A Levitating Frictionless_Vertical Windmill

The need for energy and electricity has been increasing globally, and this means more power is required from the power plants. Power plants, however, will then continue harming the earth because of the greenhouse gasses produced while generating energies that contribute to global warming. Using renewable sources to produce clean energies is one of the sustainable methods to deal with such challenges. Wind energy is one of the renewable sources, which is accessible anywhere on earth, creating green energy. Wind turbines are mainly categorized into Horizontal Axis Wind Turbines (HAWT) and Vertical Axis Wind Turbines (VAWT). This paper firstly presents a general comparison between the HAWTs and VAWTs. Then, it presents mathematical modelling for the aerodynamic factors of HAWT and Darrieus VAWT to assist the researchers to understand some key design aspects of wind turbines, such as lift/drag ratio, tip speed ratio, power coefficient, and torque coefficient. Also, this paper presents a review of the aerodynamic performance of the recent VAWT designs to help researchers to identify and choose the best model among the Savonius and Darrieus rotors for further development or designing a new model at different wind conditions. This comparison review shows that for a large scale HAWT upwind 3 bladed wind turbines are the most optimum. The helical Savonius rotors perform better by having positive torque coefficient at all azimuth angles. Moreover, helical Darrieus was found to produce lesser noise and suitable for conventional areas. hybrid Savonius-Darrieus rotors can solve the self-starting challenge of the VAWTs, and they are suitable at low wind speeds. At last, this review shows some of the recent hybrid Savonius-Darrieus rotors which would help to solve the low efficiency of Savonius rotor and self-starting challenge of Darrieus rotors.

I.IntroductionThe vertical axis wind turbine has been widely concerned because of its advantages such as multiphase wind, stable force, easy installation and maintenance, and small starting wind speed. Vertical axis wind turbines mostly use permanent magnet synchronous generators or doubly fed induction wind turbines, and most of them are axial flux permanent magnet generators[1]. Compared with doubly fed induction wind turbine, permanent magnet synchronous generator (PMSG) has the advantage of high power density and is the main research object of vertical axis wind turbine. However, the direct coupling of the high power axial flux permanent magnet synchronous generator and wind turbine causes the starting of the wind turbine to become more difficult. In order to improve the starting performance of vertical axis wind turbines, maglev technology is considered to reduce the starting resistance as the development direction of vertical axis wind turbines. Therefore, an asymmetric-primary axis-flux hybrid- electricity generator is proposed in this paper, and the decoupling control of levitation force and output power is implemented using asymmetric primary and hybrid excitation.II.operation principleThe proposed asymmetric-primary axis-flux hybrid-excitation generator for the vertical axis wind turbine structure is shown in the Fig.1.The generator is composed of double stator primary and single actuator. The double stator primary has an asymmetric structure design, and the rotor shaft is connected with the wind turbine shaft to realize direct drive wind power generation. The rotor adopts the spacing design of permanent magnet and modulating tooth to reduce the consumption of permanent magnet. Both the excitation winding and the armature winding are located in the primary stator, so the mixed excitation and magnetic field can be adjusted without adding any mechanism such as brush slip ring, which reduces the complexity of the structure.In general, the proposed generator has the following characteristics(1) The flat structure shortens the axial length of the generator and is suitable for direct drive of vertical axis wind power generation system.(2) The levitation force is provided by bilateral unbalance design of axial flux. The two sides adopt different primary sizes, and then the axial electromagnetic force imbalance of the bilateral air gap forms the suspension force, which avoids adding active and passive levitation mechanisms and reduces the complexity of the overall system.(3) The levitation force and output power are controlled by hybrid excitation. The primary tooth DC excitation is adopted to realize zero crosslinking of the excitation with permanent magnet and armature, and the levitation force regulation does not affect the output power. The system can start at low wind speed, and the levitation force and total output power can be adjusted according to the change of wind speed. Through free distribution of bilateral power to achieve the total power following the wind speed and the levitation force following the lift force of the wind turbine.(4) Using magnetic field modulated axial magnetic field structure, the rotor structure is simple and reliable. If the pole pair numbers of rotor and armature are pr and ps, and the number of the stator tooth is pn, there is pr = pn±ps. The design makes it have the magnetic field modulation effect, which can increase the magnetic field change rate under the low speed, thus increasing the generation power.(5) The use of concentrated armature windings and excitation windings reduces the end, thus reducing magnetic leakage and losses.III.simulation and resultsA three-dimensional finite element model of the asymmetric-primary axis-flux hybrid-excitation generator is established, and the no-load characteristics and load characteristics of the generator are obtained. The no-load characteristics under different excitation current are simulated, and the flux linkage of armature coils and DC excitation coils are shown in Fig.2.We can see that when different excitation currents are applied, the crossing flux linkage between DC excitation winding and secondary permanent magnet is almost 0, and DC flux has little effect on the armature flux. Therefore, When the excitation changes, the unilateral levitation force changes only in amplitude, but there is no harmonic phase shift, and positioning torque is almost unaffected. he proposed generator has good decoupling performance of levitation force, output power, and DC excitation. In addition, the optimization design of the generator is further studied such as pole arc coefficient, positioning moment and pole slot ratio. IV.conclusionIn this paper, we proposed an asymmetric-primary axis-flux hybrid-excitation generator, studied the no-load characteristics, load characteristics and excitation characteristics, and optimized the structural parameters of the generator. The simulation results are obtained, and state that the generator can realize the decoupling of the levitation force of excitation and power, which is suitable for vertical axis wind turbine. **

