Horizontal Axis Wind Turbine Efficiency Optimization Through Tip Radius Modification on 4:5 Flat Taper Blades

Today’s wind turbines are designed in a wide range of vertical and horizontal axis types. In this study, several wind turbines are designed for low wind speed areas around the world mainly for domestic energy consumption. The wind speed range of 4–12 mph is considered, which is selected based on the average wind speeds in the Atlanta, GA and surrounding areas. These areas have relatively low average wind speeds compared to various other parts of the United States. Wind energy has been identified as an important source of renewable energy. Traditionally wind energy utilization is limited to areas with higher wind speeds. In reality a lot of areas in the world including Atlanta, GA., have low average wind speeds and demand high energy consumption. In most cases, wind turbines are installed in remote offshore or away from habitat locations, causing heavy investment in installation and maintenance, and loss of energy transfer over long distances. Therefore, the main focus of this study is to extract wind energy domestically at low wind speeds. A few more advantages of small scale wind turbines include reduced visibility, less noise and reduced detrimental environmental effects such as killing of birds, when compared to traditional large turbines. With the latest development in wind turbine technology it is now possible to employ small scale wind turbines that have much smaller foot print and can generate enough energy for small businesses or residential applications. The low speed wind turbines are typically located near residential areas, and are much smaller in sizes compared to the large out of habitat wind turbines. In this study, several designs of wind turbines are modeled using SolidWorks. Virtual aerodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and acceleration. From flow simulations, forces on the wind turbine blades and structures are calculated, and used in subsequent stress analysis to confirm structural integrity. Critical insight into the low wind speed turbine design is obtained using various configurations and the results are discussed. The study will help identify bottlenecks in the practical and effective utilization of low speed wind energy, and help devise possible remedial plans for the areas around the globe that get low average wind speeds.

A possible method for analytically modeling a CC-VAWT (Circulation Controlled Vertical Axis Wind Turbine) is the momentum model, based upon the conservation of momentum principal. This model can consist of a single or multiple stream tubes and/or upwind and downwind partitions. A large number of stream tubes and the addition of the partition can increase the accuracy of the model predictions. The CC-VAWT blade has blowing slots located on the top and bottom trailing edges and have the capability to be site controlled in multiple sections along the span of the blade. The turbine blade, augmented to include circulation control capabilities, replaces the sharp trailing edge of a standard airfoil with a rounded surface located adjacent to the blowing slots. Circulation control (CC), along with a rounded trailing edge, induces the Coanda effect, entraining the flow field near the blowing slots thus preventing or delaying separation. Ultimately, circulation control adds momentum due to the mass flow of air coming out of the blowing slots, but is negligible compared to the momentum of the free stream air passing through the area of the turbine. In order to design for a broader range of operating speeds that will take advantage of circulation control, an analytical model of a CC-VAWT is helpful. The analytical modeling of a CC-VAWT could provide insight into the range of operational speeds in which circulation control is beneficial. The ultimate goal is to increase the range of operating speeds where the turbine produces power. Improvements to low-speed power production and the elimination or reduction of startup assistance could be possible with these modifications. Vertical axis wind turbines are typically rated at a particular ratio of rotational to wind speed operating range. In reality, however, wind speeds are variant and stray from the operating range causing the power production of a wind turbine to suffer. These turbines, unless designed specifically for low speed operation, may require rotational startup assistance. The added lift due to circulation control at low wind speeds, under certain design conditions, will allow the CC-VAWT to produce more power than a conventional VAWT of the same size. Circulation control methods, such as using blowing slots on the trailing edge are modeled as they are applied to a VAWT blade. A preliminary CC-VAWT was modeled using a standard NACA 0018 airfoil, modified to include blowing slots and a rounded trailing edge. This paper describes an analytical momentum model that can be used to predict the preliminary performance of a CC-VAWT.

