This section include information on the various ways that electricity is generated in Virginia and the U.S.
Select the fuel source:
Biomass (organic matter) can be used to provide heat, make fuels, and generate electricity. This is called bioenergy.
Bioenergy technologies use renewable biomass resources to produce energy-related products such as electricity, liquid, solid, and gaseous fuels, heat, chemicals, and other materials.
Bioenergy ranks second (after hydropower) in renewable primary energy production. It accounts for 3% of the primary energy production in the US (with 10 gigawatts of installed capacity).
Wood, the largest source of bioenergy, has been used to provide heat for thousands of years.
Biomass includes: pitch, peat, railroad ties, sludge wood, wood/wood waste, spent fuels, agricultural byproducts, fish oil, landfill gas, municipal solid waste, sludge waste, straw, and tires.
Today, many bioenergy resources are replenished through the cultivation of energy crops, such as fast-growing trees and grasses, called bioenergy feedstocks.
Heat can be used to chemically convert biomass into a fuel oil, which can be burned like petroleum to generate electricity.
Biomass can also be burned directly to produce steam for electricity production or manufacturing processes.
In the lumber and paper industries, wood scraps are sometimes directly fed into boilers to produce steam for manufacturing processes or to heat buildings.
Some coal-fired power plants use biomass as a supplementary energy source in high-efficiency boilers to significantly reduce emissions.
Unlike other renewable sources, biomass can be converted directly into transportation fuels. The two most common biofuels are:
Ethanol: An alcohol, is made by fermenting biomass high in carbohydrates (for example, corn). It is mostly used as a fuel additive to cut down a vehicle's carbon monoxide and other smog-causing emissions.
Biodiesel: An ester, is made using vegetable oils, animal fats, algae, or even recycled cooking grease. It can be used as a diesel additive to reduce vehicle emissions or, in its pure form, to fuel a vehicle.
Even gas can be produced from biomass for generating electricity
Gasification systems use high temperatures to convert biomass into a gas (a mixture of hydrogen, carbon monoxide, and methane). The gas fuels a turbine, which is very much like a jet engine, only it turns an electric generator instead of propelling a jet.
The decay of biomass in landfills also produces a gas-methane-that can be burned in a boiler or fuel a turbine to produce steam for electricity generation or for industrial processes.
Formation of Coal
Coal, a combustible mineral, began to form about 300 million years ago when large plants died. Throughout time, these plants were buried underneath vast amounts of water and dirt. The continuous pressure caused by the overlaying material along with periods of extreme heat created this mineral.
Coal is considered a "non-renewable" resource, because it takes so log to form. It is mainly located in three large regions in the United States: the Appalachian Coal Region, the Interior Coal Region and the Western Coal Region. The Western Coal mines are the largest in the world. Coal was first discovered in Virginia in 1701, but mining production did not begin until 1748.
There are four basic varieties of coal: anthracite, bituminous, sub-bituminous and lignite. Anthracite has the highest energy content with an average of 25 million British Thermal Units (Btu) per ton of coal. Lignite only averages 14 million Btu per ton. A Btu is a measurement of energy. It is the amount of energy needed in order to raise the temperature of 1 pound of water 1 degree Fahrenheit at a temperature of 39.2 degrees Fahrenheit.
Uses of Coal
The four major uses of coal mined in the U.S. are electric power generation, industrial use, steel making, and export to other countries. It is estimated that more than 90% of all the coal mined in the United States is used to generate electricity. Roughly 52% of the electricity generated in the U.S. comes from burning of coal. Coal is such a great resource because it is the cheapest source of power per million Btu. It costs less then half the price of natural gas and petroleum. The United States is the 4th largest coal exporter in the world, sending approximately 60 million tons of coal to other countries annually, at a price of close to $2 billion. Coal generates about 40% of the total energy consumed worldwide.
Tons and Tons of Coal
The United States produces more than a billion short tons of coal each year. Roughly 85% of the known US fossil fuels remaining in this country are coal; which is nearly 275 billion short tons of future recoverable coal. If current consumption levels continue, the US has more than 250 years of supply. Currently, Wyoming is the largest coal producing state in the country, producing close to 340 million short tons per year. Coal ranks third of all fuel and non-fuel commodities mined today behind crushed stone, and sand and gravel.
