Will wind farms ever become an efficient, large-scale source of energy

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Will wind farms ever become an efficient, large-scale source of energy?

Viewpoint: Yes, wind power is already the fastest-growing source of renewable energy in the world, and economic trends, technological advances, and environmental concerns will eventually transform it into a large-scale contributor of energy.

Viewpoint: No, wind power will not be a large-scale contributor of energy because wind doesn't blow sufficiently everywhere and doesn't blow all of the time.

Wind exists because Earth rotates and has an irregular surface—variable terrain, bodies of water, plants, and trees—and because the Sun heats the atmosphere unevenly. With the right equipment, energy produced by wind flow can be harvested and used to generate electricity.

As early as 5000 b.c., people used wind energy to move boats up and down the Nile. In 200 b.c., people used simple windmills to pump water in China, and vertical-axis windmills to grind grain in Persia and the Middle East. By A.D. 1000, Mid-Easterners used windmills extensively to produce food.

Over time the Dutch refined windmill technology and used more powerful wind turbines to drain lakes and marshes. Wind turbines convert kinetic wind energy to mechanical power that can be used to grind grain or pump water, or be converted to electricity.

By 1910, wind turbine generators produced electricity in many European countries. American settlers used windmills to pump water and generate electricity until the 1930s, when the Rural Electrification Administration brought electric power to the rural United States. Industrialization reduced the numbers of small windmills, but contributed to the development of wind turbines.

In the 1940s the world's largest wind turbine, operating on a Vermont hilltop called Grandpa's Knob, fed electric power to a local utility network for months during World War II. In the 1970s, oil embargoes prompted research and development that introduced new ways of turning wind energy into useful power.

Today, modern wind technology utilizes advances in materials, engineering, electronics, and aerodynamics. Wind farms—large groups of turbines—feed electricity into local utility grids in the United States and Europe. Wind energy is the world's fastest-growing source of electricity generation. But the debate continues about whether wind farms will ever become an efficient, large-scale energy source.

Those who believe in the large-scale potential of wind farms base their convictions on an increasing demand for power and the need for forms of energy other than those provided by fossil fuels and natural gas. Supplies of coal, oil, and natural gas are finite and most often controlled by countries, governments, and private enterprises that can restrict supplies or increase prices, ultimately increasing energy costs to the consumer.

Some experts say the ultimate success of wind power depends on its cost compared to other electricity sources, and on the value to society of reducing pollution. When the 1970s energy crisis caused oil prices to skyrocket, people started considering wind energy as a serious future power source. Wind energy costs are slightly higher today than the cost of energy from natural gas or coal-fired power plants, but wind-energy costs continue to decrease while costs for energy from other sources rise.

Wind-energy proponents say that refining raw materials and producing nuclear power cause serious environmental hazards. In contrast, wind power is a clean, nonpolluting, renewable energy source. Modern wind turbines have a 98% or higher reliability rating, and their larger capacity means fewer turbines generate more kilowatt-hours of energy.

New wind farms added more than 3,800 megawatts (MW) to world wind-energy production in 2000, and four of the largest wind farms ever built were scheduled for completion by year-end 2001, enough power to provide electricity to 1.7 million homes. With strong legislative and policy support, the capacity of wind farms in the United States could increase to 30,000 MW by 2010, providing electricity for 10 million homes and reducing excess utility sector emissions by 18%.

Those who doubt that wind farms will ever become an efficient, large-scale source of energy base their beliefs on the inconsistency of wind as an energy supply, on environmental issues, and on competition from other renewable energy sources.

The big challenge to using wind as a source of power is that it doesn't always blow, it never blows on command, and not all winds can be harnessed to meet the timing of electricity demands. Good wind areas cover only 6% of the contiguous U.S. land area.

