Project of a Mini Wind Turbine by An Engineering Project Submitted to the Graduate Faculty of Preston University of Islamabad in Partial Fulfillment of the Requirements for the degree of BACHELOR OF TECHNOLOGY IN MECHANICAL ENGINEERING
Table of contents Acknowledgment…………………………………………………. 1 Abstract………………………………………………………… ....2 Introduction……………………… ..…………………………… ..……………………………...3 ...3 Objectives……………………………………………………… ....4 Methodology…………………………… Methodology……………………………............ ....................... ...................... .................5 ......5 Wind Turbine Design……………………………………………...6 Design…………………………………………….. .6 Aerodynamics…………………………………………………… ..7 Bicycle Dynamo………………………………………………… Dynamo…………………………………………………...8 ...8 Wind as a Resource………………… Resource…………………..……………………………. …………………………….9 9 Budget……………………………………………………………. 10 What is Wind Turbine……….…… Turbine……….……...............................................11 ...............................................11 History of Wind Turbine………………………………………....12 Turbine……………………………………… ....12 Types of Wind Turbine…………………………………………..13 Turbine………………………………………… ..13
Table of contents Acknowledgment…………………………………………………. 1 Abstract………………………………………………………… ....2 Introduction……………………… ..…………………………… ..……………………………...3 ...3 Objectives……………………………………………………… ....4 Methodology…………………………… Methodology……………………………............ ....................... ...................... .................5 ......5 Wind Turbine Design……………………………………………...6 Design…………………………………………….. .6 Aerodynamics…………………………………………………… ..7 Bicycle Dynamo………………………………………………… Dynamo…………………………………………………...8 ...8 Wind as a Resource………………… Resource…………………..……………………………. …………………………….9 9 Budget……………………………………………………………. 10 What is Wind Turbine……….…… Turbine……….……...............................................11 ...............................................11 History of Wind Turbine………………………………………....12 Turbine……………………………………… ....12 Types of Wind Turbine…………………………………………..13 Turbine………………………………………… ..13
1. Acknowledgment I have taken efforts in this project. However, it wo uld not have been possible p ossible without the kind support and help of many individuals and organizations. I would like to extend my sincere thanks to all of them. I am highly indebted to Fatima Group of Companies for their guidance and constant supervision as well as for providing necessary information regarding the project & also for their support in completing the project. I would like to express my gratitude towards my p arents & member of Fatima Group f Companies for their kind co-operation and encouragement which help me in completion of this project. I would like to express my special gratitude and thanks to industry persons for giving me such attention and time. My thanks and appreciations also go to my colleague in developing the project and people who have willingly helped me out with their abilities.
2. Abstract The objective of this project is to design a small wind turbine that is optimized for the constraints that come with residential use. The design process includes the selection of the the wind turbine type and the determination of the blade airfoil, pitch angle distribution along the radius, and chord length distribution along the radius. The pitch angle and chord length distributions are optimized basedon conservation of angular momentum and theory of aerodynamic forces on an airfoil. airfoil. Blade Element Momentum(BEM) theory theory is first derived then used to conduct a parametric study that will determine if the optimized values of blade pitch and chord length create the most
efficient blade geometry.
Finally, two
different airfoils are analyzed to determine which one creates the most efficient wind turbine blade. The project includes a discussion of the most important parameters parameters in wind turbine blade design to maximize efficiency.
3. Introduction A wind turbine is a device that converts kinetic energy from the wind energy, or also wind energy convert in to mechanical energy and mechanical energy converted in to electric energy by electric generator. In this wind turbine Preston University Student WaqasMumtaz building a wind turbine from PVC pipe and bicycle dynamo (Generator) this generator max power is 5 watts and PVC pipe wind blade efficiency approximately 10 to 15 %. If bicycle dynamo (Generator) is not available in your area you can make electric generator, this wind turbine can design by teacher for their science fair project. We are trying to make it simple cheap and efficient.
4. Objectives The objective of this project is to generate electric power through the of wind mill.Now day's power demand is increased so this project is used to generate the electrical power in order to compensate the electric power demand.
5. Methodology Material: 1. New 5 watts bicycle dynamo (Generator) 2. PVC pipe 4 inch diameter and 14 inch in length 3. Some nut bolts 4. Super glue 5. Iron strip 6. Paper 7. Cutter 8. Marker 9. Iron saw 10.LED Lights
Diagrams and Photos
Wind Turbine Blades Paper Template
Construction: Make a paper template according to diagram and take 14 inch and 4 inch diameter PVC pipe then attach the paper template on PVC pipe and trace out line at pipe. After marking lines on pipe cut the pipe with iron saw carefully. you have to cut 2 pieces of blades from PVC pipe after cutting the blade attach both blades to each other with the help of iron strip and drill in the center of iron strip by drill machine then fix with generator.
6. Wind Turbine Design Terms and Concepts You should be familiar with the terms below, as well as the names of the parts of the wind turbine. Wind power Wind turbine Blades Work Aerodynamics Energy Generator
Material: 1. Old or new 5 watt bicycle dynamo (Generator) 2. PVC pipe 4 inch diameter and 14 inch in length 3. some nut bolts 4. super glue 5. Iron strip 6. paper 7. cutter 8. marker 9. iron saw
Diagrams and Photos
wind turbine blades paper template
Wind Turbine Blades Paper Template
Wind Turbine Blade Side View
Wind Turbine Construction Tools and Material
Wind Turbine's Electric Generator
Wind Turbine's PVC Pipe
Construction: Make a paper template according to diagram and take 14 inch and 4 inch diameter PVC pipe then attach the paper template on PVC pipe and trace out line at pipe. After marking lines on pipe cut the pipe with iron saw carefully. you have to cut 2 pieces of blades from PVC pipe after cutting the blade attach both blades to each other with the help of iron strip and drill in the center of iron strip by drill machine then fix with generator .
7. Aerodynamics Air flow over a stationary airfoil produces two forces, a lift force perpendicular to the air flow and a drag force in the direction of air flow, as shown in Fig. 3. The existence of the lift force depends upon laminar flow over the airfoil, which means that the air flows
smoothly over both sides of the airfoil. If turbulent flow exists rather than laminar flow, there will be little or no lift force. The air flowing over the top of the airfoil has to speed up because of a greater distance to travel, and this increase in speed causes a slight decrease in pressure. This pressure diff erence across the airfoil yields the lift force, which is perpendicular to the direction of air flow.