Wind energy has been identified as an important source of renewable energy. In this study, several wind turbine designs have been analyzed and optimized designs have been proposed for low wind speed areas around the world mainly for domestic energy consumption. The wind speed range of 4–12 mph is considered, which is selected based on the average wind speeds in the Atlanta, GA and surrounding areas. These areas have relatively low average wind speeds compared to various other parts of the United States. Traditionally wind energy utilization is limited to areas with higher wind speeds. In reality a lot of areas in the world have low average wind speeds and demand high energy consumption. In most cases, wind turbines are installed in remote offshore or away from habitat high wind locations, causing heavy investment in installation and maintenance, and loss of energy transfer over long distance. A few more advantages of small scale wind turbines include reduced visibility, less noise and reduced detrimental environmental effects such as killing of birds, when compared to traditional large turbines. With the latest development in wind turbine technology it is now possible to employ small scale wind turbines that have much smaller foot print and can generate enough energy for small businesses or residential applications. The low speed wind turbines are typically located near residential areas, and are much smaller in sizes compared to the large out of habitat wind turbines. In this study, several designs of vertical and horizontal axes wind turbines are modeled using SolidWorks e.g. no-airfoil theme, airfoil blade, Savonius rotor etc. Virtual aerodynamic analysis is performed using SolidWorks Flow simulation software, and then optimization of the designs is performed based on maximizing the starting rotational torque and ultimate power generation capacity. From flow simulations, forces on the wind turbine blades and structures are calculated, and used in subsequent stress analysis to confirm structural integrity. Critical insight into low wind speed turbines is obtained using various configurations, and optimized designs have been proposed. The study will help in the practical and effective utilization of wind energy for the areas around the globe having low average wind speeds.

Relevance Wind power in the Republic of Bashkortostan, as in any other region, has its drawbacks. Bashkortostan is not a region with a high level of wind energy. According to meteorological stations, the average annual wind speed at a height of up to 10 m varies from 1.6 to 4.4 m/s. The nominal wind speed at which the wind generator produces maximum power is in the range of 12–15 m/s. To solve the problem of generating electricity in areas with low wind speed, where the potential of wind energy is small, new technical solutions are needed. One of them is proposed in this article in the form of a wind turbine based on two five-phase magnetoelectric generators with voltage stabilization. Aim of research To investigate the possibility of stabilizing the output voltage at low wind speeds in a wind turbine based on two five-phase magnetoelectric generators. Research methods Modeling of operating modes at low and normal wind speeds of a wind turbine based on two five-phase magnetoelectric generators in the Matlab (Simscape) software package. Results A study was conducted of the operating modes at low and normal wind speeds of a wind turbine based on two five-phase magnetoelectric generators in the Matlab (Simscape) software package. Such a method of voltage regulation can provide the ability to stabilize the voltage and maintain high efficiency at an acceptable level in a wider range of low and normal wind speeds.

Traditional vortex-induced vibration energy harvesters could transform wind or water energy into electricity at low flowing speeds. However, it has the disadvantage of narrow working speed band, which limits wide application in velocity-changing environments. A piezoelectric harvester with an inner beam for harvesting wind energy at both low and high wind speed regions is presented. A comprehensive nonlinear distributed fluid–solid–electric governing equations for vortex-induced vibration piezoelectric energy harvesting are derived and the theoretical results show that dimensions of outer beam and diameter of attached cylinder can affect optimal wind speed and maximum power output at both low and high wind speeds. In contrast, the dimensions of the inner beam and mass block only have impacts at high wind speeds. The equivalent circuit modeling method is utilized to analyze energy harvesting output characteristics. Analogies between mechanical and electrical domains are built, and the governing equations are converted to circuit equations. Then the circuit equations are settled in electrical software for time-varying analysis. The electrical circuit simulation results show that the optimal load resistance is 400 kΩ at low wind speed and 500 kΩ at low wind speed, which is consistent with theoretical results. The prototypes were fabricated and experiments were carried out in a wind tunnel. Experimental results indicate that energy harvester could generate power at both low and high speeds. Mass block has great impact on optical speed and working wind speed band. The energy harvester with 7.06 g mass block could output 127.36 μW at 2.65 m s−1 and 63.63 μW at 4.4 m s−1. Numerical and circuit simulation results are consistent with experimental results on optical load resistances and optical wind speeds. This design provides a feasible method for broadening wind speed region for energy harvesting.

