Search Results (39,136)

Unmanned Aerial Vehicles (UAVs) have limited flight time, which strongly depends on energy efficiency. This study investigates how control strategies based on fixed and variable roll, pitch, and yaw axes influence UAV energy consumption. Experimental tests were carried out during hovering and circular flights, with measurements of current, battery voltage, and total energy usage. The results show that different control configurations significantly affect power demand, with some dynamic maneuvers reducing energy consumption by up to 7% compared to hovering. These findings demonstrate that optimizing control algorithms and flight strategies can extend UAV endurance, which is particularly important for autonomous missions and applications requiring long operation times. Full article

With the increasing penetration of renewable energy, the frequency regulation burden on thermal power units is growing significantly. Among them, combined cycle gas turbine (CCGT) units are playing an increasingly important role in grid ancillary services due to their high efficiency and low emissions. This paper investigates coordinated control strategies to improve the auxiliary frequency regulation capability of CCGTs, addressing the limitations of traditional control approaches where gas turbines dominate while steam turbines respond passively. A decentralized model predictive control (MPC) strategy based on rate-limited signal decomposition is proposed to improve auxiliary frequency regulation. First, a dynamic model of the F-class CCGT systems oriented towards control is established. Then, predictive controllers are designed separately for the top and bottom cycles, with control accuracy improved through a fuzzy prediction model, Kalman filtering and state augmentation. Furthermore, a multi-scale decomposition method for AGC (Automatic Generation Control) signals is developed, separating the signals into load-following and high-frequency components, which are allocated to the gas and steam turbines respectively for coordinated response. Comparative simulations with a conventional MPC strategy demonstrate that the proposed method significantly improves power tracking speed, stability, and overshoot control, with the IAE (Integral of Absolute Error) index reduced by 83.7%, showing strong potential for practical engineering applications. Full article

The accelerating deterioration of the global environment underscores the urgent need to transition from the conventional fossil fuels to renewable energy, particularly the abundant solar energy. However, large-scale solar power integration could cause the severe grid fluctuations and compromise the operational stability. Existing studies have attempted to address this issue using hydrogen-based energy storage for peak shaving, but most suffer from low system efficiency. To overcome these limitations, this study proposes a novel solar-driven integrated energy system (IES) for hydrogen production and combined heat and power (CHP) generation, in which advanced hydrogen storage technologies are employed to achieve the efficient system operation. The system couples four subsystems: parabolic trough solar collector (PTSC), transcritical CO₂ power cycle (TCPC), Kalina cycle (KC) and proton exchange membrane electrolytic cell (PEMEC). Thermodynamic analysis of the proposed IES was conducted, and the effects of key parameters on system performance were investigated in depth. Simulation results show that under design conditions, the PEMEC produces 0.514 kg/h of hydrogen with an energy efficiency of 54.09% and an exergy efficiency of 51.59%, respectively. When the TCPC evaporator outlet temperature is 430.35 K, the IES achieves maximum energy and exergy efficiencies of 46.52% and 18.62%, respectively, with a hydrogen production rate of 0.51 kg/h. The findings highlight the importance of coordinated parameter optimization to maximize system efficiency and hydrogen productivity, providing theoretical guidance for practical design and operation of solar-based hydrogen integrated energy system. Full article

The growing demand for renewable energy positions biorefineries as key to enhancing biofuel competitiveness. This study proposes a novel MILP superstructure integrating resource seasonality, process selection, and heat integration to optimize biomethanol production in a sugarcane biorefinery. A multi-objective optimization balancing net present value (NPV) and avoided CO₂ emissions reveals that energy integration improves environmental performance with limited economic impact. The model estimates the production of up to 66.85 kg of biomethanol/ton sugarcane from bagasse gasification, 40.7 kg e-methanol/ton sugarcane via CO₂ hydrogenation, and 3.68 kg of biomethane/ton sugarcane from biogas upgrading. Hydrogen production through biomethane reforming and photovoltaic-powered electrolysis increases methanol output without raising emissions. The integrated system achieves energy efficiencies of up to 57.3% and enables the avoidance of up to 493 kg of CO₂/ton sugarcane over the planning horizon. When thermal integration is excluded, efficiency drops by 8% and net energy production per area falls by 11%, due to the need to divert bagasse to cogeneration. Although economic challenges remain, CO₂ remuneration ranging from USD 3.27 to USD 129.79 per ton could ensure project viability. These findings highlight the role of integrated energy systems in enabling sustainable and economically feasible sugarcane biorefineries. Full article