The air moving over the airfoil also produces a drag force in the direction of the air flow. This is a loss term and is minimized as much as possible in high performance wind turbines.
Figure 3: Lift and drag on a stationary airfoil. Both the lift and the drag are proportional to the air density, the area of the airfoil, and the square of the wind speed.
Suppose now that we allow the airfoil to move in the direction of the lift force. This motion or translation will combine with the motion of the air to produce a relative wind direction shown in Fig. 4. The airfoil has been reoriented to maintain a good lift to drag ratio. The lift is perpendicular to the relative wind but is not in the direction of airfoil translation.
Figure 4: Lift and drag on a translating airfoil.
The lift and drag forces can be split into components parallel and perpendicular to the direction of the undisturbed wind, and these components combined to form the net force F 1 in the direction of translation and the net force F 2 in the direction of the undisturbed wind. The force F 1 is available to do useful work. The force F 2 must be used in the design of the airfoil supports to assure structural integrity.
A practical way of using F 1 is to connect two such airfoils or blades to a central hub and allow them to rotate around a horizontal axis, as shown in Fig. 5. The force F 1 causes a torque which drives some load connected to the propeller. The tower must be strong enough to withstand the force F 2.
Figure 5: Aerodynamic forces on a turbine blade . These forces and the overall performance of a wind turbine depend on the construction and orientation of the blades. One important parameter of a blade is the pitch angle, which is the angle between the chord line of the blade and the plane of rotation, as shown in Fig. 6. The chord line is the straight line connecting the leading and trailing edges of an airfoil. The plane of rotation is the plane in which the blade tips lie as they rotate. The blade tips actuallytrace out a circle which lies on the plane of rotation. Full power output would normally be obtained when the wind direction is perpendicular to the plane of rotation. The pitch angle is a static angle, depending only on the orientation of the blade.
Figure 6: Definition of pitch angle β and angle of attack γ.
.Another important blade parameter is the angle of attack, which is the angle γ between the chord line of the blade and the relative wind or the e ff ective direction of air flow. It is a dynamic angle, depending on both the speed of the blade and the speed of the wind. The blade speed at a distance r from the hub and an angular velocity ωm is rωm. A blade with twist will have a variation in angle of attack from hub to tip because of the variation of rωm with distance from the hub. The lift and drag have optimum values for a single angle of attack so a blade without twist is less efficient than a blade with the proper twist to maintain a nearly constant angle of attack from hub to tip. Even the blades of the Old Dutch windmills were twisted to improve the efficiency. Most modern blades are twisted, but some are not for cost reasons. A straight blade is easier and cheaper to build and the cost reduction may more than off set the loss in performance.
When the blade is twisted, the pitch angle will change from hub to tip. In this situation, the pitch angle measured three fourths of the distance out from the hub is selected as the reference.
8. Wind as a Resource Renewable Energy Sourcesare those energy sources which are not destroyed when their energy is harnessed. Human use of renewable energy requires technologies that harness natural phenomena, such as sunlight, wind, waves, water flow, and biological processes such as anaerobic digestion, biological hydrogen production and geothermal heat. Amongst the above mentioned sources of energy there has been a lot of development in the technology for harnessing energy from the wind. Wind is the motion of air masses produced by the irregular heating of the earth’s surface by sun. These differences consequently create forces that push air masses around for balancing the global temperature or, on a much smaller scale, the temperature between land and sea or between mountains. Wind energy is not a constant source of energy. It varies continuously and gives energy in sudden bursts. About 50% of the entire energy is given out in just 15% of the operating time. Wind strengths vary and thus cannot guarantee continuous power. It is best used in the context of a system that has significant reserve capacity such as hydro, or reserve load, such as a desalination plant, to mitigate the economic effects of resource variability.
The power extracted from the wind can be calculated by the given formula:
PW=0.5ρπR3Vw3CP (λ, β) Pw= extracted power from the wind, ρ= air density, (approximately 1.2 kg/m3at 20¤ C at sea level) R = blade radius (in m), (it varies between 40-60 m) Vw= wind velocity (m/s) (velocity can be controlled between 3 to 30 m/s) Cp = the power coefficient which is a function of both tip speed ratio (λ), and blade pitch angle, (β)(deg.) Power coefficient (Cp) is defined as the ratio of the output power produced to the power Available in the wind.
Betz Limit: No wind turbine could convert more than 59.3%of the kinetic energy of the wind into mechanical energy turning a rotor. This is known as the Betz Limit, and is the theoretical maximum coefficient of power for any wind turbine. The maximum value of CPaccording to Betz limit is 59.3%. For good turbines it is in the range of 35-45%. The tip speed ratio (λ) for wind turbines is the ratio between the rotational speed of the tip of a blade and the actual velocity of the wind. High efficiency 3-blade-turbines have tip speed ratios of 6 – 7. The total capacity of wind power on this earth that can be harnessed is about 72 TW. There are now many thousands of wind turbines operating in various parts of the world, with utility companies having a total capacity of 59,322 MW. The power generation by wind energy was about 94.1GW in 2007 which makes up nearly 1% of the total power generated in the world. Globally, the long-term technical potential of wind energy is believed to be 5 times current global energy consumption or 40 times current electricity demand. This would require covering 12.7% of all land area with wind turbines. This land would have to be covered with 6 large wind turbines per square kilometer. Some 80 percent of the global wind power market is now centered in just four countries — which reflects the failure of most other nations to adopt supportive renewable energy
policies. Future market growth will depend in large measure onwhether additional countries make way for renewable energy sources as they reform their electricity industries
Country Germany Spain U.S.A India Denmark Pakistan
Installed Capacity in (MW) 18,428 10,027 9,149 4,430 3,122
9. Bicycle Dynamo
Optimum Utilization of a Bicycle Abstract- In 21 century the world is going towards a new era of invention. Every rising day st
comes with new invention or discovery. But all this is for what? Just to enhance the life of human being and to improve the living standard of human. The basic thought behind all this is that everyone is working for getting more and more comfort in this life. Now a day, our country and human life is mostly affected by load shedding. This is all from the shortage of electricity due to break down of power plant several times. So the production of electricity is affected. Therefore it is not possible to supply electricity as per requirement. It has badly affected the daily
human life. Thus taking this point of view a human power generator should be designed that can work according to the human comfort requirement. Different type of generator is available in market, but they are not economical for common people. By keeping this point, the human power generator is useful for production or generation of electricity to fulfill our preliminary requirement of electricity in daily life by use of dynamo and solar panel for its use in stationary and mobile condition.
