Energy sources are used as fuels. Fuel is burned in machinery to create motion that we use in our cars or heat in a home energy 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.
Fossil fuels were formed from the fossilized remains of tiny plants and animals that lived long ago. Most electricity used in the world is generated from power plants that burn fossil fuels to heat water and make steam. The highly pressurized steam is directed at turbine blades to make them spin. Nonrenewable resources cannot be replenished. We have limited supplies of them, and when these supplies are gone we will not have any more.
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. Renewable energy resources can be replenished in a short period of time, so they will never be all used up. 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. Energy companies around the country are using renewable resources more and more to generate electricity.
Renewable energy resources can be replenished in a short period of time, so they will never be all used up. Most renewable energy comes either directly or indirectly from the sun. Sunlight, or solar energy, can be used directly for heating and lighting homes and other buildings, for generating electricity, and for hot water