This video is well worth five minutes of your time. The technology is harvesting not tidal energy, but wave energy, and as noted it can be incorporated into preexisting or planned barriers that are needed for other purposes (harbors, erosion control).
I find it interesting that the turbines are driven not by the salt water, but by the displaced air, and that they use the incoming air, not the "blowhole" air - presumably to minimize contact with salt.
Fascinating. And logical.
Addendum: One month later, a report entitled "Giant, megawatt-scale wave energy generator to be tested in Scotland."
Irish company OceanEnergy has already tested its oscillating water column generators at significant scale in Hawaii, and it's just signed on to a four-year project to test, validate and commercialize its biggest unit yet off Orkney, in Scotland... In testing, it ran at a capacity of 500 kW, but the device was, and is, capable of 1.25 MW...OceanEnergy makes use of a piece of Northern Irish technology to harvest energy from this bidirectional air pressure: the Wells turbine, invented in Belfast in the late 70s. These use a series of symmetrically-designed fan blades, designed to convert air pressure coming through in either direction into the same direction of rotation. Thus, the turbine turns continuously in one direction as the air pumps in and out of the wave chambers, rather than requiring the turbine to keep switching directions every time the air flow reverses.This is in contrast with Wave Swell Energy's (WSE's) blowhole generator, which works on similar principles, but only harvests energy from air on the in-stroke, allowing the out-stroke air to push out through a valve.