How do we get it?
Coal is mined from the surface of the earth, as well as from underground. Approximately 70% of all coal comes from surface operations. Once mined and processed, coal travels by trains, ships, barges, trucks and slurry pumps to its final destination. Railroads transport more coal then any other commodity--about 70% of all coal shipments.
Coal: Yesterday, Today and Tomorrow
For many years coal mining was known as a destructive assault on the environment and an extremely dangerous occupation. Over the past 30 years, however, many precautionary measures have been taken in attempts to preserve the environment and promote a safe working environment.
Technology advances have enabled coal to burn more efficiently with reduced sulfur and nitrogen oxide emissions. For instance, even with electricity demand up 124% since 1970, the United States Environmental Protection Agency (EPA) reports that harmful emissions have been lowered by 33% and expectations of lowering emissions by 47% by 2015 are not out of the question.
Currently, over 120,000 people are employed in the coal industry in the US. Even though more coal is being mined per coal miner per hour, a lower rate of nonfatal injuries and illnesses is being reported. In 2001, mining accounted for 2.1% of all fatal injuries in the United States. This percentage is down substantially from the 1970s.
The American Coal Foundation (ACF) provides standards-based lesson plans and other information for teachers about coal -- its formation, production and use. ACF is a 501(c)(3) organization and does not engage in lobbying.
It is very easy to turn on an electrical device and have it work; but have you ever wondered what powers a television set, a Playstation 2 game console, a telephone, the lights in your house, the ceiling fan above your bed or the radio in your room? Electricity is the reason that all of these devices work and meet your daily demands each and everyday. The force of electricity is relied by all of mankind as a building block for modern society.
Electricity is a form of energy and is the flow of electrical power. In order to power electrical devices, an uninterrupted flow of electricity is key. Atoms make up every form of matter in the universe. All atoms have a nucleus, or center/core, which contains positively (+) charged particles known as protons, and uncharged particles, neutrons. Surrounding the nucleus are negatively (-) charged particles called electrons. Electrons and protons, if added together will usually equal zero, a neutral charge, this is because in a balanced atom the number of protons will equal the number of electrons. When an outside force upsets the balancing force between protons and electrons, an atom may gain or lose an electrical charge. An electrical current is caused when a charge is lost from an atom.
Many pioneers have experimented with electricity to better comprehend how it works. Following Benjamin Franklin's notorious kite experiment, the principles of electricity became more understood. Thomas Edison invented the electric light bulb, which was safer inside buildings. Prior to Nikola Tesla's inventions, direct current was the only use for outdoor lighting. Tesla pioneered the generation, transmission and began to use alternating current electricity. Alternating current can be transmitted over greater distances than direct current.
A transformer was invented by George Westinghouse to send electricity over long distances in order to supply customers with electricity that were located far from the generating plant. Transformers change electricity from low voltage to high voltage allowing for the electricity to travel more efficiently.
Electricity is measured in units known as watts (W), named for their founder, James Watt. James Watt invented the steam engine also. One watt of power is extremely small; therefore, they are usually designated as kilowatts (kW), which is equal to 1000 watts. The amount of electricity used over a specified period of time is known as a kilowatt-hour (kWh). Prices of kilowatt-hours vary throughout the country from a low price of 4.26 cents per kWh in Kentucky, to a high price of 13.39 cents per kWh in Hawaii. The major difference in price is due to the location of readily available electricity. Kentucky is a major producer of coal. The overall national average price is 7.21 cents per kWh.
The basic devices used in the generation of electricity are generators; these generators convert mechanical energy into electrical energy. Generators are a method based on the relationship between magnetism and electricity. A large magnet is positioned so that when it rotates, a small electric current is induced in each section of wire. All of the currents in each wire when summed up equal a current of considerable size. This large current is used for electric power.
Several different types of electrical generating units are operated with a wide range of fuel sources. Electric utility power stations use turbines, engines, or water wheels to convert mechanical or chemical energy to electricity by driving an electric generator. The most common methods of generating electricity is by the use of steam turbines, internal-combustion engines, gas combustion turbines, water turbines and wind turbines. Most of the electricity in the United States is produced using steam turbines.