Improving the self-starting and operating characteristics of vertical axis wind turbine by changing center distance in part of blades

In recent decades, wind turbines have emerged as substantial renewable energy technologies, particularly for offshore applications. However, the utilisation of conventional wind turbine in regions characterised by a low wind speed profile, such as Malaysia, remains limited. To address this gap, this study develops an unconventional small-scale Vertical Axis Wind Turbine (VAWT) provision for offshore application in Malaysia’s low wind speed regions. The study commenced with a wind feasibility analysis which aimed to determine the viable range of offshore wind speeds prior conducting wind tunnel tests. The VAWT model was designed using SolidWorks software, fabricated using a 3D printer and tested in the National Defence University of Malaysia (UPNM) wind tunnel lab facilities. Through a systematic analysis and optimisation of blade diameters, stages and angles using Taguchi method, this study aimed to enhance the wind turbine performance in terms of power coefficient (Cp) and tip speed ratio. The result highlighted the pivotal role of blade diameter and the number of stages as a key design factor for VAWT, with the optimal configuration of blade diameter of 16 cm, a single stage and Angle of Attack (AoA) of 7°, resulted in a Cp value of 0.622. It is important to note that this Cp value exceeds the typical wind turbine power coefficient benchmarks, which range from 0.3 to 0.45, indicating that the optimised design offers a higher-than-average efficiency for small-scale VAWTs. Additionally, variations in AoA were found to be the least significant design factor, as all models demonstrated peak Cp values corresponding to wind speeds. Although tested in a controlled wind tunnel environment, these results suggest that the optimum design could perform efficiently under Malaysia's real-world offshore conditions, where wind speeds are typically low. This study provides key design considerations for small-scale VAWTs in low wind profile regions, contributing to the sustainable development of wind energy in Malaysia.

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.

Research of asymmetric airfoil on aerodynamic characteristics of vertical axis wind turbines

In South East Asia countries such Malaysia, wind turbine is generally not suitable to be used in large scale to generate electricity due to inconsistent wind speed and suitable land site availability. However, a small scale application is of preference as the wind speed in the region lies within the low speed range of approximately 2-5 ms−1 with intermittent highs up to 8 ms−1. The performance of Vertical Axis Wind Turbines (VAWTs) is known to be better compared to Horizontal Axis Wind Turbines (HAWTs) in urban conditions due to its omnidirectionality, which allows it to operate in fluctuating turbulent wind conditions. However, the major drawback of VAWTs is the inability to self-start under low wind speed conditions. Hence, the objective of this work is to investigate the Pivoting Panel Mechanism (PPM) which aims to assist VAWT models to self-start at low wind speed condition. Three sets of PPM width configurations (70mm, 80mm, 90mm) are used to study the effect of increasing the pivot panel surface area on the VAWT performance. Performance test showed that the PPM model improved the power coefficient values at the tip wind speed range of TSR<0.75 (PPM 70mm>80mm>90mm). Further investigation revealed that the larger PPM surface area (90mm) was able to assist the VAWT model to achieve a shorter RPM response time at wind speed of v = 2.5ms−1 and 2.9ms−1. These findings have considerable implications for future researches for the optimization of PPM design parameters and its adaptations in VAWT turbine design.

