Alternative Alternative energyenergy

Wind energy in the upwindWind energy in the upwind

By:Vasilescu Tiberiu By:Vasilescu Tiberiu AurelAurel

And Brata SorinAnd Brata Sorin

ContentsContents1. Short presentation2. History of wind energy3. Wind Turbines: Upwind Machines 4. How wind machines work5. Types of wind turbines

5.1. Vertical-axis wind turbines5.1.1.Presentation5.1.2.Advantages and disadvantages

5.2. Horizontal-axis wind turbines5.2.1.Presentation5.2.2.Advantages and disadvantages

6. Small wind turbines 7. Turbine design and construction 8. The benefits of wind energy9. Wind and the environment10. The costs of wind energy

Short preShort presentationsentation Wind is simple air in motion. It is caused by the uneven

heating of the earth’s surface by the sun. Wind energy converts kinetic energy that is present in the

wind into more useful forms of energy such as mechanical energy or electricity.

During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air rushes in to take its place, creating winds. At night, the winds are reversed because the air cools more rapidly over land than over water.

In the same way, the large atmospheric winds that circle the earth are created because the land near the earth's equator is heated more by the sun than the land near the North and South Poles.

Today, wind energy is mainly used to generate electricity. Wind is called a renewable energy source because the wind will blow as long as the sun shines.

Windmills that were used to grind grain are an example of early uses of wind energy. Modern uses of wind energy include generation of electricity and pumping water. Current wind energy machines are called "wind turbine generators", "wind pumps", or more generally, "wind turbines".

History of wind and wind History of wind and wind energyenergy Since ancient times, people have harnessed the Since ancient times, people have harnessed the

winds energy. Over 5,000 years ago, the ancient winds energy. Over 5,000 years ago, the ancient Egyptians used wind to sail ships on the Nile Egyptians used wind to sail ships on the Nile River. Later, people built windmills to grind River. Later, people built windmills to grind wheat and other grains. The earliest known wheat and other grains. The earliest known windmills were in Persia (Iran). These early windmills were in Persia (Iran). These early windmills looked like large paddle wheels. windmills looked like large paddle wheels. Centuries later, the people of Holland improved Centuries later, the people of Holland improved the basic design of the windmill. the basic design of the windmill.

American colonists used windmills to grind wheat American colonists used windmills to grind wheat and corn, to pump water, and to cut wood at and corn, to pump water, and to cut wood at sawmills. As late as the 1920s, Americans used sawmills. As late as the 1920s, Americans used small windmills to generate electricity in rural small windmills to generate electricity in rural areas without electric service. areas without electric service.

The oil shortages of the 1970s changed the The oil shortages of the 1970s changed the energy picture for the country and the world. It energy picture for the country and the world. It created an interest in alternative energy sources, created an interest in alternative energy sources, paving the way for the re-entry of the windmill to paving the way for the re-entry of the windmill to generate electricity. In the early 1980s wind generate electricity. In the early 1980s wind energy really took off in California, partly energy really took off in California, partly because of state policies that encouraged because of state policies that encouraged renewable energy sources. renewable energy sources.

Humans have used wind energy for thousands of Humans have used wind energy for thousands of years. Ancient Persians used wind energy to years. Ancient Persians used wind energy to pump water before the birth of Christ. pump water before the birth of Christ.

The current interest in wind energy was started The current interest in wind energy was started by the need to develop clean, sustainable energy by the need to develop clean, sustainable energy systems that can be relied on for the long-term systems that can be relied on for the long-term future. future.

Wind Turbines: Upwind Wind Turbines: Upwind MachinesMachines

Upwind MachinesUpwind Machines Upwind machines have the rotor Upwind machines have the rotor

facing the wind. The basic facing the wind. The basic advantage of upwind designs is that advantage of upwind designs is that one avoids the wind shade behind one avoids the wind shade behind the tower. By far the vast majority the tower. By far the vast majority of wind turbines have this design. of wind turbines have this design.

On the other hand, there is also On the other hand, there is also some wind shade in front of the some wind shade in front of the tower, i.e. the wind starts bending tower, i.e. the wind starts bending away from the tower before it away from the tower before it reaches the tower itself, even if the reaches the tower itself, even if the tower is round and smooth. tower is round and smooth. Therefore, each time the rotor Therefore, each time the rotor passes the tower, the power from passes the tower, the power from the wind turbine drops slightly. the wind turbine drops slightly.