In a turbine, the kinetic energy of a moving fluid, either liquid or gas, is converted into mechanical energy. A wide range of fuel sources are used as a form of force to turn a series of blades mounted on a shaft, which rotates the shaft connected to the generator, thus creating electricity.
Electricity is a secondary source of energy that comes from the conversion of other primary sources. These primary sources include fossil fuels, uranium and renewable sources.
Coal, petroleum and natural gas encompass the use of fossil fuels in electricity generation. These fossil fuels are burned in gas turbine generators where the hot gases produced from combustion are used to turn the turbine blades, which in turn spins the generator to produce electricity. Petroleum is also burned in generating units with internal-combustion engines; these internal-combustion engines are where the combustion occurs inside cylinders of the engine that are connected to the shaft of the generator. The engine drives the generator to produce energy off of the mechanical energy provided from the generator. In 2001, roughly 51% of the country's kilowatt-hours of electricity used coal as its source of energy. Less then 17% of the nation's electricity was fueled by natural gas, while only 3% of all the electricity was generated using petroleum.
Another means of electricity generation comes from the method of nuclear power. Nuclear power takes place from a process known as nuclear fission, in which atoms of uranium fuel are hit by neutrons. When this collision of uranium and neutrons occurs fission takes place, releasing heat and more neutrons. This process occurs continuously, forming a chain reaction releasing heat. The heat is used to transform water into steam, which spins the turbine that generates the electricity. Nuclear generating units accounted for the second largest portion of electricity generation in the United States at a share of nearly 21%.
Hydroelectric power units use flowing water to spin a turbine that is connected to a generator. There are two types of hydroelectric systems that produce electricity, the falling water system and the run-of-the-river system. The falling water system uses dams. Flowing water accumulates in reservoirs that release water through a pipe and applies pressure against the turbine blades to drive the generator. The run-of-the-river system uses the forces created by the rivers current to apply pressure to the turbine blades to produce electricity. Approximately 7% of all electricity production in the United States was produced by the use of hydropower.
The use of non-water renewable sources of electricity generation currently contributes about 2% of the total power production in this country. Geothermal power comes from heat energy trapped beneath the surface of the earth. In geothermal powered units of electricity generation, the underground water is heated to extreme temperatures as it reaches the surface thus, being released as steam. Solar power comes from the energy emitted from the sun. The uses of photovoltaic cells, which generate electric power directly from the light of the sun, have proven to be more costly then fossil fuels. Radiant energy from the sun is used to produce steam to drive turbines in solar-thermal electric generators. Wind power is the conversion of wind-generated energy into electricity with the use of windmills. The burning of biomass materials provides another means of generating electricity. Biomass includes wood, garbage and agricultural waste. These sources are burned in the same manner as fossil fuels, thus creating electricity by producing stream to rotate the turbines.
Electricity is an important aspect of modern society. Think about how often you use and rely on your electrical appliances, now think about the process that goes into producing the electricity that enables you to have the modern comforts that you are so dependent upon. With the ever-increasing prices of electricity and the depletion of the ozone layer by greenhouse gases, a discovery in cleaner burning methods of generating electricity is vital. As many of the resources in use today are being used to supply the world with electricity, technological advances are constantly being realized with the renewable resources and more ecologically safe methods of electricity generation.
What is Geothermal Energy?
Geothermal energy technologies use the heat of the earth for direct-use applications, geothermal heat pumps, and electrical power production.
In the US, most geothermal resources are concentrated in the West, but geothermal heat pumps can be used nearly anywhere.
Geothermal energy is clean and sustainable.
Resources of geothermal energy range from the shallow ground to hot water and hot rock found a few miles beneath the Earth's surface, and down even deeper to the extremely high temperatures of molten rock called magma.
In the US, most geothermal reservoirs of hot water are located in the western states, Alaska, and Hawaii.
Some geothermal power plants use the steam from a reservoir to power a turbine/generator, while others use the hot water to boil a working fluid that vaporizes and then turns a turbine.
Direct Use: Geothermal hot water near the Earth's surface can be used directly for heating buildings and as a heat supply for a variety of commercial and industrial uses. Geothermal direct use is particularly favored for greenhouses and aquaculture.
