Tidal power has become economically feasible as a result of the continuous rise in price of fossil fuels, and a number of nations already possess working tidally driven electric generating facilities. A tidal power plant is similar in principle to hydropower generation facilities in rivers. For the simplest design, the basin is allowed to fill during flood tide through floodgates and powerhouse, with turbines spinning freely.
Power is produced on ebb tide.
Environmental concerns at issue with tidal power include alterations of primary and secondary productivity, fish mortality, changes in the tidal regime, local weather patterns, and local and regional socioeconomic structure. Tidal hydropower developments may encompass large embayments and affect wide geographic areas. Removing energy from the tide and reducing volume of seawater exchange across the barrage site, will alter water circulation patterns and tidal regimes both behind and seaward of the barrage. Seaward of the barrage tidal amplitudes may increase as far as 500 km from the barrage site, inundating narrow but substantial portions of nearby coasts and raising long-term storm damage potential. Within the headpond tidal range will be reduced but mean water level will rise causing increased stratification, producing greater extremes in surface temperatures and more ice cover in temperate climes.