Big problems for dependence upon wind and solar as sources of energy are that the wind is not always blowing and the sun is not always shining everywhere.
In today’s Austin American-Statesman, there is an article about a company in Kyle that makes battery backup available.
“Kyle Energy Storage Company at Center of Key Debate over Power Rates” by Laylan Copelin, Austin American-Statesman, February 19, 2012.
There still may be problems with cost effectiveness for power generated from wind or solar farms even with battery backup.
See, for example,
“A (Load) Balancing Act: The Challenge of Clean Power” by Lauren Sommer, npr, August 18, 2010.