Degradation Issues Research Articles

Recent progress of interface modification of layered oxide cathode material for sodium‐ion batteries

AbstractWith the advantages of similar theoretical basis to lithium batteries, relatively low budget and the abundance of sodium resources, sodium ion batteries (SIBs) are recognized as the most competitive alternative to lithium‐ion batteries. Among various types of cathodes for SIBs, advantages of high theoretical capacity, nontoxic and facile synthesis are introduced for layered transition metal oxide cathodes and therefore they have attracted huge attention. Nevertheless, layered oxide cathodes suffer from various degradation issues. Among these issues, interface instability including surface residues, phase transitions, loss of active transition metal and oxygen loss takes up the major part of the degradation of layered oxides. These degradation mechanisms usually lead to irreversible structure collapse and cracking generation, which significantly influence the interface stability and electrochemical performance of layered cathodes. This review briefly introduces the background of researches on layered cathodes for SIBs and their basic structure types. Then the origins and effects on layered cathodes of degradation mechanisms are systematically concluded. Finally, we will summarize various interface modification methods including surface engineering, doping modification and electrolyte composition which are aimed to improve interface stability of layered cathodes, perspectives of future research on layered cathodes are mentioned to provide some theoretical proposals.

Thermo-rheological improvement of magnetorheological foam with the addition of silica nanoparticles

Magnetorheological (MR) foam has become a potential soft robotic gripper-based material that can provide a better grasping force and handling objects due to its ability in varying stiffness in correspond to applied magnetic fields. However, MR foams are facing degradation issue that may reduce the storage modulus when often exposed to thermal exposure from the operating system of a device. Therefore, this study focuses on improving the storage modulus and simultaneously enhancing the thermal properties of MR foam. Hence, silica nanoparticles were introduced as an additive to achieve the improvement target. MR foams were embedded with different concentrations of silica nanoparticles from 0 to 5 wt.%, and the corresponding rheological properties was examined under different temperature conditions from 25 °C to 65 °C. The results revealed that increasing temperatures have reduced the storage modulus of MR foams, however, the embedded silica has countered the drawbacks by strengthening the interfacial interactions between CIP-polyurethane foam matrix. In addition, the morphological characteristics of MR foams also showed less debris or peel-off PU foam with silica nanoparticles. Besides, the silica nanoparticles have delayed the thermal degradation of MR foam for approximately 30 °C.

Maximizing Hybrid Microgrid System Performance: A Comparative Analysis and Optimization using a Gradient Pelican Algorithm

The development of hybrid systems that combine different energy sources has become increasingly important to meet the growing demand for clean and sustainable energy. These systems can offer a reliable and efficient solution to reduce dependence on conventional energy sources and address the issues of climate change and environmental degradation. This study focuses on two types of hybrid systems, namely PV/biomass and PV/diesel, which are commonly used in off-grid areas or places with limited access to electricity. The proposed optimization framework aims to determine the optimal sizing of each component in the system, including PV panels, batteries, and backup sources, to maximize the performance and efficiency of the hybrid system. The Gradient Pelican Optimization Algorithm (GPOA), which is an advanced optimization technique, is proposed to solve the optimization problem. The algorithm is modified to include a local escaping operator, which allows the algorithm to escape local optima and achieve better solutions. The outcomes of the simulation show that the GPOA algorithm outperforms other well-known algorithms in terms of accuracy and computational efficiency. The simulation results also demonstrate that the PV/biomass hybrid system outperforms the PV/diesel hybrid system in terms of cost and environmental impact. The proposed framework and optimization methodology can be useful for designing and optimizing other hybrid systems and can be applied to various applications, including off-grid and remote areas, distributed power systems, and microgrids. The findings of this study can also contribute to the development and promotion of renewable energy and sustainable development.

