Wind Tower Research Articles

Wake asymmetry of yaw state wind turbines induced by interference with wind towers

Wind turbine wakes are known to cause significant reductions in power generation and increased load on downwind wind turbines. Therefore, controlling wind turbine wakes is crucial, and yaw steering is considered one of the most effective methods of doing so. In this study, wind tunnel experiments using a wind turbine model and Large-eddy simulations (LES) were conducted to gain a better understanding of the wake of a yawed wind turbine. The results showed a clear difference in the horizontal distribution of wake velocity at hub height for positive and negative yaw angles, as well as both lateral and vertical wake deflections. Further investigation revealed that wind towers have a significant effect on the wakes of yawing wind turbines. For positive yaw angles, the velocity deficit is larger above the rotor, resulting in a vertical wake shape caused by the interference between the blade wakes and detached flow from the tower. Conversely, for negative yaw angles, the velocity deficit is larger below the rotor, resulting in a horizontal wake shape. These findings will facilitate the development of more accurate wake models and control methods.

Designing and testing the applicability of a natural green ventilation building block in an Egyptian Climatic zone using waste materials

Natural ventilation is one of the ways used to enhance building spaces' indoor air quality, especially after the COVID-19 pandemic. It also saves energy by utilizing natural wind forces to provide internal building spaces with fresh air instead of energy-consuming mechanical systems. For a multiple-floor building, adding external wall ventilation blocks can improve natural cross ventilation by catching and directing fresh air from the external prevailing wind into its internal spaces. This research aimed to enhance the building's natural ventilation by using environmentally friendly blocks. This was done by designing a green block using marble and granite waste materials as a partial substitute for conventional materials in the block. Styrofoam beads were added to the block’s mixture to reduce its weight. The block’s shape was designed to direct fresh air through building side walls by the use of natural wind pressure. The block was developed from the initial shape of the standard hollow block to a block with a wind catcher. Ventilation block shape simulations were done using (ANSYS fluent) computational fluid dynamics (CFD) software to determine the best inlet angle, catcher angle, and catcher length. The study revealed that by increasing the block inlet angle more than 45°, the block outlet air velocity starts to decrease due to the flow separation in the front part of the block inlet. The catcher angle ranged from 65° to 85°, and the catcher’s ability to redirect the airflow is decreased at a catcher angle greater than 85°. The best nondimensional catcher length-to-block length ratio (height /length) h/L was 0.625. Substitution of 5% of cement by granite in the presence of 0.15 Kg of Styrofoam (C5G) produced a lightweight green ventilation block of weight 19.3 kg. Whereas, the substitution of 15% of sand for marble in the presence of 1 Kg of Styrofoam (S15M) produced a lightweight green ventilation block of weight 15.9 kg. The produced block was tested in a building located in New Cairo City (a region currently having a tremendous increase in the building construction sector) as a study sample representing one of the Egyptian Climatic zones. The research concluded that it is preferred to allocate the building corners towards the prevailing wind direction to prevent airflow separation and to magnify the quantities of air along the building sides.

Analysis of fugitive emission dispersion from urban industrial buildings and optimization using wind catchers

The fugitive emissions from industrial buildings in urban areas have significant impacts on the surrounding environment. Therefore, it is necessary to investigate the key factors affecting the dispersion of these fugitive emissions and to find methods to mitigate their impact on the surrounding environment. This study investigates the dispersion characteristics of fugitive emissions from industrial buildings in relation to atmospheric stability and emission location. Additionally, this study explores the efficacy of wind catchers in mitigating the impact of fugitive emissions on the surrounding environment. The findings reveal that as atmospheric stability increases, the area range of building wake effect expands, and the turbulence intensity of the air flow diminishes, leading to more fugitive emissions entering the building wake area and diffusing near the ground. The wind catchers heighten the flow height of the polluted airflow and amplifies the turbulence intensity, effectively preventing fugitive emissions from entering the building wake area and accelerating the dilution of pollutants dispersed into the atmosphere. Consequently, the installation of wind catchers is highly effective in reducing the downstream impact of fugitive emissions, thereby improving the air quality of the surrounding environment.

