Wind energy is playing a critical role in the establishment of an environmentally sustainable low carbon economy. This paper presents an overview of wind turbine generator technologies and compares their advantages and drawbacks used for wind energy utilization. Traditionally, DC machines, synchronous machines and squirrel-cage induction machines have been used for small scale power generation. For medium and large wind turbines (WTs), the doubly-fed induction generator (DFIG) is currently the dominant technology while permanent magnet (PM), switched reluctance and high temperature superconducting generators are all extensively researched and developed over the years. In this paper, the topologies and features of these machines are discussed with special attention given to their practical considerations involved in the design, control and operation. It is hoped that this paper provides quick reference guidelines for developing wind turbine generation systems.
This is report prepared by me on Airborne Wind Turbines (AWT). It consists of the types of wind turbines used today. Types of prototypes in the airborne sector, and a brief working of them.
Review Paper of Savonius Vertical Axis Wind Turbine Rotor BladeIJMER
This paper involves study of Savonius Vertical Axis Wind Turbine (SVAWT) blades. In
past few years more research works are carried out to increase efficiency of Vertical Axis Wind
Turbine. Review of all these papers shows that the experiments are conducted only on semi
cylindrical bucket shape blades, twisted blades, blades with end flap edges and blades having frames
with cavity vanes, for two blades, three blades and four bladed Savonius Vertical Axis Wind
Turbine(SVAWT) to increase performance. They also conducted experiments by providing curtains or
flow guide to the rotor, increasing in the stages of rotor and combining both Savonius and Darrieus
rotor (i.e. hybrid rotors) to increase the efficiency of rotor. Research work or experiments on semi
cylindrical bucket rotor blade edges, having extrusion or leading edges with different angles are not
carried out. Development of these designs includes a multidisciplinary design optimization approach
for optimizing the Vertical Axis Wind Turbine blade, considering both structural and fluid flow
performance requirements. Weighted Property Method, Cost Property Method, limits Property
Methods are used for Selection of suitable material. ANSYS and Computational Fluid Dynamics are
used for structural analysis and fluid flow performance of newly designed blade.
Train Mounting T Box for Wind Power Generationijtsrd
Today many industries are rapidly growing to the wind energy generation. Nowadays, the need of energy resources is increasing at a much faster rate. We need to capitalize all the available options to complete all our needs with ease. For this, inventions such as T BOX are very helpful. As it needs only wind from passing trains to produce the energy. Since fasting is going on for alternative forms of treatment, T box has created hope. This device introduces a new generation of wind energy generator producing very prominent in techno buffs. That's it however, it is important to remember, that the design is still in a conceptual state, so that in the future, the ‘use and maintenance of this device has not been resolved. Our evolution shows that i Constructing electricity Using the concept of rotation of wind turbine by hawking rail. ii Using air tight coat to reduce large pressure and use it to control wind flow. The mouth of casing provided with valve to control the wind flow. To provide full mechanical support to the Train. Vaghela P. M | Thorat P. D | Lakudzode K. B | Prof. Udamle S. R ""Train Mounting T-Box for Wind Power Generation"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23933.pdf
Paper URL: https://www.ijtsrd.com/engineering/electrical-engineering/23933/train-mounting-t-box-for-wind-power-generation/vaghela-p-m
This is report prepared by me on Airborne Wind Turbines (AWT). It consists of the types of wind turbines used today. Types of prototypes in the airborne sector, and a brief working of them.
Review Paper of Savonius Vertical Axis Wind Turbine Rotor BladeIJMER
This paper involves study of Savonius Vertical Axis Wind Turbine (SVAWT) blades. In
past few years more research works are carried out to increase efficiency of Vertical Axis Wind
Turbine. Review of all these papers shows that the experiments are conducted only on semi
cylindrical bucket shape blades, twisted blades, blades with end flap edges and blades having frames
with cavity vanes, for two blades, three blades and four bladed Savonius Vertical Axis Wind
Turbine(SVAWT) to increase performance. They also conducted experiments by providing curtains or
flow guide to the rotor, increasing in the stages of rotor and combining both Savonius and Darrieus
rotor (i.e. hybrid rotors) to increase the efficiency of rotor. Research work or experiments on semi
cylindrical bucket rotor blade edges, having extrusion or leading edges with different angles are not
carried out. Development of these designs includes a multidisciplinary design optimization approach
for optimizing the Vertical Axis Wind Turbine blade, considering both structural and fluid flow
performance requirements. Weighted Property Method, Cost Property Method, limits Property
Methods are used for Selection of suitable material. ANSYS and Computational Fluid Dynamics are
used for structural analysis and fluid flow performance of newly designed blade.
Train Mounting T Box for Wind Power Generationijtsrd
Today many industries are rapidly growing to the wind energy generation. Nowadays, the need of energy resources is increasing at a much faster rate. We need to capitalize all the available options to complete all our needs with ease. For this, inventions such as T BOX are very helpful. As it needs only wind from passing trains to produce the energy. Since fasting is going on for alternative forms of treatment, T box has created hope. This device introduces a new generation of wind energy generator producing very prominent in techno buffs. That's it however, it is important to remember, that the design is still in a conceptual state, so that in the future, the ‘use and maintenance of this device has not been resolved. Our evolution shows that i Constructing electricity Using the concept of rotation of wind turbine by hawking rail. ii Using air tight coat to reduce large pressure and use it to control wind flow. The mouth of casing provided with valve to control the wind flow. To provide full mechanical support to the Train. Vaghela P. M | Thorat P. D | Lakudzode K. B | Prof. Udamle S. R ""Train Mounting T-Box for Wind Power Generation"" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-3 | Issue-4 , June 2019, URL: https://www.ijtsrd.com/papers/ijtsrd23933.pdf
Paper URL: https://www.ijtsrd.com/engineering/electrical-engineering/23933/train-mounting-t-box-for-wind-power-generation/vaghela-p-m
what is air borne wind energy system and how it is work and types of wind energy system history of air borne wind energy system mathematical calculation related to awes all are in this pdf
Design & Analysis of a Helical Cross Flow TurbineAnish Anand
We investigate the flow past a cross flow hydrokinetic turbine (CFHT)in which a helical blade turns around a shaft perpendicular to the free stream under the hydrodynamic forces exerted by the flow. The ability of a cross flow turbine to rotate in the same direction independent of the water flow direction gives an advantage for hydrokinetic applications.
This type of turbine, while very different from the classical horizontal axis turbine commonly used in the wind energy field, presents advantages in the context of hydro kinetic energy harvesting, such as independence from current direction, including reversibility, stacking, and self-starting without complex pitch mechanisms.
Design And Analysis Of Savonius Wind Turbine BladesIJERA Editor
There are two kinds of wind turbines according to the axis of rotation to the ground, horizontal axis wind
turbines (HAWT) and vertical axis wind turbines (VAWT). VAWTs include both a drag type configuration like
Savonius wind turbine and a lift-type configuration like Darrieus wind turbine. Savonius wind rotor has many
advantages such as low starting speeds and no need for external torque for its starting. Moreover it is cheaper in
construction and has low maintenance. It is independent of the wind direction and has a good starting torque at
lower wind speeds. The experimental study conducted in this paper aims to investigate the effect of number of
blades and other criteria that can affect the performance of the model of Savonius type wind turbine. The
experiments used to compare 2, 3, and 4 blades wind turbines to show tip speed ratio, torque and power
coefficient related with wind speed. A simulation using ANSYS 13.0 software will show pressure distribution of
wind turbine. The results of study showed that number of blades influence the performance of wind turbine.
Savonius model with three blades has the best performance at high tip speed ratio.
POWER PLANT- PORTABLE MICRO POWER GENERATIONvivatechijri
This project gives on idea of "POWER PLANT- PORTABLE MICRO POWER GENERATION". In this project we considered wind as a renewable source of energy to generate electricity with the help of aeroleaves are leaf like structure of wind turbine. Which are placed in the form of tree called Wind tree. These aeroleaves are small vertical Axis Wind Turbine (VAWT) and able to generate power. They are also silent, so they could be installed along buildings, street or even in people’s backyards. The rotation of aeroleaves depends on wind speed and wind direction. VAWT will catch wind from all directions. When wind blows, aeroleaves rotate and energy get produced .In this project , the power generated from wind tree is eco-friendly, less noise polluted and can provide electricity to remote locations.
