Super Eco

Photo credit: tlbcml, Flickr

Tidal power plants harness the energy of the oceans' tides, the energy produced by the force of gravity from the moon and the sun pulling against the rotation of the Earth. Tidal power is virtually limitless and inexhaustible. It's availability depends only on the strength of the tide in a given location. Tidal power promises to be an important renewable energy source.

There are two main types of tidal power: tidal stream systems and hydraulic head systems. The tidal stream system uses the energy of moving water to power submerged turbine generators in much the same way that wind generators harness the power of the wind. Hydraulic head systems take advantage of the difference in height between high tide and low tide. Hydraulic head (or Barrage) systems require damming to create a water containment lagoon. The inbound tide turns the generators as the lagoon fills; then, as the outbound tide recedes, a controlled release of water over the dam produces electricity in the same way that hydroelectric power is generated by a dam on a river.

Tidal stream generators are an emerging technology. Prototypes of several different designs have been developed and are being deployed around the world, at sites as varied as Strangford Lough, Ireland, the East River in New York City, the mouth of the Clarence River in Australia, and the Strait of Messina in Italy.

The Annapolis River in Nova Scotia is the site of the only operational barrage system in North America. The river was dammed, and at low tide a sluice gate is opened, then closed at high tide. The Bay of Fundy is known for having one of the world's highest vertical ranges between high and low tide. Environmental impacts of barrage systems have been illustrated on the Annapolis River where whales have followed fish through the open sluice gate and been trapped in the upper part of the river.