Seawater energy


Tidal energy is the energy that takes advantage of the rise and fall of sea water produced by the gravitational action of the sun and the moon to generate electricity in a clean way. It is, therefore, a renewable and inexhaustible source of energy that uses the tidal energy produced in our oceans. Other ways of extracting energy from the sea are: waves (wave energy), the difference in temperature between the ocean’s surface and deep waters, the ocean’s thermal gradient, salinity, ocean currents or offshore wind energy.

Tidal power generation methods

Tidal power generation methods can be classified in three different ways:

Tidal current generator:

Tidal current generators Tidal current generators (TSGs) make use of the kinetic energy of moving water for power turbines, similar to the wind (moving air) used by wind turbines. This method is gaining popularity due to lower costs.

Tidal dams:

Tidal dams take advantage of the potential energy that exists in the difference in height (or pressure drop) between high and low tides. Dams are essentially dams across an estuary and suffer from the high costs of civil infrastructure, a global shortage of viable sites, and environmental problems.

Dynamic tidal energy:

Dynamic tidal energy is a theoretical generation technology that explores the interaction between kinetic and potential energies in tidal currents. It is proposed to build very long dams (30 to 50 km long) from the coasts to the sea or ocean, without delimiting an area. Introduced by the dam from tidal phase differences, leading to a large water level difference (at least 2.3 meters) in shallow coastal marine waters with tidal currents that oscillate parallel to the shoreline, such as the United Kingdom, China and South Korea.

Categories of actions to generate tidal power

The three categories of movement of sea waters:

Due to the joint actions of the sun and the moon three types of changes in the surface of the sea: marine currents, waves and waves, tides.

Sea currents are large masses of water, the result of heating by direct and exclusive action of the sun, that move horizontally; therefore, they are true salty rivers that cross the surface of the ocean.

In their formation they also influence the salinity of the water. The width and depth of ocean currents are sometimes considerable, in some cases reaching hundreds of meters. The feeling that progress is different in the northern and southern hemispheres. Some flows pass from one hemisphere to another, others originate, move, move or die and are diluted in the same hemisphere at birth.

The trajectories of such currents are constant, and this circumstance is the advantage of man during the long time of navigation; it was the first and only use of the force of ocean currents.

Knowledge of ocean currents, their amplitude, direction, speed, etc., is of considerable importance to mariners. One of his actions is to divert his route towards the ships that enter them; favor or hinder navigation in the sense that it is parchment. The great and warm Gulf Stream, which flows from the Gulf of Mexico to the western shores of Europe, not only softens its climate due to its temperatures, but also facilitates the crossing of the Atlantic for ships heading west towards the East.

No other man-friendly effect of enormous kinetic energy could be obtained from ocean currents. But the results and advantages of another order (climatic, anthropogenic, economic, etc.) are incalculable.

It is a type of renewable energy, while the primary energy source is not exhausted by its exploitation, and it is clean, because in the transformation of the energy no polluting by-products, liquid or solid, are produced.

However, the relationship between the amount of energy that can be obtained with current means and the economic and environmental cost of installing the devices for its process has prevented a notable penetration of this type of energy.

Other ways of extracting energy from the sea are: waves (wave energy), the difference in temperature between the ocean’s surface and deep waters, the ocean’s thermal gradient, salinity, ocean currents or offshore wind energy.

Advantages of tidal energy

The most important advantages of these plants are the conventional characteristics of any hydroelectric plant. Respond quickly and efficiently to load changes, generating energy free of pollution and seasonal or annual variations. They have a low maintenance and a practically unlimited useful life. This type of energy is renewed, it does not pollute, it is silent, the raw material is the tide and it is very cheap, it works in any climate and time of year, and it helps to avoid floods.

  1. Renewable Non-polluting Silent
  2. Low cost of raw material.
  3. It does not concentrate the population.
  4. Available in any climate and time of year.

The main disadvantage is that it requires a large initial investment and it takes several years to build the facilities. Other drawbacks are possible changes in the ecosystem and the visual and structural impact on the coastal landscape.

Disadvantages of tidal energy

  1. Visual and structural impact on the coastal landscape. Location of the point.
  2. Depending on the tidal range. Very expensive power transfer.
  3. Negative effect on flora and fauna. Limited

How does tidal energy work?

Tidal energy is produced by the movement generated by the tides, this energy is used by the turbines, which in turn move the mechanics of an alternator that generates electricity, finally the latter is connected to a central ground that distributes energy to the community and to industries.