Groundwater quality of south India is depending on climate condition and bedrock geology but may also be impacted by pollution, particularly from industrial sources and agricultural activity. In the current study, 15 groundwater samples were collected from different locations in the Kinathukkadavu Taluk, Coimbatore to assess water quality for drinking as well as for irrigation purpose by analyzing the major cations (Ca2+, Mg2+, Na+ and K+) and anions (Cl-, NO3-, SO42- and F-) besides some physical and chemical parameters (pH, total hardness, electrical conductivity and total alkalinity). Statistical analysis like correlation, R- mode factor and cluster analysis were performed for demarcate the association of hydro geochemical parameters. Also groundwater quality mapping was developed using geographic information system.
Extending the longevity, is a significant job to be accomplished by these sensor networks. The traditional routing protocols could not be applied here, due to its nodes powered by batteries. Nodes are often clustered in to non-overlapping clusters, so as to provide energy efficiency. A concise overview on clustering processes, within wireless sensor networks is given in this paper. But it is difficult to replace the deceased batteries of the sensor nodes. A distinctive sensor node consumes much of its energy during wireless communication. This research work suggests the development of a hierarchical distributed clustering mechanism, which gives improved performance over the existing clustering algorithm LEACH. The two hiding concepts behind the proposed scheme are the hierarchical distributed clustering mechanism and the concept of threshold. Energy utilization is significantly reduced, thereby greatly prolonging the lifetime of the sensor nodes.
what is air borne wind energy system and how it is work and types of wind energy system history of air borne wind energy system mathematical calculation related to awes all are in this pdf
Design & Analysis of a Helical Cross Flow TurbineAnish Anand
We investigate the flow past a cross flow hydrokinetic turbine (CFHT)in which a helical blade turns around a shaft perpendicular to the free stream under the hydrodynamic forces exerted by the flow. The ability of a cross flow turbine to rotate in the same direction independent of the water flow direction gives an advantage for hydrokinetic applications.
This type of turbine, while very different from the classical horizontal axis turbine commonly used in the wind energy field, presents advantages in the context of hydro kinetic energy harvesting, such as independence from current direction, including reversibility, stacking, and self-starting without complex pitch mechanisms.
Design And Analysis Of Savonius Wind Turbine BladesIJERA Editor
There are two kinds of wind turbines according to the axis of rotation to the ground, horizontal axis wind
turbines (HAWT) and vertical axis wind turbines (VAWT). VAWTs include both a drag type configuration like
Savonius wind turbine and a lift-type configuration like Darrieus wind turbine. Savonius wind rotor has many
advantages such as low starting speeds and no need for external torque for its starting. Moreover it is cheaper in
construction and has low maintenance. It is independent of the wind direction and has a good starting torque at
lower wind speeds. The experimental study conducted in this paper aims to investigate the effect of number of
blades and other criteria that can affect the performance of the model of Savonius type wind turbine. The
experiments used to compare 2, 3, and 4 blades wind turbines to show tip speed ratio, torque and power
coefficient related with wind speed. A simulation using ANSYS 13.0 software will show pressure distribution of
wind turbine. The results of study showed that number of blades influence the performance of wind turbine.
Savonius model with three blades has the best performance at high tip speed ratio.
POWER PLANT- PORTABLE MICRO POWER GENERATIONvivatechijri
This project gives on idea of "POWER PLANT- PORTABLE MICRO POWER GENERATION". In this project we considered wind as a renewable source of energy to generate electricity with the help of aeroleaves are leaf like structure of wind turbine. Which are placed in the form of tree called Wind tree. These aeroleaves are small vertical Axis Wind Turbine (VAWT) and able to generate power. They are also silent, so they could be installed along buildings, street or even in people’s backyards. The rotation of aeroleaves depends on wind speed and wind direction. VAWT will catch wind from all directions. When wind blows, aeroleaves rotate and energy get produced .In this project , the power generated from wind tree is eco-friendly, less noise polluted and can provide electricity to remote locations.
Groundwater quality of south India is depending on climate condition and bedrock geology but may also be impacted by pollution, particularly from industrial sources and agricultural activity. In the current study, 15 groundwater samples were collected from different locations in the Kinathukkadavu Taluk, Coimbatore to assess water quality for drinking as well as for irrigation purpose by analyzing the major cations (Ca2+, Mg2+, Na+ and K+) and anions (Cl-, NO3-, SO42- and F-) besides some physical and chemical parameters (pH, total hardness, electrical conductivity and total alkalinity). Statistical analysis like correlation, R- mode factor and cluster analysis were performed for demarcate the association of hydro geochemical parameters. Also groundwater quality mapping was developed using geographic information system.
Extending the longevity, is a significant job to be accomplished by these sensor networks. The traditional routing protocols could not be applied here, due to its nodes powered by batteries. Nodes are often clustered in to non-overlapping clusters, so as to provide energy efficiency. A concise overview on clustering processes, within wireless sensor networks is given in this paper. But it is difficult to replace the deceased batteries of the sensor nodes. A distinctive sensor node consumes much of its energy during wireless communication. This research work suggests the development of a hierarchical distributed clustering mechanism, which gives improved performance over the existing clustering algorithm LEACH. The two hiding concepts behind the proposed scheme are the hierarchical distributed clustering mechanism and the concept of threshold. Energy utilization is significantly reduced, thereby greatly prolonging the lifetime of the sensor nodes.
The establishment of sensor systems has elated recompenses such as measurement in flammable and explosive atmospheres, resistance to electrical noises, trimness, geometrical suppleness, measurement of slight sample volumes, remote sensing in unreachable sites or harsh atmospheres and multi-sensing. Biosensors are logical devices composed of a recognition component of biological origin and a physico-chemical transducer. Immobilization plays a foremost character in developing the biosensor by incorporating both the above mentioned mechanisms. In this paper, the real world applications pertaining the analysis of fiber optic sensors and biosensors for environmental and clinical monitoring have been reviewed.
Every cluster comprise of a leader which is known as cluster head. The cluster head will be chosen by the sensor nodes in the individual cluster or be pre-assigned by the user. The main advantages of clustering are the transmission of aggregated data to the base station, offers scalability for huge number of nodes and trims down energy consumption. Fundamentally, clustering could be classified into centralized clustering, distributed clustering and hybrid clustering. In centralized clustering, the cluster head is fixed. The rest of the nodes in the cluster act as member nodes. In distributed clustering, the cluster head is not fixed. The cluster head keeps on shifting form node to node within the cluster on the basis of some parameters. Hybrid clustering is the combination of both centralized clustering and distributed clustering mechanisms. This paper gives a brief overview on clustering process in wireless sensor networks. A research on the well evaluated distributed clustering algorithm Low Energy Adaptive Clustering Hierarchy (LEACH) and its followers are portrayed artistically. To overcome the drawbacks of these existing algorithms a hybrid distributed clustering model has been proposed for attaining energy efficiency to a larger scale.
5G–“connect anytime, anywhere, anyhow” promising everywhere network access at high speed to the end users, has been a topic of great interest mainly for the wireless telecom industry. 5G seems to be the solution for the growing user necessities of wireless broadband access and the boundaries of the existing wireless communication system. The wireless industry is busy with the standardization of the 4th generation (4G) cellular networks. 4G wireless system cannot exist in today’s market without standardization. The 4G concept shave already moved to the standardization phase, we must begin to work on the structure blocks of the 5G wireless networks. The major difference, from a user point of view, between current generations and expected 5G techniques must be something else than increased maximum throughput; other requirements include low battery consumption, more secure. We refer to this goal as enabling the 4A’s paradigm i.e. Any rate, Anytime, Anywhere and Affordable. In particular, this paper focuses on the features such as broadband internet in mobile phones with a possibility to provide internet facility in the computer by just connecting the mobile and with a speed of 10Gbps and more. In 5G researches are being made on development of World Wide Wireless Web (WWWW), Dynamic Adhoc Wireless Networks (DAWN) and Real Wireless World.