Efficient Protection of Paper‐Based Cultural Relics via In Situ Synthesis of Carbon Dots/Layered Double Hydroxide

AbstractPaper‐based cultural relics are of great value and have been facing irreversible damage caused by multiple factors, among which acid hydrolysis and ultraviolet photodegradation are the main processes leading to paper deterioration. Paper protection highly relies on a limited range of materials with single functions, and the design of new materials that ensure long‐term safety and efficiency by simultaneously addressing the issues of acidification and UV degradation in paper is highly desired. In this study, the introduction of carbon dots (CDs)‐enhanced layered double hydroxides (LDH) 0D/2D nanohybrids (CDs/Mg‐Al LDH)  is proposed as novel dual‐functional materials for paper protection against UV degradation and acidification. Through a CDs‐assisted in situ growth strategy, CDs/Mg‐Al LDH with ultrathin thickness (≈9.1 nm) and CDs‐intercalated structure are achieved. The CDs/Mg‐Al LDH nanohybrids demonstrate high dispersibility, strong UV absorption, and remarkable photostability, resulting in protected‐paper with decelerated acidification, oxidation, and yellowing degradation processes under both accelerated UV‐aging and dry‐heat conditions. Additionally, the protected‐paper can emit uniform blue light under 365 nm UV excitation allows for easy identification of the distributed CDs/Mg‐Al LDH within the paper, marking a unique and practical feature. This research paces a new direction for the protection of paper‐based relics with emerging carbon dots‐based 0D/2D nanomaterials.

Design of solid-liquid composite lubrication coatings based on thermal sprayed ceramic templet

A solid-liquid composite lubrication coating capable of controlling friction and wear has received widespread attention among researchers. Here, a novel self-lubricating ceramic coating was created through a combination of thermal spraying, hydrothermal reactions, and vacuum impregnation. Its mechanical properties, tribological performance, and self-lubrication mechanism were thoroughly analyzed. The results indicate that the thermally sprayed ceramic coating contained carbon spheres and perfluoropolyether. As a result of the in-situ synthesis of carbon spheres, the coating exhibited enhanced mechanical properties. Compared to the single solid lubricant coating, the solid-liquid composite coating decreased the coefficient of friction by 46.7% to 0.112 and decreased the wear rate from 1.25 × 10−6 mm3/m N to 3.70 × 10−7 mm3/m N. It is proposed in this work that solid-liquid composite coatings can be prepared by utilizing the defects such as pores and microcracks inherent in thermal spray coatings for introducing solid lubricating phases and liquid lubricating phases. This strategy addresses the issue of degradation of the mechanical properties of conventional ceramic-based self-lubricating coatings due to their tribological design.

Area-selective atomic layer deposition (AS-ALD) of low temperature (300 °C) cobalt thin film using octadecyltrichlorosilane (ODTS) self-assembled monolayers (SAMs)

As the semiconductor industry advances, manufacturing technologies encounter challenges in achieving precise alignment and thickness control with smaller and more intricate 3D structures. Addressing this, Area-selective atomic layer deposition (AS-ALD) emerges as a promising “bottom-up” approach, offering an alternative to current nano-patterning techniques. To achieve AS-ALD, self-assembled monolayers (SAMs) are employed as inhibitor agents. In this study, we employed plasma-enhanced atomic layer deposition (PEALD) to promote self-limiting surface reactions and enable low-temperature processing, thereby facilitating the implementation of high purity cobalt (Co) film through AS-ALD using octadecyltrichlorosilane (ODTS) SAM as an inhibitor. The selective deposition is achieved by employing SAMs as an inhibitor, belonging to the deactivation process, a common method for realizing a bottom-up approach. SAMs can form a thin organic film on a solid surface, allowing for surface modifications to become hydrophobic or hydrophilic. Through the selective deposition of Co in the PEALD low-temperature process (300 °C), we successfully addressed the degradation issue of ODTS SAM and verified the successful achievement of a high-purity selectively deposited 13.4 nm Co film. Our findings highlight the potential of selective Co deposition for realizing complex 3D structures and narrow interconnection layers.