On three types of sea breeze in Qingdao of East China: an observational analysis

Our knowledge of sea breeze remains poor in the coastal area of East China, due largely to the high terrain heterogeneity. Five–year (2016–2020) consecutive wind observations from a 10-m wind tower and radar wind profiler are used to characterize the sea–land breeze at Qingdao, a coastal city in East China. The sea surface temperatures at the nearby buoy station in the Yellow Sea are further used to elucidate the land–sea thermal contrast. First of all, three types of sea breeze are determined according to the temporal evolution of wind direction, including pure sea breeze (PSB), corkscrew sea breeze (CSB) and backdoor sea breeze (BSB). Statistically, there are 522 days experiencing sea breezes, of which 61 days belong to pure sea breeze, 40 days witness corkscrew sea breeze, and only 2 days see the backdoor sea breeze. The occurrence of sea breeze is found to peak from April to September and the average wind speed lies at 3–5 m s−1. This suggests a salient seasonality of sea breeze at Qingdao, which is likely caused by the seasonal dependence of land–sea thermal contrast. In terms of the diurnal variability, the sea breezes tend to occur more frequently and have more intensity in the afternoon compared with in the morning, irrespective of sea breeze types. Interestingly, the backdoor sea breeze is merely observed in autumn, whereas corkscrew sea breeze and pure sea breeze can be found year round. Among all types of sea breeze, the pure sea breeze has the highest intensity and most frequency throughout the daytime, same in the seasons of spring, summer and autumn. Further analyses are conduced of the atmospheric circulation, lower troposphere stability and bulk Richard number (Ri) for three types of sea breeze. Both pure sea breeze and corkscrew sea breeze in Qingdao are characterized by prevailing westerlies at 500 hPa. In contrast, the backdoor sea breeze is generally accompanied with easterlies at 850 hPa. Meanwhile, the backdoor sea breeze has the lowest lower troposphere stability, in sharp contrast to the highest lower troposphere stability for the pure sea breeze. This indicates that the backdoor sea breeze (pure sea breeze) tends to occur in an unstable (stable) lower troposphere. The findings obtained here highlight the importance of typing sea breeze.

Influence of natural ventilation design on the dispersion of pathogen-laden droplets in a coach bus

Natural ventilation is an energy-efficient design approach to reduce infection risk (IR), but its optimized design in a coach bus environment is less studied. Based on a COVID-19 outbreak in a bus in Hunan, China, the indoor-outdoor coupled CFD modeling approach is adopted to comprehensively explore how optimized bus natural ventilation (e.g., opening/closing status of front/middle/rear windows (FW/MW/RW)) and ceiling wind catcher (WCH) affect the dispersion of pathogen-laden droplets (tracer gas, 5 μm, 50 μm) and IR. Other key influential factors including bus speed, infector's location, and ambient temperature (Tref) are also considered. Buses have unique natural ventilation airflow patterns: from bus rear to front, and air change rate per hour (ACH) increases linearly with bus speed. When driving at 60 km/h, ACH is only 6.14 h−1 and intake fractions of tracer gas (IFg) and 5 μm droplets (IFd) are up to 3372 ppm and 1394 ppm with ventilation through leakages on skylights and no windows open. When FW and RW are both open, ACH increases by 43.5 times to 267.50 h−1, and IFg and IFd drop rapidly by 1–2 orders of magnitude compared to when no windows are open. Utilizing a wind catcher and opening front windows significantly increases ACH (up to 8.8 times) and reduces IF (5–30 times) compared to only opening front windows. When the infector locates at the bus front with FW open, IFg and IFd of all passengers are <10 ppm. More droplets suspend and further spread in a higher Tref environment. It is recommended to open two pairs of windows or open front windows and utilize the wind catcher to reduce IR in coach buses.