The basic drawback of upwind The basic drawback of upwind designs is that the rotor needs to be designs is that the rotor needs to be made rather inflexible, and placed made rather inflexible, and placed at some distance from the tower (as at some distance from the tower (as some manufacturers have found out some manufacturers have found out to their cost). In addition an upwind to their cost). In addition an upwind machine needs a yaw mechanism to machine needs a yaw mechanism to keep the rotor facing the wind. keep the rotor facing the wind.

How wind machines workHow wind machines work Like old fashioned windmills, today’s Like old fashioned windmills, today’s

wind machines use blades to collect wind machines use blades to collect the wind’s kinetic energy. Windmills the wind’s kinetic energy. Windmills work because they slow down the work because they slow down the speed of the wind. The wind flows speed of the wind. The wind flows over the airfoil shaped blades causing over the airfoil shaped blades causing lift, like the effect on airplane wings, lift, like the effect on airplane wings, causing them to turn. The blades are causing them to turn. The blades are connected to a drive shaft that turns connected to a drive shaft that turns an electric generator to produce an electric generator to produce electricity. electricity.

With the new wind machines, there is With the new wind machines, there is still the problem of what to do when still the problem of what to do when the wind isn’t blowing. At those the wind isn’t blowing. At those times, other types of power plants times, other types of power plants must be used to make electricity.must be used to make electricity.

Types of wind turbinesTypes of wind turbines There are two types of wind machines (turbines) used today based on the There are two types of wind machines (turbines) used today based on the

direction of the rotating shaft (axis): horizontal–axis wind machines and direction of the rotating shaft (axis): horizontal–axis wind machines and vertical-axis wind machines. The size of wind machines varies widely. vertical-axis wind machines. The size of wind machines varies widely. Small turbines used to power a single home or business may have a Small turbines used to power a single home or business may have a capacity of less than 100 kilowatts. Some large commercial sized turbines capacity of less than 100 kilowatts. Some large commercial sized turbines may have a capacity of 5 million watts, or 5 megawatts. Larger turbines may have a capacity of 5 million watts, or 5 megawatts. Larger turbines are often grouped together into wind farms that provide power to the are often grouped together into wind farms that provide power to the electrical grid.electrical grid.

Types

Vertical-axis

Horizontal-axis

Vertical-axisVertical-axis Vertical-axis wind turbines (or (or

VAWTs) have the main rotor shaft VAWTs) have the main rotor shaft running vertically. Key advantages running vertically. Key advantages of this arrangement are that the of this arrangement are that the generator and/or gearbox can be generator and/or gearbox can be placed at the bottom, near the placed at the bottom, near the ground, so the tower doesn't need to ground, so the tower doesn't need to support it, and that the turbine support it, and that the turbine doesn't need to be pointed into the doesn't need to be pointed into the wind. Drawbacks are usually wind. Drawbacks are usually pulsating torque that can be pulsating torque that can be produced during each revolution and produced during each revolution and drag created when the blade rotates drag created when the blade rotates into the wind. It is also difficult to into the wind. It is also difficult to mount vertical-axis turbines on mount vertical-axis turbines on towers, meaning they must operate towers, meaning they must operate in the often slower, more turbulent in the often slower, more turbulent air flow near the ground, resulting in air flow near the ground, resulting in lower energy extraction efficiency.lower energy extraction efficiency.

Exemples of vertical-axis wind Exemples of vertical-axis wind turbines: turbines: Darrieus wind turbineDarrieus wind turbine    Savonius wind turbine Savonius wind turbine 

Savonius wind turbine

Darrieus windturbine

Vertical-axis wind Vertical-axis wind turbinesturbines DisadvantagesDisadvantages : :

Most VAWTs produce energy at only 50% of Most VAWTs produce energy at only 50% of the efficiency of HAWTs in large part because the efficiency of HAWTs in large part because of the additional drag that they have as their of the additional drag that they have as their blades rotate into the wind. This can be blades rotate into the wind. This can be overcome by using structures to funnel more overcome by using structures to funnel more and align the wind into the rotor or the and align the wind into the rotor or the "vortex" effect of placing straight bladed "vortex" effect of placing straight bladed VAWTs closely together VAWTs closely together

There may be a height limitation to how tall a There may be a height limitation to how tall a vertical wind turbine can be built and how vertical wind turbine can be built and how much sweep area it can have. However , this much sweep area it can have. However , this can be overcome by connecting a multiple can be overcome by connecting a multiple number of turbines together in a triangular number of turbines together in a triangular pattern with bracing across the top of the pattern with bracing across the top of the structure . Thus reducing the need for such structure . Thus reducing the need for such strong vertical support , and allowing the strong vertical support , and allowing the turbine blades to be made much longer . turbine blades to be made much longer .

