Tapped on a large-scale for use as a power source, tidal power can provide a power base source for any grid system. There are actually a number of countries using tidal power, including one of the oldest and the world’s first tidal barrage, the Rance Tidal Power Station in France.
The Rance power station, located in Saint-Malo in northern France, was opened in November 1966. At 240 megawatts (MW), it was the largest in the world until South Korea opened its Sihwa Lake Tidal Power Station in 2011, producing 254 MW. South Korea is so pleased with the results of their tidal barrage system., several more are planned for other areas around the country.
What is a tidal barrage?\
A tidal barrage is a dam-like structure used to harness the energy produced when masses of water are moving in and out of a bay or river due to tidal movement. This method of harnessing power is the oldest form of energy production known to man. According to the World Commission on Dams, a key difference between a barrage and a dam is that a dam is built for water storage while a barrage is used to divert water.
Instead of harnessing water like a conventional dam, a barrage allows water to flow into a bay or river during high tide. The water is then released back out to sea during low tide. This is all accomplished by controlling the sluice gates. Turbines are placed at the sluice gates to capture the energy as the water flows in and out.
Using tidal currents to harness energy
Somewhat different from tidal barrages, extracting energy from tidal currents involve the use of undersea turbines in estuaries and shallow water along the continental shelf. Because water is denser than air, the same size turbine blades used in wind power can produce four times more electricity in water.
Twenty sites around the world have been identified as being possible sites for this type of power production. The sites are in shallow waters with strong currents. The very best sites are in between islands or in narrow stretches of sea where the current flows fast. Eight sites have been found in the UK with the sites capable of producing 20 percent of the country’s electrical power.
The very best place in the world to use underwater turbines to harness ocean currents is in Pentland Firth between Scotland and the Orkney Islands. One company, MeyGen has already begun building 64 turbines, out of a planned total of 269. When finished, it will be the world’s largest undersea power station, generating 398 MWs of clean power, which is enough for 175,000 homes.
Canada may be ahead of the game when it comes to harnessing tidal energy, though. Canada’s Bay of Fundy has the highest tides in the world. The Fundy Ocean Research Centre for Energy project has already begun installing the infrastructure for their tidal energy project which will be capable of providing electricity for 10,000 homes.
Are there environmental concerns?
There are still questions that need to be addressed in any type of tidal or ocean current energy production. Looking at tidal barrages, damage to marine life is still an important consideration as well as the negative impact on aquatic and shoreline ecosystems, navigation, and recreation.
The thing is, each site will be different, and in turn, have different impacts depending on the site itself, and local tides. The La Rance barrage has been studied for years, and there has been negligible damage to the environment and marine life. In the case of the Bay of Fundy project, it is estimated that there could be a decrease in tides of as much as 15 centimeters, but that is not very much considering natural variations.
As far as competing with solar or wind energy, tidal energy is dependent on the waters of the ocean, so this source of power would not work in regions far from the sea. But tidal energy, along with solar and wind energy will have to be the way we go if we want to tackle greenhouse gas emissions.
