We have been harnessing the wind's energy for hundreds of years. From old Holland to farms in the United States, windmills have been used for pumping water or grinding grain. Today, the windmill's modern equivalent — a wind turbine — can use the wind's energy to generate electricity. To meet the electricity needs of a power company, a number of large wind turbines (50 kilowatts up to 2 megawatts) can be built close together to form a wind plant. Several power providers today use wind plants to supply power to their customers. [Source: U.S. Department of Energy]
Wind energy is cheaper than other, more ineffective renewables, such as solar, tidal, and ethanol. Wind power generates electricity for 20 percent of the cost of solar power. It can produce energy at a rate of 4 or 5 cents per kilowatt hour. Increased efficiency could drop the price one or two cents. The use of wind turbines has increased ten-fold between 2001 and 2011. Wind power growth was 52 percent in 2006.
Wind is created by the unequal heating of the Earth's surface by the sun. Wind turbines convert the kinetic energy in wind into clean electricity. When the wind spins the wind turbine's blades, a rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. Most turbines have automatic overspeed-governing systems to keep the rotor from spinning out of control in very high winds.
There are large windmill parks in coastal and mountain areas where there are strong winds. Governments often offer generous subsidies for wind generator construction. The Danish government runs a program of offering subsidies for windmill production and laws that require utilities to buy excess electricity from wind turbines at 85 percent of retail price.
Wind Power in Different Countries
The amount of wind power alone generated worldwide could expand by roughly 30 percent annually, based on most conservative estimates. Denmark already generates one-fourth of its power from wind, while three German states meet nearly 60 percent of their needs from this ever-pervasive source. In Iowa, which is the US benchmark for wind-power investment, wind is generating about one-fifth of the state’s energy needs.
A report in Science magazine contends that the Chinese could increase the country’s current output by a factor of 16 from wind-generated electricity. A single wind-generating complex in Gansu Province in northwestern China will, when completed, have 38,000 megawatts of generating capacity, enough to supply the total electricity needs of entire countries like Poland and Egypt.
Countries with the most existing wind-energy capacity (gigawatts in 2008): 1) the United States (25,170); 2) Germany (23,903); 3) Spain (16,754); 4) China (12,210); 4) India (9,645); 6) France (4,404); 7) Italy (3,736); 8) Britain (3,231); 9) Denmark (3,180); 10) Portugal (2,862); Rest of the World (16,686) Countries with most wind-energy capacity per capita (megawatts in 2008): 1) Denmark (581.6); 2) Spain (414.2); 3) Germany (290.1); 4) Portugal (268); 5) United States (83.6); 6) Italy (64.3); 7) France (53.4); 8) Britain (53.3); 9) China (9.2); 10) India (8.5); Rest of World (4.7). Wind power capacity in 2003: leaders: 12,000 megawatts in Germany, the world leader, and 1,700 in India 500 megawatts in Japan.
Proponents of wind energy in Europe assert that wind could supply much of the continent’s electricity. The biggest obstacle is resistance to the technology because the wind turbines are regarded as eye sores.
Wind Energy Technology
Windmills have existed at least since the A.D. 7th century. Experiments with electrical generation from windmills was done at the end of the 19th century by Denmark inventor Poul la Cour. Small wind power turbines used, say, by a farmer to power his home and farm is about 10-meters tall and has a two-meter-in-diameter blade It generates 1.5 kilowatts an hour, enough to power the average light bulb for about 15 hours. [Source: U.S. Department of Energy]
The rare earth neodymium is a critical ingredient in wind turbine magnets. The industry is also hampered by shortages of gearboxes and German ball bearings that are essential components for wind power turbines. Gearboxes are the second most expensive part of a wind turbine unit after the supporting tower.
Since the 1970s, wind energy technology has been steadily improved. At the beginning of the 1980s, the average wind turbine was 20 meters high and had a rotor diameter of 10.5 meters and had a 26 kW generator. Now they are 60 metes tall and have a rotor diameter of 50 meters and have a 700 kW generator. Each produce 1 to 2 million kilowatt-hours a year, enough to power
300 European households.
Large industrial varieties are as tall as football fields. There are plans for 100-plus megawatt offshore wind farms with hundred of turbines that will generate as much electricity as a coal or gas power station.
