Tidal Energy Definition, Principle and Sustainability Explained
Tidal energy is clean, renewable energy that occurs in kinetic and potential form in oceanic tides, and which can be harnessed for any of various purposes.
This article discusses tidal energy definition, principle and sustainability, as outlined below;
-Tidal Energy Definition: 5 Ways to Define Tidal Energy
-Is Tidal Energy Renewable? The Sustainability of Tidal Energy
Tidal Energy Definition: 5 Ways to Define Tidal Energy
Tidal energy is a type of renewable energy that is derived from the rise and fall of water masses in oceans, under the influence of gravitational and extraterrestrial factors.
The above is a most basic form of tidal energy definition.
It highlights the essential nature of energy from tides, and states its sources to include solar, lunar and gravitational influences [1].
Another important aspect that can bring more clarity to the tidal energy definition is its uses. Below is an alternative tidal energy definition that mentions some of the uses of tidal energy;
Tidal energy is a variant form of hydro energy that is extracted from ocean tidal surges, and can be used for electricity generation and milling operations, and can play a role as a clean source of energy for sustainable development and effective energy transition [5].
The next tidal energy definition lists some examples of tidal energy utilization;
Tidal energy is renewable energy from the rise and fall of ocean tides, which is exemplified by tidal power plants and projects like MeyGen project (Scotland), Jiangxia power station (China), Annapolis power station (Canada), Sihwa Lake power station (South Korea), and Kislaya Guba power station (Russia).
Aside power plants, there are other concepts and terms used to describe the systems and technologies behind effective tidal energy harnessing. The tidal energy definition below acknowledges this by mentioning some types of tidal energy systems and technologies;
Tidal energy is clean, renewable energy from kineto-mechanical sea level fluctuations, that can be harnessed using any of different systems like; tidal barrages, streams, lagoons; ans technologies such as hydrofoil, vertical axis and horizontal axis turbines.
Lastly, the tidal energy definition is outlined to highlight how tidal energy works; which is also the principle of tidal energy utilization;
Tidal energy is renewable ocean energy from the periodic surge and recession of sea water, which works by the production, capture and conversion of kinetic energy from ocean tides.
It is important to note that the question of how tidal energy works is different from that of why tidal energy works. Tidal energy works because of the dynamic effects of Earth's rotation, electromagnetism, gravity and solar radiation, on the density and flow of ocean water.
How Tidal Energy Works
Tidal energy works by a three-step process of energy production, capture and conversion. It must be noted that this is also referred to as the process of tidal energy utilization.
Each of these steps is discussed briefly below;
1). Energy Production (in explanation of How Tidal Energy Works)
Energy production is the first step or stage in the working principle of tidal energy.
Tidal energy is produced by the interaction of water masses in oceans, with the gravitational pull of extraterrestrial bodies like the Moon, the heat from solar thermal radiation, and the Coriolis effect of Earth's rotation.
The Moon's gravitational pull on the Earth (1.63 m/s^2) is particularly effective in causing the volumetric dynamics that lead to ocean tidal processes. Solar thermal radiation and the Coriolis effect contribute to tidal energy production by inducing temperature, density and velocity gradients in the ocean.
2). Energy Capture
Tidal energy can be harnessed only if it is effectively captured in a manner that achieves both energy conservation and high efficiency.
There are two aspects of tidal energy capture. These are; capture at the oceanic level, and capture at the conversion level.
Tidal energy capture at the oceanic level deals with how ocean water masses can be channeled effectively in a manner that allows the kinetic energy in tides to be harnessed.
Here, tidal energy is captured using systems and mechanisms that exert some form of control on the flow of ocean water; such as tidal barrages, lagoons and streams.
The tidal barrage is similar to a conventional water dam in that it allows large amounts of water to accumulate, so that they can be released after maximum tidal energy storage has been achieved. The water then flows down from a height under the influence of tidal processes, with sufficient amount of kinetic energy to be used for significant purposes [4].
