What is tidal energy:a renewable, clean and predictable source

Tidal energy uses the tides to produce electricity, thanks to dams and turbines.Advantages and challenges of a still little exploited source.

Tidal energy consists in exploiting the force of the tides in coastal areas with strong level variations, i.e. those most subject togravitational effect caused by two stars close to our Planet:there Moon and the Sun.It is, therefore, an energy renewable.Contrary to the case of hydroelectric power, however, it is not exploited kinetic energy of currents, but that potential:the aim is therefore to produce energy thanks to the difference in height of two basins, separated by a dam.

Tidal energy:what is it and how does it work?

What are the characteristics of the systems

The central of Rance, in Brittany (France), represented the first large plant for the exploitation of tidal energy in the world, with an installed capacity of 240 megawatts.The principle of operation it's simple:in a stretch of sea where there is a large difference between low and high tide, an infrastructure is installed capable of activating turbines thanks to the passage of a flow of water between two basins located at different levels.Ideally, the tide should be dthe 10-15 meters, and it is necessary for the seabed to have a rocky layer, in order to be able to fix the foundations of the infrastructure.

They typically exist two types of systems.One consists of a "simple" basin, which implies the construction of a dam on an arm of the sea, equipped with passages for water and turbines.This is precisely the case of Rance power station, located between the municipalities of La Richardais and Saint-Malo, in France, which can count on a 115 meter long mobile dam and 24 turbines connected to alternators.

In general, you can either use the effect of emptying of a basin than that of filling, always with a view to operating energy production systems.But some plants plan to spin the turbines in both phases.

The "double" pelvis, on the other hand, consists of adding a pelvis to the natural one artificial reservoir, located lower than sea level.This allows you to exploit the potential whatever the tide level is at any given time, which allows you to manage more flexible production as it is, in fact, an energy "storage" tool.

Development and history of tidal energy

Historical evolution and technological progress

Historically, the exploitation of tides to produce energy is certainly nothing new.Already during the Middle Ages numerous were built mills in places where the phenomenon is particularly important.However, it is in the sixties of the twentieth century that the first exploitation projects were launched industrial for the purposes of electricity production.

The three nations that have most designed or developed systems for exploiting tidal energy are South Korea, France and the United Kingdom.In the Asian nation, the Sihwa power station was inaugurated in 2012 and has an installed power of 254 megawatts (for an estimated production of 550 gigawatt hours/year).A second, larger plant is in the planning stage Incheon, on the north-west coast.It is expected to reach an installed capacity of 1,320 megawatts, similar to that of a nuclear power plant), thanks to 44 turbines.The cost for construction is estimated at 3.4 billion dollars (a quarter of what will be spent, for example, on the EPR nuclear reactor under construction in Flamanville, France).

The aforementioned Rance plant has been in operation for decades in the European nation.Started way back in 1966 it represented the largest in the world of its kind until 2011, when the Korean one from Sihwa entered service.According to what indicated by the transalpine company Edf on its website, the site is able to answer the question of 225 thousand inhabitants of Brittany.

Even in the United Kingdom the tides are particularly strong, and for this reason the feasibility of exploiting their potential is being studied.In March 2015, the London government announced the construction of a reservoir for a power station in Swansea Bay.Finally, also the Russia had started studies on the subject, and in Canada And China there are two facilities.

But it should not be forgotten that other nations could also, in theory, launch themselves into the exploitation of tidal energy:in this sense Argentina, Australia, and India they could be candidate countries.The overall production potential from this renewable source is estimated at approximately 380 terawatt hours/year, which would represent between 1.5 and 2% of global electricity production.

Advantages and disadvantages of tidal energy

Ecological benefits and climate impact

Tidal energy, as mentioned, is renewable.Therefore, its impact in terms of climate-changing emissions it is very low, even considering the construction and disposal of the systems at the end of their life.The source is also unlimited, by definition, being generated by the gravitational attraction of the Moon and Sun.Unlike then solar And wind power, it doesn't depend on weather conditions and therefore provides constant energy production, at all times.

It is also clean energy, since it does not harm the surrounding environment or the climate.The facilities are also silent, which does not disturb the fauna.And above all, as mentioned, it is a predictable energy, since the tides - times and heights - are easily predictable:in this way it is also possible to predict the quantity of energy produced.There density of water, finally, it makes the systems particularly efficient, and the systems do not require expensive or complex maintenance.

On the other hand, the construction of tidal power stations can lead to risks for plant and animal species, also due to the fact that they can affect the salinity and on quality of water.Added to this is an important visual impact, since the structures are built on the coasts and therefore clearly visible.In economic terms, then, the energy produced is currently more expensive compared to other types of renewable sources.Finally, exploitation is only possible in some areas of the world where the tides are sufficiently important.

The challenges in using tidal energy

Technological and logistical obstacles

It must be said, however, that the greater efficiency of the turbines can significantly improve the yield, and therefore allow you to significantly reduce costs of production. An analysis by GreenFacts based on data from Irena, the International Renewable Energy Agency, underlined how currently "the development of tidal technologies is linked above all to small and medium-sized enterprises”, often “scattered” across the economic landscape.This generates a “lack of cohesion” and cooperation.

From the point of view financial, however, “the main obstacle is linked to the relatively high initial costs for the construction of dams and barriers.Most of the projects are supported by government funds”.In terms of infrastructure, Furthermore, according to the document, there could actually be a competitor to help the spread of systems for the exploitation of tidal energy: offshore wind.It could lead to the spread of electricity networks on site and make the connection of systems easier.

Tidal energy in Italy and in the world

The presence of tidal energy in the world

Even in Italy There is the possibility of exploiting tidal energy. According to the Acea company, our country "has shown itself to be attentive to the use of this renewable energy source, to the point of planning the construction of various plants, especially in the port”.

One of these is present in Tuscany, a Punta Righini (started in 2013).Another a Ganzirri, near Messina (a turbine anchored to the seabed with a power of 25kW).“The port of Civitavecchia, Furthermore – continues Acea – it has prepared the installation of two devices:Review And Wavesax, to produce electricity by exploiting compressed air from the movement of water".

For now, these are isolated experiences and small-sized plants.However, Italy - although it does not present tidal coefficients like those of the Nordic countries, has well available eight thousand kilometers of coastline can think of exploiting this possibility.In particular, Sardinia is the region that presents the best conditions.