Wind resources are characterized by wind-power density classes that range from class 1 (lowest) to class 7 (highest). Good wind resources (class 3 and above) with an average annual wind speed of at least 13 mph (21 kph) are found along the east coast, the Appalachian Mountain chain, the Great Plains, the Pacific Northwest, and others. Because many of these good wind sites are remote areas far from places of high electric power demand, the cost and logistics of transmitting and distributing power to where it's needed have to be considered when siting wind resources.

Environmental issues include noise pollution, hazards to birds, and aesthetic considerations. And wind resource development may compete with other uses for the land that may be more highly valued than for electricity generation.

Competition from other renewable resources will keep wind energy from becoming a large-scale resource. Significant energy alternatives in the renewables category are biomass power, concentrating solar power, geothermal, hydropower, photovoltaics, and solar thermal.

Today wind is one of many clean, renewable sources of electric power. Wind farms will be efficient contributors to the energy mix, but some believe that wind power will never be a large-scale contributor.

—CHERYL PELLERIN

Viewpoint: Yes, wind power is already the fastest-growing source of renewable energy in the world, and economic trends, technological advances, and environmental concerns will eventually transform it into a large-scale contributor of energy.

Overview

By the year 2001 wind power was the fastest growing renewable energy source in the world, and its market was expanding rapidly. An article in a 1999 issue of the Environmental Business Journal declared that wind power in the United States surged in 1998 and accelerated in 1999 after a slump of several years. Randall Swisher, executive director of the American Wind Energy Association (AWEA), Washington, D.C., was quoted in that article as saying: "We are celebrating the revitalization of the American wind market."

Europe is the center of this US$16.5 billion industry, generating 14,200 megawatts (MW) of the almost 20,000 MW produced annually worldwide. Germany (6,900 MW), the United States (2,600 MW), Spain (2,582 MW), and Denmark (2,346 MW) were country leaders, with Denmark producing 7% of its entire electricity supply from wind farms at a cost of 4 cents (US) per kilowatt-hour (kWh). That percentage is projected to increase to 40% by the year 2030.

What Are Wind Farms?

Wind farms are areas either on land or offshore where wind turbines (often as many as 500) are clustered together to capture energy from the wind to generate electricity. Wind turbines are tall towers atop which propeller-like blades spin in the wind, transforming the wind's kinetic energy into mechanical power, which, in turn, is generated as electricity.

More than 30 years of experience, accompanied by developments in the aerospace industry and a greater understanding of aerodynamics, have led to major advances in materials and methods used to build turbines and strategically locate wind farms. New-generation turbines are manufactured from resilient composite materials, with blades capable of withstanding constant winds, salt spray, snow, and ice over a 20-year or longer life span. The largest units have a rotor diameter of more than 65.6 yd (60 m) with a maximum output of 1.5 MW. Modern units have a 98% or higher reliability rating, and their larger capacity means fewer turbines generate more kilowatt-hours of energy.

New wind farms added more than 3,800 MW to world wind-energy production in 2000 alone. In the United States four of the largest wind farms ever built were scheduled for completion by year-end 2001, increasing installed capacity in that country by 2,000 MW, market growth by more than 50%, and total production to 4,600 MW—enough power to provide electricity to 1.7 million homes.

In the Beginning

When did humans begin using wind to their advantage? As far back as earliest recorded history boats caught wind in their sails to propel them through the waters, and windmills blades spun in the breeze turning stones that ground grain. Simple windmills in China pumped water centuries before the birth of Christ and windmills dotted rural landscapes in the United States and other countries as late as the end of the nineteenth century. Windmills still spin in some places, pumping water from wells or streams into cattle troughs and irrigation ditches.

By the beginning of the 1900s small wind systems generated electricity in isolated locations but were superceded in the 1930s as large-scale grid power systems wired their way into rural areas. However, modern wind turbines are an energy alternative for individual homes and small industry.

