Renewable Sources of Energy, Wind, Solar, Geothermal, etc. Why do we need them? How do they work? How clean are they? Where do they stand? How efficient are they? Which are the more promising ones? The concept of Micro Grids and Smart cities. The important role of batteries in the switch to renewable sources. Limitations and challenges. Other futuristic options for energy and their realistic possibilities. A look at what countries and regions are leading the conversion to renewable energies.