Tidal energy is generated by the surge of ocean waters during tide rise and fall. Tidal energy is a renewable energy source.
Engineers developed methods to use tidal movement to generate electricity in areas where there is a significant tidal range—the difference in area between high tide and low tide—during the twentieth century. To convert tidal energy into electricity, all methods employ special generators.
Tidal energy production is still in its early stages. So far, the amount of power produced has been minimal. There are only a few commercial-scale tidal power plants in operation around the world. The first one was in La Rance, France. The Sihwa Lake Tidal Power Station in South Korea is the largest.
There are no tidal plants in the United States, and only a few locations where tidal energy could be produced at a reasonable cost. China, France, England, Canada, and Russia have far greater potential for this type of energy.
There are legal concerns in the United States about underwater land ownership and environmental impact. Investors are skeptical of tidal energy because there is no certainty that it will make money or benefit consumers. Engineers are working to improve the technology of tidal energy generators in order to increase the amount of energy they produce, reduce their environmental impact, and find a way for energy companies to profit.
Generators of Tidal Energy On Environment
Tidal energy is currently obtained through three methods: tidal streams, barrages, and tidal lagoons.
Tidal streams
Turbines are placed in tidal streams for the majority of tidal energy generators. Tides create a fast-flowing body of water known as a tidal stream. A turbine is a machine that extracts energy from a fluid flow. This fluid can be either air (wind) or liquid (water). Tidal energy is more powerful than wind energy because water is much denser than air. Tides, unlike wind, are predictable and stable. Tidal generators produce a consistent, dependable stream of electricity wherever they are used.
The installation of turbines in tidal streams is complicated because the machines are large and disrupt the tide. Depending on the size of the turbine and the location of the tidal stream, the environmental impact could be severe. In shallow water, turbines are most effective. This generates more energy and allows ships to maneuver around turbines. The turbine blades of a tidal generator also turn slowly, which helps marine life avoid becoming entangled in the system.
The world’s first tidal power station was built in Northern Ireland in 2007 at Strangford Lough. The turbines are located in a narrow strait between the inlet of Strangford Lough and the Irish Sea. The tide can move across the strait at a rate of 4 meters (13 feet) per second.
Tidal Barrage
A large dam known as a barrage is used in another type of tidal energy generator. Because the dam is low, water can spill over the top or through turbines in the dam with a barrage. Barracudas can be built across tidal rivers, bays, and estuaries.
Turbines inside the barrage harness the power of tides in the same way that a river dam does. As the tide rises, the barrage gates open. The barrage gates close at high tide, forming a pool or tidal lagoon. The water is then released through the barrage’s turbines, producing energy at a rate that engineers can control.
A barrage system can have a significant environmental impact. The land within the tidal range has been completely destroyed. The tidal lagoon’s changing water level may endanger plant and animal life. The salinity of the tidal lagoon decreases, affecting the organisms that can live there. Fish are prevented from entering or leaving the tidal lagoon, as with dams across rivers. Turbine barrages move quickly, and marine animals can become entangled in the blades. Birds may migrate to different locations if their food supply is limited.
A tidal energy barrage is far more expensive than a single turbine. Despite the absence of fuel costs, barrages necessitate more construction and machinery. Barrages, unlike single turbines, require constant supervision to adjust power output.
A barrage is used in the tidal power plant at the Rance River estuary in Brittany, France. It was built in 1966 and is still operational today. The plant derives its energy from two sources: tidal energy from the English Channel and river current energy from the Rance River. The barrage has increased the amount of silt in the habitat. Silt suffocates native aquatic plants, and plaice, a flatfish, is now extinct in the area. Other organisms, such as cuttlefish, a squid relative, are now flourishing in the Rance estuary. Cuttlefish prefer cloudy, muddy environments.
The Tidal Lagoon
The construction of tidal lagoons is the final type of tidal energy generator. A tidal lagoon is an area of ocean water that is partially surrounded by a natural or man-made barrier. Tidal lagoons may also be estuaries with freshwater flowing into them.