Geothermal or Ground-source Heat Pumps: Use the relatively constant temperature of soil or surface water as a heat source and sink for a heat pump, which provides heating and cooling for buildings.
Electricity Production: Underground reservoirs of hot water or steam, heated by an upwelling of magma, can be tapped for electrical power production.
Issues in Geothermal Energy
Environment: Geothermal technologies release little or no pollution into the air. Geothermal power production produces much lower air emissions than conventional energy technologies.
Resources: In the United States, geothermal resources are concentrated in the West, although low-temperature resources can also be found in the rest of the country. Geothermal heat pumps can be used nearly anywhere.
The Early Years
The use of hydropower is one of the oldest sources of energy. It has been dated back many thousands of years to its beginnings in which a simple paddle wheel was used to grind grain. The first industrial use of hydropower to generate electricity occurred in 1880 in Grand Rapids, Michigan, when 16 brush-arc lamps were illuminated. The first hydroelectric power plant opened in 1882. Up to this time coal had been the main fuel source for production of electricity. Even following the initial use of hydropower, the technology needed to transmit electricity over long distances was not sufficient.
Types of Plants
Hydroelectric power units use flowing water to spin a turbine that is connected to a generator. There are two types of hydroelectric systems that produce electricity. The falling water system uses dams. Flowing water accumulates in reservoirs that release water through a pipe and applies pressure against the turbine blades to drive the generator.
The run-of-the-river system uses the forces created by the river's current to apply pressure to the turbine blades to produce electricity. The water is accumulated in reservoirs created by dams and is released when there is a high demand for electricity.
Approximately 7% of all electricity production in the United States is produced by the use of hydropower. Over half of all the United States' hydroelectric capacity for electricity generation comes from Washington, California and Oregon. Washington has close to 27% of all the electricity generation. The largest hydroelectric facility in the U.S. is the Grand Coulee Dam. Niagara Falls provides New York State with a great deal of its hydropower needs.
The Future of Hydropower
Hydropower is viewed as an ideal renewable resource for electricity generation because it is almost free, it does not produce waste products, and it does not pollute the environment like so many other electricity-generating fuels. The only complaints that hydropower receives are those dealing with the disturbances of natural habitats, such as fish reproduction.
Formation of Natural Gas
Natural gas is tiny bubbles of odorless gas. This odorless gas is a mixture of light hydrocarbons that include methane, ethane, propane, butane, pentane, carbon dioxide, helium, hydrogen sulfide and nitrogen. If formed millions of years ago as sea plants and animals died and became buried on the bottom of the ocean floor. As the years passed, the remains of these dead plants and animals were placed under enormous amounts of heat and pressure caused by the continual addition of sediment deposits. This organic material became coal, crude oil and natural gas.
The oil and gas are then squeezed out of the shale where they were initially deposited and begin to rise through porous sedimentary rocks. These sedimentary rocks include sandstone and limestone. Because natural gas and oil are less dense than water, migration continues until these hydrocarbons reach a layer of impermeable rock. Many times vast amounts of natural gas and oil are collected beneath domes formed by folded sedimentary rocks. A majority of these domes are located along the Gulf of Mexico; therefore, it is no surprise that Texas and Louisiana account for close to 60% of all the natural gas production yearly. The largest reserves are in the former Soviet Union and throughout the Middle East.
Exploration of Natural Gas
Natural Gas was first discovered because of flames shooting up from the earth's surface. Upon further study, it was found that the natural gas escaped through small gaps in the rocks into the air and if there was enough activation energy a fire would burn.
Today, geologists and engineers use seismic surveys to study the underlying rocks. The seismic surveys aid in determining where to drill wells into reservoir rocks for extraction of the gas.
Uses of Natural Gas
Natural gas is used for numerous activities in our society. These uses include industrial, residential, commercial, electrical power generation, propane fuel and vehicle fuel. Heating and the generation of electricity are the main uses of natural gas, using about 90% of the resource. Approximately 23% of all the energy consumption in the United States is from the use of natural gas.
More then 62 million households use it to fuel stoves, furnaces, water heaters and many other appliances around the house. In industry, natural gas is burned to produce heat, which boils water that creates steam to pass through giant turbines. A turbine is used to generate electricity at about a 50% efficiency rate. The downfall to using natural gas is that it is generally more expensive than other forms of fuel.
