Search Results (4,930)

With the high-proportion integration of renewable energy, integrated energy systems face greater demands regarding renewable energy utilisation, power balancing, and operational efficiency. By aggregating distributed generation, energy storage and load resources, integrated energy systems can provide effective support for multi-energy coordinated scheduling. This paper proposes a 24 h day-ahead multi-objective optimal scheduling framework for an integrated hydro–wind–photovoltaic–storage energy system based on multi-objective particle swarm optimisation (MOPSO). Firstly, this paper establishes mathematical models for wind power, photovoltaic (PV), hydropower, and energy storage units. Subsequently, it incorporates the outputs of hydropower, wind power, PV, and storage, along with the charging and discharging of energy storage and the process of purchasing electricity from and selling electricity to the main grid, into a unified optimisation model. The objectives are to maximise economic benefit and variable renewable energy utilisation while minimising the peak-to-valley difference in residual load. To address the conflicts between these multiple objectives, a MOPSO algorithm combined with a normalised weighted scoring method is employed to select a compromise optimal solution. Results from case studies based on typical days of the four seasons and various operational strategies demonstrate that the proposed method can rationally allocate the outputs of different energy sources, reduce the system’s dependence on the main grid, and improve variable renewable energy utilisation, thereby providing a reference for the optimal scheduling of integrated energy systems. Full article

With the increasing penetration of wind and photovoltaic generation, microgrids are playing an increasingly important role in promoting renewable energy accommodation, enhancing operational flexibility, and enabling low-carbon energy management. However, the strong uncertainty of renewable generation and load demand, together with the coupling effects of electricity, hydrogen, and carbon markets, poses significant challenges to the optimal planning and operation of microgrid energy storage systems. To address these issues, this paper proposes a bi-level optimal sizing framework for an electric–hydrogen hybrid energy storage system (EHH-ESS) in a microgrid under multi-market coupling. First, typical wind–solar–load scenarios are generated using a Wasserstein generative adversarial network with gradient penalty (WGAN-GP), so as to capture the stochastic characteristics and temporal correlations of renewable generation and load demand. Then, a multi-market coupling index (MCI), integrating electricity price, hydrogen price, and carbon price signals, is constructed to characterize time-varying economic and low-carbon operating incentives and to guide coordinated dispatch decisions. On this basis, a bi-level multi-objective optimization model is established. The upper level determines the optimal capacities of battery storage, electrolyzers, fuel cells, and hydrogen tanks, while the lower level performs hourly coordinated operation of the microgrid under multi-market conditions. The model considers annual equivalent total cost, renewable energy curtailment rate, and carbon emissions as objective functions, and is solved using the NSGA-III algorithm. Compared with the no-storage benchmark, the proposed scheme improves the annual operating economics and renewable-energy accommodation under the studied market conditions. The proposed method significantly reduces annual operating cost and improves renewable energy accommodation. However, under the current carbon price and grid emission factor settings, the optimal economic solution increases carbon emissions relative to the baseline, indicating a trade-off between economic arbitrage and low-carbon operation. Full article

