One of the questions most often asked about wind power is ‘what happens when the wind doesn’t blow’. On a local level, this is mainly a question of grid integration, but in the big picture the wind is a vast untapped resource capable of supplying the world’s electricity needs many times over. In practical terms, in an optimum, clean energy future, wind will be an important part of a mix of renewable energy technologies, playing a more dominant role in some regions than in others. However, it is worthwhile to step back for a minute and consider the enormity of the resource.
Researchers at Stanford University’s Global Climate and Energy Project recently did an evaluation of the global potential of wind power, using five years of data from the US National Climatic Data Center and the Forecasts Systems Laboratory. They estimated that the world’s wind resources can generate more than enough power to satisfy total global energy demand. After collecting measurements from 7,500 surface and 500 balloon-launch monitoring stations to determine global wind speeds at 80 meters above ground level, they found that nearly 13% had an average wind speed above 6.9 meters per second , sufficient for economical wind power generation. Using only 20% of this potential resource for power generation, the report concluded that wind energy could satisfy the world’s electricity demand in the year 2000 seven times over.
North America was found to have the greatest wind power potential, although some of the strongest winds were observed in Northern Europe, whilst the southern tip of South America and the Australian island of Tasmania also recorded significant and sustained strong winds. To be clear, however, there are extraordinarily large untapped wind resources on all continents, and in most countries; and while this study included some island observation points, it did not include offshore resources, which are enormous.
For example, looking at the resource potential in the shallow waters on the continental shelf off the densely populated east coast of the US, from Massachusetts to North Caroline, the average potential resource was found to be approximately four times the total energy demand in what is one of the most urbanized, densely populated and highest-electricity consuming regions of the world.
A study by the German Advisory Council on Global Change (WBGU), “World in Transition – Towards Sustainable Energy Systems” (2003) calculated that the global technical potential for energy production from both onshore and offshore wind installations was 278,000 TWh (Terawatt hours) per year. The report then assumed that only 10–15% of this potential would be realisable in a sustainable fashion, and arrived at a figure of approximately 39,000 TWh supply per year as the contribution from wind energy in the long term, which is more than double current electricity demand.
The WBGU calculations of the technical potential were based on average values of wind speeds from meteorological data collected over a 14 year period (1979–1992). They also assumed that advanced multi-megawatt wind energy converters would be used. Limitations to the potential came through excluding all urban areas and natural features such as forests, wetlands, nature reserves, glaciers and sand dunes. Agriculture, on the other hand, was not regarded as competition for wind energy in terms of land use.
Wind Energy Associations Links
- World Wind Energy Association (WWEA)
- Global Wind Energy Council (GWEC)
- IEA Wind
- WEC Survey of Energy Resources
- European Wind Energy Association (EWEA)
- American Wind Energy Association (AWEA)
- NREL Wind Energy
- EERE Wind Energy
Since early recorded history, people have been harnessing the energy of the wind. Wind energy propelled boats along the Nile River as early as 5000 B.C. By 200 B.C., simple windmills in China were pumping water, while vertical-axis windmills with woven reed sails were grinding grain in Persia and the Middle East.
Early in the twentieth century, windmills were commonly used across the Great Plains to pump water and to generate electricity.
New ways of using the energy of the wind eventually spread around the world. By the 11th century, people in the Middle East were using windmills extensively for food production; returning merchants and crusaders carried this idea back to Europe. The Dutch refined the windmill and adapted it for draining lakes and marshes in the Rhine River Delta. When settlers took this technology to the New World in the late 19th century, they began using windmills to pump water for farms and ranches, and later, to generate electricity for homes and industry.
Industrialization, first in Europe and later in America, led to a gradual decline in the use of windmills. The steam engine replaced European water-pumping windmills. In the 1930s, the Rural Electrification Administration’s programs brought inexpensive electric power to most rural areas in the United States.
However, industrialization also sparked the development of larger windmills to generate electricity. Commonly called wind turbines, these machines appeared in Denmark as early as 1890. In the 1940s the largest wind turbine of the time began operating on a Vermont hilltop known as Grandpa’s Knob. This turbine, rated at 1.25 megawatts in winds of about 30 mph, fed electric power to the local utility network for several months during World War II.
- Early in the twentieth century, windmills were commonly used across the Great Plains to pump water and to generate electricity.