The evolution of CSR reporting in the oil and gas industry and its future direction: A conceptual review

Corporate Social Responsibility (CSR) reporting has become increasingly important for industries worldwide, particularly in sectors with significant environmental and social impacts such as the oil and gas industry. This paper presents a conceptual review of the evolution of CSR reporting within the oil and gas sector, examining its historical development, current practices, and future directions. The evolution of CSR reporting in the oil and gas industry can be traced back to growing societal and stakeholder pressures for transparency and accountability. Initially, CSR reporting focused primarily on philanthropic activities and compliance with regulations. However, with mounting concerns over environmental degradation, climate change, and social justice issues, stakeholders demanded more comprehensive reporting practices. In response, oil and gas companies have adopted various frameworks and standards, such as the Global Reporting Initiative (GRI) and the United Nations Sustainable Development Goals (SDGs), to guide their CSR reporting efforts. These frameworks help companies disclose their environmental, social, and governance (ESG) performance in a systematic and comparable manner, enhancing accountability and facilitating stakeholder engagement. Looking ahead, the future direction of CSR reporting in the oil and gas industry is likely to be shaped by emerging trends such as increased emphasis on climate-related disclosures, integration of ESG factors into corporate strategy and decision-making, and the rise of digital technologies for data collection and reporting. Moreover, there is a growing recognition of the need for industry-wide collaboration and standardization to improve the credibility and effectiveness of CSR reporting. This conceptual review highlights the evolving landscape of CSR reporting in the oil and gas industry and underscores the importance of continuous improvement and innovation in meeting the evolving expectations of stakeholders and society.

How natural resources and technological advancements affect environmental quality: Evidence from load capacity factor in N‐11 nations

AbstractThe pressing issues of global climate change and environmental degradation necessitate the development of novel sustainable growth models by humanity. The efficacy of growth policy is strongly contingent upon the fundamental principles of productivity, such as efficient resource management. This study contributes to the investigation of the influence of natural resources (NRs) and several indices measuring productive capacity index (CI) on the environment of developing N‐11 countries (Bangladesh, Egypt, Indonesia, Iran, Mexico, Nigeria, the Philippines, South Korea, Pakistan, Turkey, and Vietnam) during 2000–2022. The research employed the cross‐sectional Autoregressive Distributed Lag (CS‐ARDL) model to examine the relationship between the variables. The empirical evidence indicates that there is a positive relationship between CI, technical innovation (TEC), NR, and gross domestic product (GDP) with the load capacity factor (LCF). Evidently, the sub‐indicators of CI present diverse results. The enhancement of productive CI in human capital, information, and communication technology (ICT), structural change, and governance has been found to foster ecological sustainability. Conversely, the domains of transport, private sector development, and energy utilization have been observed to contribute to the reduction of environmental pollution. This study posits that enhancing operational efficiencies and productive CI is associated with improved ecological outcomes.

Influence of Structural Discontinuity on Slope Stability using Numerical Modelling and Sirovision

The rock mass consists of heterogeneous and anisotropic materials, with smaller and larger blocks of rock, and the presence of structural discontinuities is a significant concern. Characterising the rock mass is crucial for the success of engineering excavations in such areas. A detailed study of joints, their orientation, and discontinuities in the exposed rock mass is crucial as they greatly influence stability and fragmentation. Existing rock mass classifications like Rock Mass Rating (RMR) and Q-classification require various geological parameters and physico-mechanical properties of the rock. However, determining these parameters conventionally can be time-consuming, requiring careful on-site measurements. The number of opencast coal mines is increasing compared to underground mines due to shorter gestation periods, higher productivity, and quicker returns. However, opencast mining raises environmental concerns such as air and water pollution, solid waste management, land degradation, and socio-economic issues. Additionally, many opencast coal mines, regardless of size, are reaching greater depths, making analysing bench slopes and ultimate pit slope design crucial. Slope failure in these mines leads to production loss, additional costs for recovery and handling of failed material, pit dewatering, sometimes mine abandonment or premature closure, and loss of life. A study was conducted at Prakash Khani Opencast Mine – IV, Manuguru area, M/s The Singereni Company Collieries Limited (SCCL), to investigate the influence of structural discontinuities on slope stability. SIROVISION software was used to assess rock mass characterisation, while PLAXIS-2D software was employed to analyse the influence of structural discontinuities on slope stability. A comparative conclusion was drawn based on the results obtained from SIROVISION and PLAXIS-2D analyses. The study revealed that the RMR of the mine ranged from very poor to fair due to numerous discontinuities. It was also found that discontinuities in the slope decrease the Factor of Safety (FOS), indicating an impact on slope stability.

