Unit 12 – Electricity From The Wind
STUDENTS’ GUIDE
SUSTAIN US - Sustainable Energy Curriculum
Unit 12 – Electricity From The Wind
Page 1 of 5
Procedure
- In your group, think of as many ways as you can that people interact with the energy of the wind. Make a group record of your ideas.
- Think about and be ready to discuss the energy transfers and transformations that take place in your group’s examples.
- Reading – “Wind Energy and The Environment”
What is wind energy?
Did you ever wonder about wind and what forces cause air to move? What would Earth's environment be like without wind?
Think about this for a moment. The air in our atmosphere moves in many directions and at different speeds. It can be as gentle as a spring breeze or as dangerous as a cyclone or a tornado.
Why is there such a difference in the speed of wind? Here’s how it works. The Sun's radiation heats different parts of the Earth at different rates. For example, during the day there would usually be more radiation, but less at night. Also, the Earth’s surfaces, such as land or water absorb or reflect the Sun’s radiation at different rates, so some places on earth become warmer than others. This causes parts of the atmosphere to warm differently. When hot air rises, this reduces the atmospheric pressure of the Earth’s surface. Cooler air is then drawn in to replace it, which creates the environment for flowing air movement. We call this air movement wind.
How does this explain the gentle breeze on the one hand and the force of a tornado on the other hand? It is not obvious to the naked eye, but air has mass and when it is moving, it contains the energy of that motion. This is one form of kinetic energy.
What is a wind turbine and how does it work?
People have used the wind as an energy source for a long time. The Dutch people harnessed wind energy by building windmills to grind grains into flour. In ancient China, the people used wind power to pump water for irrigating crops. Today, we can use the wind to generate electricity. We can use the energy in the wind by building a tall tower with a large propeller on top. The wind blows the propeller around, which turns a generator to produce electricity. We cluster many of these towers together to make a wind farm, which produces more electricity. The more towers built, the more wind and the larger the propellers, the more electricity we can make. It is important to build the wind farms in places that have strong steady winds, such as mountains, open plains or in coastal areas.
The wind energy system changes the kinetic energy of the wind into mechanical and then into electrical energy that is used in homes or businesses. This energy is normally collected and then fed into utility power lines, where it is mixed with electricity from other power plants and delivered to utility customers. The output of a wind turbine depends on the turbine's size and the wind's speed through the rotor. Wind speed is a crucial element in projecting turbine performance, and a site's wind speed is measured through wind resource assessment prior to a wind system's construction. Generally, an annual average wind speed greater than four meters per second (m/s) (9 mph) is required for small wind electric turbines (less wind is required for water-pumping operations by windmills). Utility-scale wind power plants require minimum average wind speeds of 6 m/s (13 mph).
The important thing to understand is that what seems like a small difference in wind speed can mean a large difference in available energy and in electricity produced.
What are wind turbines made of?
The towers are mostly tubular and made of steel. The blades are made of fiberglass-reinforced polyester or wood-epoxy.
How big is a wind turbine?
Utility-scale wind turbines come in various sizes, with rotor diameters ranging from about 50 meters to about 90 meters, and with towers of roughly the same size. A 90-meter machine would have a total height from the tower base to the tip of the rotor of approximately 135 meters (442 feet).
What is the "energy payback time" for a wind turbine?
The "energy payback time" is a term used to measure the net energy value of a wind turbine or other power plant. The question of how long the plant has to operate to generate the amount of electricity that was required for its manufacture and construction is what “energy payback time” is about. Wind energy has one of the shortest energy payback times of any energy technology. It only takes a wind turbine a few months to "pay back" the energy needed for its making, installation, operation and then eventually its retirement.
What are the environmental tradeoffs of wind power?
There are many advantages to using wind energy. Wind energy systems do not generate air or water emissions and do not produce hazardous waste. They do not use up natural resources such as coal, oil, or gas. In addition, they do not cause environmental damage or use great amounts of water during operation. In fact, wind's pollution-free electricity can help avoid environmental damage.
Wind power is a clean, renewable form of energy, which during operation produces no carbon dioxide. After about 20-25 years, when wind farms have to be upgraded and some or all of the towers and blades replaced, the only environmental impact is the making of the new parts, their installation and the reuse and/or disposal of the old parts. If it is decided tono longer operatea wind farm and the towers, propellers and buildings are removedthey leave no pollution for future generations. Using wind instead of coal reduces carbon dioxide (CO2)emissions by 99%, using wind instead of gas by 98%. The small percentage of CO2 emissions is caused during the construction and maintenance of the wind turbine.
These are all the positive effects of wind turbines, however, other issues have been raised. For example, when considering the wildlife and thehabitats,more research is needed to better understand if installation and operation of turbines might have a negative impact on birds and other wildlife in the area. It is noted that some people who live near proposed wind projects have raised concerns about them. Very often, they need to be given accurate information and understanding of what wind energy is. When people develop this understanding, usually initial concerns are reduced and support for wind farms increases. Other concerns people have are that large wind turbines can interfere with radio or TV signals if a turbine is in the "line of sight" between a receiver and the signal source. This problem can usually be easily dealt with improving the receiver's antenna or installing relays to transmit the signal around the wind farm. Use of satellite or cable television is also an option. But some people just don’t want to see wind turbines from their homes.
How much energy can wind supply worldwide?
As of the end of 2003, there were over 39,000 megawatts of wind generating capacity operating worldwide, producing some 90 billion kilowatt-hours each year, as much as a dozen large nuclear power plants could generate. Yet, this is but a tiny fraction of wind's potential.
According to the U.S. Department of Energy, the world's winds could in theory supply the equivalent of 5,800 quadrillion British Thermal Units (BTUs) (quads) of energy each year - more than 15 times current world energy demand (A quad is equal to about 172 million barrels of oil or 45 million tons of coal).
In the future, wind can improve the quality of life in the world's developing countries. In these countries, more than two billion people live with no electricity or prospect of utility service in their foreseeable future. The prospect for improving the quality of their lives by using wind energy is vast.
Wind speed varies with the weather. When the wind is not blowing, some other sources are needed for energy.
- Investigating Your Model Wind Turbine
Observe the model wind turbine your group has to use. Find the propeller, the small generator it is attached to and the two small light emitting diodes (LED), a kind of electric light it powers. Investigate your model wind turbine by blowing on the propeller in different ways. As a group decide how to get the lights to glow the brightest and the dimmest. Discuss what you are doing and as a group prepare a report answering the following two questions.
- How can your group vary the brightness of the bulbs on your model wind turbine?
- What are the energy transfers and energy transformations involved in the use of your model wind turbine?
- In Your Own Words
Answer the following questions in your own words in your science notebook. Imagine you will use your answers to explain to a friend not in your class what you have learned about wind energy.
What is wind energy?
What is a wind turbine and how does it work?
What are wind turbines made of?
How big is a wind turbine?
What is the "Energy Payback Time" for a wind turbine?
What are the environmental tradeoffs of wind power?
How much energy can wind supply worldwide?
- Draw an energy chain showing the major energy transfers that take place when wind energy is converted to electrical energy in a commercial wind farm. Explain the energy transformation involved.
SUSTAIN US - Sustainable Energy Curriculum
Unit 12 – Electricity From The Wind
Page 1 of 5