The industrial application of CO₂ methanation in Power-to-X (P2X) systems requires the development of highly active catalysts capable of operating at milder temperatures to ensure energy efficiency, while exhibiting high activity, stability and selectivity. This study reports the synthesis and optimization of Ni-based catalysts on Al₂O₃ supports, guided by a Design of Experiments (DoE, 2⁴ factorial design) approach. Initial optimization afforded a robust catalyst achieving 80% CO₂ conversion and >99% CH₄ selectivity at 325 °C. Remarkably, the incorporation of CeO₂ traces to the Ni-based catalyst substantially boosted catalytic activity, enabling higher conversions at temperatures up to 75 °C lower than the unpromoted catalyst. This improvement is attributed to Ni–CeO_x synergy, which facilitates CO₂ activation and Ni reducibility. Both formulations exhibited exceptional long-term stability over 100 h. Furthermore, process intensification via the Sorption-Enhanced Reaction Process (SERP) with the Ni-based catalyst demonstrated even superior efficiency, rapidly increasing CO₂ conversion beyond 95% with the same selectivity range. Our findings establish a clear and consistent pathway for industrial CO₂ valorization through next-generation P2X technology for high-purity synthetic natural gas (SNG) production. This process offers an efficient and sustainable route toward industrial defossilization by converting captured CO₂ and green H₂ into SNG that is readily usable within the existing energy infrastructure. Full article

Occupant modeling has emerged as a critical component in human-centric building design and operation, offering detailed insights into energy performance, comfort optimization, and behavior-driven control strategies. This study systematically examines occupant modeling (OM) in building design through a review of 312 articles, highlighting critical gaps between theoretical frameworks and real-world applications. Key dimensions of occupant modeling, including methodological classification, data frameworks, application scenarios and model selection strategies, are examined. The interpretability, advantages and disadvantages of 5 modeling methods are demonstrated, and the tools, algorithms and applications are analyzed. In addition, common input, output and application scenarios are sorted out and the data streams are presented. Results have shown that hybrid models represent breakthroughs but require validation beyond idealized scenarios. Meanwhile, with 88.7% of output derived from simulated results, risking self-reinforcing biases despite empirical inputs. Standardized protocols for model validation and hybrid modeling frameworks are urgently needed. To support model selection, a decision-oriented framework is proposed, integrating modeling goals, data characteristics, behavioral complexity, and platform interoperability. Future priorities include merging high explanatory methods with powerful predictive methods, advancing BIM-IoT symbiosis for adaptive digital twin, expanding to interdisciplinary projects, and establishing ethical data governance to align technical advancements with equitable, occupant-centric design. Full article

The investigation of environmentally friendly, Pb-free ceramic dielectric materials with excellent energy storage capability represents a fundamental yet challenging research direction for the development of next-generation high-power capacitors. In this study, linear dielectric Ca_0.7La_0.2(Mg_1/3Nb_2/3)O₃ was added into [0.65BaTiO₃–0.35(Na_0.5Bi_0.5)TiO₃] to form a solid solution. The introduction of Ca_0.7La_0.2(Mg_1/3Nb_2/3)O₃ modified the crystal structure, enhanced insulation performance and breakdown strength, and reduced hysteresis loss. These improvements collectively contributed to higher energy storage density and efficiency (η). The ceramic pellet with the optimal 10 mol% Ca_0.7La_0.2(Mg_1/3Nb_2/3)O₃ demonstrated a higher retrievable energy density (~3.40 J cm⁻³) and efficiency (~81%) at a breakdown strength of 340 kV cm⁻¹ compared to BaTiO₃-based ferroelectric ceramics. The sample also exhibited good stability across a temperature range of 30–90 °C and a frequency range of 0.5–300 Hz. Thus, the as-prepared ceramics sample exhibited significant potential for pulsed power device applications. Full article

With the penetration of renewable power generation (RPG) in the distribution network (DN), power quality issues caused by RPG fluctuations have become more prominent than ever, let alone the integration of new types of power loads like electrified trains and electric vehicles that are major harmonic sources. Traditional power quality enhancement approaches are mostly dedicated to the smoothing of RPG power output or active compensation of harmonics, but fail to incorporate both routines into one single power quality enhancement scheme. Out of this research motivation, this paper aims to propose a synergetic allocation scheme for the hybrid energy storage system (HESS) and the unified power quality conditioner (UPQC) to achieve superior power quality enhancement. Firstly, a novel comprehensive vulnerability index of the DN suited for the power quality issues is presented to reflect the key factors that may impact the bus voltage security. Afterwards, the capacity specifications of HESS and UPQC for power smoothing and load side harmonic compensation are deduced with variational mode decomposition and inverter capacity configurations. Subsequently, the synergetic allocation method of HESS and UPQC are proposed by formulating an optimization problem, with the former obtained capacity specifications acting as the main constraints. After that, a dynamic hourly network reconfiguration approach is proposed to enhance the vulnerability level of the DN by dynamically changing its topology, and ensuring better power quality with the optimally allocated HESS and UPQC. Finally, simulation tests and comparative studies are conducted to evaluate the effectiveness and performance of the proposed scheme by comparing with existing methods. The comparative study has shown that the proposed method can reduce bus voltage deviation by 2.63%; meanwhile, it can reduce the total harmonic distortion by 1.83%. Full article

