wind energy energy and the environment. wind basics

Wind Energy

Energy and the Environment

Wind basics

What is wind?

Wind is air in motion. It is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s radiation unevenly. Two factors are necessary to specify wind: speed and direction.

What causes the wind to blow?

As the sun warms the Earth's surface, the atmosphere warms too. Some parts of the Earth receive direct rays from the sun all year and are always warm. Other places receive indirect rays, so the climate is colder. Warm air, which weighs less than cold air, rises. Then cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow.

What are the global wind patterns?

The equator receives the Sun's direct rays. Here, air is heated and rises, leaving low pressure areas behind. Moving to about thirty degrees north and south of the equator, the warm air from the equator begins to cool and sink. Between thirty degrees latitude and the equator, most of the cooling sinking air moves back to the equator. The rest of the air flows toward the poles.

Global Wind Patterns

What is a sea breeze?

On a warm summer day along the coast, this differential heating of land and sea leads to the development of local winds called sea breezes. As air above the land surface is heated by radiation from the Sun, it expands and begins to rise, being lighter than the surrounding air. To replace the rising air, cooler air is drawn in from above the surface of the sea. This is the sea breeze, and can offer a pleasant cooling influence on hot summer afternoons.

Sea breeze

What is a land breeze?

A land breeze occurs at night when the land cools faster than the sea. In this case, it is air above the warmer surface water that is heated and rises, pulling in air from the cooler land surface.

Land Breeze

History of Wind Energy

Wind Power's Beginnings (1000 B.C. - 1300 A.D.)

SailboatsThe first windmills were developed to

automate the tasks of grain-grinding and water-pumping and the earliest-known design is the vertical axis system developed in Persia about 500-900 A.D.

Persian style vertical axis windmill

Pumping water in Crete

One of the most scenic and successful applications of windpower (and one that still exists), is the extensive use of water pumping machines on the island of Crete. Here, literally hundreds of sail-rotor windmills pump water for crops and livestock

Windmills in the Western World (1300 -

1875 A.D.)

The first windmills to appear in western Europe were of the horizontal-axis configuration. The reason for the sudden evolution from the vertical-axis Persian design approach is unknown, but the fact that European water wheels also had a horizontal-axis configuration -- and apparently served as the technological model for the early windmills -- may provide part of the answer.

The Dutch

As early as 1390, the Dutch set out to refine the tower mill design.

standard post mill to the top of a multi-story tower, separate floors devoted to grinding  grain, removing

chaff, storing grain, and (on the bottom) living quarters for the windsmith and his family.

Oriented into the wind manually, by pushing a large lever at the back of the mill.

Optimizing windmill energy and power output and protecting the mill from damage by furling the rotor sails during storms were among the windsmith's primary jobs.

Dutch Windmill

Role of Smaller Systems

For hundreds of years, the most important application of windmills at the subsistence level has been mechanical water pumping using relatively small systems.

These systems were perfected in the United States during the19th century.

Fan-type wind mill or Multi-Blade wind pump

First Use of Wind for "Large Scale"  Generation of Electricity

1888 Charles Brush Cleveland, Ohio

In 1891, the Dane Poul La Cour developed the first electrical output wind machine to incorporate the aerodynamic design principles (low-solidity, four-bladed rotors incorporating primitive airfoil shapes) used in the best European tower mills.

The higher speed of the La Cour rotor made these mills quite practical for electricity generation.

By the close of World War I, the use of 25 kilowatt electrical output machines had spread throughout Denmark, but cheaper and larger fossil-fuel steam plants soon put the operators of these mills out of business.

Poul La Cour wind turbine in Denmark 1897

Small System Pioneers

By the mid-1920's, 1 to 3-kilowatt wind generators found widespread use in the rural areas of the midwestern Great Plains

These systems were installed at first to provide lighting for farms and to charge batteries used to power crystal radio sets. But their use was extended to an entire array of direct-current motor-driven appliances, including refrigerators, freezers, washing machines, and power tools.

But the more appliances were powered by the early wind generators, the more their intermittent operation became a problem.

The demise of these systems was hastened during the late 1930s and the 1940s by two factors: the demand of farmsteads for ever larger amounts of power on demand, and the Great Depression, which spurred the U.S. federal government to stimulate the depressed rural economies by extending the electrical grid throughout those areas.

"Bulk" Power from Wind

Russia 1931 100kW Balaclava wind generator. Operated for about two years on the

shore of the Caspian Sea, Generating 200,000 kWh of electricity.

"Bulk" Power from Wind

The largest was the 1.25 megawatt Smith-Putnam machine (Figure 8, at right), installed in Vermont in 1941. This horizontal-axis design featured a two-bladed, 175-foot diameter rotor oriented down-wind of the tower.

European Development

In Denmark, the 200 kW Gedser Mill wind turbine operated successfully until the early 1960s,

European Development

In Germany, Professor Ulrich Hutter developed a series of advanced, horizontal-axis designs of intermediate size that utilized modern, airfoil-type fiberglass and plastic blades with variable pitch to provide light weight and high efficiencies.

The Great California Wind Rush

Literally thousands of these machines were delivered to the wind program in California in the early eighties. The Macon 55 kW is one example of such a machine, delivered to one huge park of more than 1000 machines in Palm Springs, California

Questions

What is a sea breeze?What is a land breeze?What was the name of the wind turbine

in Denmark in 1897?The Macon 55 kW is one example of

such a machine, delivered to one huge park of more than 1000 machines in

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Answer questions on the back of the handout that you were given.