definition
strict definition
tidal power harnessing
A facility generating electricity from the regular movement of ocean water caused by the tides.
A tidal power plant is a facility which converts mechanical energy from regular movements of ocean water, driven by tidal effects of the moon's and sun's gravity, into usable electric power.
The movement harnessed is tidal rather than simply any motion of water at sea. The distinction concerns the energy source, not a single required turbine or enclosure design.
The lunar and solar gravitational effects produce the tides. A plant using ordinary river flow instead belongs to hydroelectric generation.