Tidal streams and lagoons represent sections of water where tidal energy is abundant, in kinetic and potential form respectively.
At the conversion level, tidal energy capture is achieved using tidal turbines; which are simple kineto-mechanical devices with similar design to steam and wind turbines. The tidal turbine is usually installed underwater in tidal streams, lagoons or in integration with tidal barrages.
Tidal energy is captured by the turbine using its blades, which are caused to rotate when tide-driven water masses exert kinetic pressure on them.
3). Energy Conversion (in explanation of How Tidal Energy Works)
Tidal energy conversion occurs in two phases;
1). Kinetic-to-mechanical conversion
2). Mechanical-to-electric power conversion
These two phases are largely handled by the tidal turbine [2].
Kinetic energy of tides is converted to mechanical energy when these tides collide with the blades of a tidal turbine, causing them to rotate.
In order to generate electricity, the mechanical energy of the rotating turbine-blades is transferred through a shaft to an electric generator, which is usually equipped with magnetic components that induce electric charge-flow in the rotating conductor.
Power generated from tidal energy can be transmitted to the point(s) of use with underwater cables, and may be reserved for later use, with energy storage systems like batteries.
The tidal energy process consists of tidal energy production, capture, and conversion. Other steps like storage and transmission are secondary components of the process.
Is Tidal Energy Renewable? The Sustainability of Tidal Energy
Tidal energy is renewable because it comes from materials and processes that are inexhaustible; like water, solar radiation, wind propagation, and gravity..
Sea water is itself the medium of storage of tidal energy, and it is both abundant and naturally recycled.
Solar, wind and gravitational processes are likely to remain existent as long as the Earth exists.
The fact that it is renewable means that tidal energy is above conventional energy resources like fossil fuels, in terms of sustainability. It is however still in its developmental stage, and cannot be considered a potential replacement as of yet.
However, ocean tides can be harnessed as an alternative energy resource alongside geothermal, wave, wind and solar resources.
Conclusion
Tidal energy is renewable energy from the rise and fall of ocean water masses, which can be captured and converted using turbines, to generate electricity.
Tidal energy works by a three-step process comprising of;
1. Energy Production
2. Energy Capture
3. Energy Conversion
References
1). Adushkin, V. V.; Riabova, S.; Spivak, A. (2017). "Lunar–solar tide effects in the Earth’s crust and atmosphere." Izvestiya Physics of the Solid Earth 53(4):565-580. Available at: https://doi.org/10.1134/S1069351317040012. (Accessed 10 February 2023).
2). Assad, M. E.; Banihani, E.; Sedaghat, A.; Al-Muhaiteeb, A.; Khanafer, K.; Khalil, M. (2016). "New Pneumatic System for Tidal Energy Conversion." Journal of Power and Energy Engineering 4:20-27. Available at: https://www.scirp.org/journal/paperinformation.aspx?paperid=72826. (Accessed 10 February 2023).
3). Chen, B-F.; Chen, L-C.; Huang, C-C.; Jiang, Z. L.; Liu, J-Y; Lu, S-Y.; Leu, S-S.; Tien, W-M.; Tsai, D-M.; Wu, S. (2018). "The deployment of the first tidal energy capture system in Taiwan." Ocean Engineering 155:261-277. Available at: https://doi.org/10.1016/j.oceaneng.2018.02.052. (Accessed 10 February 2023).
4). Etemadi, A.; Emami, Y.; AsefAshar, O.; Emdadi, A. (2011). "Electricity Generation by the Tidal Barrages." Energy Procedia 12. Available at: https://doi.org/10.1016/j.egypro.2011.10.122. (Accessed 10 February 2023).
5). Khare, V.; Bhuiyan, M. A. (2022). "Tidal energy-path towards sustainable energy: A technical review." Cleaner Energy Systems, Volume 3, December 2022, 100041. Available at: https://www.sciencedirect.com/science/article/pii/S2772783122000395. (Accessed 10 February 2023).
