storage architecture to enhance the reliability of storage systems. In PCM-based storage systems, the major challenge falls on how to prevent the frequently updated (meta)data from wearing out their residing PCM cells without excessively searching and moving metadata around the PCM space and without extensively updating the index structures of file systems. In this work, we propose an adaptive wear-leveling mechanism to prevent any PCM cell from being worn out prematurely by selecting appropriate data for swapping with constant search/sort cost. Meanwhile, the concept of indirect pointers is designed in the proposed mechanism to swap data without any modification to the file system's indexes. Experiments were conducted based on well-known benchmarks and realistic workloads to evaluate the effectiveness of the proposed design, for which the results are encouraging.

Minimizing data redundancy for high reliable cloud storage systems

Cloud storage system provides reliable service to users by widely deploying redundancy schemes in its system – which brings high reliability to the data storage, but inversely introduces significant overhead to the system, consisting of storage cost and energy consumption. The core behind this issue is how to leverage the relationship between data redundancy and data reliability. To optimize both concurrently is apparently difficult. As such, to fix one as a constraint and then to reach another one becomes the consensus. We aim in the paper to pursue a storage allocation scheme that minimizes the data redundancy while achieving a given (high) data reliability. For this purpose, we have provided a novel model based on generating function. With this model, we have proposed a practical and efficient storage allocation scheme, which is proved to be able to minimize the data redundancy. We analytically demonstrate that the suggested solution brings several advantages, in particular the reduction of the search space and the acceleration to the computation. We also assess the improvement on the savings of data redundancy experimentally by adopting availability traces collected from real world – which encouragingly shows that the reduction of data redundancy by our solution can reach up to more than 30% as compared to the heuristic method recently proposed in the research community.

On-board Thermal Fault Diagnosis of Lithium-ion Batteries For Hybrid Electric Vehicle Application

Lithium-ion batteries with different applications in industries need to be safe, reliable and long-lasting energy storage systems. The internal temperature of the battery, which is higher and more critical compared to the surface temperature, can be affected by internal thermal failures. Hence, internal temperature estimation and fault diagnosis is necessary for Lithium-ion batteries to avoid the problem of overheating. In this paper, a Luenberger observer is designed to detect and isolate three main thermal failures in the battery, consisting of thermal runaway, convective cooling resistance fault, and internal thermal resistance fault. The primary residuals generated by the observer are fed into two designed filters to create secondary residuals. By using the secondary residuals, an estimation of effect of the faults on the system can be obtained.