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This review highlights the latest advancements in thermal energy storage systems for renewable energy, examining key technological breakthroughs in phase change materials (PCMs), sensible thermal storage, and hybrid storage systems. Practical applications in managing solar and wind energy in residential and industrial settings are analyzed. Current challenges and research opportunities are discussed, providing an overview of the field's current and future state. Following the PRISMA 2020 guidelines, 1040 articles were initially screened, resulting in 49 high-quality studies included in the final synthesis. These studies were grouped into innovations in TES systems, advancements in PCMs, thermal management and efficiency, and renewable energy integration with TES. The review underscores significant progress and identifies future research directions to enhance TES's efficiency, reliability, and sustainability in renewable energy applications. [ABSTRACT FROM AUTHOR]

Diesel multiple units (DMU) offer an affordable alternative to electric trains on lines in which infrastructural and maintenance costs of electrification are not justified. A further improvement of sustainability involves the abandonment of internal combustion engines in favour of an electric power train sustained by an on-board storage system. In this work, the authors propose a model to perform a rapid simulation of hybrid storage systems based on hydrogen fuel cells,a technology that should be complementary with respect to battery-operated trains. The proposed tool is applied, as a benchmark test case, to a modular passenger train devoted to regional service. Obtained results clearly demonstrate the capabilities of proposed tools and give useful indications for a feasible optimization and integration of fuel cells for railway applications. [ABSTRACT FROM AUTHOR]

The Internet of Things (IoTs) is attracting the attention of scientists worldwide. With its explosive growth along with applications that require real-time computing power, a new technology called edge computing has emerged. As a result, edge computing has changed the way data are processed and handled back and forth for millions of devices worldwide, such as autonomous vehicles and electric cars. The confinement of cloud computing technology, such as a content delivery network (CDN), contributed significantly to edge computing development. Currently, this technology can meet the demands of ever-growing mobile devices and the IoTs. This paper describes a novel secure framework consisting of a hybrid storage architecture consisting of CDN, edge computing, and centralized storage. Centralized storage consists of multilevel storage systems that comprise solid-state drivers (SSDs) and hard disk drivers (HDDs), which provide optimal data storage solution for a wide variety of real-time data processing applications. Transforming the data back and forth between SSDs and HDDs is crucial for achieving high performance while meeting the edge device request deadline. Additionally, a new dynamic solid-state disk partitioning mechanism is introduced to optimize security for the proposed framework among hard disk drives. A partition from the solid-state disks to hard disk drives is assigned based on hard disk drive workloads.

In recent years, the massive increase in the data generation has given rise to enormous challenges in storage systems. Single storage media, such as hard disk drives (HDDs) or solid state drives (SSDs), cannot meet the actual needs owing to their inherent physical characteristics. One feasible solution is to adopt a hybrid storage architecture that uses both an SSD and HDD. In this case, the management of the cache replacement strategy of the hybrid storage becomes key in improving storage performance. Based on the cuckoo filter, this study proposes a counting cuckoo filter (CCF) hot-probe method that exhibits a high space and time efficiency and supports deletion. Moreover, a CCF-least recently used (LRU) cache replacement strategy is proposed by combining CCF and the adaptive two-level LRU technique. This strategy uses CCF to identify hot data and the adaptive two-level LRU technique to manage the cache. Experimental results indicate that in comparison with traditional strategies, the cache replacement strategy combined with the hot-probe method can significantly improve cache hit ratios. Furthermore, in comparison with other cache replacement strategies that use hot-probe methods, CCF-LRU exhibits a lower time and space complexity and a higher hit ratio. [ABSTRACT FROM AUTHOR]

Multisource inverters (MSIs) as a new approach for the integration of the energy and the power sources in electric vehicle applications have gained considerable attraction. Such structures offer the active control of the dc sources without using any dc/dc converters or magnetic elements, which reduces the weight, and the volume of the power electronics interface between the sources and the load. Moreover, high power density and improved efficiency due to the elimination of the magnetics are the other significant features of an MSI. This article proposes a novel three-phase MSI for integration and active control of a high-voltage dc source and a low-voltage dc source. The proposed MSI structure employs a smaller number of semiconductor devices at the current path in various operating modes in comparison to the previously published counterparts, which results in an improved efficiency operation. Performance of the proposed MSI using a modified space vector modulation technique for all possible operating modes is verified through simulations and experiments on a laboratory prototype [ABSTRACT FROM AUTHOR]

