ABSTRACT
The modern technologies currently being considered for some “renewable” energy sources (including direct and indirect solar energy, as well as tidal and geothermal sources) are still mostly in exploratory stages. Some of the renewables represent old technologies that are being revived in newer and larger scale contexts. Others are technologically established but not yet proven out commercially. Consequently, cost estimates for many of them rely heavily on theoretical studies prepared by proponents, and tend to be optimistic.