Because natural gas is a clean burning fuel it is excellent for co-generation. Co-generation plants capture the excess heat let off during the burning of natural gas and sell the heat to local industries for processing or heating.
How do we get it?
Once the gas is found, it flows up through the ground to the surface and into large pipelines for domestic transport. Most of the time natural gas is under tremendous pressure, thus exiting the hole on its own. Sometimes, however, pumps are used for the collection of natural gas from beneath the surface. It is then transported by pipeline in its natural state or liquefied and transported by ship or rail.
Natural gas is measured in British Thermal Units (Btu) and cubic feet. A Btu is a measurement of energy. It is the amount of energy needed to raise the temperature of 1 pound of water 1 degree Fahrenheit at a temperature of 39.2 degrees Fahrenheit. One cubic foot of natural gas is equal to 1031 Btu. The United States currently produces 18,964 billion cubic feet of natural gas yearly, but it consumes 23,018 billion cubic feet.
The Future of Natural Gas
Natural gas is the cleanest burning fossil fuel, produces very few pollutants and has fewer emissions than coal and oil. There will be an increase in the use of natural gas in the very near future in order to combat acid rain, global warming and the deterioration of the ozone layer.
Fuel cells appear to be an environmentally friendly use of natural gas. Fuel cells are used to generate electricity, operating very much like a battery.
How Important is Nuclear Power?
According to the Nuclear Energy Institute (www.nei.org), about 20% of the United States' electricity comes from nuclear power plants. There are 103 commercial nuclear reactors with operating licenses at 64 sites in 31 states. Most of these are found in the eastern half of the US. The newest plant is Watts Bar 1, built in Tennessee in 1996. The oldest operating plant is Nine Mile 1, built in New York in 1969.
In 2002, 20.2% of the electricity generated in the US came from nuclear reactors. This amounted to 780.2 billion kilowatt-hours (KWh). Only a tiny part of this, 27,346,163 megawatt hours (MWh) was generated in Virginia. Virginia has four commercial nuclear reactors: North Anna 1, North Anna 2, Surry 1 and Surry 2.
Generation from nuclear power has generally increased since the 1950s, and this trend continues. Since 1984, nuclear plants have provided the second largest share of total U.S. electric utility generation of electricity, after coal-fired plants.
How a Nuclear Power Plant Works
Nothing is burned or exploded in a nuclear power plant. Rather, the uranium fuel generates heat through a process called fission. In this process, the nucleus of a heavy element, such as uranium, splits when bombarded by a free neutron in a nuclear reactor. With uranium atoms, this yields two smaller atoms, one to three free neutrons, plus energy. Because more free neutrons are released during uranium fission than are required to initiate it, the reaction can become self-sustaining-a chain reaction.
Rods inserted among the tubes holding the fuel control the nuclear reaction. These control rods are made of a material that absorbs neutrons and prevents them from hitting atoms that can fission. That way, the nuclear reaction can be sped up or slowed down by varying the number of control rods withdrawn and the extent that they are withdrawn. When atoms split, heat energy is produced.
The heat boils water, creating steam. The steam or water turns a turbine, which spins the shaft of a generator. Inside the generator, coils of wire spin in a magnetic field and electricity is produced. The steam condenses and changes back to water, and then is returned to the generator to be heated again, producing more steam. The white cloud you can see coming out of the top of a nuclear power plant isn't radioactive-it's just steam rising from the cooling tower.
Nuclear power has unique advantages thanks to its fuel source-uranium. Uranium has huge energy potential compared with fossil fuels like coal and oil. When uranium is used in a Magnox reactor, a 10-kilogram fuel element produces enough energy to generate electricity equal to burning 150 tons of coal.
The uranium is formed into ceramic pellets about the size of the end of your finger. These pellets are inserted into long, vertical tubes within the reactor.
Nuclear fuel is a solid material containing two kinds, or isotopes, of uranium atoms. One isotope - U-235 - makes up less than one percent of natural uranium but fissions readily. The other isotope - U-238 - makes up most of natural uranium but is practically non-fissionable.
Through a process known as "enrichment," the concentration of U-235 in the uranium is increased to three or four percent. Enrichment allows the reactor to be smaller than it would be if fueled with natural uranium. The concentration of U-235 is so low that a bomb-like nuclear explosion is impossible.