Most VAWTS need to be installed on a Most VAWTS need to be installed on a relatively flat piece of land and some sites relatively flat piece of land and some sites could be too steep for them but are still usable could be too steep for them but are still usable by HAWTs. by HAWTs.

Most VAWTs have low starting torque, and Most VAWTs have low starting torque, and may require energy to start the turning.may require energy to start the turning.

Advantages:Advantages: Easier to maintain because most of their moving parts Easier to maintain because most of their moving parts

are located near the ground. This is due to the vertical are located near the ground. This is due to the vertical wind turbine’s shape. The airfoils or rotor blades are wind turbine’s shape. The airfoils or rotor blades are connected by arms to a shaft that sits on a bearing and connected by arms to a shaft that sits on a bearing and drives a generator below, usually by first connecting to a drives a generator below, usually by first connecting to a gearbox. gearbox.

As the rotor blades are vertical, a yaw device is not As the rotor blades are vertical, a yaw device is not needed, reducing the need for this bearing and its cost. needed, reducing the need for this bearing and its cost.

Vertical wind turbines have a higher airfoil pitch angle, Vertical wind turbines have a higher airfoil pitch angle, giving improved aerodynamics while decreasing drag at giving improved aerodynamics while decreasing drag at low and high pressures. low and high pressures.

Low height useful where laws do not permit structures Low height useful where laws do not permit structures to be placed high. to be placed high.

Smaller VAWTs can be much easier to transport and Smaller VAWTs can be much easier to transport and install. install.

Does not need a free standing tower so is much less Does not need a free standing tower so is much less expensive and stronger in high winds that are close to expensive and stronger in high winds that are close to the ground. the ground.

Does not need to be pointed into the wind, can turn Does not need to be pointed into the wind, can turn regardless of the direction of the wind. regardless of the direction of the wind.

They can potentially be built to a far larger size than They can potentially be built to a far larger size than HAWT's , for instance floating VAWT's hundreds of HAWT's , for instance floating VAWT's hundreds of meters in diameter where the entire vessel rotates , can meters in diameter where the entire vessel rotates , can eliminate the need for a large and expensive bearing .eliminate the need for a large and expensive bearing .

Horizontal-axisHorizontal-axis Horizontal-axis wind turbines have the main rotor shaft and Horizontal-axis wind turbines have the main rotor shaft and

electrical generator at the top of a tower, and must be pointed electrical generator at the top of a tower, and must be pointed into the wind. Small turbines are pointed by a simple wind vane, into the wind. Small turbines are pointed by a simple wind vane, while large turbines generally use a wind sensor coupled with a while large turbines generally use a wind sensor coupled with a servo motor. Most have a gearbox, which turns the slow rotation servo motor. Most have a gearbox, which turns the slow rotation of the blades into a quicker rotation that is more suitable to of the blades into a quicker rotation that is more suitable to drive a generator.drive a generator.

Since a tower produces turbulence behind it, the turbine is Since a tower produces turbulence behind it, the turbine is usually pointed upwind of the tower. Turbine blades are made usually pointed upwind of the tower. Turbine blades are made stiff to prevent the blades from being pushed into the tower by stiff to prevent the blades from being pushed into the tower by high winds. Additionally, the blades are placed a considerable high winds. Additionally, the blades are placed a considerable distance in front of the tower and are sometimes tilted up a distance in front of the tower and are sometimes tilted up a small amount.small amount.

Downwind machines have been built, despite the problem of Downwind machines have been built, despite the problem of turbulence, because they don't need an additional mechanism turbulence, because they don't need an additional mechanism for keeping them in line with the wind, and because in high for keeping them in line with the wind, and because in high winds, the blades can be allowed to bend which reduces their winds, the blades can be allowed to bend which reduces their swept area and thus their wind resistance. Since turbulence swept area and thus their wind resistance. Since turbulence leads to fatigue failures, and reliability is so important, most leads to fatigue failures, and reliability is so important, most HAWTs are upwind machines.HAWTs are upwind machines.

