Sources and Forms of Energy

Fuels, or primary sources of energy for conversion to other forms, include fossil fuels, renewable fuels, and nuclear fuels.

Renewable energy sources include the following:

• Biomass
  1. Wood
  2. Alcohol (from corn, sugar cane, etc.)
  3. Waste (municipal solid waste, paper, manufacturing waste, refuse-derived fuel, and methane recovered from landfills)
  4. Switchgrass, corn stalks, wheat straw, or other agricultural waste
• Direct Solar
  
  1. Passive thermal (solar home, no moving parts)
     
  2. Active solar (uses pumps for moving solar-heated fluid around)
     
  3. Photovoltaic (converts solar energy to electrical energy)
• Wind (could be considered a form of solar energy, since heating and cooling of the earth by the sun sets up wind patterns)
• Hydroelectric (could also be considered a form of solar energy, since solar energy evaporates water from oceans and moves it to high elevations where it condenses out as rain or snow and eventually flows downhill)
• Geothermal (drawing heat from deep in the earth)
• Ocean thermal (drawing heat from the ocean)
• Ocean tidal (using the incoming tide or other low-frequency oscillation of sea level to raise an object, thereby creating potential energy)

Another way of categorizing energy is by its form:

• Electrical
• Chemical (batteries, chemical bonds in fossil or biomass fuels)
• Nuclear
• Radiant (solar or infrared radiation)
• Potential (water behind a dam, spring in a mechanical watch)
• Kinetic or mechanical (moving air, spinning flywheel)

Chemical, nuclear, potential, and kinetic forms of energy can be used for storage, whereas electrical and radiant cannot.

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