The massive integration of variable renewable energy sources (vRES) in Central Europe is fundamentally transforming electricity price formation and straining transmission grids. However, existing academic metrics, such as the RES Capture Price, offer only a static view of investor revenues and fail to capture dynamic market rigidity and systemic risks during periods of high instantaneous vRES penetration. This study addresses this literature gap by introducing two novel and transparent methodological parameters: Market Exposure to Green Overproduction (MEGO) and the Price Divergence Coefficient (PDC). Formulated as conditional non-parametric indicators, the MEGO index quantifies the conditional probability of price collapse and the loss of market elasticity during hours when vRES penetration exceeds critical thresholds (α = 0.50 to 0.80) of systemic load. Conversely, the PDC index measures the frequency of substantial price non-convergence across neighbouring bidding zones (CZ, PL, FR) relative to the German reference market (DE). Based on an extensive dataset spanning from 2015 to mid-2026—capturing the transition to 15 min market time units— the empirical results reveal a distinct change in market behaviour. While the frequency of price collapse during high-vRES periods was lower in earlier years and temporarily reduced during the 2022 energy crisis, the post-crisis period (2024–2026) exhibits substantially higher MEGO values, with periods in which wind and solar generation exceeded 80% of instantaneous system load being associated with prices at or below 0 EUR/MWh in up to 60% of the evaluated intervals. Concurrently, the PDC analysis reveals persistent spatial price non-convergence, particularly in France and Poland. These patterns coincided with major changes in European electricity-market conditions, including the implementation of Core Flow-Based Market Coupling, variations in nuclear availability and evolving cross-border network conditions; however, the PDC indicator alone does not permit causal attribution to any individual factor. The proposed MEGO and PDC parameters provide policymakers, transmission system operators (TSOs), and investors with an intuitive diagnostic framework for dimensioning grid flexibility, energy storage, and cross-border infrastructure in the decarbonization era. Full article

Static wake steering can increase wind-farm power production, but its application to floating offshore wind farms requires assessment of the coupled wake, platform, structural, and station-keeping response. This study evaluates whether power-maximizing static yaw setpoints identified using the steady, control-oriented FLORIS model retain their benefit when transferred without re-optimization to a coupled FAST.Farm floating wind-farm model. The reference farm comprises four IEA Wind 15 MW turbines mounted on VolturnUS-S semi-submersible platforms. Greedy and static wake-steering operations are compared at three below-rated wind speeds, three sea states, and five matched turbulent-inflow realizations, resulting in 90 farm-level FAST.Farm simulations. Wake behavior is characterized through wake-center deflection, meandering, and velocity-deficit profiles, while turbine and mooring fatigue responses are evaluated using paired damage-equivalent-load statistics. Static wake steering increases mean farm power under all nine investigated wind–wave conditions. The gains are approximately 5.1–$5.2\%$ at $7\mathrm{m}{\mathrm{s}}^{-1}$, $5.0$–$5.1\%$ at $8\mathrm{m}{\mathrm{s}}^{-1}$, and $4.0$–$4.2\%$ at $9\mathrm{m}{\mathrm{s}}^{-1}$, with all paired $95\%$ confidence intervals remaining above zero. The gain results from a power redistribution in which the intentionally yawed upstream turbine incurs a local loss that is exceeded by the combined recovery of the downstream turbines. The fatigue response is strongly component- and turbine-dependent. The paired farm-mean blade-root DEL decreases by $0.82$–$2.24\%$, whereas the tower-base DEL increases by $0.76$–$2.78\%$, and the FairTen1 response generally increases by $0.88$–$2.92\%$. The farm-mean yaw-bearing response is mixed, ranging from a $1.15\%$ reduction to a $4.32\%$ increase. Turbine-level analysis reveals larger localized penalties, reaching approximately $10.4\%$ for the yaw-bearing DEL and $12.8\%$ for FairTen1. Spectral analysis associates the yaw-bearing response with yaw-induced aerodynamic and structural excitation, while the tower-base response is strongly influenced by low-frequency wave–platform dynamics. A complementary FLORIS sensitivity analysis demonstrates that the optimized aerodynamic benefit depends strongly on wind direction, spacing, wind speed, and turbulence intensity. For a Tampen-derived 11-turbine layout, resource weighting over the modeled 4–$13\mathrm{m}{\mathrm{s}}^{-1}$ interval produces an annual energy-contribution increase of $3.653\mathrm{GWh}{\mathrm{year}}^{-1}$, or $0.921\%$. These results provide numerical evidence that static wake steering can retain a positive power benefit in a coupled floating wind-farm environment, but controller assessment must include turbine- and component-specific dynamic loads rather than farm power alone. Full article