Based on the assumption that taking the KPP model as the vertical vortex viscosity coefficient, the unsteady Ekman equation modified by wave and linear friction terms is solved numerically with the finite difference method and the influence of wave and linear friction terms on the unsteady Ekman current are studied. Based on the measured data of AWAC, the Stokes drift is calculated by the Stokes drift formula; and on the basis of the measured data of wind speed, the average wind speed of the 3 hours is divided into three different sections: low wind speed (0∼4) m/s, medium -low wind speed (4∼8) m/s and medium-high wind speed (8∼12) m/s. The results show that: Stokes drift has the greatest impact on Ekman current under the low wind speed, which is accounted for 27.4%, the second is under the medium-low wind speed of 7.5%, and the smallest effect is under the medium-high wind speed of 4.2%. In additon, the effect of linear friction term on Ekman current is also studied. It is shown that under the medium-high wind speed and the medium-low wind speed, together with the ratio of the linear friction term to the Coriolis force is, the influence of the linear friction term on the Ekman current has exceeded that of the Stokes drift on the Ekman current; while under the low wind speed, the effect of linear friction term on Ekman current can not exceed that of Stokes drift on Ekman current until. Furthermore, the comparison between the numerical solution and the actual measured data also shows different characteristics. In the perspective of relevance, the correlation between the numerical simulation results and the measured data is above 0.7 under the medium-high wind speed, which is higher than the correlation between the both of 0.4∼0.5 under the low wind speed and the medium-low wind speed; and in the perspective of the root mean square deviation degree, the root mean square deviation between the numerical simulation results and the measured data under the medium-high wind speed is lower than that under the low wind speed and the medium-low wind speed. The above results show that the influence of Stokes drift, linear friction term and the unsteady wind on Ekman model can not be ignored.

This study investigates dust transport over photovoltaic (PV) panels, considering the effects of particle size, wind velocity, and direction. The particle's motion, governed by Newton's second law, yields a system of non-linear second-order differential equations. An algorithm is developed to solve these equations, accounting for forces including gravity, buoyancy, drag, wind, Van der Waals, electrostatic, liquid bridge forces. Results show that large wet dust particles primarily falls on ground due to gravity, especially at low wind speeds, while smaller particles remain airborne longer and deposit more at higher wind velocities. Minimal deposition on solar panel occurs at low wind speeds, but significantly increases at moderate wind speeds, especially for smaller particles. Deposition is highest at smaller wind angles and drops sharply at larger wind angles, due to strong vertical wind components. Algorithm predictions were validated against MATLAB's ‘ode45’ and Simulink solvers. To assess the accuracy of the developed model, error metrics such as Mean Bias Error (MBE), Root Mean Square Error (RMSE), and average percentage error were employed. The consistently low values of these metrics confirm the model's strong reliability in predicting dust particle trajectories across varying particle sizes, wind speeds, and directions.

An optimization framework for load and power distribution in wind farms: Low wind speed

Wind speed adaptive triboelectric nanogenerator with low start-up wind speed, enhanced durability and high power density via the synergistic mechanism of magnetic and centrifugal forces for intelligent street lamp system

In recent years, sites with low annual average wind speeds have begun to be considered for the development of new wind farms. The majority of design methods for a wind turbine operating at low wind speed is to increase the blade length or hub height compared to a wind turbine operating in high wind speed sites. The cost of the rotor and the tower is a considerable portion of the overall wind turbine cost. This study investigates a method to trade-off the blade length and hub height during the wind turbine optimization at low wind speeds. A cost and scaling model is implemented to evaluate the cost of energy. The procedure optimizes the blades’ aero-structural performance considering blade length and the hub height simultaneously. The blade element momentum (BEM) code is used to evaluate blade aerodynamic performance and classical laminate theory (CLT) is applied to estimate the stiffness and mass per unit length of each blade section. The particle swarm optimization (PSO) algorithm is applied to determine the optimal wind turbine with the minimum cost of energy (COE). The results show that increasing rotor diameter is less efficient than increasing the hub height for a low wind speed turbine and the COE reduces 16.14% and 17.54% under two design schemes through the optimization.