Wind turbines operate on a simple principle. The energy in the wind turns two or three propeller-like blades around a rotor. The rotor is connected to the main shaft, which spins a generator to create electricity. The blades act much like airplane wings. When the wind blows, a pocket of low-pressure air forms on the downwind side of the blade. The low-pressure air pocket then pulls the blade toward it, causing the rotor to turn. This is called lift. The force of the lift is actually much stronger than the wind's force against the front side of the blade, which is called drag. The combination of lift and drag causes the rotor to spin like a propeller, and the turning shaft spins a generator to make electricity. [Source: U.S. Department of Energy]
Wind turbines, like windmills, are mounted on a tower to capture the most energy. At 100 feet (30 meters) or more aboveground, they can take advantage of the faster and less turbulent wind. Turbines catch the wind's energy with their propeller-like blades. Usually, two or three blades are mounted on a shaft to form a rotor. Wind turbines can be used to produce electricity for a single home or building, or they can be connected to an electricity grid for more widespread electricity distribution.
Wind turbines can be used as stand-alone applications, or they can be connected to a utility power grid or even combined with a photovoltaic (solar cell) system. For utility-scale (megawatt-sized) sources of wind energy, a large number of wind turbines are usually built close together to form a wind plant, also referred to as a wind farm. Several electricity providers today use wind plants to supply power to their customers. Stand-alone wind turbines are typically used for water pumping or communications. However, homeowners, farmers, and ranchers in windy areas can also use wind turbines as a way to cut their electric bills.
Small Wind Electric Systems
Small wind electric systems are one of the most cost-effective home-based renewable energy systems. These systems are also nonpolluting. If you live on at least one acre of land with an ample wind resource, you can generate your own electricity using a small wind electric system. You can also use a small wind turbine for pumping water. [Source: U.S. Department of Energy]
Small wind electric system can help you to: 1) Lower your electricity bills by 50 percent-90 percent ; 2) Help you avoid the high costs of having utility power lines extended to a remote location; 3) Help uninterruptible power supplies ride through extended utility outages. Small wind systems also have potential as distributed energy resources. Distributed energy resources refer to a variety of small, modular power-generating technologies that can be combined to improve the operation of the electricity delivery system.
A small wind system can be connected to an electric distribution system (grid-connected) or it can stand alone (off-grid). Most small wind turbines manufactured today are horizontal-axis, upwind machines that have two or three blades. These blades are usually made of a composite material, such as fiberglass.
The turbine's frame is the structure onto which the rotor, generator, and tail are attached. The amount of energy a turbine will produce is determined primarily by the diameter of its rotor. The diameter of the rotor defines its "swept area," or the quantity of wind intercepted by the turbine. The tail keeps the turbine facing into the wind. The wind turbine is mounted on a tower to provide better access to stronger winds. In addition to the turbine and tower, small wind electric systems also require balance-of-system components.
Wind Towers and Balance-of-System Components
Because wind speeds increase with height, a small wind turbine is mounted on a tower. In general, the higher the tower, the more power the wind system can produce. The tower also raises the turbine above the air turbulence that can exist close to the ground because of obstructions such as hills, buildings, and trees. [Source: U.S. Department of Energy]
Relatively small investments in increased tower height can yield very high rates of return in power production. For instance, to raise a 10-kilowatt generator from a 60-foot tower height to a 100-foot tower involves a 10 percent increase in overall system cost, but it can produce 25 percent more power. The estimated annual energy output and turbine size you'll need can help determine the best tower height.
Most turbine manufacturers provide wind energy system packages that include towers. There are two basic types of towers: self-supporting (free-standing) and guyed. There are also tilt-down versions of guyed towers. Most home wind power systems use a guyed tower, which are the least expensive. Guyed towers can consist of these components: Lattice sections; pipe; tubing, depending on the design; and supporting guy wires. Guyed towers are easier to install than self-supporting towers. However, because the guy radius must be one-half to three-quarters of the tower height, guyed towers require enough space to accommodate them.
While tilt-down towers are more expensive, they offer the consumer an easy way to perform maintenance on smaller light-weight turbines, usually 10 kilowatt or less. Tilt-down towers can also be lowered to the ground during hazardous weather such as hurricanes. Aluminum towers are prone to cracking and should be avoided.
The balance-of-system parts — those in addition to the wind turbine and the tower — you'll need for a small wind electric system depend on your application. For example, the parts required for a water pumping system will be much different from what you need for a residential application.The balance-of-system parts required will also depend on the type of system: Grid-connected; Stand-alone; and Hybrid.
Most manufacturers can provide you with a system package that includes all the parts you need for your particular application. For a residential grid-connected application, the balance-of-system parts may include the following: a controller; storage batteries; an inverter (power conditioning unit); wiring; electrical disconnect switch; grounding system; and Foundation for the tower.
Problems with Wind Power
Wind is unreliable. It is unpredictable and often fails to blow when it is most needed. With electricity generation power has to be available when it is most needed during peak hours. In this way wind is useful saving fuel but is not a good enough source to mothball existing plants. The practicality of wind energy could be improved if better ways to store electricity and organize regional grids is found.