The popularity of using the energy in the wind has always fluctuated with the price of fossil fuels. When fuel prices fell after World War II, interest in wind turbines waned. But when the price of oil skyrocketed in the 1970s, so did worldwide interest in wind turbine generators.
The wind turbine technology R&D that followed the oil embargoes of the 1970s refined old ideas and introduced new ways of converting wind energy into useful power. Many of these approaches have been demonstrated in “wind farms” or wind power plants — groups of turbines that feed electricity into the utility grid — in the United States and Europe.
Today, the lessons learned from more than a decade of operating wind power plants, along with continuing R&D, have made wind-generated electricity very close in cost to the power from conventional utility generation in some locations. Wind energy is the world’s fastest-growing energy source and will power industry, businesses and homes with clean, renewable electricity for many years to come.
Continue reading History of Wind Energy
What is Wind Energy or Wind Power ?
Wind energy is a teeming energy source which never seems to expire.Wind is a form of solar energy. Winds are caused by the uneven heating of the atmosphere by the sun, the irregularities of the earth’s surface, and rotation of the earth. Wind flow patterns are modified by the earth’s terrain, bodies of water, and vegetative cover. This wind flow, or motion energy, when “harvested” by modern wind turbines, can be used to generate electricity.
How Wind Power Is Generated
The terms “wind energy” or “wind power” describe the process by which the wind is used to generate mechanical power or electricity. Wind turbines convert the kinetic energy in the wind into mechanical power.If the mechanical energy is used to produce electricity, the device may be called a wind generator. If the mechanical energy is used to drive machinery, such as for grinding grain or pumping water, the device is called a windmill or wind pump.
Wind turbine, like aircraft propeller blades, turn in the moving air and power an electric generator that supplies an electric current. Simply stated, a wind turbine is the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.
How Wind Turbines Work
A wind turbine works the opposite of a fan. Instead of using electricity to make wind, like a fan, wind turbines use wind to make electricity. The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity.
This aerial view of a wind power plant shows how a group of wind turbines can make electricity for the utility grid. The electricity is sent through transmission and distribution lines to homes, businesses, schools, and so on.
Types of Wind Turbines
Wind turbines fall into two basic categories.
The horizontal-axis variety, like the traditional farm windmills used for pumping water.
The vertical-axis design, like the eggbeater-style Darrieus model.
Most large modern wind turbines are horizontal-axis turbines.Horizontal-axis wind turbines typically either have two or three blades. These three-bladed wind turbines are operated “upwind,” with the blades facing into the wind.
Parts of Wind Turbine
Measures the wind speed and transmits wind speed data to the controller.
Most turbines have either two or three blades. Wind blowing over the blades causes the blades to “lift” and rotate.
A disc brake, which can be applied mechanically, electrically, or hydraulically to stop the rotor in emergencies.
The controller starts up the machine at wind speeds of about 8 to 16 miles per hour (mph) and shuts off the machine at about 55 mph. Turbines do not operate at wind speeds above about 55 mph because they might be damaged by the high winds.
5. Gear Box
Gears connect the low-speed shaft to the high-speed shaft and increase the rotational speeds from about 30 to 60 rotations per minute (rpm) to about 1000 to 1800 rpm, the rotational speed required by most generators to produce electricity. The gear box is a costly (and heavy) part of the wind turbine and engineers are exploring “direct-drive” generators that operate at lower rotational speeds and don’t need gear boxes.
Usually an off-the-shelf induction generator that produces 60-cycle AC electricity.
7. High-Speed Shaft
Drives the generator.
8. Low-Speed Shaft
The rotor turns the low-speed shaft at about 30 to 60 rotations per minute.
The nacelle sits atop the tower and contains the gear box, low- and high-speed shafts, generator, controller, and brake. Some nacelles are large enough for a helicopter to land on.
Blades are turned, or pitched, out of the wind to control the rotor speed and keep the rotor from turning in winds that are too high or too low to produce electricity.
The blades and the hub together are called the rotor.
Towers are made from tubular steel, concrete, or steel lattice. Because wind speed increases with height, taller towers enable turbines to capture more energy and generate more electricity.
13. Wind Direction
This is an “upwind” turbine, so-called because it operates facing into the wind. Other turbines are designed to run “downwind,” facing away from the wind.
14. Wind Vane
Measures wind direction and communicates with the yaw drive to orient the turbine properly with respect to the wind.
