Production of electricity from the difference between high and low tide has been an area of interest since for centuries water turbines have turned in many areas of the world to drive heavy wheels used to grind wheat or make gunpowder. Electricity-producing turbines are installed in tidal basins that capture water at high tide and release it at low tide. Tidal power plants with a capacity around 250MW have been installed in LaRance, France(1966) and in Korea(2011). A similar-sized plant is completing construction in Swansea, South Wales and there is now renewed interest in this technology, which would take its place next to solar and wind as the most basic form of renewable energy. The one billion Pound Sterling plant, which takes advantage of one of the largest high tide/low tide height differentials in Europe, is based on a man-made lagoon where a seawall encloses 11.5 square miles of ocean off the coast.
The initial cost of power generation from a plant of this kind is high at around $250 per megawatt hour versus $ 210 from wind and $ 150 from fossil fuels. However, economics of scale can bring the cost down to that of wind power. If Swansea builds five more tidal lagoons the projected cost of power will be comparable to nuclear and the plant would then produce about 8 percent of the U.K.’s demand for electricity. If the cost of solar power had not been coming down so dramatically, the U.S.,with promising locations, would have been looking at tidal power more seriously as interest in renewable, zero carbon, energy has grown in recent years. Canada could long have installed tidal power at the Bay of Fundy (largest known tide differential globally with studies showing three locations that could each provide between 1000 and 3000 MW), but the country has built much lower cost hydropower generation so no reason to build high capital cost tidal power plants.
The downside for tidal power plants is possible effect on marine life, but the LaRance plant in northern France has not been a problem in that respect.