Revival of Wind Power

When the energy crisis of the early 1970s sent oil prices skyrocketing, wind energy began to be considered seriously as a future source of power. In the 1980s California purchased large amounts of wind power at about 38 cents/kWh. The most expensive form of power in 1996 was nuclear power, at between 11.1 and 14.5 cents/kWh. Taking into consideration the inflation factor over 20 years, 38 cents/kWh was a sizeable investment in 1980. However, that investment paid off as experience, knowledge, and new technologies consistently reduced the cost of wind power. In fact, the U.S. Department of Energy (DOE) anticipates wind energy production costs will fall from the 3-6 cents/kWh in 2001, to 2 cents/kWh by the year 2005. If trends continue conventional forms of energy will continue to escalate in cost, making wind power the most economical form of energy.

As with most new technologies wind power ran into its share of snags during its experimental period, causing a temporary slowdown in the industry; however, interest in wind-generated power is bolstered by:

new and more economical technology that significantly increases wind energy production and decreases mechanical breakdowns and failures
scientific investigations into, and computerized models of, wind patterns and aerodynamics that allow placement of farms where wind capacity is highest and harvest is most consistent
public recognition world-wide of the need to reduce greenhouse gas emissions
domestic and international policies that require emission reductions by a specified date
governmental subsidy and incentive programs for green energy development
legislation that requires utility providers to offer consumers the choice of purchasing green energy

Into the Future—Of What Value Is the Planet?

As the demand for power increases, forms of energy other than those provided by fossil fuels and natural gas will become increasingly essential. Supplies of coal, oil, and natural gas are not only finite, they are most often controlled by countries, governments, and private enterprise that can, at any given time, restrict supplies or increase prices, ultimately increasing energy costs to the general public.

Also, refining raw materials and producing nuclear power causes serious environmental hazards: fossil fuels spew billions of tons of polluting gasses into the atmosphere every year, damaging human and other life forms, creating greenhouse gasses that cause global warming. Global warming is predicted ultimately to lead to serious and even catastrophic climate changes, melting of the polar ice caps, and subsequent rise in sea level. Generating nuclear energy creates waste that is deadly to all living things and that science has not yet found a way to neutralize. This waste will remain radioactive for hundreds of thousands of years, and no truly safe way has yet been devised to dispose of it.

Environmental pollutants ultimately become huge financial burdens. Cleanup of hazardous waste costs untold billions of dollars annually, while health care costs due to these pollutants are incurred by individuals, corporations, and governments alike. These costs are not reflected on the itemized utility bill that arrives in mail but include lost work hours, increased utility prices to help utility companies pay for medical insurance, and increased taxation to pay for federally funded insurance programs and cleanup of waste sites. The biggest cost, however, is to human, animal, and plant life. Accidental pollution, such as the Chernobyl nuclear power plant malfunction in Russia and the oil spill after the tanker Valdez ran aground off the coast of Alaska, leave in their wake death, destruction, and suffering to countless numbers of people and animals. These factors are all apart from the monetary costs required in the cleanup process. In the case of nuclear pollution effects continue for generations.

In contrast, wind power is a clean, nonpolluting, renewable energy source. Wind is actually a form of solar energy created by the uneven heating of the Earth's atmosphere by the Sun. As long as there is a sun there will be wind. Wind-power potential is therefore infinite, cannot be controlled by one particular country nation, and is healthy for the planet and its people. Every kilowatt of electricity produced by wind power displaces one kilowatt of power generated by traditional methods. For 51,000 homes powered by wind-generated electricity, annual environmental pollution is reduced by 94,000 metric tons of carbon dioxide, 830 metric tons of sulfur dioxide, and 280 metric tons of nitrous oxides.

Legislation, Incentives, and Consumer Options

Following the 1992 Kyoto Climate Change Treaty established at the Earth Summit in Kyoto, Japan, 38 industrialized nations, including the United States, must reduce greenhouse gas emissions to below 1990 levels by 2008-2012. Major shortfalls of this objective are expected in the United States—by 2010 carbon dioxide emissions from electricity generation alone will exceed the 1990 levels by more than half a billion metric tons. The AWEA believes that, with strong legislative and policy support, the capacity of U.S. wind farms can be increased to 30,000 MW by 2010, providing enough electricity for 10 million homes and reducing the utility sector's excess emissions by 18%.