Keywords – : Dynamo, Generator, Solar cell, Electricity & Human Power Generator
I. INTRODUCTION Human invented most of the things for his comfort and convenience. Electricity is one of them. Now days, the production of electricity more hydraulic power plant, thermal power plant, wind power plant etc are constructed. In the hydraulic power plant the kinetic energy of water is used to run turbine and convert into mechanical energy and again into electrical energy by connecting generator. In the thermal power plant, the kinetic energy of pressurized steam is used to rotate the turbine and generate electricity. In wind power plant, the kinetic energy of wind is converted into electricity. In the human power generator, it works on the principle of convert muscular or physical energy of human being into the electrical energy by means of applying pulley arrangement. The pulley arrangement converts the efforts which is applied by human being into the rotating motion which is used to generate electricity and this electricity will be used as a preliminary requirement of electricity and also use of solar energy by means of solar cell for generation of electricity for use in stationary and mobile condition and also use of AC appliances by use of inverter. The dynamo in the bicycle uses rotating coils of wire and magnetic fields to convert mechanical rotation into a pulsing direct electric current through Faraday's law of induction. A dynamo machine consists of a stationary structure, called the stator, which provides a constant magnetic field, and a set of rotating windings called the armature which turn within that field. The motion of the wire within the magnetic field causes the field to push on the electrons in the metal, creating an electric current in the wire. On small machines the constant magnetic field may be provided by one or more permanent magnets; larger machines have the constant magnetic field
provided by one or more electromagnets, which are usually called field coils. Thus by the above mechanism dynamo charges the battery. Renewable energy is rapidly gaining importance as an energy resource as fossil fuel prices fluctuate. One of the most popular renewable energy sources is solar energy .More and more people are getting on the solar energyBandwagon. Installing residential solar panels for our home can bring big financial benefits, especially in the form of permanently reduced energy bills. Solar energy is virtually inexhaustible. The total energy we receive from the sun far exceeds our energy demands. It is probably the most reliable form of energy available everywhere and to everyone, unlike other sources. With dwindling supplies of petroleum, gas and coal, tapping solar energy is a logical and necessary course of action. Solar Power is a way of converting sunlight into a useful energy source. There are two ways of using solar energy; as heat and as electricity. Devices like solar water heaters, driers and solar cookers use the heat to produce hot water, to dry grains or to cook food respectively. This way of using solar energy is called solar thermal. On th e other hand, solar panels use the light to produce electricity, which can then be used for a multitude of purposes. The main advantages of solar energy are as follows One of the cleanest forms of energy Harmonious with nature Easy to install, operate and maintain Long life. Solar panels can last up to 20 years or more Modular design, hence easy to expand Ideal for remote areas, where electricity is not reliable. Safe to handle Freedom from grid, which is often unreliable especially in remote areas.
Many companies in the world are gradually promoting quality as the central customer value and regard it as a key concept of company strategy in order to achieve the competitive edge. Quality improvement decisions are viewed as the catalyst for substantial technological developments being made in the manufacturing sector. Quality Costs are a measure of the costs specifically associated with the achievement or non-achievement of product or service quality – including all product or service requirements established by the company and its contract with customers and society. Measuring and reporting the quality cost is the first step in a quality management program. Quality costs allow us to identify the soft targets to which improvement efforts can be applied.
II. LITERATURE REVIEW In 1817 Baron von Drais invented a walking machine that would help him get around the royal gardens faster: two same-size in-line wheels, the front one steerable, mounted in a frame which you straddled. The device was propelled by pushing your feet against the ground, thus rolling yourself and the device forward in a sort of gliding walk. The machine became known as the Draisienne or hobby horse
The next appearance of a two-wheeled riding machine was in 1865, when pedals were applied directly to the front wheel. This machine was known as the velocipede ("fast foot"), but was popularly known as the bone shaker, since it was also made entirely of wood, then later with metal tires, and the combination of these with the cobblestone roads of the day made for an extremely uncomfortable ride.
In 1870 the first all metal machine appeared. (Previous to this metallurgy was not advanced enough to provide metal which was strong enough to make small, light parts out of.) The pedals were still attached directly to the front wheel with no freewheeling mechanism. Solid rubber tires and the long spokes of the large front wheel provided a much smoother ride than its predecessor. The front wheels became larger and larger as makers realized that the larger the wheel, the farther you could travel with one rotation of the pedals.
Pedaling History has on display even the recent history of the bicycle in America that we are more familiar with: the "English 3-speed" of the '50s through the '70s, the 10-speed derailleur bikes which were popular in the '70s (the derailleur had been invented before the turn of the century and had been in more-or-less common use in Europe since), and of course the mountain bike of right now. There are also many oddball designs that never quite made it, including the Ingo.
1980-1991 A Los Angeles based company called Luz Co. produced 95% of the world's solar based electricity. They were forced to shut their doors after investors withdrew from the project as the price of non-renewable fossil fuels declined and the future of state and federal incentives were not likely. The chairman of the board said it best: "The failure of the world's largest solar electric company was not due to technological or business judgment failures butrather to failures of government regulatory bodies to recognize the economic and environmental benefits of solar thermal generating plants."
Solar energy history played a big part in the way society evolved and will continue to do so there is a renewed focus as more and more people see the advantages of solar energy and as it becomes more and more affordable.Governments across the world offer financial assistance.
Solar energy in the future As the number of people longing for a cleaner environment grows, so does the solar industry. Solar cells are becoming increasingly cost-effective as more distributors enter the market and new technologies continue to offer more choice and new products. We might even see the end of the combustion age in our lifetime. Cars might soon be powered by new fuel cells that create electricity through chemical reaction. Screen-printed solar cells are expected to drive prices down even more. Roofing shingles are capturing the sun's rays and turning them into electricity Solar panels are being mounted to the sides of houses when roof space is not an option. Pools are being heated with solar energy for a fraction of the price of conventional heaters.
In our design Use of dynamo which on just moving the shaft by hand produces electricity. Use of inverter so that both AC and DC equipments can be used. Use of solar panel so that bicycle can be used in stationary condition. Use of dry cell battery for storing energy and weigh t consideration of bicycle Voltage limiting circuit for limiting fluctuating current of dynamo. Use of pulley arrangement so wearing of tyre does not take place and frictional developed is less.
