Renewable energy and grid integration

Emerged Fossil-based fuels like coal, natural gas and petroleum provide about 85% of the developed world´s energy[1]. The World Energy Resources 2013 indicates that around 82% of the total energy in the world is being supplied by fossil fuel[2]. All fossil fuel sources are being constantly depleting and can´t be replaced within any practical timespan. The estimates mentioned in Table I below provide a sense of reality that our fossil fuel energy resources are not endless in supply[3].