The Role of Leadership to Employees’ Behaviors: A Signaling Theory Perspective

ABSTRACT The issues of climate change and environmental degradation are substantial human concerns that have resulted in numerous consequences. The responsibility lies with human behaviors. Every company must adhere to environmental laws and regulations and emphasize employees’ pro-behaviors towards the environment (EPBTE). The primary aim of this academic investigation is to utilize the signaling theory to find the variables that influence EPBTE. The EPBTE is influenced by two main variables: spiritual leadership (SPL) and organizational support towards the environment (OSTE). The proposed model was evaluated in the banking industry using SEM analysis, employing the snowball sampling technique. The data support the influence of OSTE on EPBTE, and SPL also plays a substantial role in moderating this association. The present study contributes to the existing knowledge in the field of EPBTE research by investigating the significance of OSTE and SPL. Furthermore, the role of OSTE and SPL in the signaling theory perspective also adds knowledge to the existing literature.

Watch Your Head: Assembling Projection Heads to Save the Reliability of Federated Models

Federated learning encounters substantial challenges with heterogeneous data, leading to performance degradation and convergence issues. While considerable progress has been achieved in mitigating such an impact, the reliability aspect of federated models has been largely disregarded. In this study, we conduct extensive experiments to investigate the reliability of both generic and personalized federated models. Our exploration uncovers a significant finding: federated models exhibit unreliability when faced with heterogeneous data, demonstrating poor calibration on in-distribution test data and low uncertainty levels on out-of-distribution data. This unreliability is primarily attributed to the presence of biased projection heads, which introduce miscalibration into the federated models. Inspired by this observation, we propose the "Assembled Projection Heads" (APH) method for enhancing the reliability of federated models. By treating the existing projection head parameters as priors, APH randomly samples multiple initialized parameters of projection heads from the prior and further performs targeted fine-tuning on locally available data under varying learning rates. Such a head ensemble introduces parameter diversity into the deterministic model, eliminating the bias and producing reliable predictions via head averaging. We evaluate the effectiveness of the proposed APH method across three prominent federated benchmarks. Experimental results validate the efficacy of APH in model calibration and uncertainty estimation. Notably, APH can be seamlessly integrated into various federated approaches but only requires less than 30% additional computation cost for 100x inferences within large models.

Comparative Analysis of LiCo0.6Sr0.4O2 Cathode Electrochemical Performance in Oxide- and Proton-Conducting Intermediate-Temperature Solid Fuel Oxide Cells

Solid fuel oxide cells (SOFCs) are made up of three main parts: anode, electrolyte, and cathode. The main challenge in SOFCs is their high operating temperature, which can reach 1000 °C and lead to cell degradation issues. To address this, the utilization of lithium-based materials is suggested for the cathode component, facilitating intermediate-temperature SOFC operation within the temperature range of 500 to 800 °C. Previous studies have demonstrated the potential of producing high-quality lithium-based cathode ink using a triple-roll mill (TRM). By employing the fabrication parameters recommended in these studies, the lithium-based cathode (LCSO) was tested in different working environments, specifically the oxide-conducting SOFC and proton-conducting SOFC. The LCSO inks were screen-printed on SDC for oxide-conducting SOFC and BCZY for proton-conducting SOFC electrolyte before the analysis. Electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) are used to characterize the electrochemical performance and morphology of the LCSO cathode. Based on the results, the LCSO cathode is found to respond well in oxide-conducting SOFC environment with an area-specific resistance (ASR) value of 0.75 ohms-cm2 compared to proton-conducting SOFC which shows an ASR value higher by 11.45 ohms-cm2.

