Lesson 2 described how generators turn motion energy into electrical energy. A generator works on the phenomenon of electromagnetic induction, discovered by Faraday nearly 200 years ago. When an electrical current passes through a wire, a magnetic field is generated around it. Likewise, if the magnetic field around a wire is changed (for example by rotating magnets inside a stationary coil or by rotating a coil inside a stationary magnet), electricity will move through the wire.
Commercial generators used in power plants are very large quantities of copper wire spinning around inside very large magnets, at very high speeds. A turbine spins the shaft that runs the generator. A turbine is an assembly with blades attached that converts the motion of liquids or gases into mechanical motion. Water wheels and windmills are familiar examples of turbines.
There are many different kinds of turbines. Many power plants use steam turbines to generate electricity. These plants use any of a variety of methods to create steam to drive the generator. They may burn fuels (such as coal, natural gas, oil, and biomass), use nuclear, or concentrated solar to heat the water and create the steam, or use geothermal energy directly from the earth. In all cases, the steam runs through a huge multi-stage turbine to spin an output shaft that drives the plant's generator.
Hydroelectric plants use water turbines to generate power. The turbines used in a hydroelectric plant look completely different from a steam turbine because water is so much denser (and slower moving) than steam, but it is the same principle. Flowing (or falling) water pushes against the turbine blades, causing it to spin.
Wind turbines, also known as wind mills, use the wind as their motive force. A wind turbine looks nothing like a steam turbine or a water turbine because wind is slow moving and very light. The principle is the same though—the wind pushes against the turbine blades, causing it to spin.
In a gas turbine, a pressurized gas spins the turbine—fuels are burned to generate hot gases which go through a turbine, causing it to spin.
Steam turbine generators (e.g., coal, natural gas, biomass, nuclear), hydroelectric power plants, wind farms, gas turbine generators all operate on the same principle—magnets + conductor (wire) + motion = electric current. The electricity produced is the same, regardless of the energy source used to turn the turbine.
(Sources for much of the information on this page: Mass Engineers [2] and The Electricity Forum [3].)
From Diesel Service and Supply, read “The Role of Turbines in Power Generation [4]”
Shown below, the U.S. Energy Information Administration [5] describes energy sources used for electricity generation in the U.S. in 2016.
In 2016, the United States generated about 4 trillion kilowatthours of electricity at utility-scale facilities. About 65% of the electricity generated was from fossil fuels (coal, natural gas, and petroleum).
Energy sources and percent share of total for electricity generation in 20161
1 Preliminary data; based on generation by utility-scale facilities.
Links
[1] http://www.energyquest.ca.gov/story/chapter06.html
[2] http://www.massengineers.com/Documents/howgasturbinework.htm
[3] http://www.electricityforum.com/electricity-generation.html
[4] http://www.dieselserviceandsupply.com/Turbines.aspx
[5] http://www.eia.gov/tools/faqs/faq.cfm?id=427&t=3