Powered by the kinetic energy from the natural rise and fall of ocean currents and tides, tidal energy is a renewable source of energy that is primarily used to generate electricity. It is caused by the gravitational attraction between earth, moon, and sun, thus producing tidal forces. As the earth rotates, these forces correspond to the movements leading to a changing ocean currents’ motion. As a result, tides are stable and predictable and can produce a steady stream of electricity. Therefore, owing to its infinite capacity, it is often considered an inexhaustible renewable energy source for the future.
But tidal energy extraction gained momentum only in the early 20th century. In the early 1920s, US and Canada conducted many state-sponsored studies to understand the tidal force’s potential to replace non-renewable energy resources and the developmental costs for the same. Despite being widely accepted as a potential renewable energy source, the amount of power produced from tidal force has been minimal. Even today, there are very few commercial tidal power plants operating worldwide. As tidal energy is relatively new, there are no multiple power-generating techniques to extract tidal energy; nevertheless, there is a prominent use of special energy generators to convert tidal force into electricity. Currently, there are three known methods of tidal energy generation. These include Tidal Turbines, Tidal Barrage, and Tidal Lagoon.
Turbine: A turbine takes energy from flowing fluid; this fluid could be wind or water. A wind turbine converts kinetic energy into electrical energy to generate power from a windmill. Similarly, as tides are fast-flowing waves of water, turbines are placed to capture the kinetic energy of the moving water. As tides are denser than winds, tidal energy produced is more powerful than wind energy. While turbines can operate at any depth, it is best to position them in shallow water. Tidal stream generators use breeze turbines placed in clusters under the water to generate power from underwater currents. Besides, stream generators also include float turbines. These turbines are anchored to the seafloor using cables, and energy is produced from the turbines that rotate due to the water stream movement. As tidal turbine blades are slow in their motion, it is less likely to affect marine biodiversity. However, local conditions and the turbine size are significant in determining the impact of tidal generators. In addition, turbines are large and disrupt the motion of tides and currents; therefore, it becomes difficult for the machines to capture and harness the energy.
Barrage: Barrages are dam-like structures built across rivers or ocean bays for generating power using potential energy. The turbines inside the barrage take advantage of the differences between the high and low tides. Water from the high tide is released through the turbine, generating electricity. The water level changes in the area surrounding a barrage, which changes the water salinity of the region around the barrage. These changing ecosystem conditions might harm the organisms that live in the water body. In the case of a barrage, a cluster of turbines is placed horizontally; with the fast movement of the blades, there is a high likelihood of marine life getting caught in the quick action resulting in injury or loss of life. Consequently, the sea birds in the region whose primary feed is based on fish may migrate as their food source is limited.
Tidal Lagoon: Lagoons are large water structures created by reservoirs similar to tidal barrages and seem like separate bodies of water away from the tides. Lagoons are usually constructed alongside natural coastlines. They appear like a seawall at low tides, submerged at high tides, and are enclosed by a human-made or natural barrier. Accelerating turbines attached to the sea walls generate power from the tidal streams. Lagoon power generation involves extracting electricity from the tide when it comes in and goes out. Though the energy produced from a lagoon is considered more eco-friendly than that produced in a barrage, they are less environmentally damaging. This is because lagoons are smaller in size, and due to their size, small fishes thrive in a lagoon, which may attract birds that prey on marine life.
Regardless of the methods and technologies, why is tidal energy still at the start point in the run for renewability and sustainability while wind, solar and nuclear are on their paths to accomplishing their mark? Despite being a clean energy source, why is tidal energy not as popular as the others? Why are only a few industrial units producing tidal energy on a broader scale? It is crucial to find answers to these questions to understand the potential for the large-scale production of this alternative form of energy. Though it is not enough to suffice everyone’s energy demands, it plays a key role in reducing our reliance on fossil fuels and non-renewable energy sources. These projects can be horrific to local communities such as coastal communities involved in marine livelihoods in cases of community displacement. Hence, numerous studies have been conducted to understand the socio-ecological impact of tidal energy.
Most studies show that the environmental consequences are site-specific based on local geography and ecology. Tidal range projects like the barrages are enormous stress on the local environment; these projects alter the water levels, reducing the population of migratory fish in the ecosystem. These projects are located in sites with high tides that generate energy based on high and low tide differences, such as in Canada, South Korea, Russia, China, New Zealand, etc. Furthermore, electricity is generated when the temporarily stored tidal water flows through the turbines, which on fast movement, have the potential to injure or kill marine plants and animals, thereby affecting the bird population that depends on these sea creatures as a source of food. Additionally, as tidal energy equipment is often placed near the shore, there is a possibility that the electromagnetic fields and acoustics may affect marine organizations in the region. Moreover, as these equipment are placed offshore, the soil around the region is also disturbed. Developments in tidal energies are still in their beginning phase; hence, the disposal process of used/old equipment and technologies utilized in energy extraction is not widely discussed. However, newer technologies are being introduced to balance out these negative implications.
One of the reasons why tidal energy is not very prominent is that it is not cost-effective during the initial stages of establishment. Especially, tidal barrages are costlier than the other methods owing to the money involved in constructing dams/reservoirs. Therefore, tidal energy is more expensive than other renewable energies, yet the net energy produced from tides is minimal. Another reason is that the research and developments in the field are still in their infancy stage, so investing in the resource does not guarantee a return. Therefore, given the financial constraints, only developed countries in the Global North are developing tidal energy projects.
These claims show that the current possibilities for full-fledged use of tidal energy resources are pretty bleak. Thus, in conclusion, the takers for tidal energy are divided.
National Geographic. (n.d.). tidal energy | National Geographic Society. https://education.nationalgeographic.org/resource/tidal-energy/
The potential of tidal energy production. (2015, August 30). GreenFacts. https://www.greenfacts.org/en/tidal-energy/index.htm#1