Reducing aerodynamic noise from rotating fans while preserving their aerodynamic performance remains a major challenge in the design of low-noise flow-control and ventilation systems. Motivated by this challenge, the present study performs a comprehensive numerical investigation of the coupled aerodynamic and aeroacoustic behavior of a rotating fan equipped with straight and serrated trailing-edge blades under both quiescent and inflow operating conditions. The effects of rotational speed, external inflow, and blade trailing-edge geometry on flow structure, pressure distribution, and acoustic response are systematically examined. Simulations are conducted for two rotational speeds and two inlet conditions to isolate rotation-induced mechanisms from inflow-dominated effects governing noise generation and propagation. Aerodynamic results show that under quiescent inflow, the flow field is primarily driven by fan rotation, leading to localized acceleration, non-uniform outlet mass flow, and a strong dependence on rotational speed. The presence of external inflow leads to a more uniform flow field and increased mass flow rates, while reducing the sensitivity to trailing-edge geometry. Moreover, rotational speed emerges as the dominant factor governing both aerodynamic and acoustic responses. Trailing-edge serrations mainly affect low-frequency acoustic behavior at low rotational speeds under quiescent conditions, whereas their influence diminishes at higher speeds and in the presence of inflow. External inflow also raises baseline acoustic levels and modifies the spatial distribution of the acoustic field. Overall, the results highlight the regime-dependent effectiveness of trailing-edge serrations and underscore the importance of accounting for realistic inflow environments in the aerodynamic and aeroacoustic design of low-noise rotating machinery.
This study provides a quantitative assessment of the technical and economic implications of converting the entire Italian vehicle fleet to full electric power. Investment estimates for night-time-only charging indicate a total requirement of approximately \$208.0 billion, including \$194.4 billion for generation capacity and \$13.6 billion for network reinforcement. For daytime-only fast charging at 280,000 MW, the total investment rises to approximately \$627.9 billion, with \$604.8 billion allocated to generation and \$23.1 billion to network upgrades. The combined total for both scenarios reaches approximately \$835.9 billion, underscoring the dominant role of generation in the overall expenditure. The analysis highlights that even under conservative assumptions, the expansion of installed power capacity and the doubling of supply points required for nighttime charging, along with peak power requirements up to five times current grid capabilities for daytime charging, exceed realistic infrastructure limits. The economic burden of such investments would largely fall on taxpayers and may be incompatible with the national economy. The study further suggests that the accelerated adoption of fully electric vehicles, without considering broader grid constraints and operational limits, may produce secondary effects more severe than the intended environmental benefits. A diversified strategy, incorporating hybrid systems, synthetic fuels, hydrogen, or improved internal combustion technologies, is recommended to mitigate infrastructure pressure and reduce economic risks. The work is presented as a conservative initial assessment, intended to stimulate further research on energy, infrastructure, and economic impacts to support technically feasible and economically sustainable transition strategies for the national automotive system.
The idea of freshwater production has long attracted attention due to the significant depletion of natural freshwater resources caused by human activities. At the same time, the demand for electricity continues to increase with technological advancement. The use of fossil fuels, in addition to their limited and non‑renewable nature, leads to the emission of greenhouse gases and environmental pollution. Solar desalination systems are one of the methods used for freshwater production, while photovoltaic (PV) panels are a common approach for electricity generation. In this study, two passive stepped solar stills are experimentally compared. In one system, a dark-colored plate is installed beneath the basin steps to enhance the absorption of solar energy. In the other system, PV panels that are in direct contact with the water are installed beneath the basin. This configuration enables the PV panel to operate at a lower temperature, thereby improving its efficiency. In addition, the heat generated by the PV panels accelerates the evaporation process and enhances the overall system performance. The water level in the basins was kept constant to prevent the formation of dry spots on their bottoms. Based on the results of experiments conducted on several different days during the cold season, the effects of solar radiation intensity, ambient temperature, wind speed, and inlet water temperature on the performance of the constructed systems were investigated. An increase in ambient temperature raises both the inlet and outlet water temperatures, which directly contributes to a higher evaporation rate. Ambient temperature has an inverse effect on the performance of the PV panel, while it has a direct effect on the output voltage. The results indicate that using a PV panel beneath the desalination chamber, in some hours of the experiments, increased freshwater production and energy efficiency by more than three times.
