Energy can exist in a variety of forms, such as thermal, mechanical, chemical, or nuclear, and can be transformed from one form to another. Electrical energy is caused by the movement of electric charges called electrons.  Energy sources can be primary or secondary. Primary energy sources include: Nuclear energy Fossil energy, such as oil, coal, and natural gas Renewable sources, such as wind, solar, geothermal, and hydropower  Primary energy sources are converted to electricity, which is a secondary energy source.  Renewable energy sources are generally non-depletable or naturally... Show more

Energy can exist in a variety of forms, such as thermal, mechanical, chemical, or nuclear, and can be transformed from one form to another. Electrical energy is caused by the movement of electric charges called electrons. 

Energy sources can be primary or secondary. Primary energy sources include:
Nuclear energy
Fossil energy, such as oil, coal, and natural gas
Renewable sources, such as wind, solar, geothermal, and hydropower 

Primary energy sources are converted to electricity, which is a secondary energy source. 
Renewable energy sources are generally non-depletable or naturally replenishable. They can be converted into several types of clean energy, including:
Bioenergy, Geothermal energy, Hydrogen and other renewable fuels, Hydropower, Marine energy, Solar energy, Wind energy. 

 

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