Revolving doors producing green energy

Renewable energy is the energy which comes from natural recourses such as sun light, wind, rain, tides and geothermal heat which are naturally replenished. Wind energy, solar energy, biomass, bio-fuel and geothermal energy are the main types of renewable energies used nowadays. All forms of energy are expensive but as time progresses renewable energy generally gets cheaper, while fossils fuels generally gets more expensive. As it is renewable, it is therefore sustainable and so will never run out. Renewable energy has minimal impact on the environment.