With the increasing wind power integration, the security and economy of the power system operations are greatly influenced by the intermittency and fluctuation of wind power. Due to the flexible operational modes for charging/discharging, the hybrid energy storage system (HESS) is composed of battery energy storage system and super-capacitor can effectively mitigate the wind power uncertainty. This paper proposes a probabilistic forecasting-based HESS sizing and control scheme to cost-effectively smooth wind power fluctuations. First, probabilistic wind power forecasting is combined with multivariate Gaussian copula to generate temporally correlated wind power scenarios. Then, an adaptive variational mode decomposition (VMD) method is proposed to extract the frequency components of each wind scenario and determine the pre-scheduled power of wind-HESS system adaptively. Finally, a two-stage stochastic optimization model is constructed to determine the capacity and correct the pre-scheduled power of HESS with the objective of minimizing total cost. Case studies based on actual data from a Danish wind farm demonstrate that the proposed HESS sizing and control scheme can significantly reduce the installation cost and operation cost of HESS and prominently smooth wind power fluctuations. [ABSTRACT FROM AUTHOR]

Because the solid-state drive (SSD) shows high access performance, it is usually integrated into existing hard disk drive (HDD)-based storage hierarchy to form HDD/SSD hybrid storage systems. To further improve the performance of HDD/SSD hybrid storage systems, data migration schemes have been put forward to migrate the sequential data between HDD and SSD. However, the existing schemes cannot be aware of dirty data in the buffer and then incur a large number of unnecessary page migrations. In this paper, we devise an efficient data migration scheme considering dying data for HDD/SSD hybrid storage systems. In this scheme, a new liveness state, called the dying state, is utilized to identify the live data, which will become dead shortly due to its corresponding dirty version in the buffer. To decrease the page migration count, this scheme uses the benefit-to-cost ratio to select a block for data migration and copies the up-to-date version of dying data into the free space instead of migrating the dying data. Our experimental results show that our proposed scheme can perform better than existing data migration schemes that are not aware of dying data under various benchmarks.

Hybrid object storage systems provide opportunities to achieve high performance and energy efficiency with low cost for enterprise data centers. Existing object storage systems, however, distribute data objects in the system without considering the heterogeneity of the underlying devices and the asymmetric data access patterns. Therefore, the system performance and energy efficiency may degrade as data are placed on improper storage devices. For example, energy-efficient high-density archive hard disk drives (archive HDDs) are significantly slower than normal HDDs and solid state disks (SSDs), which mean that the archive HDDs are not appropriate for storing frequently accessed objects. Besides, flash-based SSDs have limited write endurance, which makes SSDs vulnerable for storing write-intensive objects. In this paper, we analyze various real enterprise workloads and find that read and write requests are not uniformly distributed to data objects. Based on the observations, we propose a novel strategy, biased object storage strategy (BOSS), to reduce writes to SSDs and improve system performance for hybrid object storage systems. Different from conventional uniform and fixed data distribution strategies, the BOSS can distribute and migrate data objects to various types of devices dynamically, according to the data access patterns collected online. The experimental results show that the BOSS can reduce 64% of writes on SSDs and improve system performance by 29.51% on average, while maintaining a high level of load balance.

