Thursday, October 14, 2010

Wind Turbines- Lisa Dunleavy

I. Introduction

The United States has become dependent on resources that are nonrenewable and exceed our ability of produce. Therefore, it is crucial that alternative energy sources are found to support and sustain our countries energy requirement. Wind turbines are one of these solutions.

II. Discovery

Charles F. Brush, born in Euclid, Ohio in 1849, invented the first wind-powered turbine. Brush had been a wunderkind since the age of 15 when he was building microscopes, telescopes, and electrical gadgets for school friends. He graduated from the University of Michigan with a degree in mining engineering and became famous for his dynamic and arc lights. With all of these inventions, Brush became rather wealthy. In his backyard in Ohio, he conducted the first wind-powered turbine. The turbine was 60 feet tall and weighed 40 tons. It was made of wrought iron and rested on a gudgeon (an axis that an object sways or swings on). The wheel of the wind turbine had a diameter of 56 feet with 144 blades. The wind turbine made 500 revolutions every minute and at its climax, the wind turbine produced 12 kilowatts. To put this into perspective, the typical household in the United States consumes 110,655 kilowatt hours of electricity per year or around 300 kilowatts per day.

Figure 1, Brush's wind-powered turbine

Charles Brush takes the credit for the invention of the first ever-recorded inventor of the wind turbine; however, the Egyptians and Afghanis were the first to use wind energy. The Egyptians used wind energy to sail their boats and they built the first windmill in Babylon. The Afghanis made windmills around 30 feet tall with blades as long as 16 feet.

III. What is wind energy?

Wind energy is an effect of solar energy. The sun’s radiation sends waves, which heats different parts of the earth. This causes hot air to rise, which reduces the atmospheric pressure at the Earth’s surface, causing cold air to come and replace it. In turn, this creates wind, the basis for wind turbines. Another way of explaining wind energy is that the land heats up faster than the water. Since, warm air raises, the cold air that comes off the water rushes in to take the place of the warm risen air on the land, creating wind. At night this process is reversed, the land cools down faster than the water and so the warmer air from the water rises and the cooler air from the land rushes in to replace the warm ocean air. Some factors that influence these wind patterns besides night and day are seasons, humidity, and how much the land and water reflect sunlight.

IV. What is a wind turbine?

A wind turbine takes the kinetic energy from the wind, and turns it into mechanical energy. The mechanical energy is mostly used in “farm windmills” for pumping water into rural areas. Another standard use of windmills on a farm are grinding grains, propelling boats, or sawing. Wind turbines are the quintessential function to supply electricity to people’s homes and businesses.

There are two general designs of a wind turbine. The vertical axis or “egg beater” design which is less commonly used than the horizontal axis turbine. The general make up of a turbine includes: Rotor or blades that are used to convert the wind’s kinetic energy into a rotational energy, a nacelle or enclosure that usually contains a gearbox, but not always and includes a generator and drive train, a tower that is used to support the rotor of the wind mill, and all of the controls, cables, and equipment. The basic design of a wind turbine is that it is comprised of an alternator that connects to the propeller. In the alternator are magnets which when the wind blows and spins the propeller, the magnets in the alternator change the kinetic energy into mechanical energy. Wind turbines are constructed mainly of steel with rotor blades built mostly of polyester or wood epoxy.

Figure 2

Wind turbines can differ in size and figure 3 shows the different sizes and the energy produced. For a land-based wind farm, the sizes of the rotor diameter range from 50 to 90 meters with towers around the same size. For an off shore turbine, the sizes will be much larger, the largest being 100 meters for the rotor diameter. One of the major reasons that off shore wind turbines are bigger is because it is easier to transport bigger rotors on a ship than on land. Lastly, the turbines that are for small businesses or on a residential farm are much smaller, 8 meters or less.

Figure 3







Rotor (meters)







Rating (KW)







Annual MWh







The wind speed as well as the size of the wind turbine determines the productivity of electricity. There are requirements on how high the average wind speed of an area must be to qualify for a wind turbine. For the small business or residential turbines, the required wind speed is nine mph. For utility- powered wind turbines or off shore turbines, the required wind speed is 13 mph. The amount of energy that can be used from the kinetic wind energy corresponds to the speed cubed. This shows that even the most insignificant change in wind speed can drastically change the potential energy produced.

V. Impact on the world

The world is now using wind energy, a renewable energy, to bring electricity to homes all around the world replacing the use of fossil fuels that give off green house emissions. It also affects small businesses and residential farmers so they can do their daily jobs while using a free source of energy, wind. Some countries are taking greater advantage of wind energy than others; however, each country is making some effort to help the environment and become green with wind energy. Europe used the most wind energy in the year 2005. With Spain and Germany as its prime countries, Europe represented 55% of the global wind energy used in 2005. In 2008, the U.S took over that reputation. Both North and South America combined in 2005 had only 17% of the global use of wind energy with 98% of that coming from North America. The U.S was the fastest growing country to produce wind energy; however, it has now shifted to China. In 2005, Asia increased the amount of wind energy used by 48% and in 2008 acquired one third of the wind energy that was produced.

The magnitude of wind energy has grown 24% in 2005 and 29% in 2008 and is still increasing each year. This increase in the use of wind energy has led to 235,000 jobs in 2005 and in 2008 around 400,000 people were being employed by the wind business.

VI. Costs of wind turbines

The costs differ by the size of the wind turbine, the amount of wind in the area where they are located, and how much maintenance the wind turbine needs. The off shore wind turbines are more expensive as they require ships to transport the materials and workers to build and maintain the wind turbines. Making the turbines on land less expensive and easier to access. The cost of the wind energy production has lessened one-fifth of its cost from 1999 to 2005 and is predicted to continue decreasing in price. The cost of wind energy is now less than fossil fuels mainly due to the increase of the cost in oil as well as the continuous advancement in the wind turbine technology.

Wind energy companies are paying some farmers not to install wind turbines, why? If you put wind turbines too close to each other, one will steal the others wind. These wind companies pay the neighboring farmers to not buy wind turbines from a rivalry company, in order to protect the accessibility of wind.

VII. Advantages and disadvantages of wind turbines

Advantages of wind turbines and wind energy:

- Wind is a renewable resource

- Wind is free

- There is not much maintenance

- The production of wind energy does not emit greenhouse gas


- The wind doesn't always blow

- There has to be a back-up system

- Not aesthetically pleasing

- Birds and bats can be killed by the blades

- Wind turbines can’t be in a place with too little or too much wind

VIII. How efficient are wind turbines?

It is important to remember that no resource has a 100% efficiency rate. The efficiency rate of a propeller turbine (can be either horizontal or vertical axis) is about 10-20% and about 35% for the Darrieus or vertical axis turbine. The efficiency is estimated to increase with the advancement of the wind turbine technology.

IX. Journal summary on the Damage Detection in Wind Turbine Blades using two Different Acoustic Techniques:

Jungert, Anne. "Damage Detection in Wind Turbine Blades Using Two Different Acoustic Techniques." The E-Journal of Nondestructive Testing (2008). Print.

This article talks about the safety of the new and improved wind turbines that are yet to come. Also, the wear and tare on the blades of wind mills and how a breakdown of a blade could cause serious economic damage. To make sure these breakdowns are rare, the wind turbines are to be inspected regularly like buildings. The author talks about her study about light weight wind turbine equipment being more affective in producing energy while being as affective in safety.

X. References:

"How To Build A Wind Generator - Or Buy One." Alternate Energy Sources For Flourishing Future. Web. 7 Oct. 2010. .

"Wind Energy Basics." American Wind Energy Association. Web. 5 Oct. 2010.

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