Controlled-environment agriculture has emerged as a promising approach for improving food security and climate resilience in semi-arid regions. Among recent innovations, Cadmium Telluride (CdTe) photovoltaic-integrated greenhouses offer the dual benefit of renewable energy generation and sufficient photosynthetically active radiation for crop growth. However, the thermal and microclimatic performance of ventilation systems in such greenhouses remains insufficiently investigated, particularly under sub-Saharan African conditions. In this study, a gable-roof CdTe photovoltaic-integrated greenhouse structure (3.6 m × 2.25 m × 2.0 m) was numerically analyzed using a validated three-dimensional Computational Fluid Dynamics (CFD) model developed in SolidWorks Flow Simulation. Three ventilation strategies—natural, mechanical, and hybrid ventilation—were evaluated for their effects on thermal regulation and airflow distribution. Natural ventilation employed top and side vents equivalent to 10% of the floor area, while mechanical ventilation used four 13 W fans providing 40 air changes per hour (ACH). The hybrid system combined natural and mechanical ventilation. A Design of Experiments (DoE) framework was further applied to evaluate interactions among airflow, temperature, humidity, and energy demand. Experimental validation using a full-scale prototype at Busitema University showed strong agreement between simulated and measured temperatures, with a Coefficient of Determination (R2) of 0.92, a Root Mean Square Error of 1.18 °C, and a Normalized Mean Bias Error of +1.3%. The hybrid ventilation system achieved the best performance, maintaining greenhouse temperatures within the optimal range of 21–27 °C. Furthermore, the greenhouse energy and water requirements were estimated, indicating that stable tomato production could be sustained using a heating capacity of 0.5 kW and a daily irrigation demand of 44 L for 24 tomato plants operated under six precision pulse-irrigation cycles per day. These findings demonstrate that CdTe photovoltaic-integrated greenhouses can effectively balance energy efficiency and crop productivity, thereby providing a scalable and sustainable framework for protected agriculture in developing countries and semi-arid environments.
Cold thermal energy storage systems are widely employed in refrigeration, food preservation, and thermal management applications; however, their performance is often constrained by the inherently low thermal conductivity of phase change materials (PCMs), which limits the rate of solidification. Improving heat transfer during the freezing process therefore remains a central issue in the design of efficient storage systems. The present work examines the solidification behavior within a cold energy storage unit featuring a non-conventional container geometry with an elliptical cooling wall. Two enhancement strategies are considered in combination: the dispersion of a ternary nanoparticle mixture (TiO2–Ag–Al2O3) in the base fluid at a volume fraction of 0.015%, and the incorporation of a metal foam structure to promote conductive heat transfer. A transient numerical model is established using a Galerkin-based finite element approach with adaptive mesh refinement to accurately capture the evolution of the solid–liquid interface. The results indicate that the addition of ternary nanoparticles leads to a reduction in total freezing time of approximately 13.12%, while the introduction of metal foam yields a substantially greater reduction of 82.35%. When both techniques are applied simultaneously, the freezing time decreases by 84.66%, demonstrating a clear synergistic effect. A comparative analysis further shows that the influence of foam porosity on the advancement of the solidification front is approximately 6.27 times greater than that of nanoparticle concentration. These findings suggest that structural enhancement through porous media plays a dominant role in accelerating heat transfer, and that prioritizing internal thermal pathways offers a more effective design strategy than relying solely on modifications of fluid properties. The results provide a quantitative basis for the development of high-efficiency cold energy storage systems in engineering applications.
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