Tidal Power

Today hydropower usually is used to generate electricity rather than to generate mechanical energy directly, as with historical water wheels. One technology in contemporary use for doing this is tidal power. Tidal power harnesses the energy resulting from the ebb and flow of water that occurs as tides come to shore and retreat from it.

The Severn estuary in Wales has a very large difference between high and low tides, and as a result a barrier across it could generate as much energy as eight coal plants.

Tidal energy can be captured in a couple of ways. First, some technologies make use of estuaries. An estuary is a kind of coastal lake into which a river flows. Instead of being entirely enclosed like a lake, however, one part of the estuary is open to the ocean. This means that tides flow into and out of the estuary. To capture the power of the tides, engineers build tidal barrages across the estuary opening. These often look like, and work in a manner similar to, wind turbines. The tidal turbines have blades that can rotate, somewhat like those on a fan. Water flows into the estuary during the flood (or high) tide; then it flows back out during the ebb (or low) tide. The tidal flow turns the blades of the turbine, which is connected to a generator that converts the kinetic energy of the turning blades into electricity. Tidal energy can also be captured in tidal streams, which are areas of high sea currents around headlands—bits of land that jut out into the water.

The main advantage of tidal power is that it is predictable; tides are both regular and well understood. Another advantage is that the technology to harness tides is already available and functional. Still, "Although the technology required to harness tidal energy is well established, tidal power is expensive, and there is only one major tidal generating station in operation." The one working tidal power station is located at the mouth of the La Rance River estuary in northern France, and it generates 240 megawatts of energy, about a quarter of the power one would expect from a major coal or nuclear power plant. "The La Rance generating station has been in operation since 1966 and has been a very reliable source of electricity for France."2 The station was intended to be the first of many tidal power generating stations, but France chose instead to develop its nuclear power capacity.

There are currently some plans to build tidal power stations in Britain. In particular, the government has hoped to place a tidal barrage across the Severn estuary in Wales. The Severn has a very large difference between high and low tides, and as a result a barrier across it could generate as much energy as eight coal plants. This would significantly reduce Britain's greenhouse gas

The facility at the mouth of France's La Rance River uses massive turbines to extract power from the tides. Marcel Mochet/AFP/Getty Images.

The facility at the mouth of France's La Rance River uses massive turbines to extract power from the tides. Marcel Mochet/AFP/Getty Images.

emissions. Environmentalists are divided on the project, however, because they fear that "the barrage would destroy vast areas of mudflats and marshes, which are vital feeding grounds for tens of thousands of wading birds, and [would] prevent migratory fish such as salmon and eels from ascending rivers to spawn."3

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

Get My Free Ebook


Post a comment