Electric motorcycles use a battery storage system and a controlled inverter (motor drive) to drive the wheels. Given that the sale of electric motorcycles is expected to grow significantly over the next decade, the aim of this research is to add a supercapacitor storage system to this simple network in order to extend the autonomy of the motorcycle. This paper analyzes and demonstrates the benefits of two different structures for adding a supercapacitor bank to a lithium-ion battery pack: a passive filter and a buffer for the battery. The advantages of each structure are presented and design guidelines are provided. In addition, we propose a synthetic inductor filter typology based on the two analyzed structures in order to increase the autonomy of the motorcycle. Simulations and experimental results using real data validate the analysis. This paper then uses real data extracted from an electric motorcycle to compare the four topologies: batteries only, the passive filter, the buffer, and the synthetic inductor semi-active hybrid storage system. The comparison shows that battery capacity is extended up to 7.8% with a smoother current profile. However, due to the losses from the added converter in cascade, the net capacity of the whole system is extended only up to 3.7%. Therefore, improvements in the dc/dc converter can further increase the entire system capacity. [ABSTRACT FROM AUTHOR]

This study presents an advanced control structure aimed at the optimal economic energy management of a renewable energy‐based microgrid. This control scheme is applied to energy optimisation in a microgrid with non‐dispatchable renewable sources, such as photovoltaic and wind power generation, as well as dispatchable sources, as distributed generators, hybrid storage systems compound by battery bank, supercapacitors, hydrogen storage unit, and one electric vehicle charging station. The proposed controller consists of a Lyapunov‐based hybrid model predictive control based on mixed logical dynamical (MLD) framework. The main contribution of the proposed technique is the assurance of the closed‐loop stability and recursive feasibility, by a novel approach focused on MLD models, using ellipsoidal terminal constraints and the Lyapunov decreasing condition. Finally, simulation tests under different operational conditions are performed and the attained results have shown the safe and reliable operation of the proposed control algorithm compared to existing and well‐known energy management techniques. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 1:1 scale laboratory test bench for electric powertrains. • Battery and supercapacitor-based hybrid energy storage systems. • Experimental validation of supercapacitor models. • Novel analytical methods for maximizing the effectiveness of hybrid energy storage systems in real electric powertrains. Abstract This paper deals with hybrid energy storage system (HESS) management strategies, optimized for urban road electric vehicle applications. These new control strategies aim to extend battery pack durability by reducing charging/discharging current peaks by means of supercapacitors. The optimization is carried out with reference to the case study of a HESS composed of a high power unit, i.e. supercapacitor module plus a high energy unit, i.e. a battery pack, based on nickel-chloride ZEBRA (ZEolite Battery Research Africa) technology. On-board integration of the two storage devices is obtained through a DC/DC bidirectional power converter, as this configuration is particularly convenient for many kinds of urban vehicle operations. The novelty of this work consists in an analytical methodology, based on non-linear programming and calculus of variations theory, to evaluate management strategies characterized by high effectiveness in reducing battery current transients. The identification and optimization of these strategies are initially performed on the basis of a vehicle model, built in the Matlab-Simulink simulation environment. To this purpose, the experimental characterization of the supercapacitor module is obtained with reference to three different models, whose selection depends on the required fitting performance and computational effort indexes, as evaluated in the paper. The energy management strategies identified show promising results in the simulation environment, followed by experimental activities carried out by means of a dedicated 1:1 scale laboratory test bench. The various experimental results presented in this manuscript highlight that the identified λ-control strategy presents effectiveness values up to 57%, close to the ideal results obtained in the simulation environment. In fact, the methodology proposed in this paper, validated by laboratory experiments, definitely reduces the negative consequences of power peaks on the HESS, indicating the real possibility of using these results in the design and control of urban road vehicles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • 1:1 scale laboratory test bench for electric power-trains supplied by hybrid energy storage systems. • ZEBRA and super-capacitors based hybrid energy storage systems. • Rule based energy management strategies. • Laboratory experimental data on standard driving cycles. Abstract This paper is aimed to experimentally analyse the effectiveness of a hybrid storage system, when powering a commercial vehicle for urban use. The hybrid energy storage system is composed by two ZEBRA batteries, combined with an electric double layer capacitor (EDLC) module. The integration of those storage systems is obtained by means of a bidirectional DC/DC converter, which balances the electric power fluxes between batteries and super-capacitors, depending on the driving operative conditions. Modeling and simulations are preliminarily conducted with reference to the specific case study of an electric version of the Renault Master, supplied by the above described hybrid storage system. That theoretical activity allows the optimization of rule based energy management strategies for the hybrid energy storage system, in terms of the effectiveness in reducing the negative effects of high charging/discharging currents on battery durability. Then, the experimentation of the real power train, connected to the mentioned hybrid storage system, is carried out through a 1:1 laboratory test bench, able to perform the analysed energy management strategies on standard driving cycles, representative of the urban mission of the commercial vehicle under study. The obtained experimental results, expressed through electrical and mechanical parameters in a wide range of road operative conditions, show that the super-capacitors can improve the expected battery lifespan, with values of maximum effectiveness up to 52%, for driving patterns without negative road slopes. The procedure followed and presented in this paper definitely demonstrates the good performance of the evaluated hybrid storage system, controlled by the DC/DC power converter, to reduce the negative consequences of the power peaks associated with the urban use of commercial vehicles. [ABSTRACT FROM AUTHOR]