Performance investigation of a solar updraft tower concept with downdraft windcatcher

In this study, a novel solar updraft tower system that combines updraft and downdraft is examined, its functional principle is explained and its performance is presented. A prototype was built at Faculty of Engineering of Trakya University in Edirne Türkiye in 2017. The concept includes counter-rotating dual drag type vertical axis turbines, wind catchers, three prismatic diffuser towers and sloped transpired solar collector. The results showed that the downdraft wind catcher integration increased annual energy production by 8 times compared to a conventional solar updraft tower. In the diffuser-shaped downdraft tower, the incoming wind accelerated up to 2.5 times. The power potential, which is 160 W for the conventional system, becomes 83 kW at a wind speed of 10 m/s and a downdraft pressure coefficient of 1.0.

Numerical-experimental study of mixed convection in a wind tower-room system

Passive strategies are employed in buildings to minimize their total energy consumption and emissions of CO2. The wind tower (windcatcher) is a traditional natural ventilation device capable of reducing building energy consumption and improving the indoor environment. In this work, the performance of the mixed convection in a wind tower-room system is studied, considering natural convection by differential heating in the room and forced convection by the wind entering the tower. A parametric analysis has been carried out considering different values of velocities, temperatures, and relative humidity of the air. Different room wall temperatures were also considered. Ri number studied in this work was in the range of 6.6 × 10−2 and 1.5 × 102. An experimental study was also carried out to validate the numerical results. Comparison numerical-experimental results indicate a mean bias error of 0.49 °C for temperature and a percentage deviation of 24.4% for air velocity. The results showed that the wind tower achieves sensation-neutral comfort inside the room when outside temperatures are between 25 and 30 °C. Regarding Ri numbers lower than 1, the air exchange effectiveness is partially constant, while it can vary by 31% for Ri values greater than 1. The results also indicated that for Ri numbers lower than 1, the heat transfer is 71% greater than for Ri values greater than 1. The findings provided in this paper could contribute to a better understanding of the performance of mixed convection in rooms of buildings with a wind tower.

Simplified calculation model for offshore wind tower founded on monopile member

The objective of the study, concerning the soil-structure interaction of monopile foundations of wind towers consituted by steel tube with hollow cross-sections, was to determine the structural response of wind tower considering the interaction with the foundation. The study was based on elastic and plastic analyses of monopile foundation. The moment-rotation curves of the soil-foundation complex were determined, to be used in verification of the ultimate and operating limit states. The influence of foundation characteristics and type of soil was considered in the calculus of first frequency and critical length. Finally, an experimental validation of the proposed model was made with the data available from the literature in terms of both first frequency and moment rotation response.

Study on Typical Aerodynamic Faults of Variable Pitch Wind Turbine

The variable-speed variable-pitch wind turbine is an important part of China's power and energy systems, and is also the main conversion form of wind energy utilization. Aiming at the problem that the traditional blade element-momentum theory cannot achieve the modeling and simulation of wind turbine plane wind unbalance caused by wind shear and tower shadow effect, the modeling and simulation numerical calculation method of aerodynamic load of wind turbine actuation disk with different blade wind unbalance pitch angles is proposed, This method can derive the analytical expressions for solving the key variables of load calculation, axial induction factor and tangential induction factor, and realize the aerodynamic load solution. At the same time, it is also verified that the characteristic vibration component of 3 times the low speed shaft rotation frequency (3P) is a typical dynamic load feature of tower shadow effect, and is also the most important aerodynamic load fluctuation feature of variable-speed variable-pitch wind turbine, However, under normal conditions, the wind shear effect has little effect on the wind turbine load fluctuation.