Legislation and incentive programs help promote renewable energy and reduce pollution. In the United States the federal tax production credit (PTC) program allows a tax credit of 1.5 cents/kWh for the first 10 years of operation of a new wind farm. The AWEA estimates this credit reduced the levelized cost of wind-generated electricity by 0.7 cents/kWh over a 30-year period.

The United Kingdom aims to increase renewable energy sources to 10% by 2010 from its 2001 level of 2.8%. Under the Non Fossil Fuel Obligation (NFFO), a "fossil fuel levy" is added to the electricity bill of each electricity consumer. Income from this levy helps cover the huge costs of nuclear power and funds a program encouraging development of renewable energy.

In 1999 the World Bank approved a US$100 million dollar loan and a US$35 million General Energy Fund grant to China so that millions of people will receive electricity from sources that do not produce greenhouse gasses. Under this plan the proportion of wind-generated electricity will increase to those already receiving electric power.

Texas legislation mandates the generation of 2,000 new megawatts of renewable energy, much of which will come from wind energy. In July 1999 the largest wind farm in that state began generating power. At the opening of the 2,200-acre (736-hectare) facility atop a 600-ft (183-m) mesa, the president of one utility company involved in its development said: "This project's state-of-the-art, cost-effective technology demonstrates the commercial viability of wind energy." President George Bush, then the governor of Texas, praised the project for "…creating jobs, promoting new technology, and responding to customer calls for increased use of renewable energy sources."

Also in Texas, residents of El Paso can contribute to the development of wind-generated electricity under the Renewable Energy Tariff Program by voluntarily purchasing 100kWh blocks of renewable energy for an additional $1.92 per month.

Economic Trends, Viability, and Importance

Despite its youth, wind energy production continues

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to become less expensive and more economically viable. Apart from its positive economic impact on human health and the environment, wind-powered electricity provides other important economic benefits that include:

an affordable and inexhaustible source of power
a domestic resource whose cost is not influenced by other countries. (The high cost of importing fossil fuel contributes to the trade deficit that affects the economy of the nation and, ultimately, every individual in that nation.)
a reliable, sustainable source of domestic employment that fuels local, state, and national economies without depleting natural resources, polluting the environment, or creating hazardous waste
a provider of more jobs per dollar invested than any other energy technololgy (five times that of coal or nuclear power)
becoming more competitive as the cost of traditional energy increases.

Also, wind power is cubed by the wind's speed, i.e., when the wind is twice as strong, its energy content is eight times as great. Wind velocity of 26 ft (8 m) per second will produce approximately 80% more electricity than wind velocity of 20 ft (6 m) per second, with no added expense for the increased energy production because producing electricity from wind requires no purchase of raw material. Although running costs include the rental of land on which wind farms are built, local economies are stimulated as property owners receive the rental income. In many cases property owners can still graze animals and farm the land on which the turbines stand.

Importantly, wind power creates a positive "energy balance," which means the time it takes to "pay back" the amount of energy used to generate electricity is short. In the United Kingdom the average wind farm will generate enough power in three months to replace the energy it took to manufacture its turbines and build the farm. Over its lifetime, the farm will generate 30 times more power than was required in its manufacture. Fossil fuel and nuclear power plants supply just one-third of the energy required in plant construction and supply of raw materials, and never achieve an energy payback.

Falling Costs

The AWEA estimates there was an 80% decrease in the cost of producing wind energy between the 1980s (approximately 38 cents/kWh) and the year 2000 (between 3 and 6 cents/kWh). Although still slightly higher than energy produced by natural gas or coal-fired power plants, wind energy costs continue to decrease steadily while energy from other sources continues to increase. For example, in January 2001, electric power generated from natural gas power plants reached between 15 and 20 cents/kWh in some areas of the United States.