Types of Horizontal-axis wind trubines:Types of Horizontal-axis wind trubines: Modern Rural Windmills  Modern Rural Windmills  Common modern wind turbines  Common modern wind turbines 

Horizontal-axis wind Horizontal-axis wind turbinesturbines Advantages:Advantages:

Blades are to the side of the Blades are to the side of the turbine's center of gravity, turbine's center of gravity, helping stability. helping stability.

Tall tower allows access to Tall tower allows access to stronger wind in sites with wind stronger wind in sites with wind shear. In some wind shear sites, shear. In some wind shear sites, every ten meters up, the wind every ten meters up, the wind speed can increase by 20% and speed can increase by 20% and the power output by 34%. the power output by 34%.

Tall tower allows placement on Tall tower allows placement on uneven land or in offshore uneven land or in offshore locations. locations.

Can be sited in forests above Can be sited in forests above the tree line. the tree line.

Most are self-starting. Most are self-starting. Can be cheaper per unit of Can be cheaper per unit of

output because of higher output because of higher production volume, larger sizes production volume, larger sizes and, in general, higher capacity and, in general, higher capacity factors and efficiency. factors and efficiency.

Disadvantages:Disadvantages: HAWTs have difficulty HAWTs have difficulty

operating in near ground, operating in near ground, turbulent winds. turbulent winds.

The tall towers and long blades The tall towers and long blades (up to 180 feet (55 m) long) (up to 180 feet (55 m) long) are difficult to transport on the are difficult to transport on the sea and on land. sea and on land. Transportation can now cost Transportation can now cost 20% of equipment costs. 20% of equipment costs.

Supply of HAWTs is less than Supply of HAWTs is less than demand and between 2004 and demand and between 2004 and 2006, turbine prices increased 2006, turbine prices increased up to 60%. At the end of 2006, up to 60%. At the end of 2006, all major manufacturers were all major manufacturers were booked up with orders through booked up with orders through 2008. 2008.

The FAA has raised concerns The FAA has raised concerns about tall HAWTs effects on about tall HAWTs effects on radar near Air Force bases. radar near Air Force bases.

Their height can create local Their height can create local opposition based on impacts to opposition based on impacts to viewsheds. viewsheds.

Small wind turbinesSmall wind turbines Small wind turbines may be as Small wind turbines may be as

small as a four hundred watt small as a four hundred watt generators for residential use. generators for residential use. The small ones often have direct The small ones often have direct drive generators, direct current drive generators, direct current output, aeroelastic blades, output, aeroelastic blades, lifetime bearings and use a vane lifetime bearings and use a vane to point into the wind. Larger, to point into the wind. Larger, more costly turbines generally more costly turbines generally have geared power trains, have geared power trains, alternating current output, flaps alternating current output, flaps and are actively pointed into the and are actively pointed into the wind. Direct drive generators wind. Direct drive generators and aeroelastic blades for large and aeroelastic blades for large wind turbines are being wind turbines are being researched.researched.

A small wind turbine can be A small wind turbine can be installed on a roof. Installation installed on a roof. Installation issues then include the strength issues then include the strength of the roof, vibration, and the of the roof, vibration, and the turbulence caused by the roof turbulence caused by the roof ledge.ledge.

Turbine design and Turbine design and constructionconstruction Wind turbines are designed to exploit Wind turbines are designed to exploit

the wind energy that exists at a location. the wind energy that exists at a location. Aerodynamic modeling is used to Aerodynamic modeling is used to determine the optimum tower height, determine the optimum tower height, control systems, number of blades, and control systems, number of blades, and blade shape.blade shape.

Virtually all modern wind turbines Virtually all modern wind turbines convert wind energy to electricity for convert wind energy to electricity for energy distribution. As described, the energy distribution. As described, the modern wind turbine is a system that modern wind turbine is a system that comprises three integral components comprises three integral components with distinct disciplines of engineering with distinct disciplines of engineering science. The rotor component, which is science. The rotor component, which is approximately 20% of the wind turbine approximately 20% of the wind turbine cost, includes the blades for converting cost, includes the blades for converting wind energy to an intermediate low wind energy to an intermediate low speed rotational energy. The generator speed rotational energy. The generator component, which is approximately 34% component, which is approximately 34% of the wind turbine cost, includes the of the wind turbine cost, includes the electrical generator, the control electrical generator, the control electronics, and most likely a gearbox electronics, and most likely a gearbox component for converting the low speed component for converting the low speed rotational energy to electricity. The rotational energy to electricity. The structural support component, which is structural support component, which is approximately 15% of the wind turbine approximately 15% of the wind turbine cost, includes the tower for optimally cost, includes the tower for optimally situating the rotor component to the situating the rotor component to the wind energy source.wind energy source.