Modern power systems are increasingly exposed to uncertainties and face rising demands for operational resilience. To address this challenge, this paper investigates the optimal placement of thyristor-controlled series compensation (TCSC) devices within flexible AC transmission systems (FACTS). A comprehensive vulnerability evaluation index is developed by integrating network structure, load impact, and branch disconnection factors, enabling a holistic identification of vulnerable transmission links. Subsequently, a multi-objective TCSC optimization model is formulated to simultaneously minimize the system-wide comprehensive vulnerability index and the total investment cost. To solve this model, an improved multi-objective particle swarm optimization (MOPSO) algorithm is devised, incorporating chaotic initialization and adaptive inertia weight adjustment to enhance both global exploration and local exploitation capabilities. The proposed method is validated using the IEEE 39-bus and IEEE 118-bus test systems. The results demonstrate that the optimized placement significantly reduces system vulnerability, maintains a favorable economic balance and improves the system security margin. Furthermore, uncertainty tests involving load variations, line parameter perturbations, and wind power fluctuations, as well as malicious attacks, confirm the robustness of the proposed placement strategy. This work provides a practical and effective framework for resilience-oriented TCSC planning, contributing to mitigating cascading failure risks and enhancing power system security. Full article

Dust storms are a major environmental hazard across the Arabian Peninsula, affecting air quality, human health, transportation, and infrastructure. Despite their frequency in Riyadh, event-based studies integrating aerosol optical observations, atmospheric transport analyses, potential source-region identification, and surface validation remain limited. This study characterized dust events over Riyadh during 2024–2025 using AERONET aerosol observations, NOAA Integrated Surface Database (ISD) meteorological records, HYSPLIT backward trajectories, and potential source contribution function and concentration-weighted trajectory analyses. Dust events were identified using a dual optical criterion based on aerosol optical depth (AOD) at 500 nm (AOD₅₀₀ ≥ 0.50) and the 440–870 nm Ångström exponent (≤0.50) and were compared with co-located NOAA ISD present-weather and visibility observations. Among the 34 identified dust events, 82% occurred between March and May. The events were dominated by coarse-mode aerosols, with a mean Ångström exponent of 0.28 and a mean fine-mode fraction of 0.26. Same-day dust-related present-weather reports were recorded for 26 events (76%), while the remaining eight events (24%) were classified as elevated because no dust-related present-weather code was reported at the co-located ISD station during the corresponding event day. The trajectory and source–receptor analyses showed a consistent spatial association with the Mesopotamian Basin as a major potential source region and the northern Rub’ al-Khali as a secondary potential source region. Surface wind speed was significantly and positively associated with coarse-mode aerosol loading and dust-event severity, whereas sea-level pressure showed no statistically significant association with severity. These findings provide an updated observational characterization of dust events affecting Riyadh during 2024–2025 and demonstrate the complementary value of aerosol optical observations, co-located surface records, atmospheric transport analysis, and source–receptor methods for examining dust-event characteristics and transport over central Saudi Arabia. Full article

This paper proposes and analyzes a modified version of the Hănțilă Method (HM) for solving electrical circuits with nonlinear inductive elements. The method replaces the nonlinear inductor with a generator comprising a nonlinear source and a linear impedance. The value of the nonlinear source is determined by defining a Picard–Banach fixed-point sequence that converges to the solution. This approach transfers the nonlinearity from the inductance to the generator’s source. The resulting circuit consists of linear and nonlinear sources and only linear components. It is solved in the harmonic domain using classical theorems and algorithms. A comparative analysis is performed on an RL circuit (a transformer primary winding at no-load). Both accuracy and computational effort are evaluated. The proposed iterative method is compared against steady-state time-domain transient analysis and frequency-domain approaches (Harmonic Balance Method) implemented in commercial software. This method is particularly suitable for analyzing circuits with nonlinear inductive components, such as iron-core coils and equivalent circuits for electrical machines. Full article