Mechanical components use for project 1. Dynamo-15V, 2Amp. 2. Bicycle. 3. Pulley.(large:15inches,small:3inches) 4. Solar Panel-12V ,5W 5. Round belt.
Electrical components for project 1. Rectifier-15V, 5 Amp-AC TO DC (do not allow back voltage). 2. Filter Circuit-15V, 5Amp. 3. Charge Controller (LM317). 4. Inverter-500 W. 5. Battery-12V, 7.5 AH. 6. Over Voltage Protection Circuit
Dynamo Tabl e 1. Di ff er ence between dynamo bicycle and bi cycle generator
Dynamo bicycle
Bicycle generator
Fluctuating DC current.
Constant DC current.
Cannot be used to run AC equipments.
Can be used to run AC appliances.
It does not give backup.
It gives backup.
Cannot be used in stationary condition
Can be used in rest condition.
Pulley A pulley is a wheel on an axle that is designed to support movement of a cable or belt along its circumference. Pulleys are used in a variety of ways to lift loads, apply forces, and to transmit power.
Alternator It is the device by which mechanical energy is converted into electrical en ergy. It is D.C. generator for generating D.C. voltage at output.
Rectifier circuit It is a device which converts A.C. voltage into D.C. voltage. Some A.C. harmonics produced by D.C. generator with pulsating modulation of waves which is not in regular modulation, so for getting regular modulation of waves, rectifier circuit is used
Filter circuit At the output of rectifier, D.C. voltage is not in pure form some A.C. components are in there so for purification of it, Shunt capacitor filter circuit is used. Filter is a circuit which minimizes of removed the undesirable A.C. component of the rectifier output & allows only the D.C. component to reach at output.
Charging circuit It is the circuit which is used for charging the discharged battery. Voltage limiting circuit:-It is also called as voltage regulator circuit. Here, for voltage regulation of output voltage LM-317,3 pin regulator IC is used. Voltage regulator is the circuit which eliminates or reduced variations in the D.C. output voltage or rectifier and filter circuit are called Voltage Regulator.
Battery It is the source of D.C. voltage. It is the device where we want to store the D.C. voltage or it gives the D.C. source whenever we want.
Inverter We are using electronic inverter. The function of electronic inverter is to convert D.C. to A.C. In our project we are generating 15 volt D.C. supply to convert 15 volt D.C. to 230 volt A.C. with the help of electronic inverter unit.
The function of inverter is to take the 12 volt D.C. and switching the 12 volt D.C. and give the step-up transformer convert 12 volt switching supply to 230 volt A.C. supply. It is most common part of inverter.
Round belts Round belts are a circular cross section belt designed to run in a pulley with a 60 degree Vgroove. Round grooves are only suitable for idler pulleys that guide the belt, or when (soft) Oring type belts are used.
Solar cell Solar cells produce direct current electricity from sun light, which can be used to power equipment or to recharge a battery.
III. WORKING OF PROJECT Working of dynamo Basic principle on which dynamo works is ―Faraday’s law of electromagnetic induction‖. According to this law if an object or material that conducts electricity passes through a magnetic field then an electric current will begin to flow through that material.
Construction Fig. 1 shows single turn rectangular copper coil ABCD rotating about its own axis I magnetic field provided by either permanent magnet or electromagnets.
Figure 1: Rectangular copper coil The two ends of coil are joined to two slip ring ―a‖ & ―b‖ which are insulated from each other and from central Shaft. The two collecting brushes (carbon or copper). Press against slip rings. Their function is to collect current induced in coil and to convey it to external load resistance R.The rotating coil may be called ―armature‖ and the magnets are called as ―field magnets‖.
Generator parts 1. Magnetic frame or Yoke 2. Pole core or pole shoes 3. Pole coils or Field coils 4. Armature core 5. Commutator 6. Brushes & Bearings 7. Yoke
The output frame or yoke serves double purpose. It provides mechanical supports for the poles and act as a protecting cover for the machine and It carries the magnetic flux produced by poles. Yokes are made up of cast iron. But for large machine casting or rolled steel is employed.
Poles cores The field magnets consist of cores & Pole shoes. The Poles shoes two purposes. They spread out the flux in the air gap and also being of larger cross-section; reduces the reluctance of the magnetic path. They support the exciting coils or field coils. The complete poles cores & shoes are built of thin laminations of annealed steel. The thickness of lamination varies from 1mm to 0.25mm.
Poles coils When current is passes through these coils, they electromagnetic the poles which produces the necessary flux that is cut by revolving armature conductors.
Armature core It houses the armature conductors or coils and cases them to rotate and hence cut the magnetic flux of the field magnets. In addition to this, its most important function is to provide a path of very low reluctance to the flux through armature from a N-pole to a S-pole.It is cylindrical or drum shaped and it is built up of usually circular sheet discs or laminations approximately 0.5 mm thick. A complete circular laminations made up of 4 or 6 or 7.8 segmental laminations. The purpose of using laminations is to reduce eddy current loss. Thinner the lamination greater is the 2
resistance offered to the endued emf, smaller the current and hence lesser the I loss in the core.
10. Project Budget 1.Nut bolts
Rs.100/-
2. super glue
Rs.200/-
3. Iron strip
Rs.100/-
4.Paper,Pen,Scale
Rs.100/-
6.Cutter
Rs.200/-
7.Dynmo (5watts)
Rs.500/-
8.PVC Pipe
Rs:200/-
9.Material for Base
Rs:300/-
10.wire
Rs:100/-
11.LED Lights
Rs:200/-
Total
Rs:2000/-
11. What is Wind Turbine? A wind turbine is a device that converts kineticenergy from the wind into electrical power. A wind turbine used for charging batteries may be referred to as a wind charger . The result of over a millennium of windmill development and modern engineering, today's wind turbines are manufactured in a wide range of vertical and horizontal axis types. The smallest turbines are used for applications such as battery charging for auxiliary power for boats or caravans or to power traffic warning signs. Slightly larger turbines can be used for making small contributions to a domestic power supply while selling unused power back to the utility supplier via the electrical grid. Arrays of large turbines, known as wind farms, are becoming an increasingly important source of renewable energy and are used by many countries as part of a strategy to reduce their reliance on fossil fuels.
12. History of Wind Turbine
Windmills were used in Persia (present-day Iran) as early as 200 B.C.
[1]
The wind wheel
of Heron of Alexandria marks one of the first known instances of wind powering a machine in [2][3]
history.
