Tidal power involves machinery below the water, which then becomes as expensive as a boat to maintain. Wind power has just ridden the cost reduction curve so much better.
And even offshore wind turbines have most of their complexity 300 feet above the water line. The air might be salty up there, but that's nothing compared to being submerged in salt water, in a strong current that drags along seaweed or abrasive sand.
The tides are not constant but they are predictable.
The majority of tidal flow is during relative short periods of only a few hours. In order to harvest tidal energy, truly enormous volumes of reinforced marine concrete have to be deployed. The environmental consequences are massive.
It's really hard to build good tidal power plants beyond the demonstrator stage. Most are difficult to build, expensive to maintain, and require a lot of maintenance.
https://www.orbitalmarine.com/ is one company working on it. As another comment states, working offshore unbelievably challenging (corrosion++, weather, position etc). Orbital's innovation is that the rotors move to a position where they can be serviced from the surface, rather than requiring any underwater activity, so it's a lot cheaper.
There are plans for big tidal barrage projects, especially in the Severn Estuary. Apart from creating power they'd also protect cities from rising sea levels.
They always run into Nimbys who don't understand that sea birds etc are far more threatened by the direct effects of climate change than by projects that affect their habitats in a designed way.
> They always run into Nimbys who don't understand that sea birds etc are far more threatened by the direct effects of climate change than by projects that affect their habitats in a designed way.
That's incredibly dismissive of genuine environmental concerns about immediate effects on coastal ecology
Can you elaborate on where the parent comment is erring? Sounds reasonable that planned interventions like tidal power plants are more controllable than global climate change
That does not mean they are less damaging. They are definitely more damaging at a local level, and it is not clear that they are better at a global level.
If I bulldoze a corner of you house for a planned turbine and say it's less damaging than a potential hurricane from climate change, it isn't going to make you feel better.