A tidal energy generator based on tidal lagoons would work similarly to a barrage. Tidal lagoons, unlike barrages, can be built along the natural coastline. A tidal lagoon power plant could also provide continuous electricity. The turbines operate as the lagoon fills and empties.
Tidal lagoons have a negligible environmental impact. Lagoons can be built from natural materials such as rock. At low tide, they would appear as a low breakwater (sea wall), and at high tide, they would be submerged. Animals and smaller organisms could swim around and inside the structure. Large predators, such as sharks, would be unable to enter the lagoon, allowing smaller fish to thrive. Birds would most likely congregate in the area.
However, the energy output from tidal lagoon generators is likely to be low. There are currently no working examples. China is building a tidal lagoon power plant near its border with North Korea on the Yalu River. In Swansea Bay, Wales, a private company is also planning a small tidal lagoon power plant.
Impact of Tidal Energy On Environment
Marine life
One of the major issues with high flow rate sites is that marine mammals frequently visit and feed in these areas. During the years 2015-2016, no correlation was found between the number of grey and normal seals counted (increase / decrease of numbers) in the Eastern Scheldt and the presence of tidal turbines. Tocardo works hard to create fish-friendly, innovative turbine solutions. In April 2019, a fish mortality was carried out at the Afsluitdijk during the operation of three (3) T-1 turbines, with the current velocity in front of the turbine being 2.5 m/s.The results of the tests with smolts and silver eels are consistent with the model calculations, as immediate mortality is 0.00 percent for both species. Although fish clearly interacted with the turbine blades, no turbine-related injuries were observed.
Greenhouse gas emissions
Of course, the most important advantage of sustainable energy is that it is better for the environment. Combating climate change by reducing CO2 emissions by being a 100 percent renewable, 100 percent reliable, and 100 percent predictable energy source is one of the major drivers for tidal stream power generation. Every kWh of ‘tidal’ power generated saves 1,000g CO2 when compared to the same power generated by diesel. Diesel power generation is frequently used in remote island communities, and it has a carbon intensity of 250g/kWh, which, when combined with the relevant plant efficiency of 25%, results in an effective carbon intensity of 1,000g/kWh.
Aside from significantly reducing CO2 emissions, tidal energy also helps to reduce emissions of all other types of greenhouse gases, such as methane (CH4) and nitrous oxide (N2O). These gases are produced during the combustion of fossil fuels such as coal, oil, and natural gas to generate electricity. Aside from greenhouse gas emissions, tidal energy produces no air emissions, such as soot and fine particles, which are linked to human cancer, heart and lung damage, and mental functioning.
Subhub
The most environmentally friendly solution is to use a seabed mounted system that is invisible from the surface and maintains the seascape and shipping navigation channels while being beyond the diving depth of most birds. Tocardo’s business partner QED Naval designed the Subhub platform to have as little environmental impact as possible: one of the key design drivers for Subhub is to minimize the platform’s environmental impact.
Vibrations and noise
The few studies that have been conducted to date to determine the environmental impacts of a tidal power scheme have determined that each specific site is different and that the impacts are heavily dependent on local geography. What has been studied so far in the Netherlands? There have been no underwater acoustic measurements near the existing turbines in the Eastern Scheldt Storm Surge Barrier. The sounds produced by the turning turbines may or may not have an effect on porpoise behavior, depending on their spectrum and source level, as well as local propagation conditions. Porpoises, on the other hand, are expected to cross the barrier only during and around slack tides, when the turbines are not moving and thus not producing sound.
If the sound produced by the turning turbines is audible to the nearby porpoises, it will either add an extra barrier effect or assist the porpoises in locating the turbines and avoiding collisions with them. We’ve previously studied noise near the Tocardo turbines in the Dutch icon the Afsluitdijk; on site, the noise from the turbines appeared to be practically imperceptible.