There are concerns that huge offshore wind farms could hinder navigation and fishing. Environmentalists worry about the whirling blades of wind generators killing or injuring protected species of birds. In some places turbines are painted bright red and lit up at night to warn birds. Newsweek reported: “A study suggests that beaked whales — the size of a rhino and the weight of a bus — are confused by the presence of wind farms at sea, leading them to beach. Birds too find wind farms to be killers. The wind turbines in California’s Diablo Mountains chop up thousands of birds a year, including golden eagles and red-tailed hawks. [Source: Newsweek]
“There is some resistance to wind farms in densely populated Japan. In January 2007 a 68-meter-high, 179-ton windmill snapped at its base and fell over in Aomori Prefecture. The turbine was built to withstand winds of 216kph but came down in winds of only 90kph. The generator was made in Denmark and installed by a Japanese construction company. The accident was blamed on a design flaw that allowed all the reenforcement bars in the inner ring of the base to break into pieces while those on the outer rings were largely intact. The windmill was part of the Iwaya Wind Farm, which opened in 2001 and has 25 windmills across 100 to 200 meters apart.
High Costs of Wind Power
Bjorn Lomborg of Project Syndicate wrote: “In the United Kingdom wind remains significantly more costly than other energy sources. Using the UK Electricity Generation Costs 2010 update and measuring in cost per produced kilowatt-hour, wind is still 20-200 percent more expensive than the cheapest fossil-fuel options. And even this is a significant underestimate. As the UK and other developed countries have rushed to build more wind turbines, they have naturally started with the windiest places, leaving poorer sites for later. At the same time, people increasingly protest against the wind farms in their backyards. Local opposition has tripled over the past three years, and local approval rates for new wind farms have sunk to an all-time low. [Source: Bjorn Lomborg, Project Syndicate, March 16, 2012]
“Most people believe that a few wind turbines can be attractive, but it is an entirely different matter when turbines are scattered across the countryside, or when massive, industrial wind farms extend for miles. Complaints have also increased about enormous new wind turbines’ low-frequency noise. Given souring public sentiment, most of the future increase in wind turbines is expected to take place offshore, where there is less opposition, but where costs are much higher.
“With its “20-20-20" policy, the EU has promised that, by 2020, it will cut its carbon emissions by 20 percent below 1990 levels, and increase its reliance on renewables by 20 percent. For the UK, this requires a dramatic increase in wind power, especially offshore. This will be surprisingly costly. The UK Carbon Trust estimates that the cost of expanding wind turbines to 40 gigawatts, in order to provide 31 percent of electricity by 2020, could run as high as £75 billion ($120 billion). And the benefits, in terms of tackling global warming, would be measly: a reduction of just 86 megatons of CO2 per year for two decades. In terms of averted rise in temperature, this would be completely insignificant. Using a standard climate model, by 2100, the UK’s huge outlay will have postponed global warming by just over ten days.
“Moreover, this estimate is undoubtedly too optimistic. Wind frequently does not blow when we need it. For example, as the BBC reported, the cold weather on December 21, 2010, was typical of a prolonged cold front, with high-pressure areas and little wind. Whereas wind power, on average, supplies 5 percent of the UK’s electricity, its share fell to just 0.04 percent that day. With demand understandably peaking, other sources, such as coal and gas, had to fill the gap. Making up for a 5 percent shortfall in supply is manageable, but the situation will change dramatically as the UK increases its reliance on wind power to reach the 31 percent target by 2020. Wind power becomes much more expensive when we factor in the large supplies of power that must be created for backup whenever the wind dies down.
“The cheapest backup power by far is provided by open-cycle gas plants, which imply more CO2 emissions. Thus, wind power will ultimately be both costlier and reduce emissions less than officially estimated. (This is also why simple calculations based on costs per kWh are often grossly misleading, helping to make wind and other intermittent renewables appear to be cheaper than they are.)
Contrary to what many think, the cost of both onshore and offshore wind power has not been coming down. On the contrary, it has been going up over the past decade. The United Nations Intergovernmental Panel on Climate Change acknowledged this in its most recent renewable-energy report. Likewise, the UK Energy Research Center laments that wind-power costs have “risen significantly since the mid-2000s.” Like the EU, the UK has become enamored with the idea of reducing CO2 through wind technology. But most academic models show that the cheapest way to reduce CO2 by 20 percent in 2020 would be to switch from coal to cleaner natural gas.
Image Sources: U.S. Department of Energy; Wikimedia Commons
Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, U.S. Department of Energy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.
Last updated August 2012