In wireless sensor network energy cutback is considered as a principle intensive challenge which is studied largely in the Wireless Sensor Networks (WSN) literature. Wireless Sensor Networks (WSNs) are pertinent in numerous arenas where WSNs may be used for sensing, ciphering, and communication elements that give a user or administrator the ability to instrument, observe, and retort to events and phenomena in a specific environment. But sensor devices are resource curbed, positioned in an open and unattended environment, different types of attacks and conventional techniques against these attacks are not desirable due to the resource constrained nature of these kinds of networks. An energy-balanced routing method based on forward-aware factor (FAF-EBRM) in which the next-hop node is elected according to the awareness of link weight and forward energy density. FAF-EBRM is compared with Ladder Diffusion Algorithm, which balances the energy utilization, sustain the function era and guarantees high QoS of WSN. The FAF-EBRM is proposed with Secure Routing Layer (SRL) Protocol which ensures that the secure data transmission is achieved without releasing private sensor readings and without introducing significant overhead on the battery-limited sensors.
The design and optimization of rotary tillage tool on the basis of simulation and finite element method is done by using ANSYS software. The different rotary tillage tool parts are geometrically constrained with preparation of solid model of blades and simulation has been done with actual field performance rating parameters along with boundary conditions. The proposed work results are identifying sufficient tolerance in changing the material such as EN 8 steel and EN 24 steel. The dimensions of rotavator blade sections and to rise the life cycle of the blades for a reliable strength. The present geometry working model with tillage blade is analysed to new design change constraints of its geometry for the maximum weed removal efficiency by presenting its analysis results from the field performance.
In recent electronic circuits pose a reliability threat, a lot of applications are necessary to use protection against soft errors, there is no exceptions in the field of communications and signal processing systems. For several applications is to use Algorithmic Based Fault Tolerant techniques (ABFT) that try to expand the algorithmic properties to detect and correct the errors. The ABFT technique is well suitable for communications and signal processing applications. One of the examples is Fast Fourier Transforms that are a input building block in various systems. Some protection schemes are proposed. Among this, probably the use of the Parseval or sum of squares check is most broadly known. In modern communication systems are impressively use several blocks that blocks are operated in parallel. This type of technique is well suitable for FFTs protection. Consequently two enhanced protection schemes that merge the use of error correction codes and Parseval checks are proposed. The proposed technique to reduce the implementation cost of protection.
Design of PVC Bladed Horizontal Axis Wind Turbine for Low Wind Speed RegionIJERA Editor
The Project is aimed at designing a wind turbine that can be able to build by Laypersons, using readily available material which is feasible & affordable to provide much needed electricity. Since most of the high wind power density regions in the zone of high wind speed are already being tapped by large scale wind turbine and so it required creating a large scope for the development of low wind speed turbines. Our study focuses primarily on designing the blade for tapping power in the regions of low wind power density. The aerodynamic profiles of wind turbine blades have major influence on aerodynamic efficiency of wind turbine. This can be achieved by comparing the effectiveness of a crude blade fashioned from a different Size, Material & standard of PVC drainage pipe which are easily available in market. It can be evaluated by performing experimental analysis, data collection & its evaluation on different type & size of PVC Pipe & preparing an analytical tool for best Design.
Design of Savonius model wind turbine for power catchmentIJECEIAES
In this study, the fossil fuel usage by-product is carbon dioxide, which is known as the primary cause in global warming. Alternatively, wind energy is a clean alternative energy source compared the fuel consumption can cause smoke pollution. The goal of the work is to develop a pollution controller device model Savonius wind turbine to represent the characterized actual speed wind turbine concepts into convert kinetic energy into electric energy from campus and monitoring all output data display on the cloud. The wind speed operation is enabled through the use of ESP8266 as internet of things (IoT) platform and the alternating current (AC) direct current (DC) harvesting circuit into improve stability of the wind energy performance. Secondly, a magnet coil synchronous generator is used, which is a grid coupled through a diode rectifier and voltage source converter. The parameters that have been measured using wireless fidelity (Wi-Fi) module ESP8266 are considering wind speed, current, voltage and power. The wind speed with 7.8 MPH can produce a maximum output voltage and output current of 1.104 V and 4.321 µA, respectively. Blynk applications functional as role present performance monitoring kit wind turbine analysis with more precise and efficient in anywhere and anytime.
CONTRIBUTEDP A P E RHigh-Power Wind EnergyConversion S.docxdonnajames55
CONTRIBUTED
P A P E R
High-Power Wind Energy
Conversion Systems:
State-of-the-Art and
Emerging Technologies
Wind energy installed capacity increased exponentially over the past three decades,
and has become a real alternative to increase renewable energy penetration
into the energy mix.
By Venkata Yaramasu, Member IEEE, Bin Wu, Fellow IEEE, Paresh C. Sen, Life Fellow IEEE,
Samir Kouro, Member IEEE, and Mehdi Narimani, Member IEEE
ABSTRACT | This paper presents a comprehensive study on the
state-of-the-art and emerging wind energy technologies from
the electrical engineering perspective. In an attempt to de-
crease cost of energy, increase the wind energy conversion
efficiency, reliability, power density, and comply with the strin-
gent grid codes, the electric generators and power electronic
converters have emerged in a rigorous manner. From the mar-
ket based survey, the most successful generator-converter
configurations are addressed along with few promising topol-
ogies available in the literature. The back-to-back connected
converters, passive generator-side converters, converters for
multiphase generators, and converters without intermediate
dc-link are investigated for high-power wind energy conver-
sion systems (WECS), and presented in low and medium voltage
category. The onshore and offshore wind farm configurations
are analyzed with respect to the series/parallel connection of
wind turbine ac/dc output terminals, and high voltage ac/dc
transmission. The fault-ride through compliance methods used
in the induction and synchronous generator based WECS are
also discussed. The past, present and future trends in megawatt
WECS are reviewed in terms of mechanical and electrical tech-
nologies, integration to power systems, and control theory. The
important survey results, and technical merits and demerits of
various WECS electrical systems are summarized by tables. The
list of current and future wind turbines are also provided along
with technical details.
KEYWORDS | ac-ac; ac-dc; dc-ac; dc-dc power conversion;
doubly fed induction generator (DFIG); fault-ride through (FRT);
grid codes; low voltage (LV); medium voltage (MV); multilevel
converters; permanent magnet synchronous generator (PMSG);
power electronics; squirrel cage induction generator (SCIG);
wind energy conversion systems (WECS); wind farms; wound
rotor induction generator (WRIG); wound rotor synchronous
generator (WRSG)
I . I N T R O D U C T I O N
Due to depleting fossil fuels and environmental concerns
about global warming, renewable energy sources have
emerged as a new paradigm to fulfill the energy needs of
our society. In recent years, electricity production from the
hydro, solar, wind, geothermal, tidal, wave and biomass
energy sources has come under increasing attention [1],
[2]. By 2012, the power production from renewable energy
sources worldwide exceeded 1470 gigawatt (GW) repre-
senting approximately 19% of global energy co.
Wind power capacity has experienced tremendous growth in the Past decade.This paper presents the recent developments in wind energy conversion systems, and their social and environmental benefits. Integration of large scale wind farms into power systems presents some challenges that must be addressed, such assystem operation and control, system stability, and power quality
A PROPOSAL FOR WIND-ENERGY CONVERSION FOR LOW WIND–SPEED AREAS OF INDIAIAEME Publication
This is the methodology to conversion of electricity through wind energy using convergent nozzle in low wind speed area. By the help of this process of conversion we convert low wind speed in sufficient power conversion with the use of nozzle. Then this maximizes the wind speed, that maximum wind speed rotate fan blade at useful speed level. And then sufficient amount of energy are produced
In the early twentieth century, major representatives of the Jadid movement became active participants in the socio-political processes in the Turkestan region. Usmonkhoja Polatkhoja, a progressive from Bukhara, was one of the beams not only in the Emirate of Bukhara, but also in Turkestan. He first participated in the reforms and progressives, and later in the national liberation movements, and fought for the prosperity and independence of the country.This article provides information about Usmonkhoja's life and work in Jadidism, revolts, national liberation struggles, and emmigiration.
