It takes millions of years to form non-renewable energy sources and they will run out some day. Non-renewable energy comes from fossil fuels such as coal, oil, and natural gas. However, renewable energy sources will never run out. They are better for the environment and do not cause pollution. Renewable energy sources include the sun, wind, water, heat from the earth, and biomass. Renewable energy is often called green energy because it is a natural energy. It is also always available. For example, the sun always shines, water is abundant, and the winds blow throughout the year. There are five types of renewable energy: solar energy from the sun; geothermal energy from heat within the Earth; hydroelectric energy from moving water; biomass energy from dead plants and microorganisms, and finally, energy from the wind.