Ionic liquid as a cosurfactant for critical heat flux enhancement during boiling with aqueous surfactant solutions

Surfactants are often used to improve boiling heat transfer due to the ease of their implementation. While aqueous surfactant solution significantly increases the heat transfer coefficient (HTC), it is known to deteriorate the critical heat flux (CHF) relative to the base fluid water. The high foamability of most surfactant solutions causes vapor crowding on the heater surface, making surface modification techniques ineffective for CHF enhancement. Here, we address the issue of relative degradation of CHF due to surfactant by using an ionic liquid as a cosurfactant. We employ a unique boiling fluid, where 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), a low-foaming ionic liquid, is introduced as a co-surfactant in aqueous sodium dodecyl sulfate (SDS) solution. Motivated by the synergistic increase in foamability of the aqueous surfactant solution due to the addition of ionic liquid, we examine the boiling performance at various combinations of concentrations of the two additives in the solution. The mixture consistently exhibits higher CHF and HTC than an SDS only solution, with the best enhancement observed for a mixture of ≈ 30 ppm SDS and ≈ 750 ppm [C2mim][Cl], resulting in ≈1.6× and ≈1.5× enhancements in CHF and HTC, respectively, compared to the SDS only solution (≈ 30 ppm). We next fine-tune the concentration of cosurfactant to demonstrate an exceptionally high HTC of ≈93 kW/(m2 – ℃) with a CHF value comparable to that of pure water. Enhanced foamability and in-situ improvement in the wettability of the heater surface enhance the HTC and the CHF, respectively. This facile technique for enhancing HTC with water as the base fluid, without compromising on CHF, holds promise for high heat flux thermal management applications.

Performance assessment and improvement of district cooling system: A case study of enhancing energy efficiency of hospital buildings

In addressing the performance degradation issue of district cooling systems, although various evaluation methods exist, they either neglect design objectives or focus on independent equipment, overlooking the synergies between devices. Therefore, the study establishes a comprehensive performance assessment framework, encompassing efficiency, environmental impact, economic factors, and technological aspects. The Analytic Hierarchy Process (AHP) and Entropy Weight Method are employed to determine the comprehensive weights for each indicator. In a specific case study, the operational status of an existing district cooling system is assessed, considering collaborative interactions among equipment. A fault tree analysis is applied to scrutinize 13 potential events contributing to system inefficiency and their logical relationships with relevant parameter variations. Based on these findings, specific optimization measures, such as check valve replacement and adjustments to pump and fan frequencies, are recommended. The performance of the optimized system is then re-evaluated, demonstrating substantial improvements with comprehensive performance scores increasing from 18.3 to 27.8 and 29.5, respectively.

Data-driven integrated study on operational performance degradation detection and recovery control of VFDR

