Tidal power – is it eco-friendly or not?

You might remember, from your geography classes, the standard presentation of alternative energy sources. Along with geothermal power, tidal power was also mentioned at the end. But I will admit this, I was left with many questions… how can you harness the energy of tides? And is it an eco-friendly process?

The energy of tides is a way to obtain electricity from the motion of water. In a broader manner, Wikipedia offers us the following definition: “Tidal energy is the energy that can be harnessed by exploiting the potential energy that results from the vertical motion of water at different levels or from the kinetic energy created by water currents. Tidal energy comes from the gravitational attraction of the Sun and the Moon, and also from the Earth’s rotation”. There are other sources of ocean energy, such as wave and current energy, osmotic energy (created by differences in salinity) and the ocean’s thermal energy (which comes from the different temperature of water located at various depths).

Tidal power is one of the earliest energy sources known to man, and it was used since the times of the Roman Empire and also throughout the Middle Ages. For example, on the coasts of France, Spain and Britain, partially submerged mills were used to grind cereals (Picture 1). Such mills date back to 787 CE (oceanenergycouncil.com). Despite all this, the world’s first major tidal power station began to operate only in 1966, in France, at La Rance, on the estuary of a river bearing the same name (Picture 4).

In order to find out more about La Rance, CLICK Here.


Fig.1. Tidal mill, Brehat, France (from the Middle Ages). Source: listverse.com

How does tidal power work?

Nowadays, the key components of a tidal power station are the turbines and the dam. The latter allows the filling of a gulf or estuary with water during high tide, and the discharge of water through the turbines at low tide (See picture 2). There are presently numerous technologies and equipments available, but the basic principle is similar: the flow of water through a turbine,”guided” by an obstacle (dam or dyke). Then, a generator turns this movement into energy.


Fig. 2: The principle of harnessing tidal energy. Source: ro.wikipedia.org

Greater tidal amplitudes and current speeds offer more energy potential. Therefore, the following conditions need to be met: high tidal amplitude (at least 7 meters) and the presence of a natural basin (estuary, gulf) that communicates with the ocean through a narrow opening. Such conditions are rarely found around the world (for example, in places on France’s, Great Britain’s and Canada’s Atlantic coasts, on the Pacific coast of the US, China and Australia)

Some of the tidal power stations found around the world:

-  Sihwa Lake power station (South Korea); It is the world’s largest tidal power station, completed in 2011; installed capacity – 254 MW (Figure 3)


Fig.3. Sihwa Lake power station (South Korea) Source: advancedtechnologykorea.com

-  France – in the estuary of Rance, installed capacity – 240 MW; tides here have an amplitude of around 13 meters (Figure 4);

4 Fig. 4. La Rance tidal power station (France) Source: knowledge.allianz.com

-  In North America – “Annapolis Royal Generating Station”, began to operate in 1984, FundyBay; installed capacity: 20 MW.

Advantages of tidal power:

-         It is an alternative, renewable and infinite power source

-         Tides are predictable, unlike solar or wind power.

-        It does not generate atmospheric emissions and does not contribute to global warming.


-   It affects marine life, due to the chemicals that leak into the water (for example, lubricating oils used in the equipment); the spinning blades of turbines also harm natural habitats;

-   The mechanical parts are exposed to corrosion from sea water. Maintenance is difficult, because of the size of the equipments used and the deep water where they are located. Because manual labor is difficult when repairing the machines, more mechanical substances (such as oils) will be used instead (which brings us to the first disadvantage);

-   There are few areas with good potential, and thus, this is a resource many countries will not have access to;

-   Relatively high construction costs.

5Obviously, there are many other technological aspects (positive or negative) which need to be discussed, but because we lack technical studies in this field, we invite you to express your opinions or knowledge in the comments section.

It is certain that tidal power technology will be improved. We hope that scientists and engineers will find solutions to minimize the impact on marine life. Surely, the energy of tidal waves is a subject that will be closely studied in the future.


-          www.oceanenergycouncil.com

-          www.theecologist.org

-          www.waterhistory.org

-          www.ecology.com

-          www.instalatii.ro/energii-neconventionale

-          http://en.wikipedia.org

Article written by Ioana Stoicescu and translated by Mihail Mitoșeriu

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