Wind energy, being renewable, cost-effective, and environmentally friendly, has attracted global attention. However, due to suboptimal performance and limited research, vertical axis wind turbines (VAWTs) lag behind horizontal axis wind turbines (HAWTs) in commercial applications, particularly for large-scale installations. This study aims to improve the self-starting capability of the Darrieus VAWT. While some parameters, such as the number of blades (N) and solidity (σ), have been studied extensively, the airfoil shape has not received as much attention. This study compares the performance of National Advisory Committee for Aeronautics (NACA) airfoils and Selig airfoils at a Reynolds number (Re) of 40,673. The investigation revealed that the NACA0015 airfoil exhibited the highest peak power coefficient (Cp). Further analysis utilizing an advanced double multiple stream tube (DMST) code in MATLAB increased the peak Cp by adjusting the thickness-to-camber ratio (t/c) of the NACA0015 airfoil, resulting in a 12.50 % increase in the maximum achievable Cpat a Re of 40,673. This study compared four modes of VAWT operation, utilizing the NACA0015 airfoil and a modified NACA0015 airfoil for both straight-bladed and embossed-bladed VAWTs. The results showed that the modified NACA0015 airfoil for embossed-bladed VAWTs exhibited the best self-starting capability and rotation at wind velocities of 1 to 9 m s-1. Additionally, the self-starting force required by embossed-bladed VAWTs was lower than that needed by straight-bladed VAWTs due to the ability of the embossed material to enhance airflow attachment to the VAWT and suppress turbulence.

Experimental investigation of solidity and other characteristics on dual vertical axis wind turbines in an urban environment

Green energy harvester, known as wind turbine, able to convert mechanical works to electrical power. There are two main type of wind turbine that considered thoroughly, which are the horizontal and vertical axis wind turbine respectively. This project mainly focus on the design of new wind turbine that can operate well together in low wind speed condition in Malaysia. For the first stage of this project, the problems, purpose, and planning regarding with the project properly determined. Literature survey then furthered analyzed in order to know the wind power or behavior across the world, and specifically in Malaysia, research of turbine that can work in low wind speed condition, as well as parameter that often used in designing wind turbine by previous researcher. From the literature survey, the selected turbine was a Three-Bladed Savonius Wind Turbine, which is one type of Vertical Axis Wind Turbine (VAWT). That turbine will be attached to another VAWT turbine system to help generate more power and better performance. Design theoretical calculation and material selection have been properly analyzed before fabrication can be done. Upon completion of the fabrication, Savonius wind turbine section properly tested through experimental works by using simple wind tunnel in Faculty of Engineering Mechanical Workshop, and all readings and data collected using applicable tools and equipment. For the experimental works of Savonius rotor, the variable includes of blades curve angle from its center at different wind speeds. The data collected then interpreted through charts and graph for comparison and performance analysis, and conclude that 1200 blades curve angle from its center was the best among the other type of blades. From this project, it can be concluded that this type of mix wind turbine able to works in low wind speed condition in Malaysia, but a better improvisation and modification of the mix wind turbine will certainly improve its further performance and efficiency.

The Design and Flow Simulation of a Power-augmented Shroud for Urban Wind Turbine System

Increasing environmental concerns have led to a demand for more environmentally friendly energy options. Worldwide, wind energy is one of a clean, renewable source of green electricity. Fossil fuel is one of our most important sources of energy and its quantities are decreasing. However, wind is a renewable resource that can as stand by source with fuel. Wind turbines are used to harness the wind to generate energy. Vertical axis wind turbines (VAWTs) are suitable for use in built sites because to their outstanding features, attractiveness, low noise, and safety. To achieve these objectives, vertical axis wind turbines with multiple blades (blades are made from polyvinyl chloride (PVC) material) have been designed, manufactured and studied experimentally to investigate its performance. Turbine’s blade is a half cylinder in its shape. The blades rotational speed of the blades, the resulted torque (T), and generated power (P) of each configuration of the suggested turbine were determined for different wind speeds (1.5m/s, 2.5m/s, and 3m/s) and rotor radius of (30cm, 40cm, and50cm), respectively. The graphical relation between coefficient of power (Cp) and the tip speed ratio (TSR) and between coefficient of power (Cp) and angles of the blades were constructed. It was noted that performance of wind turbine is largely depends on wind speed, blade locations, and blade angle. The maximum value of the power coefficients (Cp = 13.056%) is noticed at 40cm and 1.5 m/s for blade radius and wind speed, respectively, specifically at TSR=1.3 and 450 blade angle. The maximum values of the Cp for all values of the effective parameters are noticed at 450 blade angle. In addition, higher values of Cp are achieved at the lower wind speeds and high blade radius, and that corresponds to higher TSR. Finally, VAWT is able to generate electricity for local use even at low wind speeds.