TheThe benefits of wind energybenefits of wind energy Wind energy is an ideal renewable energy because: Wind energy is an ideal renewable energy because:

It is a pollution-free, infinitely sustainable form of energy     It is a pollution-free, infinitely sustainable form of energy     It doesn’t require fuel    It doesn’t require fuel    It doesn’t create greenhouse gasses    It doesn’t create greenhouse gasses    It doesn’t produce toxic or radioactive waste. It doesn’t produce toxic or radioactive waste.

Wind energy is quiet and does not present any significant hazard to birds or Wind energy is quiet and does not present any significant hazard to birds or other wildlife.     other wildlife.    

When large arrays of wind turbines are installed on farmland, only about 2% of When large arrays of wind turbines are installed on farmland, only about 2% of the land area is required for the wind turbines. The rest is available for farming, the land area is required for the wind turbines. The rest is available for farming, livestock, and other uses.     livestock, and other uses.    

Landowners often receive payment for the use of their land, which enhances Landowners often receive payment for the use of their land, which enhances their income and increases the value of the land.    their income and increases the value of the land.   

Ownership of wind turbine generators by individuals and the community Ownership of wind turbine generators by individuals and the community allows people to participate directly in the preservation of our environment.    allows people to participate directly in the preservation of our environment.   

Each megawatt-hour of electricity that is generated by wind energy helps to Each megawatt-hour of electricity that is generated by wind energy helps to reduce the 0.8 to 0.9 tonnes of greenhouse gas emissions that are produced by reduce the 0.8 to 0.9 tonnes of greenhouse gas emissions that are produced by coal or diesel fuel generation each year. coal or diesel fuel generation each year.

Wind and the Wind and the environmentenvironment In the 1970s, oil shortages pushed In the 1970s, oil shortages pushed

the development of alternative the development of alternative energy sources. In the 1990s, the energy sources. In the 1990s, the push came from a renewed concern push came from a renewed concern for the environment in response to for the environment in response to scientific studies indicating potential scientific studies indicating potential changes to the global climate if the changes to the global climate if the use of fossil fuels continues to use of fossil fuels continues to increase. Wind energy is an increase. Wind energy is an economical power resource in many economical power resource in many areas of the country. Wind is a clean areas of the country. Wind is a clean fuel; wind farms produce no air or fuel; wind farms produce no air or water pollution because no fuel is water pollution because no fuel is burned. Growing concern about burned. Growing concern about emissions from fossil fuel generation, emissions from fossil fuel generation, increased government support, and increased government support, and higher costs for fossil fuels have higher costs for fossil fuels have helped wind power capacity in the helped wind power capacity in the United States grow substantially United States grow substantially over the last 10 years. over the last 10 years.

The most serious environmental The most serious environmental drawbacks to wind machines may be drawbacks to wind machines may be their negative effect on wild bird their negative effect on wild bird populations and the visual impact on populations and the visual impact on the landscape. the landscape.

The costs of wind energy The costs of wind energy  The cost of wind energy is determined by:The cost of wind energy is determined by:

The initial cost of the wind turbine The initial cost of the wind turbine installation  installation 

The interest rate on the money invested  The interest rate on the money invested  The amount of energy produced  The amount of energy produced 

Any wind turbine that is installed in a very Any wind turbine that is installed in a very windy area generates less expensive windy area generates less expensive electricity than the same unit installed in a electricity than the same unit installed in a less windy area. So it’s important to assess less windy area. So it’s important to assess the wind at the potential site.the wind at the potential site.

Modern wind turbine generators cost Modern wind turbine generators cost between $1500 and $2000 per kilowatt for between $1500 and $2000 per kilowatt for wind farms that use multiple-unit arrays of wind farms that use multiple-unit arrays of large machines. Smaller individual units cost large machines. Smaller individual units cost up to $3000 per kilowatt. In good wind up to $3000 per kilowatt. In good wind areas, the costs of generating electricity areas, the costs of generating electricity range between five and ten cents per range between five and ten cents per kilowatt hour. That cost is somewhat higher kilowatt hour. That cost is somewhat higher than the costs associated with an electrical than the costs associated with an electrical facility, but wind energy costs are facility, but wind energy costs are decreasing every year, whereas most decreasing every year, whereas most conventional generation costs continue to conventional generation costs continue to increase. increase.