In 1996, comparative levelized costs per kilowatt-hour were:

wind (with PTC): 3.3-3.5 cents
wind (without PTC): 4.0-6.0 cents
gas: 3.9-4.4 cents
coal: 4.8-5.5 cents
hydro: 5.1-11.3 cents
biomass: 5.8-11.6 cents
nuclear: 11.1-14.5 cents

Potential Power—Potential Growth

Although wind power is the fastest-growing renewable energy source in the world, it is still the smallest percentage of America's renewable energy, estimated by The Energy Information Agency of the DOE to be only 1% of all renewable energy sources in the United States. Worldwide, total kinetic wind energy is estimated at more than 80 times greater than the amount of all energy consumed by the planet's population. Variability of wind patterns and viability of locating farms in areas with the highest wind-power potential make harvesting only a small portion of that energy feasible. However, conservative estimates suggest the United States, the United Kingdom, Denmark, and the Netherlands alone could generate 20%-40% of their entire electricity supply from this cost-effective, energy-efficient, and environmentally friendly renewable resource.

Wind potential is plentiful. If, as some experts speculate, the ultimate success of wind power depends upon its cost compared to other sources of electricity, accompanied by the value society places on reducing pollution, wind power has a bright future.

—MARIE L. THOMPSON

Viewpoint: No, wind power will not be a large-scale contributor of energy because wind doesn't blow sufficiently everywhere and doesn't blow all of the time.

Ever is a strong word. In the case of wind farms, what is holding them from ever becoming an efficient, large-scale source of energy? The answer is the wind: it does not always blow and it does not blow enough in many locations. Add to that, the competition. There are also some environmental factors. Wind power does not produce toxic emissions, a fact which makes it popular with green energy enthusiasts. However, there are other environmental issues like noise pollution, hazards to birds, and aesthetic considerations. Wind farms are a tourist attraction

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in Palm Springs, California, in 2001. Rows and rows of humming turbines towering 200 ft (60 m) and higher, with rotors of 144 ft (44 m) diameter for a 600 kW generator, may be spectacular to some. But, would those tourists want a wind farm in their back yard? If the tourists do not live where there is good wind, they will not have to worry.

Wind Power: Not a Large Part of the Energy Mix

The Energy Information Administration of the U.S. Department of Energy (DOE) published in its Annual Energy Review 2000 information on energy consumption by source. Not surprising, petroleum is the main source at 39% with natural gas at 24% coming in second. Coal is used for 23% of the energy used in the the United States, and nuclear electric power makes up 8% of the supply. That leaves only 7% for all renewable energy sources. These sources include conventional hydroelectric power which is 46% of the 7%. Wood is 38%, and "waste" is 8%. Waste includes some waste wood and other biomass materials, in a catchall category of municipal solid wastes. Geothermal is 5% of the renewable energy sources, alcohol fuels 2%, and solar and wind are each 1% of the 7% renewable energy consumption by source. (The percents have been rounded in the government data available, and so appear to be more than 100%) This indicates that wind is a very small-scale source in the big picture of all energy sources in the U.S. in 2000.

According to the DOE Office of Energy Efficiency and Renewable Energy (EREN), wind energy has been the fastest growing source of electricity generation in the 1990s. Most of that growth has been in Europe, although the DOE recently announced the Wind Powering America initiative that has a goal to provide at least 5% of the nation's electric power from wind by 2020. Whereas renewables in total were only 7% in 2000, that is a very debatable goal and should it come even close to reality, 5% would still not be large-scale .

