Energy Source Classifications

Just as a quick overview, energy sources can be classed as:

I. Non-renewable energy sources

A. Fossil fuels:

• coal
• petroleum (oil)
• natural gas

B. Nuclear

II. Renewable energy sources

A. Biomass

• wood
• alcohol (from corn, sugar cane, etc.)
• waste (municipal solid waste, manufacturing waste, refuse-derived fuel, and methane recovered from landfills)
• switchgrass, corn stalks, wheat straw, etc.

B. Direct solar

• passive (solar home, no moving parts)
• active (uses pumps for moving solar-heated fluid around)
• photovoltaic (converts solar energy to electrical energy)

C. Wind (could be considered a form of solar energy)

D. Geothermal (drawing heat from the deep in the earth)

In the EIA report you will find a discussion on Figure 3 and more details about the recent changes in use of renewable energy.