This work carries out a comparison of non-isolated topologies for power electronic converters applied to Hybrid Energy Storage Systems. At the considered application, several options for three-port circuits are evaluated when interfacing a DC link with two distinct electrical energy storage units. This work demonstrates how the proposed structure, referred to as Series-Parallel Connection, performs as a simple, compact and reliable approach, based on a modification of the H-bridge configuration. The main advantage of this solution is that an effective large voltage gain at one of the ports is attained by means of a simple topology, preventing the use of multilevel or galvanic-isolated power stages. The resulting structure is thoroughly compared against the most significant direct alternatives. The analysis carried out on the switching and conduction losses in the power switches of the target solution states the design constraints at which this solution shows a performance improvement. The experimental validations carried out on a 10 kW prototype demonstrate the feasibility of the proposed scheme, stating its benefits as well as its main limitations. As a conclusion, the Series-Parallel Connection shows a better performance in terms of efficiency, reliability and controllability in the target application of compensating grid or load variations in Non-Isolated Hybrid Storage Systems, with large mismatch in the storage device voltage ratings. [ABSTRACT FROM AUTHOR]

Harnessing renewable resources such as solar energy and biogenic waste for hydrogen production offers a path toward a carbon-neutral industrial economy. This study suggests the development of a renewable-based hydrogen and power supply facility (HPSF) that relies on fermentation and solar-driven electrolysis technologies to achieve penetration of renewable hydrogen and electricity in the industrial symbiosis. Literature studies reported that the hybrid battery-hydrogen storage system could effectively improve the sustainability and reliability of renewable energy supplies, yet its application under diurnal and seasonal renewable resource variations has not been well studied. Hence, this work develops a multi-criteria optimisation framework for the configuration design of the proposed HPSF that concurrently targets industrial hydrogen and electrical loads with the consideration of diurnal and seasonal renewable resource variations. Case scenarios with different storage applications are presented to evaluate the role of storage in improving economic and environmental sustainability. The results show that the application of hybrid storage with molten carbonate fuel cell (MCFC) systems is preferred from a comprehensive sustainability standpoint, which improves the sustainability-weighted return-on-investment metric (SWROIM) score by 4%/yr compared to HPSF without storage application. On the other hand, the application of a single-battery system is the most economical solution with a return on investment (ROI) of 0.7%/yr higher than the hybrid storage approach. The research outcome could provide insights into the integration of fermentative and solar-driven electrolytic hydrogen production technologies into the industrial symbiosis to further enhance a sustainable economy. • Optimisation of renewable-based hydrogen and electricity supply network configuration. • Hydrogen production is derived from both fermentative and solar-powered electrolysis technologies. • Assessed the role of the hybrid battery-hydrogen storage systems in the supply-demand network. • Mathematically modelled based on the sustainability-weighted return-on-investment metric (SWROIM). • The incorporation of a hybrid storage system results in the highest SWROIM score. [ABSTRACT FROM AUTHOR]

