Tidal

Tidal Barrages

Annapolis Royal tidal generation plant, Nova Scotia © Travel and Transitions, used with permission (http://www.travelandtransitions.com/stories_photos/evangeline_trail.htm)

Tidal energy can be converted into electricity either by building a tidal barrage—a dam at the mouth of an inlet or bay—or by installing a turbine in an area with a strong natural tidal current.

The only existing tidal installations are of the barrage type, including a commercially operating 240 MW system on the estuary of the Rance River in France, and a 16 MW demonstration unit at Annapolis Royal, Nova Scotia, in the Bay of Fundy.

The Rance and Annapolis Royal barrages were built in 1966 and 1984 respectively, and no other large-scale tidal barrage systems have been constructed in the meantime.  There are several reasons for this:

1. Tidal barrages are extremely expensive to build.
2. A barrage changes the timing and extent of flooding of tidal flats, and this can have serious implications for intertidal life.
3. A barrage can impede fish migration.
4. A barrage can change the nature of the tidal regime downstream.