This study evaluates a disturbance-informed, planning-level workflow for assessing steady-state feeder performance and post-disturbance frequency security in renewable-rich distribution networks. The workflow links feeder operation in DIgSILENT PowerFactory to reduced-order frequency-security screening in OpenModelica and PSAT, with Pandapower used as an independent steady-state cross-check. The IEEE 33-bus feeder includes distributed photovoltaic units, DFIG-based wind generation, and a grid-forming battery energy storage system (BESS). Hourly feeder time-series results are used to identify renewable-output deficits, and each deficit is converted from MW to the common 10 MVA dynamic-system base before being applied as a conservative step disturbance. The steady-state validation gives a maximum voltage mismatch of 0.0155 pu, within the adopted 2% screening limit. The cross-tool frequency benchmark shows close agreement for nadir and settling time, while RoCoF is interpreted conservatively because of its sensitivity to numerical differentiation and event implementation. As renewable penetration increases from 0% to 100%, the minimum bus voltage remains close to 1.0 pu (0.9999–0.9991 pu), the maximum bus voltage rises from 1.0295 pu to 1.0826 pu, and feeder losses increase from 0.0246 MW to 0.1531 MW. The 24 h assessment gives a maximum daily voltage of 1.0755 pu at 100% penetration, while loading remains below thermal limits. For the corrected 75% severe event (0.3048 MW; −0.0305 pu on the 10 MVA base), the 2 MW droop-plus-FFR case improves the nadir from 49.9695 Hz without support to 49.9924 Hz. Voltage therefore becomes the earliest binding screening constraint from 50% penetration onward, whereas thermal loading and supported frequency nadir remain non-binding under the studied conditions. Full article

Conventional flux-reversal permanent magnet motors have problems such as excessive torque ripple and rich harmonic content in direct drive applications such as oil exploration, which restrict their application in high-precision scenarios. To address this issue, this paper presents a hybrid excitation topology that integrates double-armature windings, stator Halbach hybrid permanent magnet arrays, rotor-staggered unequal-tooth and rotor-hybrid permanent magnets. Two-dimensional finite element analysis was conducted using ANSYS Maxwell 2023 R1 to evaluate electromagnetic performance under rated steady-state conditions, rated power 300 kW, rated speed 83 rpm, rated voltage 660 V, rated phase current 307 A, and axial core length 200 mm. The simulation results show that the proposed topology has an average output torque of 34.5 kN·m at rated conditions compared with the traditional flux-to-reverse permanent magnet motor of the same size, and the torque ripple rate is reduced from 27.5% to 17.4%, a relative reduction of 36.8%. The results are based only on numerical simulation and have not been verified by physical prototype experiments. Dynamic control strategies, multi-load transient responses and experimental verification will be carried out in subsequent work. Full article

Thermosetting epoxy resins commonly used in wind turbine blades pose significant recycling challenges. This study addresses this limitation by using an eco-friendly, recyclable liquid polymethyl methacrylate (PMMA) resin to fabricate thermoplastic sandwich panels and by investigating their in-plane compressive buckling behavior. The experimental results demonstrated that the proposed PMMA thermoplastic sandwich panels exhibited improved in-plane compressive performance, with a 5.22% higher ultimate load than traditional epoxy counterparts. Furthermore, to investigate the effect of groove configuration on the buckling stability of composite sandwich panels, a finite element (FE) model for PMMA sandwich panels with initial geometric imperfections was established in this paper, and the reliability of the FE model was validated via compression and buckling tests. Finally, a Kriging surrogate model coupled with the NSGA-II algorithm was adopted to carry out multi-objective optimization, with groove parameters set as design variables. Based on the FE verification results, the optimized configuration (Point A) reduced the structural mass by 2.24%, while increasing the critical buckling load and shear modulus by 5.71% and 10.27%, respectively. Research on the buckling performance and groove configurations of PMMA sandwich panels, which can be applied to wind turbine blade webs and airfoils, can provide crucial data support for the engineering application of sustainable PMMA-based large-scale wind turbine blades. Full article