A novel reduced column section approach for the seismic protection of wind turbines

The rapid increase in global energy demand over the coming decades must be sustained by a more consistent increment of energy production from renewable sources of which wind energy is currently one of the fast-growing resources. New onshore and offshore wind farms will be rapidly constructed in challenging environments, especially in earthquake-prone areas. As a result, the mitigation of the dynamic vibrations of the wind turbines becomes a fundamental aspect of the seismic design to guarantee their normal operativity and structural safety. Different from past proposals based on traditional passive control devices such as tuned mass dampers or tuned liquid column dampers, this study aims to propose a novel approach, the Reduced Column Section (RCS), to derive an innovative mitigation device which replaces the traditional transition piece of the wind turbine. Analytical formulas to design the proposed RCS will be established. The benefits of the proposed device will be assessed on a real onshore wind turbine located in Italy. Modal properties obtained from the continuous dynamic monitoring of the wind turbine will be used to characterize the numerical finite element model. Therefore, a direct integration analysis with spectrum-compatible real earthquakes and an incremental dynamic analysis will be conducted to evaluate the dynamic mitigation induced by the proposed RCS. Soil-structure interaction effects will be also considered. This study shows that RCS can efficiently mitigate the effective stresses on the wind tower wall by up to 70% compared to the stresses computed on the existing structure.

Simplified method for determining the moment-rotation curve in eco-sustainable wind tower foundations

The objective of the study, concerning the soil-structure interaction of eco-sustainable reinforced concrete foundations of wind towers, was to determine the moment-rotation capacity curve including the soil plasticization or RC structure crisis in flexure and shear. The study was based on elastic and plastic analyzes of shallow and deep foundations. The moment-rotation curve of the soil-foundation complex was determined, useful for the purposes of the ultimate and operating limit state verifications of wind towers. The displacement component induced by the rotation of the foundation on the overhead displacement of the wind tower was calculated. Finally, an experimental validation of the proposed model was made with the data available from the literature.

Experimental and numerical study of wind tower integrated with solar heating unit to meet thermal comfort in buildings during cold and sunny climate conditions

Natural ventilation techniques are increasingly being adopted in recent times due to the need to cut down on greenhouse gases emission and energy cost. A classic natural ventilation technique, the wind tower, may be utilised to minimize the load on typical HVAC systems. One of the major disadvantage limiting the deployment of wind tower is the additional heating load it demands on the HVAC system during the winter months. The work focusses on improving the year-round capability of a wind tower by attaching a solar heating unit (SHU) that would heat the incoming ambient air through a conjugate heat transfer system before being circulated into the space to be ventilated. For performance validation, the numerical technique was utilised initially, then an experimental setup was created based on the numerical results to validate for practical situations. Using the CFD simulation, ventilation performance of this tower system was evaluated in terms of mean age of air (MAA) and air change effectiveness (ACE). The commercial ANSYS Fluent was used to solve the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) turbulence model. The results showed that SHU has been able to heat up the incoming air of 18 °C by 5 °C–23 °C which is generally considered as a comfortable temperature range. According to the analyses of airflow rate at different incident angles through the four quadrants of tower, the maximum flow rate (0.45 m3/s) of air steam was observed at 45° incident angle. The ACE values in the inhabited space were typically near to 1.0, indicating that the ventilation air mixed up well in the ventilated zone. The wind tower performance was experimentaly investigated in terms of solar radiation variations, wind velocity variations, temperature variation in SHU and inside wind tower, and air change rate (ACR) on the experimental setup. Experimental study shows a variation of 2–4 °C in the indoor temperature and thereby ensuring optimal thermal comfort. The recommended wind speed for an effective mass flow rate is in the range of 3 m/s, and an average ACR of 25 per hour indicates that the air is being ventilated properly.

Optimizing indoor thermal comfort with wind towers and earth to air heat exchangers: a sustainable solution for energy-efficient housing

Abstract The conditioning of living and working spaces in the building sector consumes a significant amount of energy. Among the natural ventilation techniques that rely on renewable energy sources such as geothermal and wind, wind towers and earth to air heat exchangers (EAHEs) hold prominence. This research paper presents a series of experiments conducted in the arid region of Bechar, Algeria, to investigate the effectiveness of combined natural ventilation systems employing wind towers and EAHEs. The test chamber, constructed from plywood, and the tower, along with the buried polyvinyl chloride (PVC) pipe EAHE at a depth of 150 cm in sandy-loam soil, constitute a completely natural system with zero energy consumption. Two scenarios were examined: one with closed windows and the other with open windows measuring 40 × 40 cm2. The results indicate a noteworthy improvement in thermal comfort within the chamber, with an increase from 18.75% for the closed window system to 50% when the window is open. By employing a completely natural system without energy consumption, it becomes possible to fulfill 50% of the thermal comfort requirements during both summer and winter seasons. Consequently, this approach reduces at least half of the energy demands in a region that experiences six months of discomfort.