The Variable Flow Ducted Rocket (VFDR) serves as the preferred propulsion system for hypersonic aircraft. However, it is prone to health degradation issues due to component failures, aging, and changes in operational conditions, which significantly challenge flight safety. This study introduces a data-driven integrated control approach for modeling, diagnosing, and remedying performance deterioration. Initially, a method for open-set modeling of performance degradation is developed using the Linear Parameter-Varying (LPV) modeling technique and gap metric theory, tackling the hurdles of data collection, overlapping fault classes, and modeling of unidentified faults in the VFDR system; thus, providing vital data support for detecting performance degradation. Moreover, employing the LPV model for performance degradation, a hybrid deep neural network combining multi-scale CNN and LSTM is trained to diagnose system performance issues online using multi-dimensional time-domain sequential data. Subsequently, a smooth transition control method utilizing sliding mode compensation is applied to regain control of system performance based on diagnostic outcomes and a pre-established VFDR performance recuperation controller. Simulations of three types of performance deterioration scenarios caused by changes in actuators, sensors, and the system's operational environment are conducted to demonstrate the efficiency of the proposed approach. The simulation outcomes affirm that the proposed approach is capable of effectively modeling system performance deterioration, diagnosing faults, and controlling recovery, offering promising technical support for the secure operation of intricate closed-loop control systems with stringent precision and reliability requirements.

MXene-mediated Interfacial Growth of 2D-2D Heterostructured Nanomaterials as Cathodes for Zn-based Aqueous Batteries.

In this study, we introduce a novel approach for synthesizing two-dimensional (2D) MXene heterostructures featuring a sandwiched and cross-linked network structure. This method addresses the common issue of activity degradation in 2D nanomaterials caused by inevitable aggregation. By utilizing the distinct surface characteristics of MXene, we successfully induced the growth of various 2D nanomaterials on MXene substrates. This strategy effectively mitigates self-stacking defects and augments the exposure of surface areas. In particular, the obtained 2D-2D MXene@NiCo-layered double hydroxide (MH-NiCo) heterostructures exhibit enhanced structural stability, improved chemical reversibility, and heightened charge transfer efficiency, outperforming pure NiCo LDH. The aqueous MH-Ni4 Co1 //Zn@carbon cloth (MH-Ni4 Co1 //Zn@CC) battery demonstrates exceptional performance with a remarkable specific capacity of 0.61 mAh cm-2 , maintaining 96.6 % capacitance after 2300 cycles. Additionally, it achieves an energy density of 1.047 mWh cm-2 and a power density of 32.899 mW cm-2 . This research not only paves the way for new design paradigms in energy-related nanomaterials but also offers invaluable insights for the application and optimization of 2D-2D heterostructures in advanced electrochemical devices.

MXene‐mediated Interfacial Growth of 2D‐2D Heterostructured Nanomaterials as Cathodes for Zn‐based Aqueous Batteries

AbstractIn this study, we introduce a novel approach for synthesizing two‐dimensional (2D) MXene heterostructures featuring a sandwiched and cross‐linked network structure. This method addresses the common issue of activity degradation in 2D nanomaterials caused by inevitable aggregation. By utilizing the distinct surface characteristics of MXene, we successfully induced the growth of various 2D nanomaterials on MXene substrates. This strategy effectively mitigates self‐stacking defects and augments the exposure of surface areas. In particular, the obtained 2D‐2D MXene@NiCo‐layered double hydroxide (MH−NiCo) heterostructures exhibit enhanced structural stability, improved chemical reversibility, and heightened charge transfer efficiency, outperforming pure NiCo LDH. The aqueous MH−Ni4Co1//Zn@carbon cloth (MH−Ni4Co1//Zn@CC) battery demonstrates exceptional performance with a remarkable specific capacity of 0.61 mAh cm−2, maintaining 96.6 % capacitance after 2300 cycles. Additionally, it achieves an energy density of 1.047 mWh cm−2 and a power density of 32.899 mW cm−2. This research not only paves the way for new design paradigms in energy‐related nanomaterials but also offers invaluable insights for the application and optimization of 2D‐2D heterostructures in advanced electrochemical devices.

