Quetzalcoatl Hernandez-Escobedo

Helical vertical-axis wind turbines are well suited to small-scale distributed generation because they need no yaw mechanism and can operate effectively in changing wind conditions. However, their aerodynamic design requires comparing configurations without relying solely on computationally expensive simulations. This article describes the design and numerical evaluation of a helical rotor for a vertical-axis wind turbine coupled to a 1.5 kW generator. It combines wind resource analysis, rotor sizing, and a double multiple streamtube (DMST) model, and compares the results with computational fluid dynamics (CFD) simulations. The resulting three-bladed rotor, designated DU-H-18, uses the DU-06-W-200 airfoil and a 63° helix angle. The DMST model predicted a maximum power coefficient of 0.4071 at a tip-speed ratio of 2.5, whereas CFD yielded a maximum of 0.3806 at a tip-speed ratio of 3, with torque and drag coefficients of 0.1269 and 0.0326, respectively. At the common operating condition near λ = 3, the predictions obtained with the selected DMST and CFD numerical settings differed by approximately 3%. However, a three-level temporal-resolution assessment using Δt = 0.005, 0.0025, and 0.00125 s showed that the CFD integral torque remained sensitive to temporal discretization. Therefore, this difference of approximately 3% is interpreted as conditional on the selected numerical settings rather than as demonstrated agreement between time-step-independent solutions. DMST nevertheless captures the overall performance trend and can support preliminary geometric assessment, whereas CFD remains necessary to characterize viscous losses, flow separation, blade–wake interactions, and three-dimensional vortex structures.

Designing trailing-edge flaps for utility-scale wind turbines requires balancing aerodynamic power extraction against blade-root loading. This study formulates the design of a trailing-edge flap on the NREL 5 MW rotor as a Pareto optimization of power coefficient and single-blade flapwise root moment at a prescribed steady operating point. To examine this trade-off, four flap variables: chord ratio, radial extent, radial position, and deflection were first sampled using a Latin-hypercube design and then optimized with NSGA-II. Selected points from the resulting Pareto front were recalculated with a refined NeuralFoil–BEM model that updates Reynolds and Mach numbers iteratively, and three representative designs were reconstructed independently in QBlade using XFOIL polars. A separate three-dimensional CFD calculation was then carried out for the Baseline and selected Win–win configuration. The search yielded 63 unique Pareto designs, ranging from cases that preserve power to solutions providing progressively greater root-moment relief. For the selected Win–win design, the refined model, QBlade, and CFD predict power-coefficient increases of 0.12%, 0.29%, and 0.31%, together with flapwise root-moment reductions of 6.39%, 6.06%, and 4.98%, respectively. A Practical-compromise design achieves approximately 12% root-moment reduction with a power penalty below 2% in the refined BEM and QBlade chains. Across all three aerodynamic models, the selected configuration consistently predicts a lower flapwise root moment while maintaining approximately the same power at the investigated operating point.

This wind farm study provides a detailed and deep investigation into numerous aspects of both wind dynamics and the associated wind turbine performance via a wind data analysis utilizing an extrapolated timeframe of 50 years. The major wind characteristics assessed included wind speed and direction, flow inclination, turbulence intensity, and wind speed (average based on extremes) over the entire duration of the evaluated data set. A majority of study results indicated only narrow wind speed ranges (6.3 m/s to 7.0 m/s) for turbine operation within the wind farm. Higher turbine operation speeds than the average measured wind speed may significantly increase turbine energy output. Turbines were evaluated across numerous geographic locations, resulting in average flow inclination (−4.12° to 1.57°) from the vertical to horizontal directions. The variation in flow inclination indicates that there is a geographic component that likely creates a localized terrain impact on turbine performance. Similarly, the measurement of turbulence intensity was also assessed, which indicated elevated levels of turbine mechanical stress and additional requirements for turbine maintenance. Energy production analyses from each turbine in the wind farm exhibited various regions of energy loss, with the highest energy losses associated with select turbines.

Diffuser-augmented wind turbines (DAWTs) represent a promising alternative for expanding wind energy use worldwide, especially in low-wind environments where conventional small wind turbines perform poorly. Implementing concentrating devices in these systems can significantly increase the power captured. This article aims to experimentally validate a novel high-performance diffuser for DAWTs based on the AF300 blunt trailing-edge airfoil. The diffuser and wind turbine were fabricated using 3D printing and tested in a subsonic wind tunnel at speeds of 3.5–5 m/s. Aerodynamic performance was evaluated by the power coefficient-tip speed ratio and compared to a bare turbine configuration. The results revealed that the AF300-based diffuser significantly improves aerodynamic performance, increasing the peak power coefficient by up to 48.8%. These findings confirm the potential of the proposed diffuser geometry to improve the efficiency of small wind turbines operating at low wind speeds.

