Comment by worik

> * Tidal energy is valuable but geographically constrained

Yes, of course. I do not get the point, this is not a solution to every electricity generation problem

> * Only a few countries have suitable locations for it (UK, Canada, France, South Korea)

There are more than that. I have a seven knot tidle current 5km from my house, not mentioned in your list. I know of others. The costal conditions are quite common for this. The same technology will be useful in rivers too