However, the first known practical windmills were built in Sistan, an Eastern
province of Iran, from the 7th century. These "Panemone" were vertical axle windmills, which [4]
had long vertical driveshafts with rectangular blades. Made of six to twelve sails covered in
reed matting or cloth material, these windmills were used to grind grain or draw up water, and were used in the grist milling and sugarcane industries.
[5]
Windmills first appeared in Europe during the middle ages. The first historical records of their use
in
England
date
to
the
11th
or
12th
centuries
and
there
are
German crusaders taking their windmill-making skills to Syria around 1190.
[6]
reports
of
By the 14th
century, Dutch windmills were in use to drain areas of the Rhine delta. The first electricity-generating wind turbine was a battery charging machine installed in July [7]
1887 by Scottish academic James Blyth to light his holiday home in Marykirk, Scotland.
Some
month’s later American inventor Charles F Brush built the first automatically operated wind [7]
turbine for electricity production in Cleveland, Ohio. uneconomical in the United Kingdom
[7]
Although Blyth's turbine was considered
electricity generation by wind turbines was more cost
effective in countries with widely scattered populations.
The first automatically operated wind turbine, built in Cleveland in 1887 by Charles F. Brush. It [8]
was 60 feet (18 m) tall, weighed 4 tons (3.6 metric tonnes) and powered a 12 kW generator .
In Denmark by 1900, there were about 2500 windmills for mechanical loads such as pumps and mills, producing an estimated combined peak power of about 30 MW. The largest machines were on 24-meter (79 ft) towers with four-bladed 23-meter (75 ft) diameter rotors. By 1908 there were 72 wind-driven electric generators operating in the US from 5 kW to 25 kW. Around the time of World War I, American windmill makers were producing 100,000 farm windmills each year, mostly for
22 kW. The organizing of owners into associations and co-operatives lead to the lobbying of the government and utilities, which incentivized larger turbines throughout the 1980s and afterwards. Local activists in Germany, nascent turbine manufacturers in Spain, and large investors in the U.S. in the early 1990s then lobbied for policies which stimulated the industry in those countries. Later companies formed in India and China. As of 2012, Danish company Vestas is the world's biggest wind-turbine manufacturer.
13. Types of Wind Turbine Wind turbines can rotate about either a horizontal or a vertical axis, the former being both older and more common. Horizontal axis
Components of a horizontal axis wind turbine (gearbox, rotor shaft and brake assembly) being lifted into position.
A considerable distance in front of the tower and are sometimes tilted forward into the wind a small amount. Downwind machines have been built, despite the problem of turbulence (mast wake), because they don't need an additional mechanism for keeping them in line with the wind, and because in high winds the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since cyclical (that is repetitive) turbulence may lead to fatigue failures, most HAWTs are of upwind design. Turbines used in wind farms for commercial production of electric power A turbine blade convoy passing through Eden field, UK Horizontal-axis wind turbines (HAWT) have the main rotor shaft and electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to drive an electrical generator. Since a tower produces turbulence behind it, the turbine is usually positioned upwind of its supporting tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed are usually three-bladed and pointed into the wind by computer-controlled motors. These have high tip speeds of over 320 km/h (200 mph), high efficiency, and low torque ripple, which contribute to good reliability. The blades are usually colored white for daytime visibility by aircraft and range in length from 20 to 40 meters (66 to 131 ft) or more. The tubular steel towers range from 60 to 90 meters (200 to 300 ft) tall. The blades rotate at 10 to 22 revolutions per minute. At 22 rotations per minute the tip speed exceeds 90 meters per second (300 ft/s). A gear box is commonly used for stepping up the speed of the generator, although designs may also use direct drive of an annular generator. Some models operate at constant speed, but more energy can be collected by variable-speed turbines which use a solid-state power converter to interface to the transmission system. All turbines are equipped with protective features to avoid damage at high wind speeds, by feathering the blades into the wind which ceases their rotation, supplemented by brakes.
Vertical axis design
A vertical axis Twisted Savonius type turbine. Vertical-axis wind turbines (or VAWTs) have the main rotor shaft arranged vertically. One advantage of this arrangement is that the turbine does not need to be pointed into the wind to be effective, which is an advantage on a site where the wind direction is highly variable, for example when the turbine is integrated into a building. Also, the generator and gearbox can be placed near the ground, using a direct drive from the rotor assembly to the ground-based gearbox, improving accessibility for maintenance. The key disadvantages include the relatively low rotational speed with the consequential higher torque and hence higher cost of the drive train, the inherently lower power coefficient, the 360 degree rotation of the aerofoil within the wind flow during each cycle and hence the highly dynamic loading on the blade, the pulsating torque generated by some rotor designs on the drive train, and the difficulty of modelling the wind flow accurately and hence the challenges of analysing and designing the rotor prior to fabricating a prototype
When a turbine is mounted on a rooftop the building generally redirects wind over the roof and this can double the wind speed at the turbine. If the height of a rooftop mounted turbine tower is approximately 50% of the building height it is near the optimum for maximum wind energy and minimum wind turbulence. Wind speeds within the built environment are generally much lower than at exposed rural sites,noise may be a concern and an existing structure may not adequately resist the additional stress.Subtypes of the vertical axis design include:
Darrieus wind turbine "Eggbeater" turbines, or Darrieus turbines, were named after the French inventor, Georges [23]
Darrieus.
They have good efficiency, but produce large torque ripple and cyclical stress on
thetower, which contributes to poor reliability. They also generally require some external power source, or an additional Savonius rotor to start turning, because the starting torque is very low. The torque ripple is reduced by using three or more blades which results in greater solidity of the rotor. Solidity is measured by blade area divided by the rotor area. Newer Darrieus type turbines are not held up by guy-wires but have an external superstructure connected to the top bearing.
Giromill A subtype of Darrieus turbine with straight, as opposed to curved, blades. The cycloturbine variety has variable pitch to reduce the torque pulsation and is self-starting. The advantages of variable pitch are: high starting torque; a wide, relatively flat torque curve; a higher coefficient of performance; more efficient operation in turbulent winds; and a lower blade speed ratio which lowers blade bending stresses. Straight, V, or curved blades ma y be used.
[26]
Savonius wind turbine These
are
drag-type
devices
with
two
(or
more)
scoops
that
are
used
in
anemometers, Flettner vents (commonly seen on bus and van roofs), and in some high-reliability low-efficiency power turbines. They are always self-starting if there are at least three scoops.