This study aims to assess the research trends and progress in the field of district heating, a key technology for improving energy efficiency and environmental sustainability. By analyzing bibliometric indicators such as publication volume, citations, authorship, and keywords, the study provides insights into the growth, regional focus, and thematic evolution of district heating research from 2004 to 2023. The study employs a bibliometric analysis of Scopus-indexed publications on district heating, spanning from 2004 to 2023. Using the Vosviewer software, a cluster analysis was conducted to categorize the research landscape into distinct themes. The results indicate a steady increase in publications on district heating, especially over the last decade, with a significant proportion of research output originating from China and Europe. The cluster analysis identified five primary themes in district heating research: energy sustainability, thermal and geothermal energy, renewable energy integration and district heating networks, buildings, and cogeneration. Furthermore, an analysis of the evolution of research keywords reveals a transition from the focus on renewable energy integration (2014–2016) to a shift towards network optimization techniques (2018) and, more recently (2020), towards digitalization and automation. This evolution is characterised by a focus on digital storage, model predictive control, and demand-side management to enhance system efficiency. The present study provides a comprehensive bibliometric overview and introduces a novel integrative perspective by systematically linking the temporal evolution of scientific production with thematic clustering and policy-relevant implications. It highlights how emerging trends, such as digitalisation, low-temperature networks and sector coupling, are reshaping the future of district heating systems. The findings reveal the growing importance of digital and automated approaches to enhance district heating efficiency and sustainability.

The rapid growth of photovoltaic (PV) technology in recent years called for a comprehensive assessment of the global scientific landscape on fires associated with PV energy installations. This study examines the scientific literature indexed in Scopus from 1983 to 2023. It reveals a striking increase in output since 2011, with nearly one hundred publications in the most recent year under review. This growth of interest has occurred in parallel with the global expansion of photovoltaics. The majority of studies in this field are classified as engineering, with 34% of publications in this area. The USA leads the way with over 160 publications, followed by China with 125. Two institutions in the USA are particularly prominent in this field: Sandia National Laboratories in New Mexico with 22 publications, and the National Renewable Energy Laboratory in Colorado with 16 publications. The second institution is the University of Science and Technology of China, which has published 17 articles on the subject. A close examination of the evolution of keywords reveals a remarkable transformation in the scientific landscape over the past 10 years, from 2013 to 2023. The evolution of keywords suggests a maturation in the understanding of fire risks associated with photovoltaic energy. A total of seven scientific communities have been identified in which these works are grouped according to their keywords. These include Fire and Energy Storage, PV faults, Fire resistance, Fire hazard, Fire detectors, Deep learning, and Fire safety. It has been found that fires caused by PV installations are not listed as a cause of fire starts. This should be taken into account when conducting preventive analyses of this potential danger, particularly in light of the possible development of agrivoltaics, where facilities will be mainly located in the natural environment.

This article assesses the use of solar photovoltaic radiation as a renewable resource for a region of the Isthmus of Tehuantepec in Mexico, where a 163.2 kW grid-connected photovoltaic system is located. The study aims to understand the system’s performance under the specific location conditions and to demonstrate the feasibility of installing photovoltaic systems in the Isthmus region. System monitoring was conducted for one year, with monthly and daily averages of normalized performance parameters determined. A three-month study of the power quality was conducted to assess compliance with interconnection and power quality requirements for power plants with a rated power Pn ≤ 500 kW. Results show higher energy production in the spring–summer months (138.946 MWh) than in autumn–winter (136.500 MWh), while the best overall performance occurred in autumn–winter (PR = 85% vs. 79.5% in spring–summer), probably due to cooler photovoltaic module temperatures. The final yield and PR indicate stable and predictable operation, even without maintenance, with PR = 82.3%. This supports the feasibility of photovoltaic installations in the southwestern region of Mexico. The present work is particularly relevant as it advances understanding of photovoltaic performance in understudied regions with substantial solar potential, such as the Isthmus of Tehuantepec, where policy prioritizes wind resource exploitation over solar energy.

This study presents a novel approach to addressing the challenges associated with wind turbine blade fatigue, focusing on the development of a simplified method for dynamic load measurement and life estimation. Wind turbine blades are subjected to complex and varied loads during their operational life, leading to fatigue-induced damage that can significantly impact the overall performance and longevity of the turbine. The proposed method integrates advanced sensor technologies and data analytics to capture dynamic loads on the blades more effectively. Dynamic load measurement and fatigue estimation for a wind turbine blade are quite challenging tasks, since the real-time wind-induced load is irregular and stochastic, and the associated load history affects blade fatigue life in complex ways. This paper shows the implementation of a simplified method for damage and life estimation of a 1.5 kW wind turbine blade with an aerodynamic stall-limiting system. The findings from this research contribute to advancing the field of wind energy by providing a streamlined and efficient approach to addressing blade fatigue issues, ultimately promoting the sustainable and economic utilization of wind power resources. The proposed method simplifies the processes of dynamic load measurement and fatigue life estimation by employing a resonance-based approach. This reduces energy and cost requirements compared to forced displacement methods, while maintaining accuracy in replicating damage equivalent loads. Additionally, it avoids the complexities of simulating real-world turbulence by using controlled conditions, ensuring reproducibility.