Renewable Energy Renewable energy is defined as energy that is produced by natural resources-such as sunlight, wind, rain, waves, tides, and geothermal heat-that are naturally replenished within a time span of a few years. A renewable energy source means energy that is sustainable - something that can't run out, or is endless, like the sun. Sources of Renewable Energy 1. Solar energy 2. Wind energy 3. Hydro energy 4. Tidal energy 5. Geothermal energy 6. Biomass energy