Twisted Savonius Twisted Savonius is a modified savonious, with long helical scoops to provide smooth torque. This is often used as a rooftop wind turbine and has even been adapted for ships. Another type of vertical axis is the Parallel turbine, which is similar to the crossflow fan or centrifugal fan. It uses the ground effect. Vertical axis turbines of this type have been tried for many years: a unit producing 10 kW was built by Israeli wind pioneer Bruce Brill in the 1980s.
Small Wind Turbine Technology Nearly all small wind turbines today are upwind, horizontal-axis turbines, which means the rotor is spinning in front of the tower. There are some turbines using two blades, while the majority of the recent turbines comes supplied with a three-blade rotor, which in general terms makes the turbine run more smoothly and last a longer time. The prevalent blade materials are composite materials as fiberglass, while only a few products in this class still use wood. Instead of the yaw motors of the big wind turbines, small wind turbines often use tail vanes to point the rotor to the wind. Micro and Mini wind turbines use generators based on permanent-magnet alternators. The magnets in the generator are conventionally tied on the rotating shaft driven by the rotor, but there are also several wind turbines with the magnets attached in a case which rotates around the stationary part of generator. This inside-out design has two advantages: The blades can be bolted directly to the case containing the magnets and the magnets are pressed against the case wall by the centrifugal force. Contrary to this, conventionally attached magnets on the rotating shaft of a generator have to be retained by sophisticated means. In household-sized generators, besides permanent-magnet alternators conventional wound-field and induction alternators are used. Most small wind turbines generate a three-phase AC which can be rectified by a controller for battery charging applications. There are turbines with built-in controllers and also products with an external controlling entity. Because of the sometimes demanding environmental conditions, the robustness of a turbine is a very important parameter, which can be estimated only very roughly: Experience has shown, that the weight of the turbine in relation to the area swept by the rotor can be used as a criterium. For 2
example a turbine with a relative mass of 10 kg/m should be more robust than a turbine with 5 2
kg/m . To prevent damages caused by very high winds, every wind turbine needs a means for overspeed control. The preferred mechanism used by producers is furling or folding the turbine across a hinge so that the rotor swings towards the tail vane. In case of a passive furling mechanism, the thrust of very high winds overcomes the restraining force which kept the the rotor towards the wind. The threshold value (wind speed) for this mechanism is caused by the design of the hinge,
which connects the body of the turbine and the tail vane. Furling mechanisms are very common for micro and mini wind turbines, while many household-sized turbines pitch the rotor-blades for overspeed control and a few also use a combination of pitching and furling.
Classes of Small Wind Turbines Comparing Small Wind Turbines Wind turbines are usually compared by their rated power in W, kW or MW. It is important to look at these values with care, because there is no standard in rating the output of small wind turbine output. The most significant differences are revealed in the diverging wind speeds related to the rated output for a wind turbine. The power contained in a wind with 12,5 m/s is almost three times higher than at a wind speed of 9 m/s. Thus the rated power of a wind turbine given for a wind speed of 12,5 m/s is three times higher than the value given for a wind speed of 9 m/s. The same machine can be labelled with a very different rated power only depending on the wind speed which is used as basic value. It must be mentioned, that only at the windiest sites of the world turbines will operate for a significant time span at a wind speed of 12,5 m/s. At most sites such high winds are very rare. Looking at the rated power of a wind turbine one must compare the wind speed used in the rating procedure with the expected wind speeds at the site the turbine will be installed.
As an alternative the energy (in kWh) that is generated by a small wind turbine at a site with a given average wind speed can be used to compare the turbines. Finally the combination of rotor diameter and energy generated per year (at a reference wind speed) is a roughly reliable indicator for comparing small wind turbines.
Micro Wind Turbines These wind turbines have a very small rotor diameter of around 1 m or less and generate about 300 kWh per year at sites with an average wind speed of 5,5 m/s. They are typically used for low-power uses in remote areas (e.g. fence-charging, b asic lighting, electricity for sailboats).
Mini Wind Turbines Mini wind turbines typically have rotor diameters of 1,5-2,6 m an generate 1000-2000 kWh per year at sites with 5,5 m/s.
Household-size Wind Turbines This term summarizes a much broader field of wind turbines depending on the very different size of 'households' and the related applications: Household-size turbines are suitable for the supply of homes, but also for farms, ranches and even for small businesses and telecommunications. Thus in this class rotor diameters of 2.7-9 m can be found and the generated energy per year ranges from 2,000-20,000 kWh for sites with 5.5 m/s.
Siting and Safety Finding the right place for the wind turbine can be the most challenging part of the installation. The most important parameters for this choice are given by the terrain surrounding the site of the wind turbine: Tower height and distance from buildings or other obstacles have to be considered carefully, while the related costs often are a limiting factor. For siting a small wind turbine there is an old rule of thumb called the 30-foot (10-meter) rule: For good performance the wind turbine should be installed at least 10 m above all obstacles within 100 m. This is a minimum to avoid placing the wind turbine in the disturbed wind flow around trees or buildings. Thus in a perfect surrounding of a grass land without any obstacles, a tower should be at least 10 m high. To safe costs it is essential to use any given advantages of the landscape: If there is a hill near the building or village which should be supplied with electricity, the best place for the new wind turbine will be on the top of the hill. Choosing the distance between the tower and the supplied building, the cost of connecting and the burial of the cable have to be considered. Installing a wind turbine directly on a roof is problematic for three reasons: The turbulence in the wind stream caused by the building is very high and the performance will be significantly decreased. Secondly, small wind turbines can be very noisy especially in high winds and a last very important reason is the risk for the people living in the house. Modern small wind turbines are durable and reliable but nevertheless it must be avoided by all means to work or live beneath a machine with parts moving as fast as the blades of a small wind turbine.
