This textbook analyzes the full range of renewable energy supplies available to modern economies worldwide. It is widely recognized that these are necessary for sustainability, security, and standard of living. The renewable energy systems covered include power from solar radiation (sunshine), wind, biomass (plant crops), rivers (hydropower), ocean waves, tides, geothermal heat, and other such continuing resources. All of these systems are included within the following general definition:
Renewable energy is energy obtained from naturally repetitive and persistent flows of energy occurring in the local environment.