As shown in Figure 3.1, energy resources are often divided into three loosely defined categories:
Fossil fuels include oil, coal, and natural gas. Renewable energy resources include hydropower, wind, solar, hydrogen, biomass, tidal, and geothermal. All these resources can also be classified as primary and secondary resources. The primary resources are
The secondary resources include all renewable energy minus hydropower. Over 99% of all electric energy worldwide is generated from the primary resources. ...