In this work, an in-depth investigation was performed on the properties of the half-bridge current-source (HBCS) bidirectional direct current (DC)-to-DC converter, used to interface two DC-link voltage sources with a high-voltage-rating mismatch. The intended implementation is particularly suitable for the interfacing of a supercapacitor (SC) module and a battery stack in a hybrid storage system (HSS) for automotive applications. It is demonstrated that the use of a synchronous rectification (SR) modulation scheme benefits both the power-stage performance (in terms of efficiency and reliability) and the control-stage performance (in terms of simplicity and versatility). Furthermore, an average model of the converter, valid for every operating condition, is derived and utilized as a tool for the design of the control system. This model includes the effects of parasitic elements (mainly the leakage inductance of the transformer) and of the converter snubbers. A 3 kW prototype of the converter was used for experimental validation of the converter modeling, design, and performance. Finally, a discussion on the control strategy of the converter operation is included.

This work carries out a comparison of non-isolated topologies for power electronic converters applied to Hybrid Energy Storage Systems. At the considered application, several options for three-port circuits are evaluated when interfacing a DC link with two distinct electrical energy storage units. This work demonstrates how the proposed structure, referred to as Series-Parallel Connection, performs as a simple, compact and reliable approach, based on a modification of the H-bridge configuration. The main advantage of this solution is that an effective large voltage gain at one of the ports is attained by means of a simple topology, preventing the use of multilevel or galvanic-isolated power stages. The resulting structure is thoroughly compared against the most significant direct alternatives. The analysis carried out on the switching and conduction losses in the power switches of the target solution states the design constraints at which this solution shows a performance improvement. The experimental validations carried out on a 10 kW prototype demonstrate the feasibility of the proposed scheme, stating its benefits as well as its main limitations. As a conclusion, the Series-Parallel Connection shows a better performance in terms of efficiency, reliability and controllability in the target application of compensating grid or load variations in Non-Isolated Hybrid Storage Systems, with large mismatch in the storage device voltage ratings.

The wide range of performance characteristics of storage technologies motivates the use of a hybrid energy storage system (HESS) that combines the best features of multiple technologies. However, HESS design is complex, in that it involves the choice of storage technologies, the sizing of each storage element, and deciding when to charge and discharge each underlying storage element (operating strategy). We formulate the problem of jointly optimizing the sizing and the operating strategy of an HESS that can be used for a large class of applications and storage technologies. Instead of a single set of storage element sizes, our approach determines the Pareto-optimal frontier of the sizes of the storage elements along with the corresponding optimal operating strategy. Thus, as long as the performance objective of a storage application (such as an off-grid microgrid) can be expressed as a linear combination of the underlying storage sizes, the optimal vector of storage sizes falls somewhere on this frontier. We present two case studies to illustrate our approach, demonstrating that a single storage technology is sometimes inadequate to meet application requirements, unlike an HESS designed using our approach. We also find simple, near-optimal, and practical operating strategies for these case studies, which allows us to gain several new engineering insights. [ABSTRACT FROM PUBLISHER]

Cloud computing applications face the challenges of dealing with a huge volume of data that needs the support of accurate and fast approximate queries to enhance system scalability and improve quality of service. Locality-sensitive hashing (LSH) can support the approximate queries that unfortunately suffer from imbalanced load and space inefficiency among distributed data servers, which severely limits the query accuracy and incurs long query latency between users and cloud servers. In this paper, we propose a novel scheme, called NEST, which offers easy-to-use and cost-effective approximate queries for cloud computing. The novelty of NEST is to leverage cuckoo-driven locality-sensitive hashing to find similar items that are further placed closely through cuckoo-driven method to obtain load-balancing buckets in hash tables. NEST hence carries out flat and manageable addressing in adjacent buckets, and obtains constant-scale query complexity even in the worst case. The benefits of NEST include the increments of space utilization and fast query response. Moreover, due to the salient property of flat addressing in NEST, we implement NEST design in a real hybrid storage system, which consists of DRAM, SSD, and hard disk. The flat addressing allows efficient operations in SSD to improve system performance. We argue that a proper “ division of labor” among DRAM, SSD, and hard disk in the hybrid and heterogeneous storage hierarchy is desperately needed to strike an optimal balance to remove the indexing bottleneck. Theoretical analysis and extensive experiments (on LANL and Microsoft metadata) in a large-scale cloud testbed demonstrate the salient properties of NEST to meet the needs of approximate query service in cloud computing environments. We have offered open-source codes of NEST for public use. [ABSTRACT FROM PUBLISHER]