Although not always dependable, and not everywhere available in sufficient amounts, wind is free. (Of course the technology is not free.) Using wind to generate electricity does not produce any toxic emissions. Why then is wind not a larger part of the energy mix? There are reasons even the 5% goal will be difficult to meet. DOE describes wind resources in the United States as plentiful, but adds that good wind areas cover only 6% of the contiguous U.S. land area. Most of the useful wind resources are in the Great Plains from Montana east to Minnesota and south through Texas, according to the DOE. North Dakota, not a populous state, has about the best wind resources. Transmission and distribution of the power produced to where it is needed has to be part of the equation when siting wind resources. California has some good sites, mostly along the coast. California also has the energy crises which gives the state incentive to find any and all sources, including utility-scale wind farms, also called wind plants.

In Northern Europe, Denmark and Germany are leaders in developing wind as a source of electric energy. As a largely flat, small peninsular country with a long North Sea coast, Denmark is well suited to set up windmills. The Danish government has a goal to provide 50% of the country's energy from wind. The topography and geography of the United States does not lend itself to that kind of development. Northwestern Germany has a coastline abutting to Denmark, and so does the Netherlands. With the Netherlands practically synonymous with windmills, it is not surprising wind energy is big there. Even with the favorable landscape for wind to be plentiful, Denmark and Germany are building wind plants offshore now to expand where there is a more reliable high wind resource.

Competition from Other Sources

Competition from other renewable resources will also prevent wind energy from ever becoming a large-scale resource. EREN lists the technologies that are significant energy alternatives in the renewables category as biomass power, concentrating solar power, geothermal, hydropower, photovoltaics, solar thermal, and wind. For argument's sake here, the solar sources will be lumped together. Although they are quite different technologies, they use the same free energy source, the Sun.

Hydropower.

EREN documents indicate that hydropower is the nation's leading renewable energy source, providing 81% of the total renewable electricity generation. The United States is the world's second-largest producer of hydropower, second only to Canada. As with wind power, not every location is suited to hydropower. Viable hydropower sites have to have a large volume of water and a significant change in elevation. These can be met by river dams as exist along the Columbia River in Northwestern United States, or a dam-created lake as in Hoover dam on the Arizona-Nevada border. Once a dam is in place (not cheap), hydropower is the least expensive source of electricity in the United States with typical efficiencies of 85%-92% . No energy source is without some problems. There are some issues of fish migration and arguments on land covered by water.

Biomass.

Biomass is the second on EREN's list of renewable energy resources in the United States. By biomass EREN means plant matter such as trees, grasses, and agricultural crops. There is a broader term, bioenergy, that includes poultry litter and animal wastes, industrial waste, and the paper component of municipal sold waste which increases the energy resources under the bio category. Biomass conversion to electric energy involves combustion so it is not entirely clean, but it is a renewable resource. Biomass can be used directly in solid form as fuel for heat and electricity generation, or it can be converted into liquid or gaseous fuel by gasification, also a combustion process, but one that controls the available oxygen. The fuel produced by gasification has many uses, including microturbines.

Microturbines are small (micro relative to a windmill) generators designed for on-site power production, heating, and cooling. They are sometimes described as a miniature jet engine with a high speed alternator on the same shaft. They have emerged on the electric power scene as small-scale localized power sources for their reliability and high quality power that is always available and closer to the site and scale of actual needs. Such power sources are called distributed generation and are generally used for power generation of less than 1 megawatt (MW), a market well suited to microturbines.

Proliferation of the digital computing and communication devices is driving the use of microturbines, as utility electric power can fluctuate, and sometimes fail. Both are disastrous in some markets. Microturbines are also useful for stand-alone power in remote areas such as oil fields where the electric grid is not available. Windmills are sometimes used in remote areas but microturbines have two distinct advantages. They are modular so they can be combined to

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multiply the power available, and they are reasonably portable. Although the fuel for a micro-turbine is not generally free, except on an oil field where they burn waste gas, the fuel is in constant supply whereas wind is variable and not always available when and where it is needed.