Power transformers are essential for grid stability and efficient energy transfer, but their reliability declines due to aging insulation systems made of paper and mineral oil. Monitoring techniques such as oil testing, dissolved gas analysis (DGA), and furan compound analysis help assess degradation, with the degree of polymerization (DP) serving as a key indicator of insulation health. This study evaluates five DP estimation methods, namely Chendong, Heisler & Banzer, Vaurchex, Pahlavanpour, and De Pablo, using six statistical metrics consisting of average, standard deviation, determination coefficient (DC), correlation coefficient (CC), t-test, and p-value. The Chendong method proved most robust, achieving DC = 0.677, CC = 0.878, and the lowest standard deviation (0.81), meeting all criteria. Heisler & Banzer followed with DC = 0.529 and CC = 0.878, though its higher deviation (1.04) affected consistency. Vaurchex and Pahlavanpour showed moderate performance (DC = 0.674 and 0.435) but failed to meet t-test and p-value thresholds. De Pablo ranked lowest (DC = 0.071), meeting only one criterion. By quantifying each method’s strengths and limitations, this paper offers a benchmarking framework to improve insulation diagnostics and guide maintenance decisions which ultimately enhance transformer reliability, asset management, and power system efficiency. Full article

To address the worsening energy crisis from rapid fossil fuel consumption, this study synthesized Ce-FeWO₄ composites and hydrophilic carbon nanotubes. XRD and other characterizations showed all intermediates had rough, porous nanosheet morphology; Ce-doping formed disordered porous structure in FeWO₄, increasing its specific surface area. Three-electrode tests confirmed optimal parameters: 0.5% Ce-doping and 12 h growth. Ce-FeWO₄ exhibited a specific capacity of 1875 ± 28 F/g at 1 A/g (based on five parallel samples), and retained 1807 F/g after 3000 cycles (exceeding previous studies) with excellent stability. The Ce-FeWO₄//CNTs asymmetric supercapacitor achieved 152 F/g specific capacity, 81.4 Wh/g energy density, and 768 W/kg power density. The simple, efficient, eco-friendly preparation process and the material’s high capacitance and stability offer broad application prospects in the electrode field. Full article

This study presents an analysis of the temporal complementarity between photovoltaic and wind power generation based on real measurement data obtained in the Lublin Voivodeship (Poland) in 2024. The main objective of the research was to evaluate the degree of time-dependent interaction between two renewable energy sources and to determine the potential for hybrid operation in a regional renewable energy mix. The measurements were conducted under real operating conditions, with a sampling frequency of 15 min for photovoltaic data and 10 min for wind data. After synchronization and resampling to a common 30 min interval, both datasets were compared using the Dynamic Time Warping (DTW) algorithm, which allows for the nonlinear alignment of time series with phase shifts. The results confirmed significant variability in the relationship between the two sources depending on the month. In April, a higher DTW distance (174.281) indicated the predominance of source substitutability, where one source compensated for the low generation of the other. In May, the DTW distance decreased to 138.978, revealing stronger source complementarity, where both PV and wind contributed simultaneously to the total output. The study demonstrates that DTW is a useful analytical tool for identifying temporal complementarity patterns and for quantifying the synergy between renewable sources. The proposed methodology can be applied to optimize hybrid system design and to improve grid balancing in energy systems with a high share of renewables. Full article