Installation of Small Wind Turbines For micro and mini wind turbines tilt-up towers are the easiest and cheapest carrying constructions: A tube with a diameter dependent on the size and weight of the wind turbine it should carry is tilted over a hinge fixed in the ground until the tower is raised vertically. A socalled gin pole is used to raise the tower over the hinge. A gin pole is a second shorter mast at a right angle to the tower, which acts as a lever to reduce the lifting loads. Bigger household-size wind turbines require heavier lattice towers which can only be erected by a crane. The following paragraph focuses on raising a tilt-up tower, which needs only a few persons and relatively little experience and skills. Common tower tubes consist of several pieces with lengths of a few meters; some smaller towers have separations of only two meters length allowing a comfortable delivery by standard parcel services. Tilt-up towers are anchored by guy cables, whose number and diameter depends on the height of the used tower. The anchors for the guy cables could be screwed into the ground, if the soil is medium-dense. Using these screw-anchors simplifies the installation of a tower a lot, but the stability of their placement must be proven with great care. For heavier wind turbines, bad ground conditions (very low or very high density) or very high wind areas conventional concrete anchors or power-driven screw anchors are required. The power conductors carrying the generated power to the ground are threaded through the inside of the tower tube in most cases. Their attachment is a very important but often overlooked aspect of the installation: If the conducting cables are connected to the leads of the wind turbine only, the leads are likely to be pulled out and damaged by the weight of the conductor. For this reason a strain relief has to be used to support the weight of the cable. A strain relief is a finemeshed wire net which can be put around the cable. The upper side of the strain relief is fixed at a point at the top of the tower. Additionally the connection between the wind turbine leads and the cable should be done by an in-line vibration proof compression connector.
Tools for the Installation of Small Wind Turbines For the erection of a tilt-up tower with a wind turbine either an electrical winch or a type of hoist is necessary. A relatively light-weight, low-cost and very effective tool working like a hoist in principle is the so called griphoist. In contrast to a winch a griphoist does not furl the cable, wire or rope, but it pulls it directly through a hoist inside the tool. The griphoist is used manually by a lever and needs no supply of electricity. Combined with the low weight it is an ideal tool for raising tilt-up towers especially in remote areas, where an electrical winch and the necessary
battery are not available. Besides practitioners prefer these tools because of the full and direct control the operator has over the raising process. The force needed by the operator to move the lever is a good indicator for the status of the raising procedure. In this way the operator is able to react on unusual tensions on the cable and can reduce the lift, when the tower is near to vertical.
The Raising Procedure If your team has little experience in erecting a tower, it will be favourable to practise the whole work flow before you raise the tower with the much greater weight of the turbine. In this way site-specific difficulties can be identified without the risk of damaging the most expensive and important part: the wind turbine. As a first step the gin pole of the tilt-up tower must be raised connecting a cable at the end of the gin pole (with a shackle) and pulling it to a vertical position by the griphoist. Afterwards the anchor for the griphoist must be placed exactly at the position the end of the gin pole will reach, when the tower is upright. The reason is the common construction of the tower and the gin pole: Because the gin pole consists of several pieces of tube, the force executed by the griphoist has to pull downwards and must not pull from a position which is further from the tower base than the length of the gin pole. Otherwise the could tube pieces could come apart under the high tension during the lifting process endagering the tower, turbine and especially the working people. When the griphoist is anchored carefully and the lifting cable is connected to the end of the gin pole, the tower can be erected. While one person is operating the griphoist, for minimum one additional person is needed keeping a guy cable tensed and guiding the lift while preventing any jerks during the process. It is very important to keep this guiding person well outside the fall zone at right angle to the tower. Depending on the size of the mast, the raising procedure can take several hours, because with every lever-movement at the griphoist, a few inches of cable are pulled through the hoisting mechanism. Lifting weight is greatest when the tower is near the ground and decreases with every degree the tower is lifted towards vertical position. After practising the raising procedures a couple of times the wind turbine can be attached and the procedure can be repeated. When the tower reached a vertical position the guying cables have to be connected and tightened to the anchors. Again it is important to raise the tension on the guy cables step by step to prevent the thin tube material of the tower from buckling.
ADVANTAGES OF WIND POWER: The wind is free and with modern technology it can be captured efficiently. Once the wind turbine is built the energy it produces does not cause greenhouse gases or other pollutants. Although wind turbines can be very tall each takes up only a small plot of land. This means that the land below can still be used. This is especially the case in agricultural areas as farming can still continue. Many people find wind farms an interesting feature of the landscape. Remote areas that are not connected to the electricity power grid can use wind turbines to produce their own supply. Wind turbines have a role to play in both the developed and third world. Wind turbines are available in a range of sizes which means a vast range of people and businesses can use them. Single households to small towns and villages can make good use of range of wind turbines available today.
DISADVANTAGES OF WIND POWER: The strength of the wind is not constant and it varies from zero to storm force. This means that wind turbines do not produce the same amount of electricity all the time. There will be times when they produce no electricity at all. Many people feel that the countryside should be left untouched, without these large structures being built. The landscape should left in its natural form for everyone to enjoy. Many people see large wind turbines as unsightly structures and not pleasant or interesting to look at. They disfigure the countryside and are generally ugly. When wind turbines are being manufactured some pollution is produced. Therefore wind power does produce some pollution. Large wind farms are needed to provide entire communities with enough electricity. For example, the largest single turbine available today can only provide enough electricity for 475 homes, when running at full capacity. How many would be needed for a town of 100000 people.
Factors AffectingWind Turbine Output Wind energy is undoubtedly one of the cleanest forms of producing power from a renewable source. There is no pollution, there is no burning of fossil fuels, and unless something very drastic happens, you don’t run out of wind. But it’s not like you can erect a wind turbine
anywhere and it will start generating power for you. There are lots of factors that can make an impact on the amount of energy you can generate out of wind.
Wind It being a wind turbine, its output first most depends on the wind. Both the speed and force of the wind can be deciding factors. The more wind speed and force you have got, the greater is the amount of power your wind turbine generates. Different regions have different wind speeds. You can gather the available wind dynamics data and using a model like Webull Distribution you can calculate how effective the wind of a particular region is going to be.
What Causes Wind As long as there is sunlight, there will be wind. The wind is a by-product of solar energy. Approximately 2% of the sun’s energy reaching the earth is converted into wind energy. The
surface of the earth heats and cools unevenly, creating atmospheric pressure zones that make air flow from high- to low-pressure areas. Trade winds on a tropical island are fairly dependable, providing a nearly constant wind flow throughout the day and night. Unfortunately, we have no trade winds in our part of the world, and weather systems move through every few days. With alternating stormy and fair weather, wind speeds can range from gale force to total calm within a 24-hour period. An Iowa wind turbine owner must cope with these large variations. Daily and seasonal changes are important considerations for applications where electricity use is time-dependent. Seasonal winds in Iowa are strongest in winter and early spring and weakest in summer. Daily winds generally are strongest during the afternoon and lightest during the early morning. To
make the most efficient use of the energy supplied by the wind turbine (assuming little is to be fed into the utility grid), users should adjust their energy consumption to match the availability of the wind. Weather forecasts are valuable in planning for high and low wind periods. Wind direction is also variable, although the strongest winds generally prevail out of the southwest to northwest. Knowledge of the prevailing wind direction is important for siting the wind turbine in the least obstructed setting possible.