15. Yaw Drive
Upwind turbines face into the wind; the yaw drive is used to keep the rotor facing into the wind as the wind direction changes. Downwind turbines don’t require a yaw drive, the wind blows the rotor downwind.
16. Yaw Motor
Powers the yaw drive.
Wind turbines are often grouped together into a single wind power plant, also known as a wind farm, and generate bulk electrical power. Electricity from these turbines is fed into a utility grid and distributed to customers, just as with conventional power plants.
Wind Turbine Size and Power Ratings
Wind turbines are available in a variety of sizes, and therefore power ratings. The largest machine has blades that span more than the length of a football field, stands 20 building stories high, and produces enough electricity to power 1,400 homes. A small home-sized wind machine has rotors between 8 and 25 feet in diameter and stands upwards of 30 feet and can supply the power needs of an all-electric home or small business. Utility-scale turbines range in size from 50 to 750 kilowatts. Single small turbines, below 50 kilowatts, are used for homes, telecommunications dishes, or water pumping.
Wind Energy offers many advantages, which explains why it’s the fastest-growing energy source in the world. Research efforts are aimed at addressing the challenges to greater use of wind energy.
Wind energy is fueled by the wind, so it’s a clean fuel source. Wind energy doesn’t pollute the air like power plants that rely on combustion of fossil fuels, such as coal or natural gas. Wind turbines don’t produce atmospheric emissions that cause acid rain or greenhouse gasses.
Wind energy is a domestic source of energy, produced in the United States. The nation’s wind supply is abundant.
Wind energy relies on the renewable power of the wind, which can’t be used up. Wind is actually a form of solar energy; winds are caused by the heating of the atmosphere by the sun, the rotation of the earth, and the earth’s surface irregularities.
Wind energy is one of the lowest-priced renewable energy technologies available today, costing between 4 and 6 cents per kilowatt-hour, depending upon the wind resource and project financing of the particular project.
Wind turbines can be built on farms or ranches, thus benefiting the economy in rural areas, where most of the best wind sites are found. Farmers and ranchers can continue to work the land because the wind turbines use only a fraction of the land. Wind power plant owners make rent payments to the farmer or rancher for the use of the land.
Wind power must compete with conventional generation sources on a cost basis. Depending on how energetic a wind site is, the wind farm may or may not be cost competitive. Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators.
Good wind sites are often located in remote locations, far from cities where the electricity is needed. Transmission lines must be built to bring the electricity from the wind farm to the city.
Wind resource development may compete with other uses for the land and those alternative uses may be more highly valued than electricity generation.
Although wind power plants have relatively little impact on the environment compared to other conventional power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and sometimes birds have been killed by flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants.
Advantages and Disadvantages of Wind-Generated Electricity
A Renewable Non-Polluting Resource
Wind energy is a free, renewable resource, so no matter how much is used today, there will still be the same supply in the future. Wind energy is also a source of clean, non-polluting, electricity. Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases. According to the U.S. Department of Energy, in 1990, California’s wind power plants offset the emission of more than 2.5 billion pounds of carbon dioxide, and 15 million pounds of other pollutants that would have otherwise been produced. It would take a forest of 90 million to 175 million trees to provide the same air quality.
Even though the cost of wind power has decreased dramatically in the past 10 years, the technology requires a higher initial investment than fossil-fueled generators. Roughly 80% of the cost is the machinery, with the balance being site preparation and installation. If wind generating systems are compared with fossil-fueled systems on a “life-cycle” cost basis (counting fuel and operating expenses for the life of the generator), however, wind costs are much more competitive with other generating technologies because there is no fuel to purchase and minimal operating expenses.
Although wind power plants have relatively little impact on the environment compared to fossil fuel power plants, there is some concern over the noise produced by the rotor blades, aesthetic (visual) impacts, and birds and bats having been killed (avian/bat mortality) by flying into the rotors. Most of these problems have been resolved or greatly reduced through technological development or by properly siting wind plants.
Supply and Transport Issues
The major challenge to using wind as a source of power is that it is intermittent and does not always blow when electricity is needed. Wind cannot be stored (although wind-generated electricity can be stored, if batteries are used), and not all winds can be harnessed to meet the timing of electricity demands. Further, good wind sites are often located in remote locations far from areas of electric power demand (such as cities). Finally, wind resource development may compete with other uses for the land, and those alternative uses may be more highly valued than electricity generation. However, wind turbines can be located on land that is also used for grazing or even farming.