Heat exchangers are key components of advanced waste-heat recovery energy systems that operate on low-boiling working fluids. The efficiency and cost of power plants depend directly on their design characteristics. Increasing the heat-transfer surface area, on the one hand, reduces temperature differences and improves cycle efficiency, but on the other hand increases material consumption and equipment cost. For given fluid parameters and heat-exchanger duty, the required surface area is determined by the type of heat exchanger, the choice of device, the shape of the enhanced heating surface, and the methods of heat-transfer intensification. This paper provides a comprehensive analysis of the current state of heat exchangers for low-boiling working fluids and discusses their areas of application. A methodology has been developed for optimizing the main design characteristics of heat exchangers, including a search algorithm aimed at minimizing the total costs of equipment production and operation. Using this methodology, computational studies were carried out for advanced energy cycles with low-boiling working fluids (organic Rankine cycles, recompression supercritical CO₂ (s-CO₂) Brayton cycle). The relationships of weight, size, and cost parameters of heat exchangers for waste-heat recovery cycles using low-boiling fluids to exhaust-gas temperatures and external economic factors were obtained. Optimal channel geometric parameters and heat-exchanger design types were identified that ensure minimal material consumption and cost while delivering the required heat-transfer performance. Recommendations are formulated for selecting and designing heat exchangers for waste-heat recovery power plants using low-boiling working fluids, the implementation of which will improve their efficiency and reduce costs. Full article

The global transition toward sustainable and intelligent farming has positioned Electrified Agricultural Machinery (EAM) as a central focus in modern equipment development. By integrating advanced electrical subsystems, high-efficiency powertrains, and intelligent Energy Management Strategies (EMSs), EAM offers considerable potential to enhance operational efficiency, reduce greenhouse-gas emissions, and improve adaptability across diverse agricultural environments. Nevertheless, widespread deployment remains constrained by harsh operating conditions, complex duty cycles, and limitations in maintenance capacity and economic feasibility. This review provides a comprehensive synthesis of enabling technologies and application trends in EAM. Performance requirements of electrical subsystems are examined with emphasis on advances in power supply, electric drive, and control systems. The technical characteristics and application scenarios of battery, series hybrid, parallel hybrid, and power-split powertrains are compared. Common EMS approaches (rule-based, optimization-based, and learning-based) are evaluated in terms of design complexity, energy efficiency, adaptability, and computational demand. Representative applications across tillage, seeding, crop management, and harvesting are discussed, underscoring the transformative role of electrification in agricultural production. This review identifies the series hybrid electronic powertrain system and rule-based EMSs as the most mature technologies for practical application in EAM. However, challenges remain concerning operational reliability in harsh agricultural environments and the integration of intelligent control systems for adaptive, real-time operations. The review also highlights key technical bottlenecks and emerging development trends, offering insights to guide future research and support the wider adoption of EAM. Full article

As renewable energy sources increasingly penetrate power systems, ensuring operational stability during grid faults poses a significant challenge. Conventional fault-ride-through (FRT) control strategies often lack systematic parameter optimization, resulting in limited support for transient rotor angle stability and inadequate suppression of transient overvoltages. This paper introduces a comprehensive optimization framework to address these shortcomings. We first develop a novel quasi-steady-state model that accurately captures critical states governing transient stability and voltage security. Variational analysis at these states yields gradient information to guide stability enhancement. Leveraging this insight, we propose a gradient-informed optimization approach to tune FRT parameters, simultaneously improving transient rotor angle stability and mitigating overvoltages. The effectiveness of the proposed model and method is demonstrated through simulations on a benchmark renewable-integrated power system. Full article

The rapid growth of renewable energy integration in modern power systems brings new challenges in terms of stability and quality of electricity supply. Hybrid AC/DC microgrids represent a promising solution to integrate photovoltaic panels (PV), wind turbines, fuel cells, and storage units with flexibility and efficiency. However, maintaining adequate power quality (PQ) under variable conditions of generation, load, and grid connection remains a critical issue. This paper presents the modelling, implementation, and validation of a hybrid AC/DC microgrid equipped with a fuzzy-logic-based energy management system (EMS). The study combines PQ assessment, measurement architecture, and supervisory control for technical compliance and economic efficiency. The microgrid integrates a combination of PV array, wind turbine, proton exchange membrane fuel cell (PEMFC), battery storage system, and heterogeneous AC/DC loads, all modelled in MATLAB/Simulink using a physical-network approach. The fuzzy EMS coordinates distributed energy resources by considering power imbalance, battery state of charge (SOC), and dynamic tariffs. Results demonstrate that the proposed controller maintains PQ indices within IEC/IEEE standards while eliminating short-term continuity events. The proposed EMS prevents harmful deep battery cycles, maintaining SOC within 30–90%, and optimises fuel cell activation, reducing hydrogen consumption by 14%. Economically, daily operating costs decrease by 10–15%, grid imports are reduced by 18%, and renewable self-consumption increases by approximately 16%. These findings confirm that fuzzy logic provides an effective, computationally light, and uncertainty-resilient solution for hybrid AC/DC microgrid EMS, balancing technical reliability with economic optimisation. Future work will extend the framework toward predictive algorithms, reactive power management, and hardware-in-the-loop validation for real-world deployment. Full article