Flood is one of the natural disaster known to be part of the earth biophysical processes, which its occurrence can be devastating; due to mostly anthropogenic activities and climatological factors. The aim of the research is to identify and map the extent at which the impact of flood due to intense rainfall and rise in water in the study area using geospatial techniques and the specific objectives are to carry out terrain analysis of the study area and to generate flood indicator maps of the study area. The study analyzed rain fall data;, the drainage system and Shuttle Radar Topographic Mission (SRTM 30m) of the area. ArcGIS 10.8 was to modelled and to generate the contributing factors map of the study area. The drainage system was generated through on-screen digitization of topographic map of scale 1:50,000 of Ondo South-West. The mean annual rainfall of Lagos State was generated in the ArcGIS environment from the rainfall data through spatial analysis tool. The SRTM was used in terrain analysis of the study area. The results generated showed the lowest mean annual rain fall of the area 1,700mm and the highest mean annual rain fall was 2,440mm. Digital elevation model (DEM), slope, flow direction were generated from the SRTM. Drainage density of the area was generated using the drainage system. The slope map of the entire area which are classified into five slope classes of very high (14%-48.5%) to high (7.6%-13.9%) to moderately high (4.2%-7.6%) to low (1.5%-4.2%) and very low (0. % - 1.2%).
Work study is a catch-all phrase encompassing a variety of methodologies, including method research and work measurement, that are applied in a variety of contexts and lead to a systematic assessment of all elements that affect the efficiency and economy of the situation under evaluation that is meant to be improved. The main aim of this study is to examine and enhance the process token in manufacturing a Perfume of the famous, well-known, aromatic, and beautiful Taif Roses. Some changes in the process has been suggested using method study and time study method which lead to reduction in process time, labor cost and production cost.
Workers are the maximum precious method of an association. Their importance to institutions requires not most effective the want to draw the trendy bents but additionally the need to preserve them for a long term. This paper specializes in reviewing the findings of former research carried out with the aid of colourful experimenters with the quit to identify determinants factors of hand retention. This exploration almost looked at the subsequent broad factors improvement openings, reimbursement, work- lifestyles balance, operation/ management, work terrain, social aid, autonomy, training and improvement.
Watering plants during the correct time is very important due to scientific reasons. Both underwatering, as well as overwatering, can lead to the growth of unhealthy plants or in extreme cases, the death of the plant/tree. These issues which are the case with most self-gardeners and plant lovers can be solved using the smart irrigation technique. The main purpose of this innovation is to assist plant lovers to continue their passion to grow plants at home with ease. Smart irrigation system helps in monitoring the moisture level which majorly affects plant growth besides other factors such as sunlight, fertility of the soil, etc. The digital planting pot has been designed in a way that it effectively incorporates the idea of smart irrigation. Arduino Uno R3 has been used as the main chip in this project along with a few other components like a soil moisture sensor, relay, and water pump. This project requires coding to synchronize all the components, and function properly. A required test has been carried out to review the functioning of the mechanism. The project was tested by once using the soil with enough moisture in the pot and then the soil with the least moisture. Both times, it worked exactly how it was supposed to function. When the soil with the least moisture was tested, there was a clear indication of a low level of moisture and accordingly, the water pump got triggered to water the plant, and when the soil with enough moisture was tested, there was again the clear indication of the correct level of moisture and the water pump was inactive. All the readings which were displayed on the LCD were checked back and forth during the project. The outcomes were the same as expected. Hence, it shows that every component in this project is actively functioning and the whole project is effectively designed.
Because of its accessibility and flexibility, cloud technology is among the most notable innovations in today's world. Having many service platforms, such as GoogleApps by Google, Amazon, Apple, and so on, is well accepted by large enterprises. Distributed cloud computing is a concept for enabling every-time, convenient, on-demand network access to processing resources including servers, storage devices, networks, and services that may be mutually configured. The major security risks for cloud computing as identified by the Cloud security alliance (CSA) have been examined in this study. Also, methods for resolving issues with cloud computing technology's data security and privacy protection were systematically examined.
This study's goal is to present Solutions for Determining the importance level of criteria in creating cultural resources’ attractiveness from tourists’ evaluation. Data were collected from 558 international tourists who chose Vietnam as the destination for tourism.
The study points out that we need to resolve challenges such as: building a safe, friendly destination, etc., destinations need to review and re-evaluate the services of their products and tourist attractions to prepare for the largest number of visitors and stimulate the domestic tourism market is a good solution: To boost the domestic tourism market, it is necessary to increase domestic flights and train connections to major tourist destinations.
A new convenient and efficient route for the synthesis of two very important hydroxo-bridged stepped-cubane copper complexes viz: [Cu4(bpy)4Cl2(OH)4]Cl2.6H2O (1) and [Cu4(phen)4Cl2(OH)4]Cl2.6H2O (2) have been obtained. This synthetic route from the mononuclear CubpyCl2 complex is easier, more reproducible and afforded the complex in a much higher yield than the other two previously reported procedures which were equally serendipitously discovered. The purity and formation of the complexes were confirmed with elemental (C,H,N) analysis and the details of the UV-Vis, Fourier transform infrared, electrospray ionization mass spectra of both complexes and the single crystal X-ray crystallography of 1 are presented and discussed. X-ray crystallography confirms the absolute structure of the complexes. The complexes were formed via the connection of four copper atoms to four hydroxide bridging ligands and four bipyridyl ligands with two chloride ligands. There are two coordinate environments around two pairs of copper atoms (CuN2ClO2 and CuN2O3) and each copper atom is pentacoordinate with square pyramidal geometry.
Artocarpus heterophyllus Lam., which is commonly known as jackfruit is a tropical fruit, belonging to Moraceae family, native to Western Ghats of India and common in Asia, Africa, and some regions in South America. It is known to be the largest edible fruit in the world. The Jackfruit is an extremely versatile and sweet tasting fruit that possess high nutritional value. Jackfruit is rich in nutrients including carbohydrates, proteins, vitamins, minerals, and phytochemicals. The jackfruit has diverse medicinal uses especially antioxidant, anti-inflammatory, antimicrobial and antiviral properties, anticancer and antifungal activity, anthelminthic activity. Traditionally, this plant is used in the treatment of various diseases especially for treatment against inflammation, malarial fever, diarrhoea, diabetes and tapeworm infection. Jackfruit is a good natural source of phytochemicals such as phenolics, flavonoids and tannins, saponins. The health benefits of jackfruit have been attributed to its wide range of physicochemical applications. The use of jackfruit bulbs and its parts has also been reported since ancient times for their therapeutic qualities. The beneficial physiological effects may also have preventive application in a variety of pathologies.
Myogenic differentiation requires to be exactly explored for the effective treatment of fracture. The speed of healing is affected by skeletal muscle, linked to activation of specific myogenic transcription factors during the repair process. In previous study, we discovered that psoralen enhanced differentiation of osteoblast in primary mouse. In the current study, we show that psoralen stimulates myogenic differentiation through the secretion of factors to hone the quality of repair in fractured mice. 3-month old mice were treated with corn oil or psoralen followed by a tibial fracture surgery. Fractures were tested 7, 14, and 21 days respectively later by histology and images observation. Skeletal muscles including soleus muscle and posterior tibial muscle around the damaged bone were collected for quantitative real-time PCR, HE staining, as well as western blot. Daily treatment with psoralen at seven, fourteen days or twenty-one days improves protein or mRNA levels responsible for the whole myogenic differentiation process, makes the muscle fibers more tightly aligned, and promotes callus formation and development. This data shows that high levels of myogenic transcription factors in the process of fracture healing in mice foster the repair of damaged muscles, and indicates a pharmacological approach that targets myogenic differentiation to improve fracture repair. This also reflects the academic thought of "paying equal attention to both muscles and bones" in the prevention and treatment of fracture healing.
The current pandemic has generated the search for new reliable and economic alternatives for the detection of SARS-CoV-2, which produces the COVID-19 disease, one of the recommendations by the World Health Organization, is the detection of the virus by RT-qPCR methods from upper respiratory tract samples. The discomfort of the pharyngeal nasopharyngeal swab described by patients, the requirement of trained personnel, and the generation of aerosols, are factors that increase the risk of infections in this type of intake. It is known that the main means of transmission of SARS-CoV-2 is through aerosols or small droplets, which is why saliva is important as a relevant means of detecting COVID-19. In this study, a modified method based on SARS-CoV-2 RNA release from saliva is described, avoiding the isolation and purification of the genetic material and its quantification of viral copies; the results are compared with paired pharyngeal/nasopharyngeal swab samples (EF/EN). Results showed good agreement in saliva samples compared to EF/EN samples. On average, a sensitivity for virus detection of 80% was demonstrated in saliva samples competing with EF/EN samples. The use of saliva is a reliable alternative for the detection of SARS-CoV-2 by means of RT-PCR in the first days of infection, having important advantages over the conventional method. Saliva still needs to be studied completely to evaluate the detection capacity of the SARS-CoV-2 nucleic acid, however, the described process is viable, due to the decrease in materials and supplies, process times, the increment in the sampling and improvement of laboratory performance.