Nuclear power plants produce two types of radioactive waste: high-level and low-level. Nearly all high-level waste is used fuel. Low-level waste includes such things as protective clothing, tools and equipment that may contain small amounts of radioactive material. Used fuel is handled by remote control and safely stored inside the plant in steel-lined, concrete pools filled with water or on the plant property in huge steel-lined, concrete containers. Low-level waste can be shipped to a disposal facility or stored at the plant.
Used nuclear fuel is safely stored at the nation's nuclear power plants. But the plant storage facilities are only temporary. They're not designed to be permanent. The ideal permanent disposal for used nuclear fuel is deep underground in a network of tunnels that safely isolates the used fuel from people and the environment. Special containers are used to ship the used fuel from the plant to a repository. Before the Nuclear Regulatory Commission approved their designs, containers must be subjected to crash and fire tests. Used nuclear fuel has been transported without harm to people or the environment for over 30 years.
Nuclear generating plants are normally very clean. They do not produce CO2 and only produce tiny amounts of other air pollutants.
Formation of Petroleum
Petroleum, also called crude oil, is a mixture of carbon and hydrogen. It is made up of 83% carbon and 12% hydrogen, with smaller amounts of sulfur, oxygen and nitrogen. It exists as a liquid and has many different appearances in different locations around the world. In most instances it has the appearance of a black, thick and tar-like substance that is extremely volatile.
It formed millions of years ago as sea plants and animals died and became buried on the bottom of the ocean floor. As the years passed, the remains of these dead plants and animals were placed under enormous amounts of heat and pressure caused by the continual addition of sediment deposits. This organic material became coal, crude oil and natural gas.
The oil and gas are then squeezed out of the shale where they were initially deposited and begin to rise through porous sedimentary rocks. These sedimentary rocks include sandstone and limestone. Because natural gas and oil are less dense than water, migration continues until these hydrocarbons reach a layer of impermeable rock. Many times vast amounts of natural gas and oil are collected beneath domes formed by folded sedimentary rocks.
Uses of Petroleum
Refined crude oil produces many finished products such as gasoline and engine lubricants. Most of the finished products are used as a source of energy. Oil accounts for 38% of energy use worldwide.
The transportation sector is another major use for petroleum. Since the invention of the gasoline-powered internal-combustion engine, mechanized transportation has become a way of life. Today, over 95 % of the world's transportation needs are provided for by oil.
Another major use of oil is for space heating in residential areas and commercial buildings. The use of oil in heating became popular after coal was deemed too dirty to use on an everyday basis.
Plastic and rubber products come from refined petroleum. Petroleum products include crayons, bubble gum, ink, tires, ammonia, deodorant, eyeglasses, heart valves, records, televisions, water bottles, asphalt, toys, etc.
How do we get it?
A man drilling for water found petroleum in Titusville, Pennsylvania in 1859. At this time, crude oil became the foremost source of energy. Once the crude oil is found, it is mined by drilling a hole into the reservoir rock. This oil flows up through the ground to the surface and into large pipelines for domestic transport. Most of the time oil is under tremendous pressure and exits the hole on its own; however, sometimes pumps are used for the collection of petroleum from beneath the surface. It is then refined into many different products. Refining is the process in which the lighter products are separated from the heavier components found in petroleum. For instance, gasoline is separated out from other products such as fuel oil and lubricants.
The top five crude oil producing states are Texas, Alaska, California, Louisiana, and Oklahoma. Even with all the oil produced in the United States, however, the country still has to import over 60% of crude oil and petroleum products used annually. The top five producing countries around the world are Saudi Arabia, Russia, United States, Iran and China.
Petroleum: Yesterday, Today and Tomorrow
For most of the 20th century, oil was plentiful and cheap and was, therefore, the resource of choice. That period of ill-advised oil use came to a halt in 1973, when OPEC (Organization of Petroleum Exporting Countries) decided to raise prices and cut production.
Over the past 30 years, prices have skyrocketed and global warming has become a much larger concern. The combustion of oil releases carbon dioxide, sulfur dioxide and nitrous oxides; all of which are considered greenhouse gases and responsible for global warming and acid rain. These negative effects have impacts on human health and the environment.
