Wednesday, September 21, 2016

Solar Energy

I have begun to realize that almost all energy is solar energy.  People and animals do work; their fuel is food.  Food grows because of sunlight.  Plants take the solar energy and convert it into food.  Meat just requires an extra step; the animals eat plants and convert them into meat.  So, animals and men run on solar energy. The plants themselves can produce energy, for example by burning wood. 

Hydrocarbons are also solar energy.  Coal, oil and gas are simply old plants that have been under pressure underground for millions of years, but the energy they contain also came from the sun.  Other sources of energy from chemical reactions, e.g., rocket fuel made from hydrogen and oxygen, usually require energy input from traditional (solar) sources to create the chemicals that create energy when they combine.  Hydrogen and oxygen have to be separated using energy before they can be combined later. 


Nuclear energy is about the only type of energy that does not come from the sun.  There are some relatively unimportant sources of energy that are not based on solar, for example geothermal energy that comes from volcanic heat underground.  Ocean tides rising a falling similarly could produce a small amount of energy.  However, wind and even wave energy is basically solar, caused by uneven heating of the earth by sunlight.  

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