What Makes the Generators Run?

Electric generating plants use different forms of energy to run pressurized steam boilers and drive their turbines. The main sources of energy are:

Fossil Fuels
Burning releases stored chemical energy from coal, oil, or natural gas. Supplies of these mineral resources are large, but not endless.

Burning releases emissions of sulfur dioxide and nitrogen oxide. Environmental laws limit these pollutants because of potential health problems, acid rain issues, and other concerns. Burning fossil fuels also releases carbon dioxide into the atmosphere. The Intergovernmental Panel on Climate Control (IPCC) has linked carbon dioxide emissions from human activities to global climate change.

The Edison Electric Institute says that natural gas is now the fuel of choice for new power plants. “Natural gas creates far fewer emissions than would be created by the combustion of coal or oil,” notes spokesperson Jim Owen. Until recently, natural gas was also fairly cheap, compared to other fuels.

“Natural gas is an ideal peaking fuel,” adds Owen. In other words, a natural gas plant can come on-line quickly during periods of maximum, or peak, demand. It's also faster to build such a plant, versus constructing a large coal-fired plant that runs constantly to meet an area's base load demand.

Hydroelectric Power
Kinetic energy from moving water is a renewable resource. The supply won't run out within a foreseeable time period. Water power is comparatively cheap. Plus, it avoids most emissions issues linked to fossil fuels. Building plants requires careful study to protect natural habitats.
Nuclear Power
Controlled nuclear fission, or atom-splitting, releases energy to power boilers. Nuclear plants have almost no emissions. But disposal of used radioactive waste presents concerns. Operating safety is also an important issue.
Solar power uses photovoltaic cells to convert sunlight into electricity. Wind power uses the kinetic energy from moving air. Geothermal power harnesses heat energy from the Earth.

Presently, utilities use these renewable energy sources mostly to supplement other fuels to meet peak customer demand.

How is your electricity generated? It depends on where you live. In the Middle Atlantic states, coal and nuclear power each produce just over one-third of the area's electricity. In some midwestern, mountain, and southern states, coal accounts for over two-thirds of the electricity generated. Hydroelectric power generates over 40 percent of the electricity for some areas along the Pacific coast.


  • combustion: The process of burning.
  • emission: A substance discharged into the air, especially by an internal combustion engine.
  • kinetic energy: energy from a moving object
  • radioactive: Of, caused by, or having the process or property by which certain chemical elements, such as radium, give off energy in the form of rays.
  • renewable resource: A resource, such as wind, that is easily replaced.

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  1. Which type of power plants would help to conserve natural resources? Why?
    [anno: The power plants that would help to conserve natural resources are hydroelectric, nuclear, solar, wind, and geothermal.]
  2. What are some of the drawbacks of each kind of power plant?
    [anno: Fossil fuel plants release polluting emissions into atmosphere and use a nonrenewable source of energy. Hydroelectric plants can interfere with natural habitats. Nuclear plants create radioactive waste. Solar, wind, and geothermal plants are reliant upon the presence of lots of sunshine, wind, or heat energy in the Earth to run. These three plants can be built only where one of these resources is available in abundance.]
  3. Imagine that local elections are being held. Citizens are being asked to vote on whether they want to spend $30 million in tax dollars to build a wind power plant or $10 million in tax dollars to expand an existing natural gas plant. For which plan should citizens vote? Why?
    [anno: Answers will vary. Students may believe that citizens should vote for the wind power plant because the plant uses renewable resources and in the long run will be more cost effective for people buying the power from the plant. Students may believe that citizens should vote for the natural gas plant because it is less expensive and already exists. Students may make the point that less energy might be expended by expanding the natural gas plant than building a new wind power plant.]