Tidal Power Plant Definition, Principle, Components and Advantages

A tidal power plant is a system that comprises of components used to harness ocean tidal energy in order to rotate a turbine and generate electricity. This article discusses tidal power plant definition, working principle, components and advantages, as follows;

-Tidal Power Plant Definition

-How Tidal Power Plants Generate Electricity

-Components of a Tidal Power Plant

-Advantages of Tidal Power Plants

-Conclusion

Tidal Power Plant Definition

A tidal power plant is an energy facility that works by capturing the kinetic energy of ocean tides, and converting this energy to electricity using a number of components that include kineto-mechanical turbines and electric generators [1].

An alternative tidal power plant definition will highlight the fact that these plants harness renewable energy and produce not significant greenhouse emissions. These are very important attributes, especially in the light of recent concerns with sustainable development and green economy.

Such alternative definition is given below;

A tidal power plant is a system for electricity generation that harnesses renewable tidal energy from the rise and fall of sea water masses, to rotate and turbine and generate electricity.

Many studies have viewed tidal energy as simply a variant form of hydro energy, and this is true in some sense, since both tidal and hydro energies exist because of the ability of water to act as a natural energy storage system.

However, while hydro energy is present in water by virtue of its existence, tidal energy can be said to be present only when water undergoes mechanical dynamics caused by surges and recessions, in sea level (also called flows and ebbs)

Tidal power energy is used in all parts of the world that have installed tidal power plants in suitable offshore locations like estuaries and bays; and such places include; China, France, Russia, and United Kingdom.

An example of a tidal power plant is the Bluemull Sound Tidal Stream Array, commissioned in the United Kingdom in 2016, with an operational capacity of 0.4 MW.

As of 2023, there are eight (8) operational tidal power plants in the world, and one in construction. The following table presents basic information on operational tidal power plant (arranged in increasing order of capacity);

How Tidal Power Plants Generate Electricity

Tidal power plants generate electricity by harnessing tidal kinetic energy in three main steps; which include energy capture, kineto-mechanical conversion, and electromagnetic induction.

The kind of energy which a tidal power plant produces may be mechanical energy, or electric power (which is a derivative of mechanical energy), depending on the design of the tidal power system and the intended use(s).

Each of the three steps in the tidal energy working principle is discusses briefly below;

1). Energy Capture (in explanation of How Tidal Power Plants Generate Electricity)

Energy capture in tidal systems requires the accumulation of significant amount of water within a given zone from which the tidal energy in such accumulated water masses can be easily accessed and converted.

For this to be achieved, it is usually necessary to design an artificial water-retention mechanism.

The three most common mechanisms of energy capture for tidal power plants are tidal barrages, tidal lagoons and tidal streams.

Tidal barrages are similar in structure and function to conventional water dams [2]. Their role is to act as a barrier to water flow, so that sufficient accumulation can be achieved to raise the water level on one side of the barrage, above that on the other.

This arrangement is obviously similar to that which is used to generate hydroelectricity; but it is unique in that the release of water retained by the barrage is dependent on tidal energy, rather than the human-driven mechanisms often used with hydropower plants.

For tidal streams, the objective is not necessarily to retain water and create a hydro-head gradient, but rather to ensure that water flows consistently through a given zone where tidal processes and energy become abundant.

The tidal stream is effective where the water level is relatively high at all times, and it is a better option where there is need to minimize effects on the marine ecosystem as much as possible. Sometimes the tidal stream could be less effective at producing high tidal energy density from water masses, compared to the tidal barrage.

In some tidal power concepts, both streams and barrages are employed at different sections to result in a hybrid system with increased reliability.

2). Kineto-Mechanical Conversion

Kineto-mechanical conversion is the second major step in the working process/principle of tidal power plants, and it simply involves the conversion of kinetic energy from ocean tides, to mechanical energy that drives a turbine.

In order for mechanical energy to be produced in a tidal power plant, the kinetic and potential energy stored in tides must be effectively converted. This is the purpose of tidal barrages, streams and turbines.