A recent study establishes that since 1970, there has been an ecological gap between human needs and the planet's resources, with annual resource demand exceeding the bio-productivity of the planet. Specifically, humanity utilises equivalent of 1.75 earths to produce the ecological resources used, with half of this attributable to food consumption. The present work therefore seeks to provide an empirically-based insight into the environmental sustainability of the EF of food consumption in Ijebu Ode. A descriptive cross-sectional approach was used, and primary data were collected from 400 systemically sampled households via structured questionnaires and analysed descriptively using Microsoft Excel and inferentially using mathematical models for calculating ecological footprints. Findings revealed that the household EF of food consumption in Ijebu Ode is 0.05gha per capita, with the footprint of cereal consumption (0.17gha; 37%) taking the major share, followed by meat with a footprint of 0.11gha (23.9%). As a result, it was concluded that Ijebu Ode has sustainable food consumption, which is necessary for its environmental sustainability. However, the sustenance of the former requires creating awareness of the need for sustainable consumption and prioritisation of integrated and population-wide policies and food intervention initiatives to encourage attitudinal change in favour of sustainable food consumption while fostering sustainable food production strategies amidst current environmental realities.
The symmetry occurs in most of the phenomena explained by physics, for example, a particle has positive or negative charges, and the electric dipoles that have the charge (+q) and (-q) which are at a certain distance (d), north or south magnetic poles and for a magnetic bar or magnetic compass with two poles: North (N) and South (S) poles, spins up or down of the electron at the atom and for the nucleons in the nucleus In this form, the particle should also have mass symmetry. For convenience and due to later explanations, I call this mass symmetry or mass duality as follows: mass and mass cloud. The mass cloud is located in the respective orbitals given by the Schrödinger equation. The orbitals represent the possible locations or places of the particle which are determined probabilistically by the respective Schröndiger equation.
Metal-organic molybdenum complexes were synthesized by the hydrothermal method using ammonium heptamolybdate as the metallic source, and as the organic ligand terephthalic acid (BDC) or bis(2-hydroxyethyl) terephthalate (BHET), obtained via glycolysis of poly(ethylene)terephthalate (PET). The BDC-Mo and BHET-Mo complexes were characterized by XRD, N2 physisorption, TGA, ATR-FTIR, SEM, XPS and their in vitro biocompatibility was tested by porcine fibroblasts viability. The results show that molybdates (MoO4-2) are coordinated to the carbonyl functional groups of BDC and BHET by urea bonding (-NH-CO-NH-) which is related to their high biocompatibility and high thermal stability. These organic molybdate complexes possess rectangular prism particles made up of rods arrays characteristics of molybdenum oxides (MoO3). The organic complexes BDC-Mo and BHET-Mo do not show to be cytotoxic for porcine dermal fibroblasts growing on their surface for up to 48 h of culture.
Exercise training with varying intensity increases maximal oxygen intake (VO2max), a strong predictor of cardiovascular and all-cause mortality. Purpose: The aim of this study was to find out the influence of low intensity aerobic training on the vo2 max in 11 to 14 years school girls in Hyderabad district. Methodology: The research scholar has randomly selected thirty (N=30) high school girls were selected as subjects and their age ranged between 11 to 14 years. The subjects were divided into two equal groups, each group consist of 15 total 30. Group one acted as experimental group (EG) and group two acted as control group (CG). The dependent variable vo2 max was selected and it is measured by manual test. Statistical Tool: The statistical tool paired sample ‘t’ test was used for analysing of the data and the obtained ‘t’ ratio was tested for significance at 0.05 level of confidence. Results: The analysis of the data revealed that there was a significant improvement on vo2 max by the application of low intensity aerobic.
Hybrid rice has the potential to outperform existing inbred rice and was said to have the potential to produce 14-20 % more yield. In response, Malaysia Government has introduced its very own first Hybrid Rice Variety knew as Kadaria 1 developed by MARDI. This is in line with one of the strategies outlined in Dasar Agromakanan Negara (DAN) 2011-2020 as an approach to increasing rice productivity within Malaysia. The next step would be developing our hybrid seed rice production system. Therefore, an experiment to determine the planting ratio and planting distance between 0025A (A)-a hybrid with MR283 (R)-inbreed variety was carried out. Planting ratios studied in this study were 2:4, 2:6, 2:8, and 2:10 while planting distance was 14 x 30 cm, 16 x 30 cm, and 18 x 30 cm. Statistical analyses suggested that yield R, yield A, and panicle number A were significantly affected by planting ratios while yield A was significantly affected by an interaction between planting distance and planting ratios. Panicle number A performed significantly higher at planting ratios of 2:4 compared to 2:10. Yield R shows higher significant performance under ratio 2:6 compared to 2:4 and 2:8. Relatively, yield A performed the best under planting distance of 18 x 30 cm. Furthermore, under this particular planting distance, the planting ratio of 2:10 shows the highest significant figure while 2:8 exhibits statistical parity. Both yield R and yield A were significantly affected by planting ratios and have a significant positive association with each other. Therefore, the planting ratio of 2:10 should be the best since it contributed to significantly highest value for yield A while yield R under 2:10 shows statistical parity with 2:6 which was the highest significant value. In conclusion, the combination of 2:10 with a planting distance of 18 x 30 cm was the best since it shows best potential for both yields A and yield R
Cassava plays an important role in improving food security and reducing poverty in rural areas. Despite its importance, its production in Senegal remains low compared to other African countries. Nowadays, it is confronted with numerous constraints. It is in this context that a study was conducted on the cassava production system in the Thiès "cassava granary" region, with the objective of examining farmers' cultivation practices. It was conducted in eight communes located in the department of Tivaouane, some of which are located in the Niayes agro-ecological zone and others in the central-northern groundnut basin. Surveys were conducted among the largest cassava producers in these communes. Analysis of the results showed that cassava is only grown in the rainy season with the same cultivation practices that have been used for years. Of the five varieties listed by the President of the Senegalese Cassava Interprofession, only four are grown in the areas surveyed. The Terrasse (43%) and Kombo (36%) varieties are grown more by our respondents in the Niayes area. Soya (75%) and Wallet "Parydiey" (20% of our sample) dominate in the central-northern groundnut basin.
Cassava plays an important role in improving food security and reducing poverty in rural areas. Despite its importance, its production in Senegal remains low compared to other African countries. Nowadays, it is confronted with numerous constraints. It is in this context that a study was conducted on the cassava production system in the Thiès "cassava granary" region, with the objective of examining farmers' cultivation practices. It was conducted in eight communes located in the department of Tivaouane, some of which are located in the Niayes agro-ecological zone and others in the central-northern groundnut basin. Surveys were conducted among the largest cassava producers in these communes. Analysis of the results showed that cassava is only grown in the rainy season with the same cultivation practices that have been used for years. Of the five varieties listed by the President of the Senegalese Cassava Interprofession, only four are grown in the areas surveyed. The Terrasse (43%) and Kombo (36%) varieties are grown more by our respondents in the Niayes area. Soya (75%) and Wallet "Parydiey" (20% of our sample) dominate in the central-northern groundnut basin.
We are witnessing very demanding and stressful times in which we live, and an occupation that is particularly exposed to stress and different working conditions is the job of a nurse. Exposing themselves to everyday challenges and stressful situations, nurses reach a stage of great emotional and physical exhaustion, lethargy, dissatisfaction, and poorer work achievements, which we know as burnout. The aim of this paper was to determine whether there is and to what extent professional burnout is present in nurses and technicians working in nursing homes across Slovenia and Croatia. The paper is answering the questions of the extent of the burnout influenced by individual characteristics (age, education, years of service and work experience at the current workplace). The study involved a validated questionnaire “The Oldenburg Burnout Inventory (OLBI)” to measure professional burnout. Surveying of the nurses was conducted online at their home institutions. The results show that all respondents have a medium or high level of professional burnout, while no one has a low level or shows no signs of burnout. In terms of age, the group from 55-65 years of age had the highest relative level of burnout in the age group category. With regard to education, the highest burnout was measured in registered nurses.
