I found some great information on extracting energy from hot rocks. As well as solar, wave and wind energy that can be harnessed, these heat rocks, located below the earths surface, would provide energy by producing steam from using water, that could run turbines above ground.

The following link explains what these hot rocks are and provides detail on how the process works.

http://www.science.org.au/nova/046/046key.htm


Regards,

Snooz