The effect of calm conditions and wind intervals in low wind speed on atmospheric dispersion factors

Vascular epiphytes represent almost 10% of all terrestrial plant diversity. Being structurally dependent on trees, epiphytes live at the interface of vegetation and atmosphere, making them susceptible to atmospheric changes. Despite the extensive research on vascular epiphytes, little is known about wind disturbance on these plants. Therefore, this study investigated the wind-epiphyte mechanical interactions by quantifying the drag forces on epiphytic bromeliads when subjected to increasing wind speeds (5–22 m s-1) in a wind tunnel. Drag coefficients (Cd) and Vogel exponents (B) were calculated to quantify the streamlining ability of different bromeliad species. Bromeliads’ reconfiguration occurred first via bending and aligning leaves in the flow direction. Then leaves clustered and reduced the overall plant frontal area. This reconfiguration caused drag forces to increase at a slower rate as wind velocity increased. In the extreme case, drag force was reduced by 50% in a large Guzmania monostachia individual at a wind velocity of 22 m s-1, compared to a stiff model. This species had one of the smallest Cd (0.58) at the highest wind velocity, and the largest negative mean B (-0.98), representing the largest reconfiguration capacity amongst the tested bromeliads. The streamlining ability of bromeliads was mainly restricted by the rigidity of the lower part of the plant where the leaves are already densely clustered. Wind speeds used in this study were generally low as compared to storm force winds. At these low wind speeds, reconfiguration was an effective mechanism for drag reduction in bromeliads. This mechanism is likely to lose its effectiveness at higher wind speeds when continuous vigorous fluttering results in leaf damage and aspects such as root-attachment strength and substrate stability become more relevant. This study is a first step towards an understanding of the mechanical bottleneck in the epiphyte-tree-system under wind stress.

Measurements of atmospheric fluxes of heat, moisture, and momentum were made simultaneously and coincidentally with microwave backscatter measurements from an airship flown over the Pacific Ocean in 1993. The measurement technique was well suited to measure fluxes at very low wind speeds because the airship required an air speed near 10 m s−1 in order to maintain altitude. The measurements show that very low wind speeds are always associated with very low microwave cross sections and very high air/sea drag coefficients. The occurrence of regions of very low wind speed is not usually correlated with either the sea surface temperature or the air/sea temperature difference. Nevertheless, these regions can remain in place for time periods of several hours. The rate of increase of the microwave cross section at very low wind speeds agrees with that predicted by Donelan and Pierson [1987], but the absolute value of the threshold wind speed appears to be lower than their prediction. The high drag coefficient at low wind speeds is due to the fact that the friction velocity is nearly constant for wind speeds below 4–5 m s−1. Thus, at these wind speeds the increase of the microwave cross section follows the behavior of the wind speed rather than the wind stress. At higher wind speeds, however, the behavior is reversed with the cross section following the wind stress at a constant wind speed. We suggest that this behavior can be understood if momentum transfer across the air/sea interface is supported by both viscosity and the entire spectrum of waves on the surface, as many investigators have indicated.

Icing on transmission line becomes more serious in the past ten years, and the icing area gradually expanded from the traditional south to northeast area. Ice melting is an effective method to deal with the icing disaster. But the existing ice-melting research mainly focuses on traditional ice-coated areas with low wind speed and mild temperature. But it is difficult to apply to northern regions and alpine mountainous areas with low temperature and high wind speed conditions. In response to such issue, this paper establishes an equivalent thermal circuit model for ice melting process, and studies the quantitative effects of wind speed and temperature on the characteristics of ice melting current, and obtains the law of melting ice current under low temperature and high wind speed.it provides information for the parameter design of ice melting system in extremely cold regions.

It is well known that energy generated by a wind generator (WG) depends on the wind resources at the installation site. In other words, a WG installed in a high wind speed area can produce more energy than that in a low wind speed area. However, a WG installed at a low wind site can produce a similar amount of energy to that produced by a WG installed at a high wind site if the WG is designed with a rated wind speed corresponding to the mean wind speed of the site. In this paper, we investigated the power curve of a WG suitable for Korea's southwestern coast with a low mean wind speed to achieve a high capacity factor (CF). We collected the power curves of the 11 WGs of the 6 WG manufacturers. The probability density function of the wind speed on Korea's southwestern coast was modeled using the Weibull distribution. The annual energy production by the WG was calculated and then the CFs of all of the WGs were estimated and compared. The results indicated that the WG installed on the Korea's southwestern coast could obtain a CF higher than 40 % if it was designed with the lower rated speed corresponding to the mean wind speed at the installation site.