In recent years, advances in virtualization technology have enabled multiple virtual machines to run on a physical machine, such that each virtual machine can perform independently with its own operating system. The IT industry has adopted virtualization technology because of its ability to improve hardware resource utilization, achieve low-power consumption, support concurrent applications, simplify device management, and reduce maintenance costs. However, because of the hardware limitation of storage devices, the I/O capacity could cause performance bottlenecks. To address the problem, we propose a hybrid storage access framework that exploits solid-state drives (SSDs) to improve the I/O performance in a virtualization environment. [ABSTRACT FROM AUTHOR]

Storing enormous amount of data on hybrid storage systems has become a widely accepted solution for today's production level applications in order to trade off the performance and cost. However, how to improve the performance of large scale storage systems with hybrid components (e.g. solid state disks, hard drives and tapes) and complicated user behaviors is not fully explored. In this paper, we conduct an in-depth case study (we call it FastStor) on designing a high performance hybrid storage system to support one of the world's largest satellite images distribution systems operated by the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) center. We demonstrate how to combine conventional caching policies with innovative current popularity oriented and user-specific prefetching algorithms to improve the performance of the EROS system. We evaluate the effectiveness of our proposed solution using over 5 million real world user download requests provided by EROS. Our experimental results show that using the Least Recently Used (LRU) caching policy alone, we are able to achieve an overall 64 % or 70 % hit ratio on a 100 TB or 200 TB FTP server farm composed of Solid State Disks (SSDs) respectively. The hit ratio can be further improved to 70 % (for 100 TB SSDs) and 76 % (for 200 TB SSDs) if intelligent prefetching algorithms are used together with LRU. [ABSTRACT FROM AUTHOR]

In diesem Beitrag wird ein hierarchischer Ansatz zum optimalen Einsatz von stationären elektrischen Energiespeichern unter besonderer Beachtung des hybriden Speicherkonzeptes vorgestellt. An Hand eines Praxisbeispiels wird die Vorgehensweise beim Entwurf und der Implementierung einer Betriebsführungslösung für hybride Speichersysteme dargestellt und erste Ergebnisse präsentiert. In this paper a hierarchical approach for optimal management of stationary electrical energy storages is introduced with special attention to the hybrid storage concept. In a practical example, the procedure for the design and implementation of a management solution for hybrid storage systems is presented and first results are shown. [ABSTRACT FROM AUTHOR]

Highlights: [•] A battery and ultra-capacitor system for parallel hybrid vehicle is considered. [•] Optimal management using Pontryagin’s minimum principle is developed. [•] Battery stress limitation is taken into account by means of RMS current. [•] Rule based management approaching the optimal control is proposed. [•] Comparison between rule based and optimal management are proposed using Pareto front. [ABSTRACT FROM AUTHOR]

In this work, an in-depth investigation was performed on the properties of the half-bridge current-source (HBCS) bidirectional direct current (DC)-to-DC converter, used to interface two DC-link voltage sources with a high-voltage-rating mismatch. The intended implementation is particularly suitable for the interfacing of a supercapacitor (SC) module and a battery stack in a hybrid storage system (HSS) for automotive applications. It is demonstrated that the use of a synchronous rectification (SR) modulation scheme benefits both the power-stage performance (in terms of efficiency and reliability) and the control-stage performance (in terms of simplicity and versatility). Furthermore, an average model of the converter, valid for every operating condition, is derived and utilized as a tool for the design of the control system. This model includes the effects of parasitic elements (mainly the leakage inductance of the transformer) and of the converter snubbers. A 3 kW prototype of the converter was used for experimental validation of the converter modeling, design, and performance. Finally, a discussion on the control strategy of the converter operation is included. [ABSTRACT FROM AUTHOR]