For not consuming fossil elements or producing gases that favor the greenhouse effect. It is considered a clean and renewable energy. Among its advantages, being predictable and having a safe supply with potential that does not vary transcendentally annually is limited to the cycles and currents of the tides.

The installation of this type of energy is carried out in deep rivers, estuaries of the river towards the ocean and below it, taking advantage of the marine currents.

The tides:

The sun, the moon and the earth participate in this effect. The moon is the most important in this action due to its proximity. The Moon and the Earth exert a force that draws bodies towards them: this force of gravity causes the Moon and Earth to attract each other and stay together. As the force of gravity is greater the closer the masses are, the force of attraction that the Moon exerts on the Earth is greater in the areas closer to those that are further away.

There are also other solutions associated with the use of marine energy, such as:

Tidal energy: we can find it in tropical areas, it is obtained by the difference in temperatures between deep waters and those close to the sea surface.

Wave energy: this is what we get thanks to the movement of the waves.

Blue energy: it is the energy obtained by the difference in saline concentration between sea water and river water.

Characteristics of tidal energy

The exploration of the potential energy corresponding to the rise in sea level seems in theory very simple: a dam is built by closing a bay, estuary or gulf, isolating it from the outer sea, placing in it the appropriate equipment (turbines, generators, locks) and Taking advantage of the irregularity that will occur as a result of the tide, energy is generated between the reservoir thus formed and the outer sea.

This energy is, however, limited; the power dissipated by the tides of the terrestrial globe is of the order of 3 TW, of which only a third is lost in the coastal tides. In addition, for exploration efficiency, the tidal range must be greater than 4 meters and the appropriate geographical location, which eliminates almost 80% of the theoretically available energy, leaving around 350 TW per year (Bonefille, 1976) . In summary, figure 1 shows the projects for the year 1982.

One of the biggest drawbacks of use appears precisely because of the inherent characteristics of the tidal phenomenon. In fact, since sea level varies (with a period of about 12 hectares, 30 minutes in the target areas), unless the necessary precautions are taken, the available drop (and associated power) varies in the same way. . In addition, the tide follows the rhythm of the moon and not that of the sun, so there is a daily delay of 30 minutes, in the hours when this energy is available. Theoretical schemes designed to overcome this difficulty are not economical and, currently, the problem can only be solved with regulation or external interconnection.

On the contrary, an analysis of the mean amplitudes shows that, for the practical purposes pursued, it can be considered constant throughout the year and even with its course (French and Russian researchers point out differences of 4 to 5% in 18 years) ; disappearing the risk of periods of drought, characteristic of hydroelectric plants.

Future of tidal energy

Current technological advances, rapid growth in global energy demand and constantly rising fuel prices are key factors in increasingly closing the gap between tidal costs and conventional energy sources, as understood countries such as Canada and England, where it is incorporated into energy plans as a medium-term solution in the process of replacing thermal power plants. In relation to the operation and construction of the plants, some basic assumptions are currently accepted, such as:

The simple and simple effect reservoir system is assumed to be the most suitable from an economic point of view. In relation to the construction project, in most of the works the use of prefabricated coffins (coffins) is adopted, replacing even the complementary landfill dams (reserved only for intertidal areas).

The importance of the construction organization is evident in the need to reduce the closing time and the acceleration of this road at the time of commissioning. To do this, it is considered convenient to place the turbo machines after the closure of the work.

The Bulb and Strafflo turbines are used interchangeably for comparative cost studies, although the latter type reduces the dead weight (concrete and ballast) of civil works by 20%. However, there are still no large diameter Strafflo units available on the market. At Annapolis Royal (Canada), an experimental unit (d = 7.6 m) has been put into operation, which will be used to test performance characteristics under real-world conditions (Whitaker, 1982).

The most convenient form of regulation is the incorporation of production in interconnection systems or networks (whose capacity must be at least 10 times greater than the size of the plant); or, failing that, an optimized connection with pumped storage plants (Gibson and Wilson, 1979) or hydroelectric plants (Bernshtein, 1965, Godin, 1974).

One of the most important advantages of these plants is that they have the main characteristics of any conventional hydroelectric power station, allowing them to respond quickly and efficiently to fluctuations in the network load, generating free energy, external pollution, seasonal and annual variations, at a low maintenance cost and virtually unlimited service life.

Among the disadvantages are: the need for a high initial investment (on the other hand, the characteristics of any energy exploration work) added to the intermittent, variable and out-of-phase supply of the energy blocks.

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