Wind forecasting is a relatively new, and as yet not perfected, art that is intended to help with the problem of intermittent wind even at good sites. Electricity storage in batteries is a solution only on a very small scale. Power producers using wind in their energy mix have to plan for the intermittent nature of wind energy. Wind is clean and renewable, but this problem could limit the large-scale use of wind as a source of electric energy.

Geothermal Energy.

Geothermal energy is another competitor to wind power. The current production of geothermal energy places it third among renewable sources, and EREN states it has hardly been used compared to the enormous potential of geothermal energy in the United States. Geothermal energy is not limited to geysers, although that is what immediately comes to mind to the lay person. Such hydrothermal fluids are a part of the story but earth energy, the heat contained in soil and rocks at shallow depths, can also be tapped as an energy source. Earth energy is not directly used to produce electricity but the heating and cooling applications are considered as a contribution to the energy mix. Steam and hot water are used to drive turbines to generate electricity. Like wind, the energy source is free. Also like wind it is not found everywhere, but the hot water is more reliable than the wind.

Solar Power.

Solar power, whether from concentrating solar, photovoltaics, or solar thermal, is a renewable energy source that also contributes to the energy mix. Combined, solar electricity sources make up about the same percent of the renewable energy resources as wind in the year 2000 energy portfolio. Also, like wind and geothermal, concentrating solar and solar thermal depend on a resource that is not available in sufficient amounts everywhere. Latitude and average cloud cover determine the viability of solar energy as an electric power source. Because photovoltaics require much less concentrated solar energy, they are useful in a much wider region. Photovoltaic can be used for a great variety of electricity applications from a handheld device to a skyscraper in Times Square, New York.

Concentrating solar power plants produce electric power by collecting heat through one of three technologies that can then be used to generate electricity. One technology, the power tower system, uses mirrors to heat salt to the molten state. The fluid salt is used as a heat source in a steam generator to produce electricity. World record solar-to-electricity conversion efficiencies make concentrating solar power attractive in the Southwest United States and other sunbelt regions. One major advantage to these systems where they are applicable is that they produce electricity during the peak use times. Where the sun shines bright, it is a plentiful source. Enough solar electricity could be produced for the entire United States if just 9% of Nevada were covered with solar collectors.

Photovoltaic.

Photovoltaic (PV) electric sources are in a class by themselves. PV cells convert sunlight directly into electricity. The electricity can be used as it is produced, or it can be stored in a battery. Large-scale PV arrays produce electricity that is used as part of the local utility in areas of adequate sunlight. More widespread, and gaining in popularity, are building integrated PV systems. PV cells can be built into shingles, wall panels, and windows to produce electricity without being conspicuous. The systems are not cheap, but they are attracting more attention as a clean, on-site, attractive electric energy source. PV is also gaining a lot of attention for its portability. Small panels of PV cells serve as back-up power for homes, local business establishments, camping sites, and anywhere a reliable immediately available electric energy source is needed. PV is one more reason wind power is going to be a source, but not a large-scale source of electric energy.

Windmills have been around since ancient times—for water pumping and grinding grain before electricity was discovered. It might be said that wind power was the first power tapped by man. Today wind is among many good, clean, and renewable sources of electric power. Wind farms will be efficient contributors to the energy mix, but wind power will not be a large-scale contributor in the big picture, ever.

—M. C. NAGEL

KEY TERMS

GRID:

Short term for utility grid, the commercial network of wires that carry electricity from a source to the users.

MEGAWATT (MW):

An electrical power unit. Electrical power is measured in watts, kilowatts (kW—1,000 watts), and megawatts (MW—1,000,000 watts). Village power is measured in kW whereas grid-connected sources are measured in MW.

PHOTOVOLTAIC (PV) CELL:

A device that uses semiconductor materials to convert sunlight into electricity directly. One PV cell is about 4 in on a side (10 cm). A cell produces about one watt. When 40 cells are connected together it is called a PV module. When 10 modules are connected it is a PV array.