Hepatitis B and C are one of the most commonly transmitted viral infections through needlestick injury apart from HIV. It is highly prevalent in India and many other developing countries. It accounts for high mortality rate globally amongst low socio-economic groups of individuals. Healthcare workers, especially dental professionals are at higher risk of infection due to high exposure to saliva, blood and sharps. Accidental occupational exposure to non-sterile conditions and its development to more critical and fatal conditions can be reduced through vaccination, prophylactic medications and practicing high safety measures.
This review article focuses on transmission of hepatitis through sharps injuries in medicine, especially dentistry, its prevention, management, post-exposure prophylaxis and the corresponding content.
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Effectual and Lossless Electrical Power Generation Methodology using Wind-Lens Technology
1. Asian Journal of Applied Science and Technology (AJAST)
Volume 1, Issue 1, February 2017
2017 AJAST All rights reserved. www.ajast.net
Page | 12
Effectual and Lossless Electrical Power Generation Methodology using Wind-Lens
Technology
G. Ramya#
and N.Balakumar*
# Assistant Professor, Tamilnadu College of Engineering, Coimbatore, Tamilnadu, India. Email: ramyagovindasamy@gmail.com
*Assistant Professor, Tamilnadu College of Engineering, Coimbatore, Tamilnadu, India. Email: eee59_bala@yahoo.co.in
Article Received: 02 February 2017 Article Accepted: 11 February 2017 Article Published: 15 February 2017
1. INTRODUCTION
The utilization of wind energy can be dated back to 5000 B.C.
when sail boats were propelled across the river Nile. It was
recorded that from 200 B.C. onwards wind was used as an
energy source to pump water, grind grain, and drive vehicles
and ships in ancient China and Middle East. The first
documented windmill was in a book Pneumatics written by
Hero of Alexandria around the first century B.C. or the first
century A.D. Effectively, these wind mills are used to convert
kinetic energy into mechanical energy [1].
The use of wind energy to generate electricity first appeared
in the late 19th
century but did not gain ground owing to the
then dominance of steam turbines in electricity generation.
The interest in wind energy was renewed in the mid-1970s
following the oil crises and increased concerns over resource
conservation. Initially, wind energy started to gain popularity
in electricity generation to charge batteries in remote power
systems, residential scale power systems, isolated or island
power systems, and utility networks.
These wind turbines themselves are generally small (rated less
than 100kW) but could be made up to a large wind farm (rated
5MW or so). It was until the early 1990s when wind projects
really took off the ground, primarily driven by the
governmental and industrial initiatives. It was also in 1990s
there seemed a shift of focus from onshore to offshore
development in major wind development countries, especially
in Europe [2]. Offshore wind turbines were first proposed in
Germany in 1930s and first installed in Sweden in 1991 and in
Denmark in 1992. By July 2010, there were 2.4 GW of
offshore wind turbines installed in Europe. Compared to
onshore wind energy, offshore wind energy has some
appealing attributes such as higher wind speeds, availability
of larger sites for development, lower wind sheer and lower
intrinsic turbulence intensity.
But the drawbacks are associated with harsh working
conditions, high installation and maintenance costs. For
offshore operation, major components should be modernized
with additional anti-corrosion measures and
de-humidification capacity. In order to avoid unscheduled
maintenance, they should also be equipped with
fault-ride-through capacity to improve their reliability. Over
the last three decades, wind turbines have significantly
evolved as the global wind market grows continuously and
rapidly. By the end of 2009, the world capacity reached a total
of 160 GW [3].
In the global electricity market, wind energy penetration is
projected to rise from 1% in 2008 to 8% in 2035. This is
achieved simply by developing larger wind turbines and
employing more in the wind farm. In terms of the size, large
wind turbines of the MW order began to appear in the EU, the
US and now in China and India. Typically, the large installed
wind turbines in utility grids are between 1.5-5MW whilst 7.5
and 10 MW are under extensive development. Nowadays,
modern wind turbines are reliable, quiet, cost-effective and
commercially competitive while the wind turbine
technologies are proven and mature. At present, technical
challenges are generally associated with ever-growing wind
turbine size, power transmission, energy storage, energy
efficiency, system stability and fault tolerance. Currently,
wind power is widely recognized as a main feasible source of
renewables which can be utilized economically in large
quantity. Taking the United Kingdom for example, the usable
offshore wind energy alone is enough to provide three times
more than the required electricity consumption in the country,
given sufficient support. However, wind power fluctuates by
its nature and such applications demand high reliability and
high availability while the market is still looking to reduce
weight, complexity and operational costs [4].
ABSTRACT
Wind energy is playing a critical role in the establishment of an environmentally sustainable low carbon economy. This paper presents an overview of
wind turbine generator technologies and compares their advantages and drawbacks used for wind energy utilization. Traditionally, DC machines,
synchronous machines and squirrel-cage induction machines have been used for small scale power generation. For medium and large wind turbines
(WTs), the doubly-fed induction generator (DFIG) is currently the dominant technology while permanent magnet (PM), switched reluctance and high
temperature superconducting generators are all extensively researched and developed over the years. In this paper, the topologies and features of these
machines are discussed with special attention given to their practical considerations involved in the design, control and operation. It is hoped that this
paper provides quick reference guidelines for developing wind turbine generation systems.
Keywords: Diffuser, wind turbine, wind lens technology, electrical power and energy recovery system.
2. Asian Journal of Applied Science and Technology (AJAST)
Volume 1, Issue 1, February 2017
2017 AJAST All rights reserved. www.ajast.net
Page | 13
Fig.1. Progression of expected wind turbine evolution to
deeper water
2. WIND TURBINES
Clearly, wind energy is high on the governmental and
institutional agenda. However, there are some stumbling
blocks in the way of its widespread. Wind turbines come with
different topologies, architectures and design features. Some
options wind turbine topologies are as follows, Rotor axis
orientation: horizontal or vertical, Rotor position: upwind or
downwind of tower, Rotor speed: fixed or variable, Hub:
rigid, teetering, gimbaled or hinged blades, Rigidity: still or
flexible, Number of blades: one, two, three or even more,
Power control: stall, pitch, yaw or aerodynamic surfaces and
Yaw control: active or free. This section focuses only on
horizontal-axis wind turbines (HAWTs), which are the
prevailing type of wind turbine topology.
Fig.2. Schematic of a wind turbine generation system
Wind turbines include critical mechanical components such
as turbine blades and rotors, drive train and generators. They
cost more than 30% of total capital expenditure for offshore
wind project. In general, wind turbines are intended for
relatively inaccessible sites placing some constraints on the
designs in a number of ways. For offshore environments [5],
the site may be realistically accessed for maintenance once
per year. As a result, fault tolerance of the wind turbine is of
importance for wind farm development. One of key
components in the wind turbine is its drive train, which links
aerodynamic rotor and electrical output terminals.
Optimization of wind turbine generators cannot be realized
without considering mechanical, structural, hydraulic and
magnetic performance of the drive train. Generally, they can
be broken down into four types according to their structures:
Conventional: gearbox and high speed generator with few
pole pairs, Direct drive: any drive train without a gearbox and
low speed generator with many pole pairs, Hybrid: any drive
train with a gearbox and the generator speed between the
above two types and Multiple generators: any drive train with
more than one generator. Drive train topologies may raise the
issues such as the integration of the rotor and
gearbox/bearings, the isolation of gear and generator shafts
from mechanical bending loads, the integrity and load paths.
Although it may be easier to service separate wind turbine
components such as gearboxes, bearings and generators, the
industry is increasingly in favor of system design of the
integrated drive train components [6].
3. WIND TURBINE GENERATORS
One of limiting factors in wind turbines lies in their generator
technology. There is no consensus among academics and
industry on the best wind turbine generator technology.
Traditionally, there are three main types of wind turbine
generators (WTGs) which can be considered for the various
wind turbine systems, these being direct current (DC),
alternating current (AC) synchronous and AC asynchronous
generators. In principle, each can be run at fixed or variable
speed [7]. Due to the fluctuating nature of wind power, it is
advantageous to operate the WTG at variable speed which
reduces the physical stress on the turbine blades and drive
train, and which improves system aerodynamic efficiency and
torque transient behaviors.
