Many of us take “the grid” for granted — but without it, society would cease to function. Our homes, offices and communities all depend on the energy infrastructure to supply a reliable, steady stream of power. Yet every grid has its limitations…. “When too much energy wants to flow, they will overheat – just as in every home there is a fuse and that will simply shut off.” … When it comes to renewables like solar and wind, the challenges facing energy storage are manifold, because while these sources are good for the planet, they do not promise a constant stream of power.
http://www.cnbc.com/id/102766915