Dynamic energy tariffs increasingly mirror renewable generation and market conditions, yet most techno-economic assessments of residential retrofit and flexibility measures still rely on simplified, static tariffs, risking-biassed cost estimates. This study systematically maps energy tariff structures across three classification tables, showing that dynamic and weather-responsive tariffs are underrepresented in ex-ante building energy modelling. Building on this gap, four ex-ante tariff-modelling methods are developed and validated, namely a fixed tariff, a time-of-use (ToU) tariff, a weather-dependent real-time-pricing (RTP) mechanism grounded in a residual-load proxy, and a capacity-based network tariff, illustrated for the Flemish context. The RTP mechanism is calibrated against two years of Belgian day-ahead prices (ENTSO-E) and Elia demand, as well as PV- and wind-generation data, reaching a monthly correlation of ρ = 0.78 (hourly ρ = 0.43, excluding 2022) and ρ = 0.71 for the final quantile-mapped tariffs, using only weather data (.epw) and three calibratable parameters. An illustrative building-level application shows that, for an identical unoptimised demand profile, a weather-driven RTP tariff changes the projected annual electricity cost by roughly 33–44%, against only 1–3% for a static ToU tariff, confirming that tariff structure must be an explicit ex-ante modelling choice. Full article

Lake Sofia, located in the mountains of northern Madagascar (1100 m a.s.l.), has experienced increased sediment loads over the past century, which have adversely affected its biodiversity and reduced its lifespan. Lake Sofia provides critical ecosystem services and is an important habitat for threatened species, e.g., the critically endangered Madagascar Pochard (Aythya innotata). Suggested causes of the high sediment load in Lake Sofia are water erosion, wind erosion, and the stirring of mud from the bottom of the lake by recently introduced tilapia (Oreochromis spp.). Using publicly available weather reanalysis, satellite data, land cover data, soil data, and elevation data, we attribute high turbidity levels in Lake Sofia to water erosion, which explains over 90% of the variance in lake turbidity. Wind erosion was not significant, and tilapia did not contribute to sediment influx. Increased precipitation and decreased vegetation cover in agricultural areas contributed most to increased erosion risk, whereas lavaka (erosion gullies) contributed less. Erosion risk over crop lands has increased by 2% annually and is expected to increase further because of climate change and expected increased precipitation intensity. The erosion model identifies areas most at risk to be targeted for interventions, and is applicable to other catchments in Madagascar and elsewhere. Full article

Recently, microgrid (MG) structures include a mix of renewable energy sources (RES) and conventional sources. At high levels of RES penetration, reduced inertia and frequency stability have been confirmed in several studies. Properly designed and structured load frequency control (LFC) and virtual inertia control (VIC) are feasible solutions to these problems. In this paper, a new hybridized two-degree-of-freedom (2DOF) non-integer controller is proposed for multi-generation, multi-area MGs’ frequency regulation. The proposed new LFC is based on a 2DOF tilt-integral/tilt-derivative-double-derivative controller with a filter (TI-TD²F²). Meanwhile, the proposed design process considers coordinating capacitive energy storage (CES) to help regulate frequency deviation, as well as the high penetration of RESs (wind and PV). The incorporation of CES participation in frequency regulation helps provide fast VIC for the studied multi-MG system. Furthermore, an Enhanced Escape Algorithm (EESC) optimization algorithm is proposed to simultaneously optimize the control parameter set of the two-area MG system. The proposed EESC optimization algorithm identifies appropriate parameters for controller design, yielding better overall dynamic performance. An enhanced Escape Algorithm (EESC) is based on boosting the searching mechanism of the conventional Escape Algorithm by the integration of three modifications, including the Chaos map logistic mutation mechanism, the Fitness distance balance mechanism, and the Sorted Quasi-oppositional based learning (SQOBL). The proposed 2DOF TI-TD²F² controller demonstrates improved frequency stability and sustainable operation under load changes, variation in RESs, and other uncertainties of system parameters. The obtained results showed that the proposed EESC optimization algorithm adjusts the parameters of the TI-TD²F² controller, which significantly improves the dynamic performance in load frequency and tie-line power control. Compared to traditional TID and FOPID controllers, TI-TD²F² achieves up to a 70–80% reduction in tie-line power deviation and up to 60% faster settling time in many scenarios, demonstrating better robustness, faster response, and better overall system stability. Full article

