Comment by insane_dreamer

Tides happen everywhere, but not to the same extent and not always at useful times. If your peak production times don't line up with peak demand times, then you need expensive energy storage. (This would change with the phase of the moon, so sometimes you'll get lucky and sometimes you won't.)

One thing that's relatively unique about the UK is that different parts of their coastline experience tides at different phases -- meaning with carefully chosen placement of different tidal energy plants, you can always have some of them operating near peak production. Click around https://www.tidetimes.org.uk and you can find places with high tide times happening at just about any time of day.

If you look at a map like http://www.bidstonobservatory.org.uk/wp-content/uploads/2016..., the best places to use tidal energy would be red areas with lots of white lines hitting the coast -- these would give you the highest-amplitude tides with the most opportunity for phasing. The UK has both.

The issue is clarified with a map like this: https://i.redd.it/rontertecjqd1.jpeg

Most regions have very small tidal ranges. That doesn't mean they have small tidal currents (think of fjords or straights for example), but it does make it more likely.

And in those fjords and straights, I reckon yhese solutions will compete with boat traffic.