Numerical and experimental investigation of a wind rotor equipped with wind catcher system

Abstract Wind energy is a key driver for the transformation towards a sustainable energy system. From a certain point of view, the main parameter is to increase the turbines' height and the rotor's size to improve the economic aspect and performance. On the other hand, ‘ducted wind turbines’, which can significantly improve the performance of smaller wind turbines, are attracting much attention. The objective is to create system compatible with urban environments and at the same time improve the efficiency of ducted wind turbines. This article studies a configuration, namely a wind turbine equipped with a wind catcher system, by studying it both experimentally and numerically. First, the tests are carried out on the system without inserting the wind rotor. Then the results of the developed model are compared via experimental tests, showing that it is possible to accept wind from all directions and from different heights by using the wind collector system and the cones. The results also show that the maximum wind speed increases by 2.5 times in the middle of the cylindrical part where the turbine is planned to be placed. Finally, the effects of inserting a vertical axis wind turbine inside the cylindrical part of the system on its power coefficient are studied. The results show that the system significantly improves the maximum power coefficient of the turbine.

Monitoring and quantification of non-uniform corrosion induced mass loss of steel piles with distributed optical fiber sensors

Steel piles are used in foundation structures to support offshore wind power system, but they suffer from serious non-uniform corrosion in the marine environment, which can threaten the stability and safety of the overall wind tower infrastructure. Thus, real-time and in-situ monitoring of steel pile corrosion is of great significance to provide timely warning and guidance for maintenance. This study deployed a distributed optical fiber sensor beneath the simulated anti-corrosion wrapping system to monitor non-uniform corrosion of steel pile in the four marine corrosion zones: atmospheric zone, water level fluctuation zone, immersion zone, and sub-mud zone. The sensor was applied to measure corrosion products induced strain variation and analyze non-uniform corrosion influenced by different environmental factors. Two analytical models considering build-ups and run-offs of corrosion products were established to quantify non-uniform corrosion induced mass loss at any location on the surface of steel pile. Functions of volume expansion and reduction coefficients of corroded steel pile were proposed, and sensitivity of mass loss measurement with the distributed optical fiber sensor was investigated. Finally, visualization through color cloud map was applied to illustrate the severity of non-uniform corrosion on the pile surface.

Estimation of probability distribution of long-term fatigue damage on wind turbine tower using residual neural network

Fatigue is one of the most significant failure modes in structural and mechanical design. As for wind engineering, the fatigue issue on wind turbine towers is more critical since it concerns not only the structural safety but also the power production of the wind turbine. On the one hand, due to the complex fluid–solid interaction and the sophisticated control system of the wind turbine, it is impossible to predict the probability of fatigue-induced failure on wind turbine towers by analytical method. On the other hand, the structural reliability methods based on a numerical approach are usually time-consuming. To overcome these drawbacks, this work firstly proposes a probabilistic fatigue analysis framework to estimate the fatigue damage of wind turbine tower based on numerical simulations. Then, to reduce the computational cost of numerical approach, a residual neural network (ResNet)-assisted fatigue estimation approach is designed for the assessment of long-term fatigue loads under the proposed probabilistic fatigue analysis framework. The proposed probabilistic fatigue analysis framework estimates the cumulative fatigue damage on the cross-section of wind towers in a probabilistic pattern. The designed surrogate-assisted approach learns a model to approximate the relationship between wind speed and the fatigue damage. Then, this surrogate model can be used to predict fatigue damage under different wind speed so that a large number of simulation can be replaced by model prediction. Consequently, the efficiency of the proposed probabilistic fatigue analysis method can be significantly improved. Our proposed method is validated by numerical studies with a state-of-the-art wind turbine and has been applied in a wind turbine design with real-world wind loads.

