UK unveils plans to build tidal power plants. We've been planning things in the Severn Estuary my entire life and so far not lit a single lightbulb from it. As all the comments on the BBC story say: get on with it, build the thing, and tell us when it's done.
(There are a few tidal-power-through-undersea-turbines schemes in operation off Scotland, I believe)
It works alright, but unless you have a very luckily shaped coastline, it doesn't scale all that well. It's also subject to silting in the long run, which isn't great for the yield, or the local eco-system.
Re silting. If you split the pool into two or three, when one was empty (at low tide) you could use the water from a full one to flush the silt out. There is a system similar to this where I live, they use a tidal pool to flush the harbor.
That's a barrage - like the scheme discussed in the original article. The NI and Pendland Firth schemes don't rely on a barrage but on the very strong tidal streams naturally found in those areas.
(There are a few tidal-power-through-undersea-turbines schemes in operation off Scotland, I believe)