Height Places of higher altitudes have more wind due to various atmospheric factors. Besides, at higher places there is less obstruction from the surrounding hills, trees and building. In fact the height is so important that alternative energy scientists and engineers are trying to use kites (due to the heights they can easily reach) to tap the wind power.
Rotor The amount of energy produced by your wind turbine is proportional to the size of the rotor used, when all other factors have been taken into consideration. A bigger rotor certainly generates more power. Although it may cost more, in the long run, whenever you are getting a wind turbine erected, go for a big a rotor as possible.
Wind Energy Development Environmental Concerns Wi nd ener gy development envir onmental concer ns in clude, noi se, visual im pacts, and avian and bat mortali ty. Although wind power plants have relatively little impact on the environment compared to fossil fuel power plants, concerns have been raised over the noise produced by the rotor blades, visual impacts, and deaths of birds and bats that fly into the rotors (avian/bat mortality). These and other concerns associated with wind energy development are discussed below, and are addressed in the Wind Energy Development Programmatic EIS.
Noise Like all mechanical systems, wind turbines produce some noise when they operate. Most of the turbine noise is masked by the sound of the wind itself, and the turbines run only when the wind blows. In recent years, engineers have made design changes to reduce the noise from wind turbines. Early model turbines are generally noisier than most new and larger models. As wind turbines have become more efficient, more of the wind is converted into rotational torque and less into acoustic noise. Additionally, proper siting and insulating materials can be used to minimize noise impacts.
Visual Impacts Because they must generally be sited in exposed places, wind turbines are often highly visible; however, being visible is not necessarily the same as being intrusive. Aesthetic issues are by their nature highly subjective. Proper siting decisions can help to avoid any aesthetic impacts to the landscape. One strategy being used to partially offset visual impacts is to site fewer turbines in any one location by using multiple locations and by using today's larger and more efficient models of wind turbines.
Avian/Bat Mortality Bird and bat deaths are one of the most controversial biological issues related to wind turbines. The deaths of birds and bats at wind farm sites have raised concerns by fish and wildlife agencies and conservation groups. On the other hand, several large wind facilities have operated for years with only minor impacts on these animals.
To try to address this issue, the wind industry and government agencies have sponsored research into collisions, relevant bird and bat behavior, mitigation measures, and appropriate study design protocols. In addition, project developers are required to collect data through
monitoring efforts at existing and proposed wind energy sites. Careful site selection is needed to minimize fatalities and in some cases additional research may be needed to address bird and bat impact issues. While structures such as smokestacks, lighthouses, tall buildings, and radio and television towers have also been associated with bird and bat kills, bird and bat mortality is a serious concern for the wind industry.
Other Concerns Unlike most other generation technologies, wind turbines do not use combustion to generate electricity, and hence don't produce air emissions. The only potentially toxic or hazardous materials are relatively small amounts of lubricating oils and hydraulic and insulating fluids. Therefore, contamination of surface or ground water or soils is highly unlikely. The primary health and safety considerations are related to blade movement and the presence of industrial equipment in areas potentially accessible to the public. An additional concern associated with wind turbines is potential interference with radar and telecommunication facilities. And like all electrical generating facilities, wind generators produce electric and magnetic fields.
Interesting Wind Energy Facts The United States currently has 61,110 MW of installed wind project capacity, comprising 5.7% of total U.S. installed electric generating capacity. Wind mills have been in use since 2000 B.C. and were first developed in China and Persia. Wind power is currently the fastest-growing source of electricity production in the world. Iowa and South Dakota generated more than 25% of their energy from wind during 2013. A single wind turbine can power 500 homes.
In 2012, the Shepherds Flat wind project became the largest online wind project in the United States (845 megawatts), breaking the record previously held by the Roscoe Wind Farm (781.5 megawatts). In 2013, the roughly 168 million megawatt-hours generated by wind energy avoided 95.6 million metric tons of carbon dioxide (CO2) — the equivalent of reducing power-sector CO2 emissions by 4.4% or removing 16.9 million cars from the roads. There’s enough on-shore wind in America to power the country 10 times over.
In 2013, 12 states accounted for 80% of U.S. wind-generated electricity: Texas, Iowa, California, Oklahoma, Illinois, Kansas, Minnesota, Oregon, Colorado, Washington, North Dakota, and Wyoming. Source: U.S. Energy Information Administration March Electric Power Monthly report. Most wind turbines (95%) are installed on private land. Modern wind turbines produce 15 times more electricity than the typical turbine did in 1990. At times, wind energy produces as much as 25% of the electricity on the Texas power grid. American wind power is a $10 billion a year industry. Unlike nearly every other form of energy, wind power uses virtually no water. By 2030, U.S. wind power will save nearly 30 trillion bottles of water. At times, wind power produces as much as 45% of the electricity in Spain. Wind energy became the number-one source of new U.S. electricity-generating capacity for the first time in 2012, providing some 42% of all new generating capacity. In fact, 2012 was
a strong year for all renewables, as together they accounted for more than 55% of all new U.S. generating capacity. During 2013, California led the nation in new wind installations (with 269 megawatts), followed by Kansas, Michigan, Texas, and New York. 70% of all U.S. Congressional Districts are home to an operating wind project, a windrelated manufacturing facility, or both. As of May 2014, the United States is home to 46,000 operating wind turbines. Right now, 559 wind-related manufacturing facilities produce a product for the U.S. wind energy industry across 44 states. Both Nevada and Puerto Rico added their first utility-scale projects during 2012. In 2000, more than 60% of U.S. wind power capacity was installed in California, with 17 states hosting utility-scale wind turbines. Today, 39 states and Puerto Rico share 60 gigawatts of utility-scale wind project development. Wind is a credible source of new electricity generation in the United States. Wind power comprised 43% of all new U.S. electric capacity additions in 2012 and represented $25 billion in new investment. Wind power currently contributes more than 12% of total electricity generation in nine states (with three of these states above 20%), and provides more than 4% of total U.S. electricity supply. Wind energy prices have dropped since 2009 and now rival previous lows. Lower wind turbine prices and installed project costs, along with improved capacity factors, are enabling aggressive wind power pricing. After topping out at nearly $70/megawatt-hour in 2009, the average levelized long-term price from wind power sales agreements signed in 2011/2012 –
