Renewable energy sources such as wind, hydroelectric, geothermal, tidal have one big thing in common which is that they are clean sources of energy. But is this actually true? Researches show that they need to store the energy which creates some problems. As it is not fully used, the energy will lose its charge after some time creating some pollution. Even though the battery problem is better than coal energy pollution, this is still a problem and there need to be further considerations.