Wikipedia has agreat little article on solar energy. Even harvesting energy at 15% efficiency, the sun provides a LOT of power.
http://en.wikipedia.org/wiki/Solar_power
As an aside, and I DO NOT intend to hijack the thread, we have spent about a TRILLION dollars in Iraq. Think of the advances in energy technology that could have bought. The estimated cost of Lyndon Johnsons "great society" programs is estimated to be north of 7 trillion. Politicians seem uninterested in real energy policy.