Now that world oil supplies are estimated to have about 60 years of current consumption remaining; the reserves will be managed more efficiently and force society to the use of more sustainable sources of energy for the future.
Wind Energy Generation
Historically, wind energy has been used for thousands of years. Sails have been used to move boats for more than 5,000 years. Windmills have been used to grind grain, pump water and saw wood. As power lines were built in the 1930s that could transmit electricity over long distances, the use of windmills died out, although a few windmills can still be found in isolated areas such as western ranches. Today, wind energy can also be used to generate electricity and charge batteries. Availability of wind energy varies noticeably from place to place. Using wind energy is most feasible, economically, in locations where steady breezes are available.
According to the U.S. Department of Energy, at one time the U.S. led the world in wind energy generation, producing 90% of the world's wind-generated electricity. By 1996, however, the U.S. share had fallen to 30% due to other countries' increased investiture in wind generation, in which trend the U.S. did not participate.
Wind Energy Technologies
The principal behind a wind-energy generating device is very simple: the force of the wind pushes against the blades of a turbine, which turns the turbine. Today, there are two kinds of windmills. Horizontal-axis windmills look like airplane propellers and are the most common. Vertical-axis windmills look like egg-beaters and are only used about 5% of the time. Horizontal-axis machines must face into the wind, so they are built with tails like weather vanes, and swivel when the wind changes directions. Vertical-axis machines turn whichever way the wind is blowing. The turbine is connected to a drive shaft that turns an electric generator. Wind turbines can be used alone, can be connected to a utility power grid or can even be combined with a photovoltaic (solar cell) system.
People are still working on the problem of what to do when the wind isn't blowing. Turbines that are connected to the utility power network and some other kind of generator does the work when the wind isn't blowing. Stand-alone turbines sometimes are used to charge a battery, which then provides power when the turbine isn't turning. Other windmills are used together with small gas or diesel generators that burn fuel and serve as a backup when the wind's not blowing.
For utility-scale generation, a large number of turbines are usually built close together to form a wind farm. Several electricity providers today use wind farms to supply power to their customers.
Small turbines are used by homeowners and at remote locations to help meet energy needs. Stand-alone turbines are typically used for water pumping or communications. However, homeowners and farmers in windy areas can also use turbines to generate electricity.
As with all inventions, people are continually improving wind turbines. The largest wind turbine in the world, with adjustable blade tips so that it can capture more energy, is in operation in Traverse City, Michigan. Another, much smaller system has been designed that uses small turbines with wind amplifiers that funnel more wind to the turbines. In the future, turbines may be placed on top of tall buildings, offshore oil platforms and on wireless communications towers to provide electricity for them.
Issues in Wind Energy
Wind Resources: The wind is the fuel source for wind energy. The U.S. has areas with abundant winds, for example, in the Midwest, Great Plains, and mountainous regions, but wind speed varies from day to day and from season to season. Detailed knowledge of the wind at a site is needed to estimate the performance of a wind energy project.
Environment: Wind energy is considered a green power technology because it has only minor impacts on the environment. However, all types of energy production impact the environment, including wind.
In order to be efficient, wind turbines must be large and in order to generate significant amounts of electricity, there must be groups of them. Wind farms usually have dozens of turbines spread over a large area. One turbine needs about two acres of land, but the land beneath it can be used to grow crops or for grazing. Horizontal wind machines are typically about the height of a 20-story building, with blades that stretch 200 feet wide. According to the U.S. Dept. of Energy, "The largest wind machines in the world have blades longer than a football field!" Wind machines must be placed where the wind will not be obstructed: in the waters offshore, on the tops of mountain ridges or in the middle of plains. Another good location is in mountain gaps, where the wind is funneled through a small opening, giving it more power.
Their large size and placement in open or wilderness areas make wind turbines impossible to ignore. Many people do not want their views disrupted by their installation. Power lines are also necessary to transport the power generated by wind turbines, and they have their own environmental impact.
Economics: The cost of energy from the wind has dropped by 85% during the last 20 years. Incentives like the federal production tax credit promote wind energy usage. California produces more energy using wind than any other state in the U.S., because California's state policies encourage the development of renewable energy sources.