Introduction to Major Energy Sources
Energy sources are used as fuels. Fuel is burned in machinery to create motion (such as in a car) or heat (such as in a home heating system). When fuels are used for producing electricity, heat or motion causes a generator to rotate, creating electricity for everyday use in homes and businesses.
Energy sources can be classified into two types: nonrenewable and renewable. Nonrenewable resources, such as fossil fuels and nuclear material, are removed from the earth and can be depleted. These resources have been the most used type of energy in the modern era.
Renewable resources, such as wind, water, solar, and geothermal, come from sources that regenerate as fast as they are consumed and are continuously available. Some, such as biofuel produced from food crops and other plants, are replenished every growing season. In the early part of the twenty-first century, renewable sources have become more popular as nonrenewable sources have begun to be depleted.