For a same theoretical potential over 20 000 TWh/year: Hydropower supplies: 3 500 TWh/year and tidal energy supplies: 1 TWh/year. Most past designs of tidal plants have been devoted to best sites of few countries. However the proposed solutions appear usually too expensive in the very specific conditions of tidal energy: very low heads for plants, too low water speed for in-stream turbines, huge waves.
Hydropower and Tidal Energy have about the same theoretical potential, above 20 000 TWh/year. The possible energy supply per km2 of tidal basin (20 GWh/km2 with a tidal range of 5 m) is higher than the average energy supply per km2 of dam reservoirs (3 500 TWh for 350 000 km2, i.e. 10GWh/km2).
The cost per MW for manufacturing of in-stream turbines may be low but there are few natural places at sea with an efficient water speed and the cost for placing and maintaining turbines of low capacity (1 MW) is generally too high. A new solution, the “Tidal Gardens” creates conditions for the best utilization of more powerfull in-stream turbines. Large basins along shore are open to sea by wide channels about some hundred meters long in which are placed five to ten rows of turbines operating in a permanent speed about 4 m/s (fig. 1 and 2).
A new solution for tidal energy has been presented in detail in Hydropower & Dams 2014 – Issue One; corresponding potential is evaluated below for Asia.
In Asia the theoretical potential of Tidal Energy is close to its hydroelectricity potential but the tidal power supply is limited to 0,5 TWh/year when hydropower supplies 1 500 TWh/year.
Hydropower and Tidal Energy have about the same theoretical potential. Hydropower supplies 3 500 TWh/year, Tidal Energy 1 TWh/year. The reason of this gap may be that the technical solutions used successfully for hydropower and chosen for most studies of tidal energy are poorly adapted to most tidal sites. A new specific solution better adapted to the specific tidal energy is presented in this article.