DARTS-PT-CORE: Collaborative and Regularized Perturbation-based Architecture Selection for differentiable NAS

DARTS-PT is a well-known differentiable NAS method that measures the operation strength through its contribution to the supernet performance, extracting architecture from the underlying supernet. However, persistent issues of degraded architecture in DARTS-PT have been identified in recent studies. In response, we undertake a comprehensive analysis of this performance degradation issue and identify two primary contributing factors: the unfavorable competition among correlated operations during the operation selection process and the unfair advantage of parameter-free operations within DARTS-PT supernet. Building upon these findings, we propose DARTS-PT-CORE, a novel architecture selection algorithm that incorporates a collaborative operation competition mechanism and a regularization technique in the perturbation-based architecture selection approach. Our method aims to mitigate the negative effects of competition among correlated operations, yielding more reliable operation contribution scores. Furthermore, our regularization technique addresses the unfair advantage of parameter-free operations, facilitating a more balanced architecture selection process. Extensive experiments conducted on various datasets and search spaces indicate that DARTS-PT-CORE outperforms other state of-the-art methods. Specifically, in the DARTS search space, DARTS-PT-CORE achieves 2.43% test error on CIFAR10 and 16.23% test error on CIFAR100, while the search time is less than 0.8 GPU days. When transferring to ImageNet, DARTS-PT-CORE achieves 24.97% top-1 error. Such results underscore the effectiveness of our method in enhancing the reliability and balance of architecture selection in differentiable NAS.

The Potential of Tourism Sustainability through SWOT Analysis: The Case study of Pahang National Park, Malaysia

The tourism industry can have a huge impact on a location and community. Thus, it is very important for an area to know what tourism potential can be created and used as a tourism product. Thus, this study aims to explore the potential attraction of tourism activities in Pahang National Park area. As such, a qualitative study was conducted through focus group discussion and unstructured in-depth interview. The data was transcribed by N-vivo software to get the potential characteristic factors before analyzed by SWOT analysis and generate the mitigation strategies by SWOT matrix. Result shows that, Pahang National Park has great potential in the tourism industry with its natural beauty, ecological diversity, cultural heritage, and tourist adventures. However, to optimize this potential, national parks need to address weaknesses in accessibility, infrastructure, and environmental impacts while taking advantage of opportunities in tourist ecological growth, educational programs, infrastructure development, and cultural experiences. Threats such as environmental degradation, competition, natural disasters, regulatory changes, and health issues need to be faced with appropriate strategies to ensure continuity and long-term success in the Pahang National Park tourism industry. The development of potential and income opportunities based on the environment/natural resources can be a “tool” to improve the standard of living and reduce the poverty rate of the community, especially the rural population.

A Hybrid Energy Storage System Integrated with a Wave Energy Converter: Data-Driven Stochastic Power Management for Output Power Smoothing

Beyond solar and wind energy, wave energy is gaining great interest due to its very high theoretical potential, although its stochastic nature causes intermittent and fluctuating power production. Energy storage system (ESS) integration to wave energy converter (WEC) plants represents a promising solution to mitigate this issue. To overcome the technological limits of the single storage devices, the hybridization of complementary ESSs represents an effective solution, extending the operating range over different timeframes. This paper analyzes the benefits of Li-ion battery–supercapacitor hybrid ESS integration into a grid-connected WEC, aiming at smoothing the produced power oscillations. The hybridization concept involves coupling a power-intensive technology, such as a supercapacitor devoted to managing fluctuations at higher frequency, with a battery technology exploited to manage power variations over longer timeframes to mitigate degradation issues. In this study, a multi-objective data-driven power management strategy, based on the simultaneous perturbation stochastic approximation (SPSA) algorithm, is implemented to minimize power fluctuations in terms of power ramp (representing the power variation between two consecutive values with a 1 s time step), both at the Point of Common Coupling (PCC) and the Li-ion battery terminals, thanks to the supercapacitor peak-shaving function. The SPSA management strategy, together with a suitable sizing procedure, allows a reduction of more than 70% in the power oscillations at the PCC with respect to those at the WEC terminals, while decreasing battery stress by more than 25% if compared to a non-hybrid ESS consisting of a Li-ion battery. This shows how supercapacitor features can extend battery lifespan when integrated in a hybrid ESS.