 A barrage is a dam that impounds seawater from the rising tide in a tidal basin or estuary. The seawater is held in the basin until low tide, when it is released to power hydro turbines to generate electricity.

 A tidal lagoon is an enclosed dam that impounds seawater from the rising tide in a ring inside of a tidal basin or estuary. The seawater is held in the lagoon until low tide, when it is released to power hydro turbines to generate electricity.  An in-stream turbine is pretty much just like a wind turbine except it operates underwater, drawing energy from a tidal or marine current to produce electricity. These turbines turn much slower than wind turbines but can produce far more energy for their size.

1. The sluice gates are opened as the tide rises so that seawater can fill the tidal basin. Power is generated during the floodtide. 2. The sluice gates are closed as the tide ebbs in order to increase the difference in height between the water in the basin and the turbine. 3. The sluice gates are opened again at low tide and the tidal basin empties, turning the turbine to generate a great deal of power. h

Example: Seawater (  = 1020 kg/m 3 ) flows into a 10 square-kilometer tidal basin. If the tidal range in this area is 10 m, what is the average power output [megawatts]?

 Impacts on Environment/Society