Tides as green energy

I hasten to note that I'm very skeptical about tidal energy due to the huge infrastructure required and the consequent environmental impact. But it's worth reading some of the latest:

"thpr writes "The Electric Power Research Institute and its partners have completed their Offshore Wave Power Feasibility Demonstration Project [PDF file - PW], which defined potential wave energy projects off the shores of the United States. This is building off of work already done in Scotland (and elsewhere). San Francisco, New York and other areas are considering trial installations of the technology. It is interesting to note (table 1 in the report) that the energy density (kW/m^2) that can be achieved is much higher than wind or solar. In addition, harnessing 24% of available wave energy near the US at 50% efficiency is equal to all of the hydropower currently generated in the US (~7% of total electricity production)."
Source: Slashdot