Fig.3. Schematic of a DC generator system
3.1 DC Generator Technologies
In conventional DC machines, the field is on the stator and the
armature is on the rotor. The stator comprises a number of
poles which are excited either by permanent magnets or by
DC field windings. If the machine is electrically excited, it
tends to follow the shunt wound DC generator concept. It
consists of a wind turbine, a DC generator, an insulated gate
bipolar transistor (IGBT) inverter, a controller, a transformer
and a power grid. For shunt wound DC generators, the field
current (and thus magnetic field) increases with operational
speed whilst the actual speed of the wind turbine is
determined by the balance between the WT drive torque and
the load torque [8]. The rotor includes conductors wound on
an armature which are connected to a split-slip ring
commentator. Electrical power is extracted through brushes
connecting the commentator which is used to rectify the
generated AC power into DC output. Clearly, they require
regular maintenance and are relatively costly due to the use of
commutators and brushes. In general, these DC WTGs are
unusual in wind turbine applications except in low power
3. Asian Journal of Applied Science and Technology (AJAST)
Volume 1, Issue 1, February 2017
2017 AJAST All rights reserved. www.ajast.net
Page | 14
demand situations where the load is physically close to the
wind turbine, in heating applications or in battery charging.
3.2 AC Synchronous Generator Technologies
Since the early time of developing wind turbines,
considerable efforts have been made to utilize three-phase
synchronous machines. AC synchronous WTGs can take
constant or DC excitations from either permanent magnets or
electromagnets and are thus termed PM synchronous
generators (PMSGs) and electrically excited synchronous
generators (EESGs), respectively. When the rotor is driven by
the wind turbine, a three-phase power is generated in the
stator windings which are connected to the grid through
transformers and power converters. For fixed speed
synchronous generators, the rotor speed must be kept at
exactly the synchronous speed. Otherwise synchronism will
be lost. Synchronous generators are a proven machine
technology since their performance for power generation has
been studied and widely accepted for a long time. In theory,
the reactive power characteristics of synchronous WTGs can
be easily controlled via the field circuit for electrical
excitation [9].
Fig.4. Cutaway of a synchronous generator
Nevertheless, when using fixed speed synchronous
generators, random wind speed fluctuations and periodic
disturbances caused by tower-shading effects and natural
resonances of components would be passed onto the power
grid. Furthermore, synchronous WTGs tend to have low
damping effect so that they do not allow drive train transients
to be absorbed electrically. As a consequence, they require an
additional damping element (e.g. flexible coupling in the
drive train), or the gearbox assembly mounted on springs and
dampers. When they are integrated into the power grid,
synchronizing their frequency to that of the grid calls for a
delicate operation. In addition, they are generally more
complex, costly and more prone to failure than induction
generators. In the case of using electromagnets in
synchronous machines, voltage control takes place in the
synchronous machine while in permanent magnet excited
machines, voltage control is achieved in the converter circuit.
In recent decades, PM generators have been gradually used in
wind turbine applications due to their high power density and
low mass. Often these machines are referred to as the
permanent magnet synchronous generators (PMSGs) and are
considered as the machine of choice in small wind turbine
generators. The structure of the generator is relatively
straightforward. The rugged PMs are installed on the rotor to
produce a constant magnetic field and the generated
electricity is taken from the armature (stator) via the use of the
commutator, slip rings or brushes. Sometimes the PMs can be
integrated into a cylindrical cast aluminum rotor to reduce
costs. The principle of operation of PM generators is similar
to that of synchronous generators except that PM generators
can be operated asynchronously. The advantages of PMSGs
include the elimination of commutator, slip rings and brushes
so that the machines are rugged, reliable and simple. The use
of PMs removes the field winding (and its associated power
losses) but makes the field control impossible and the cost of
PMs can be prohibitively high for large machines [10].
Because the actual wind speeds are variable, the PMSGs
cannot generate electrical power with fixed frequency. As a
result, they should be connected to the power grid through
ACDC-AC conversion by power converters. That is, the
generated AC power (with variable frequency and magnitude)
is first rectified into fixed DC and then converted back into
AC power (with fixed frequency and magnitude). It is also
very attractive to use these permanent magnet machines for
direct drive application. Obviously, in this case, they can
eliminate troublesome gearboxes which cause the majority of
wind turbine failures. The machines should have large pole
numbers and are physically large than a similarly rated geared
machine.
Fig.5. Cutaway of a permanent magnet synchronous generator
A potential variant of synchronous generators is the
high-temperature superconducting generator. The machine
comprises the stator back iron, stator copper winding, HTS
field coils, rotor core, rotor support structure, rotor cooling
system, cryostat and external refrigerator, electromagnetic
shield and damper, bearing, shaft and housing. In the machine
design, the arrangements of the stator, rotor, cooling and
gearbox may pose particular challenges in order to keep HTS
coils in the low temperature operational conditions.
Fig.6. Schematic of a HTS synchronous generator system
4. Asian Journal of Applied Science and Technology (AJAST)
Volume 1, Issue 1, February 2017
2017 AJAST All rights reserved. www.ajast.net
Page | 15
Superconducting coils may carry 10 times the current than
conventional copper wires with negligible resistance and
conductor losses. Without a doubt, the use of superconductors
would eliminate all field circuit power loss and the ability of
superconductivity to increase current density allows for high
magnetic fields, leading to a significant reduction in mass and
size for wind turbine generators. Therefore, superconducting
generators provide much promise in high capacity and weight
reductions, perhaps suited better for wind turbines rated 10
MW or more. In 2005, Siemens successfully launched the
world’s first superconducting wind turbine generator, which
was a 4MW synchronous generator [11]. However, there are
many technical challenges to face especially for the long-life,
low-maintenance wind turbine systems. For instance, there is
always a necessity to maintain cryogenic systems so that the
time to cool down and restore operation following a stoppage
will be an additional issue.
3.3. AC Asynchronous Generators
Whilst conventional power generation utilizes synchronous
machines, modern wind power systems use induction
machines extensively in wind turbine applications. These
induction generators fall into two types: fixed speed induction
generators (FSIGs) with squirrel cage rotors (sometimes
called squirrel cage induction generators-SQIGs) and doubly
fed induction generators (DFIGs) with wound rotors. When
supplied with three-phase AC power to the stator, a rotating
magnetic field is established across the airgap. If the rotor
rotates at a speed different to synchronous speed, a slip is
created and the rotor circuit is energized. Generally speaking,
induction machines are simple, reliable, inexpensive and well
developed. They have high degree of damping and are
capable of absorbing rotor speed fluctuations and drive train
transients (i.e. fault tolerant). However, induction machines
draw reactive power from the grid and thus some form of
reactive power compensation is needed such as the use of
capacitors or power converters. For fixed-speed induction
generators, the stator is connected to the grid via a transformer
and the rotor is connected to the wind turbine through a
gearbox. The rotor speed is considered to be fixed (in fact,
varying within a narrow range). Up until 1998 most wind
turbine manufacturers built fixed-speed induction generators
of 1.5 MW and below. These generators normally operated at
1500 revolutions per minute (rpm) for the 50 Hz utility grid,
with a three-stage gearbox. SCIGs led the wind turbine market
until the last millennium, overtaken by the wide adoption of
DFIGs.
Nowadays, over 85% of the installed wind turbines utilize
DFIGs and the largest capacity for the commercial wind
turbine product with DFIG has increased towards 5MW in
industry. In the DFIG topology, the stator is directly
connected to the grid through transformers and the rotor is
connected to the grid through PWM power converters. The
converters can control the rotor circuit current, frequency and
phase angle shifts. Such induction generators are capable of
operating at a wide slip range (typically ±30% of synchronous
speed). As a result, they offer many advantages such as high
energy yield, reduction in mechanical stresses and power
fluctuations, and controllability of reactive power. For
induction generators, all the reactive power energizing the
magnetic circuits must be supplied by the grid or local
capacitors. Induction generators are prone to voltage
instability. When capacitors are used to compensate power
factor, there is a risk of causing self-excitation. Additionally,
damping effect may give rise to power losses in the rotor.
There is no direct control over the terminal voltage (thus
reactive power), nor sustained fault currents.