For example, tidal barrages are used to create a water-head gradient that enables water masses to flow downward under the influence of both tidal energy and gravitational acceleration.

This setup ensures that the potential energy in tides is fully converted to kinetic energy as the water falls and collides with the blades of the turbine.

In terms of basic design, it can be argued that tidal turbines are similar to wind turbines. However, they are built to be much more mechanically-resilient, due to the relatively-higher impact of sea water, which is over 800 times more dense than wind.

The end-product of kineto-mechanical conversion is mechanical energy, which can then be used to activate a generator.

3). Electromagnetic Induction (in explanation of How Tidal Power Plants Generate Electricity)

Electromagnetic induction is the last major step in the working principle of tidal power plants, which occurs in a tidal generator, and leads to the generation of usable electricity.

It must be noted that tidal energy may sometimes be used to produce only mechanical energy, which can be applied for purposes like grain-milling (although this use is generally obsolete) [3]. For such cases, the tidal power plant working process will stop at kineto-mechanical conversion.

A tidal generator works by converting the mechanical energy in a rotating shaft of the tidal turbine, into a stream of electric charges that can be transmitted away from the power plant to the point(s) of need. This is achieved by the electromagnetic effect, whereby charge-flow in induced by the interaction between a moving conductor and a magnetic field.

The working principle governing tidal generators is not much different from that which governs electric generators for other energy resources, including fossil fuels.

Other steps that can be used in describing how tidal power plants generate electricity include energy transmission and storage. However, these are secondary steps and do not directly influence tidal power generation itself.

Transmission of electricity generated by tidal power plants is possible using high-density, high-conductivity cables installed underwater.

On transmission, tidal power can be stored in batteries, from which it can subsequently be retrieved for use. The act of storing tidal power is particularly important, since tidal energy supply is not always constant.

Components of a Tidal Power Plant

The main components of a tidal power plant are;

1). Water retention systems like barrages, tidal lagoons and tidal streams

2). Turbine

3). Electric generator

Other components include;

4). Inbuilt power inverter

5). Transmission cables

Advantages of Tidal Power Plants

The advantages of tidal power plants are;

1). Minimal environmental impact

2). Large-scale power generation capability

3). Applicable for remote coastal regions

4). Backup for fossil fuel power plants

5). Job creation

Conclusion

A tidal power plant is a renewable power generation facility that captures and converts tidal energy to generate electricity.

Tidal power plants generate electricity by a three-step process comprising of;

1. Energy Capture

2. Kineto-Mechanical Conversion

3. Electromagnetic Induction

Components of a tidal power plant are; water retention system (tidal lagoon, stream, barrage), turbine, generator, power inverter, and transmission cables.

Advantages of tidal power plants are; minimal environmental impact, large-scale power generation capability, relevance in remote coastal areas, backup for fossil fuel plants, and job creation.

References

1). Benelghali, S.; Benbouzid, M.; Charpentier, J-F. (2007). "Marine Tidal Current Electric Power Generation Technology: State of the Art and Current Status." Electric Machines & Drives Conference, 2007. IEMDC '07. IEEE International Volume: 2. Available at: https://doi.org/10.1109/IEMDC.2007.383635. (Accessed 12 February 2023).

2). Etemadi, A.; Emami, Y.; AsefAshar, O.; Emdadi, A. (2011). "Electricity Generation by the Tidal Barrages." IEEE International Conference on Smart Grid and Clean Energy Technologies 2011 (IEEE ICSGCE), Energy Procedia 12. Available at: https://doi.org/10.1016/j.egypro.2011.10.122. (Accessed 12 February 2023).

3). Subhojit, D.; Sadhan, G.; Arup, D.; Debashish, B.; Indrajit, K. (2019). "Tidal Energy As Emergent Energy Source: A Review." International Journal of Computational Intelligence & IoT, Vol. 2, No. 1, 2019, Available at: https://ssrn.com/abstract=3355288. (Accessed 12 February 2023).