Wind and solar are too intermittent to comprise much of electric grid power now, according to Steven Cu, former US energy secretary. In 2010, Chu said, “Without technological breakthroughs in efficient, large-scale energy storage, it will be difficult to rely on intermittent renewables for much more than 20-30% of electricity.”
Unless a major breakthrough in batteries happens, we will continue to require natural gas fueled power plants to ramp up and down quickly to cope with intermittent sources of power. “When you ramp power plants up and down they lose efficience” according to Haresh kamath of the Electric Power Research Institute in Washington DC.
And keep in mind, for the long run, these batteries need to have a positive EROEI over their entire life cycle from mining and crushing of rocks for metals to fabrication to delivery. If they require more energy to construct across the life cycle than they more energy to create than at least 5 times the energy stored and discharged, our way of life can’t continue.
In addition, batteries must be composed of cheap and abundant materials. Platinum, lithium, and many other metals are scarce and take too much energy to extract.
Hal Hodson. 2 Feb 2013. Greening the Grid. NewScientist.