Fig.7. Per-phase equivalent circuit of the DFIG
3.4 Switched Reluctance Generator Technologies
Switched reluctance WTGs are characterized with salient
rotors and stator. As the rotor rotates, the reluctance of the
magnetic circuit linking the stator and rotor changes, and in
turn, induces currents in the winding on the armature (stator).
Fig.8. Schematic of a switched reluctance generator system
The reluctance rotor is constructed from laminated steel
sheets and has no electrical field windings or permanent
magnets. As a result, the reluctance machine is simple, easy to
manufacture and assembly. An obvious feature is their high
reliability because they can work in harsh or high-temperature
environments. Because the reluctance torque is only a fraction
of electrical torque, the rotor of switched reluctance is
generally large than other with electrical excitations for a
given rated torque. If reluctance machines are combined with
direct drive features, the machine would be extremely large
and heavy, making them less favorable in wind power
applications.
4. DESIGN CONSIDERATIONS AND CHALLENGES
Generally speaking, wind turbine generators can be selected
from commercially available electrical machines with or
without minor modifications. If a wind turbine design is
required to match a specific site, some key issues should be
taken into account. These include: Choice of machines, Type
of drive train, Brush topology, Rated and operating speeds,
Rated and operating torques, Tip speed ratio, Power and
current, Voltage regulation (synchronous generators),
Methods of starting, Starting current (induction generators),
Synchronizing (synchronous generators), Cooling
arrangement, Power factor and reactive power compensation
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(induction generators), Power converter topology, Weight
and size, Protection (offshore environment) and Capital cost
and maintenance. Among these design considerations, the
choice of operating speed, drive type, brush topology, and
power converter are focused and further analyzed in details.
Fig.9. Variable speed control system
4.1 Fixed or Variable Speed
Clearly, it is beneficial to operate WTGs at variable speed.
The reasons are several. When the wind speed is below rated,
running the rotor speed with the wind speed and keeping the
tip speed ratio constant ensure that the wind turbine will
extract the maximum energy. Variable speed operation helps
reduce fluctuating mechanical stresses on the drive train and
machine shaft, the likelihood of fatigue and damage as well as
aerodynamically generated acoustic noise. The rotor can act
as a regenerative storage unit (e.g. flywheel), smoothing out
torque and power fluctuations prior to entering the drive train.
Direct control of the air-gap torque also aids in minimizing
gearbox torque fluctuations. Since there is a frequency
converter between the wind turbine generator and the power
grid, it becomes possible to decouple the network frequency
and the rotor rotational speed. This permits variable speed
operation of the rotor and controllability of air-gap torque of
the machine. Furthermore, variable speed operation enables
separate control of active and reactive power, as well as
power factor. In theory, some wind turbine generators may be
used to compensate the low power factor caused by
neighboring consumers. In economic terms, variable speed
wind turbine can produce 8-15% more power than fixed speed
counterparts. Nonetheless, the capital costs will be increased
arising from the variable speed drive and power converters, as
well as increased complicity and control requirements.
In principle, variable speed operation can be achieved
mechanically by the use of differential gearboxes or
continuously-variable transmission systems, based on the
control of speed and angular speed of gyroscopes. But the
general practice is to achieve this goal by electrical means.
There are two major methods in use: broad range and narrow
range variable speed. The former refers to a wide operational
range from zero to the full rated speed where the latter refers
to a narrow operational range between a fractions (up to
±50%) of synchronous speed. In reality, this latter range is
practically sufficient and can saving significant costs on
power electronic converters.
In the design of variable-speed wind turbines, three control
aspects in association with the wind speed need to consider.
First, a constant optimized tip speed should be maintained to
achieve maximum aerodynamic efficiency by varying the
rotor speed with the actual wind speed. Second, the rotor
speed should be maintained constant after the rotor has
reached its rated speed but the power has not, in the case of
moderate winds. When the wind speed is higher, the control is
to maintain a constant rated power via the pitch angle control
or stall control. Whilst using the pitch angle control, the blade
pitch is varied to control the rotor speed together with the
generator torque.
4.2 Direct or Geared Drive
In a geared wind turbine, the generator speed increases with
the gear ratio so that the reduction in machine weight is offset
by the gain in gearbox weight. For instance, the wind turbine
operates at a speed of 15 rpm and the generator is designed to
operate 1200 rpm (for 60 Hz). An up-speed gearbox of 1:80 is
required to match the speed/torque of the turbine with these of
the generator. However, historically, gearbox failures are
major challenges to the operation of wind farms. This is
especially true for offshore wind turbines which are situated
in harsh and less-accessible environments. Because of this,
direct drive systems are increasingly desired in new wind
turbine systems. One example is the excited synchronous
generator with wound field rotor is a well-established design
in the marketplace; and another may be a popular neodymium
magnet generator design which also attracts much attention in
the marketplace. Obviously, direct drive configuration
removes the necessity for gears and the related reliability
problems. Therefore, some wind turbine manufacturers are
now moving toward direct-drive generators to improve
system reliability. Since wind turbine generators are operated
with power electronic converters, direct drive topology can
provide some flexibility in the voltage and power
requirements of the machines. Nonetheless, a drawback of the
direct drive is associated with the low operating speed of the
turbine generator. As the nominal speed of the machine
reduces, the volume and weight of its rotor would increase
approximately in inverse proportion for a given power output.
Fig.10. Example of a direct drive MW wind turbine generator
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4.3 Brushed or Brushless Topology
In general, DC machines, wound rotor synchronous
generators, wound rotor induction generators all employ
commutators, brushes or slip rings to access the rotating rotor
circuits. Consequently, routine maintenance and replacement
lead to some difficulties in wind power applications,
especially for offshore installations. Clearly it would be
particularly desirable to rid of any components physically
connected to the rotating parts of wind turbines. There are
several ways of achieving this. Taking the DFIG for example,
brushless doubly-fed generators (BDFGs) can be a solution.
They use two windings on the stator (a power winding and a
control winding) with different pole numbers. The rotor can
be of squirrel cage type and an indirect coupling of the two
stator windings is established through the rotor. It is also
possible to use a reluctance rotor in this topology where the
machine has become a brushless reluctance generator. By
modifying the conventional machines, a higher reliability is
achieved due to the absence of the brushes and slip rings. The
penalty is the use of two machines in a machine case.
4.4 Two-Level, Multi-Level or Matrix Converter
Power electronics is recognized as being a key and enabling
component in wind turbine systems. Broadly, there are three
types of converters widely used in the wind market. These are
two-level, multi-level and matrix converters. Two level power
converters are commonly called “back-to-back PWM
converters. They include two voltage source inverters (with
PWM control scheme) connected through a DC capacitor.
This is a mature technology but suffers from high costs, high
switching loss and large DC capacitors. Any power converters
having three or more voltage levels are termed “multi-level
converters”.
5. CONCLUSIONS
Wind energy has attracted much attention from research and
industrial communities. One of growth areas is thought to be
in the offshore wind turbine market. The ongoing effort to
develop advanced wind turbine generator technologies has
already led to increased production, reliability,
maintainability and cost-effectiveness. At this stage, the
doubly-fed induction generator technology (equipped with
fault-ride-through capacity) will continue to be prevalent in
medium and large wind turbines while permanent magnet
generators may be competitive in small wind turbines. Other
types of wind turbine generators have started to penetrate into
the wind markets to a differing degree. The analysis suggests
a trend moving from fixed-speed, geared and brushed
generators towards variable-speed, gearless and brushless
generator technologies while still reducing system weight,
cost and failure rates. This paper has provided an overview of
different wind turbine generators including DC, synchronous
and asynchronous wind turbine generators with a comparison
of their relative merits and disadvantages. More in-depth
analysis should be carried out in the design, control and
operation of the wind turbines primarily using numerical,
analytical and experimental methods if wind turbine
generators are to be further improved. Despite continued
research and development effort, however, there are still
numerous technological, environmental and economic
challenges in the wind power systems. In summary, there may
not exist the best wind turbine generator technology to tick all
the boxes. The choice of complex wind turbine systems is
largely dictated by the capital and operational costs because
the wind market is fundamentally cost-sensitive. In essence,
the decision is always down to a comparison of the material
costs between rare-earth permanent magnets,
superconductors, copper, steel or other active materials,
which may vary remarkably from time to time.
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