When we talk of renewable sources of energy, along with sun and wind, hydro power is also known to have a huge potential to generate electricity. Huge parts of the earth are covered by massive water bodies which experience tides and these tides are one form of water which is known to have the capacity of generating electricity.
Define Tidal Power
A comparatively less used form of renewable energy, it is a fact that the tides which surge in the massive water bodies like oceans have energy in them which can be used to generate electricity. From the 20th century engineers have tried to use the tidal energy with the help of generators that can convert this energy in to electricity. However, tidal power generation is still considered to be in its infancy across the world.
What is the speciality of tidal energy?
While wind may or may not blow and the sun may or may not shine, there is no doubt in the fact that both high and low tide certainly occur every day thereby making it a much more predictable source of energy. As it is dependent on the rotation of the Earth and the pulls of Sun and Moons, there are hardly any chances for the tides to stop happening. The only major limitations to use tidal power is that, the infrastructure is extremely costly and also there are not very friendly locations where one can find strong tides. However, having said that it is also important to mention that with the passage of time new technologies and designs have been launched in the form of tidal lagoons and turbines which has now eased the process of utilising tidal power.
How popular is tidal power?
On a global scale it can be said that tidal power has not yet crossed its infancy. There are not many tidal power plants which can cater to commercial needs. The largest tidal power plant is known to be situated in South Korea and in named as the Sihwa Lake Tidal Power Station. In Europe, the first tidal power plant got constructed in France and England is also considered to have the potential of using this type of energy. Amongst the developed countries United States does not have a tidal power plant so far because legal issues prevail there on the ownership of underwater land and also on the environmental hazards which are associated with the harvesting of this form of energy. While China, Canada and Russia too are known have good spots to tap tidal power but it is difficult to arrange for the financial backing as private investors continue to have doubts regarding the returns against investments. In UK as per the Department of Trade and Industry there is a potential of covering 10% of the electricity demands by tidal power.
How can tidal power be generated?
As tidal power harvesting is still a less practised option in clean technology sector so, currently there are three main harvesting means which are used.
- From tidal streams where the turbine for the tidal generator is placed in the streams. These tidal streams are actually bodies of water which happen due to the tides. The turbine gets moved due to the energy of either the water streams or also of the air. In case it gets driven by water, the energy felt by the turbine is higher because the density of water is more than that of air. With the help of these tidal generators, you can generate a steady flow of electricity. The only challenge in this process remains placing the turbine in the tidal streams. This is because the turbines are big machines which can disrupt the tides from which it tries to gather the energy. As has been observed, the tidal turbines work best in the shallow waters as here it gets more energy. The first tidal stream power station came up in 2007 in Northern Ireland. In this case the turbines got placed in the strait which was there between the inlet of Strangford Lough and the Irish Sea on the other side.
- From barrages which are kind of huge dams where the tidal generators are placed. These barrages usually come on rivers with tides and bays. As these barrages are constructed at a lower level so there remains a chance for the water to pass through or over the turbines. These turbines then gather energy from the tides in the same way as river dams make use of the rivers to generate hydro power. During the times of high tide, the gates of the barrage get closed and a pool is created which is called the tidal lagoon. Thereafter the water gets released and while passing through the turbines it generates electricity which can be moderated by the engineers. There are some implications of barrages as well. Most of the times the land which occurs in the tidal areas gets affected negatively and the plants and animals of the area may also get harmed because of the change in the water level. Fishes often get blocked in the tidal lagoon as happens with the river dams. As the turbines of the barrages tend to move at a faster speed many times marine creatures get caught in them and a fall in their numbers lead birds to fall short of food and thus migrate to other areas.
Often barrages stand out as an expensive means of tidal power generation because here more machines are needed and the generators too require more turbines.
Example of barrage is the tidal power plant on the Rance River estuary in France. Constructed in 1966, it gets tidal power from both English Channel and Rance River
- From Tidal Lagoons where tidal generators are placed in huge manmade or naturally barred water bodies which get filled by the oceans. Sometimes tidal lagoons also get formed from fresh water bodies and estuaries. The functioning of tidal generators in tidal lagoons is very much similar to that happening in the barrages with the only difference being that there is also a scope of making a tidal lagoon with a natural coastline. In this set up as the turbines more or less keep working with the lagoons getting filled and becoming empty so, the power generation from this means is also practically constant. The best part of the tidal lagoon is that its impact on the environment is said to be very less. While the barriers creating the lagoon can also be made of natural rocks, they get submerged during the times of high tide and tend to come out when the tide is low. This does not create any obstruction for the marine animals that can swim in and out all the times. Birds too get their suitable habitat in the area and so keep the place occupied. However, so far there are no mentionable tidal lagoons working in the world. Though China is in the process of making one and the second one is known to be coming up in Swansea, Wales.
- From Dynamic Tidal Power plants which is a concept still in papers but promises of tremendous potential in its intention to make use of the potential and kinetic energies present inside the tides. The set for this method would require construction of very long dams from the oceans and seas where there are no enclosures
Does tidal power create any environmental issues?
As it is the process of hampering the face of the sea or oceans the biggest problem of tapping tidal power is that it may negatively impact the marine life. There always remains the threat of fishes and other marine creatures getting tangled in the blades of the turbines which may scare the other fishes and creatures to go in that area. Sometimes the constant noise generated by the tidal generators may also be a cause for hampering the movement of sea creatures. The water quality tends to get affected and sedimentation process may also get heightened due this initiative. Creation of barrages also tends to bring changes in the shoreline which in turn affects the larger ecosystem around the area.
On the other hand, the salinity of the sea water has a tendency to bring early corrosion of the tidal generators which thus needs a close maintenance for continuation. In order to avoid this problem it is often advisable to make use of tidal generators which are made of stainless steel, alloys of nickel, alloys of copper and nickel and so on. It is not too much encouraged to use lubricant on the tidal power generators because that may cause harm to the surrounding marine life.