To address the challenges of adsorption instability and obstacle-crossing difficulties faced by wall-climbing robots in the harsh operation and maintenance (O&M) environment of offshore wind turbine (OWT) towers, this paper presents the design of a magnetic-adhesive wall-climbing robot with a planetary-gear configuration and investigates its wind resistance stability. First, the magnetic circuit layout is optimized through finite element analysis, revealing that the F-16 continuous planetary configuration (16 poles) effectively suppresses magnetic flux leakage and forms an integrated magnetic pad, maintaining adsorption force at a large air gap of 20 mm, thereby enhancing magnetic robustness during obstacle crossing and making it the optimal choice for high-load offshore conditions. Second, an unsteady flow field model based on the Kaimal turbulence spectrum is constructed to analyze aerodynamic loads. Fluid–structure interaction (FSI) simulations demonstrate that at a height of 30 m, the turbulence integral scale matches the robot dimensions, and combined with the Venturi effect of gap jet flow, this leads to peak turbulence intensity and pitching moment, creating a hazardous, pronounced aerodynamic amplification condition. Finally, an anti-slip stability model is established, revealing that vertical wall climbing represents the critical loading scenario; the magnetic adhesion system must deliver a total adsorption force of no less than 1000 N to resist a 35 m/s wind speed under low-friction conditions, providing a quantitative design basis for anti-wind safety. This study integrates magnetic circuit optimization, turbulence-resolved aerodynamics, and macroscopic anti-slip mechanics, offering theoretical support and engineering guidance for the safe deployment of intelligent O&M equipment for offshore wind power. Bench-scale measurements of magnetic adhesion force, friction coefficient, and translation force fluctuation support the exponential-decay magnetic model and the multi-wheel phase-interleaving concept; however, the current 4 × 16-pole prototype delivers ~627 N at the 2 mm working gap, below the 1000 N design target. The design methodology is therefore validated, while the current physical configuration requires further iteration of the working gap or magnet grade before it can be considered operationally adequate. Full article

Non-uniform discharge temperature during sinter cooling is a practical issue in ironmaking, as local overheating may increase the thermal load on downstream conveying equipment. To mitigate insufficient cooling in the upper sinter bed under the conventional bottom-blowing mode, this study developed a three-dimensional transient CFD model for an industrial continuous annular cooler and optimized the air-supply strategy in Zones IV and V. Under the conventional condition, ambient air is supplied independently to Zones IV and V from the bottom wind boxes. In the novel air-supply strategy, while keeping the total fresh cooling-air flow rate in the final cooling region unchanged, ambient air is introduced from the upper side of Zone V and discharged from its bottom; the outlet gas from Zone V is then supplied to the bottom of Zone IV, forming a serial air-supply path. The results show that the novel arrangement improves the spatial matching between the cooling gas and the sinter bed during final cooling and suppresses the local high-temperature region near the discharge end. The maximum discharge temperature decreases from 459 K to 410 K, below the process limit of 423 K, while the average discharge temperature decreases from 377 K to 364 K. Based on the enthalpy-flow difference calculation, the predicted recoverable waste heat also increases under the novel condition. These findings suggest that redesigning the gas-flow route in the final cooling region can effectively enhance the uniformity of the discharge temperature in industrial annular coolers. Full article