Investigation of wind characteristics of typhoon boundary layer through field experiments and CFD simulations

High-resolution observations of typhoon boundary layer above 100 m are rare as traditional wind towers are generally below 100 m, which limits the study of typhoon boundary layer and engineering applications such as wind-resistant design of tall buildings and wind turbines in typhoon-prone regions. In this study, boundary layer winds of super typhoon Lekima (2019) are observed, simulated and analyzed. Together with traditional wind tower, Doppler wind lidar is utilized for observations of typhoon boundary layer in order to obtain measured data above 100 m. Besides, Computational Fluid Dynamics (CFD) simulation based on Large Eddy Simulation (LES) method is conducted to further investigate the impact of complex terrain on the near-surface wind characteristics. The results show that the power law fits the mean wind speed profile well below 100 m. However, before and after the typhoon lands, a local reverse or low-level jet occurs in the mean wind speed profile at the height of 100–300 m, which cannot be depicted by the power law. Meanwhile, the turbulence intensity increases with height and experiences larger fluctuations. In addition, there is a significant negative correlation between the ground elevation and power exponents of the fitted mean wind speed profiles. This study provides useful information to better understand wind characteristics of the typhoon boundary layer.

Study on the improvement of ventilation performance using a wind catcher

Global warming countermeasures are needed worldwide, and Japan has set a goal of achieving carbon neutrality by 2050. In addition to the use of natural energy sources, energy-saving technologies are being considered to achieve this goal. In this study, computational fluid dynamics (CFD) analysis and field measurements were conducted to determine the increase in the ventilation rate using wind catchers (WCs), which can be employed to increase the ventilation rate without CO2 emissions. The study was conducted in a pair of symmetrical dwelling units, one of which had a pair of WCs on the south wall and the other had a double sliding window on the south wall. Field measurements and CFD analyses were performed for four cases determined using a combination of openings in the subject dwelling unit. The cause was confirmed from the analysis results based on the pressure change at the opening and wind flow, and the difference between the dwelling units with and without a WC was analyzed. We found that installing a WC in a single-sided opening improves the ventilation performance. Furthermore, the WC may prevent the original inflow and outflow depending on the wind direction angle.

Influence of Wind Turbine Structural Parameters on Wind Shear and Tower Shadow Effect

To overcome the problems of natural decreases in power quality, and to eliminate wind speed fluctuation due to wind shear and tower shadow effect arising from wind turbine structural parameters, an improved prediction model accounting for the dual effect of wind shear and tower shadow is, in this paper, built. Compared to the conventional prediction model, the proposed model contains a new constraint condition, which makes the disturbance term caused by the tower shadow effect always negative so that the prediction result is closer to the actual situation. Furthermore, wind turbine structural parameters such as hub height, rotor diameter, the diameter of the tower top, and rotor overhang on wind shear and tower shadow effect are also explored in detail. The results show that the wind shear effect became weaker with the increase in hub height. The hub height is independent of the tower shadow effect. The rotor diameter is positively correlated with the wind shear and tower shadow effect. The tower shadow effect is positively correlated with the diameter of the tower top and negatively correlated with the rotor overhang.

Wind-Solar Hybrid System for Domestic Utility

Wind-Solar Hybrid System is one of the major growing industries that can change the way using of electricity. In this era of emerging technologies, it is safe to say that the idea of Wind Solar Hybrid system technologies and to use the renewable energy sources for various tasks are some of the areas where there is a lot of scope and innovation is going on. Because wind and solar energy complement one another, the system can generate electricity almost all year long. The wind aero generator and tower, solar photovoltaic panels, batteries, wires, charge controller, and inverter are the essential elements of the wind solar hybrid system. The electricity produced by the wind-solar hybrid system can be utilised to run AC appliances as well as charge batteries. This project majorly deals with the consistent power supply, reliable energy provision and backup power. This project can also reduce the usage of energy from the grid, this may cause reducing the production of thermal energy.