The Rance Tidal Power Station in France.
The Rance tidal power plant in France, built in 1966, has a peak capacity of 240 MW, impounding 22.5 km² on an average tidal amplitude of 8 m. Because it cannot always be generating at full capacity, it effectively gets 40% of this on average, or 96 MW. The dummy model above computes 125 MW from these parameters, so not bad. The Rance station was recently surpassed as the largest tidal power plant in the world by the Sihwa facility in South Korea, edging our Rance with 254 MW of peak capacity and 30 km² of impound.
That these modest plants are the largest yet built is some indication of the limitations of tidal power. If it were easy to snatch this freebee from nature, we would see the straightforward technology implemented all over. South Korea is currently building another, larger plant expected to peak at 1.3 GW and 21% capacity factor for 2.4 TWh of annual electricity.
But some people speak of bigger plans. The large Penzhina Bay at the armpit of the Kamchatka Peninsula in Siberia (not a comment on the region or people: merely a geographic analogy) has an area of 20,000 km² and 10 m tides. Cha-ching! It is thought this could provide as much as 87 GW if fully developed. A list of proposed future concepts total about 115 GW.