This paper introduces the GWIT EHD VAWT and the logic and history behind its development. We develop a simplified model to compare the performance of EHD VAWTs with conventional propeller machines. GWIT is engaged on a path to optimize the performance of its wind turbines in a wind farm setting. The paper details the characteristics of its first two prototypes - JJ and JJ3. The turbines are designed to meet the atmospheric conditions prevailing in China. While the EHD VAWT concept can be implemented in many configurations, GWIT has developed its turbines to operate over the broadest possible atmospheric conditions with an absolute minimum of moving mechanical components. We focus on turbine designs that more than double energy capture from the wind site. More than 90% of the turbine's content is of local manufacture. I. HISTORY OF THE EHD VAWT Wind turbines can trace their origins thousands of years into the past. Modern wind turbines can trace their current mission - the conversion of wind energy into electricity-back to the closing days of World War II when some Northern Continental European nations first converted some of their water pumping and grain milling wind turbines into producers of electricity. Since that time European nations began to devote significant research efforts into developing efficient machines to produce grid usable electricity from their abundant wind resources. More recently these efforts have been joined by North American and Asian nations. While some effort was devoted to the development of vertical axis wind turbines (VAWTs) almost all European research efforts were devoted to horizontal axis wind turbines (HAWTs). In Canada and the United States significant efforts were made to develop VAWTs, but the vast majority of wind energy research was devoted to HAWTs. By 1980 European designed HAWTs were focusing on economic parameters while Canadian and American efforts were still attempting to demonstrate feasibility. Numerous HAWT powered wind farms emerged but only two VAWT powered wind farms were in development or operation. Rely- ing on a Sandia National Laboratories design, FloWind fielded 512 170 kW F-17 and 300 kW F-19 VAWTs on two wind farms in California. Both wind farms operated successfully until they were replaced with Micon HAWTs between 1998 and 2002.

The wind power generation is experiencing a rapid growth, achieving the highest number of European installations in 2010 comparing to other renewable sources. The need for a smarter grid capable of integrating several decentralized sources of energy and the increasing need for energy in urban areas, has led to an increase interest in wind turbines for the urban areas. In these environments, vertical axis wind turbines (VAWT) have several advantages over horizontal axis wind turbines (HAWT), namely: their ability to operate closer to the ground; their insensitivity to yaw wind directions; the smaller number of components; the operation at low sound emissions; the ability to generate energy from wind in skew flow. One problem with the lift-type VAWT (Darrieus wind turbines) is their natural inability to self-start at low wind speeds without extra components. Hence, a new blade profile for Darrieus type VAWT is presented in this paper, capable to self-start at low wind speeds. A methodology is developed to compare the new blade profile with other known airfoils. Finally, conclusions are duly drawn. (5 pages)

The vertical axis wind turbine (VAWT) is considered an important device to utilize the renewable and sustainable wind energy. However, the relatively lower power coefficient has hampered its development. Therefore, this paper attempts to investigate the effect of swept blade employed in a VAWT on the enhancement in aerodynamic performance. A series of swept blades were studied in a small VAWT rotor, and the RANS SST k-ω turbulence model was utilized to simulate the flow field. The numerical model was validated against experimental data, and the aerodynamic performance was investigated with respect to force coefficients, vorticity distribution, static pressure distribution, and wind turbine wake, respectively. The results indicated that the swept blade could effectively increase power outputs by about 20% for the wind turbine. By reducing the drag coefficient, a high lift-drag ratio was achieved. And this configuration prevented the blade from suffering severe dynamic stall. Besides, the swept blade changed the distribution of low wind speed area in the wind turbine wake, which should be considered in the wind farm. It was concluded that this work provided a new way for the practical design and optimization of wind turbine.