Wave energy or wave energy

Wave energy

Ocean waves contain a large amount of energy derived from the winds, so that the ocean surface can be seen as a immense collector of wind energy.

On the other hand, the seas absorb huge amounts of solar energy, which also contributes to the movement of ocean currents and waves.

Waves are waves of energy generated, as I have already said, by winds and solar heat, which are transmitted by the surface of the surface of the oceans and which consists of a vertical and horizontal movement of the water molecules.

The water near the surface not only moves from top to bottom, with the passage of the crest (it is its highest part, usually topped with foam) and the sinus (the lowest part of the wave), but, in a gentle swell, it also moves forward on the crest of the wave and backward in the bosom.

Individual molecules, therefore, have an approximately circular motion, rising as the crest approaches, then forward with the crest, down when it lags behind, and backward within the wave.

These waves of energy on the surface of the seas, waves, they can travel millions of kilometers and in some places, like the North Atlantic, the amount of energy stored can reach 10 KW for every square meter of ocean, which represents a huge amount if you take into account the size of the ocean's surface.

The areas of the ocean with the highest amount of energy accumulated in the waves are those regions beyond the 30º latitude and south, when the winds are strongest.

In the following image you can see how the height of a wave varies depending on the seabed according to its approach to land.

amplitude changes waves

Harnessing wave energy

This type of technology was initially worked on and implemented in the 1980s, and has been having great reception, due to its renewable characteristics, and its enormous viability implementation in the near future.

Its implementation also becomes even more viable between latitudes 40 ° and 60 ° due to the characteristics of the waves.

For this same reason, an attempt has been made for a long time to convert the vertical and horizontal movement of waves into energy that can be used by humans, generally wind energy, although projects have also been carried out to convert it into mechanical movement.

Wave energy project

Pioneering project in the Canary Islands

There are a wide variety of devices designed for such purposes, which can be located in the coasts, on the high seas or submerged in the ocean.

Currently, this energy has been implemented in many of the developed countries, thus achieving great benefits for the economies of these countries, this is due to the high percentage of energy supplied in relation to the total energy required per year.

For example:

  • In U.S. it is estimated that around 55 TWh per year they are replaced by energies from the movement of the waves. This value is 14% of the total energy value that the country demands per year.
  • And in Europe it is known that around 280 TWh They come from energies generated by the movement of the waves in the year.

Onshore wave energy accumulators

In areas where trade winds (These winds blow relatively constantly in summer, northern hemisphere, and less in winter. They circulate between the tropics, from 30-35º latitude towards the equator. They are directed from the high subtropical pressures, towards the low equatorial pressures.) provide continuous movement to the waves, you can build a reservoir with a sloping wall of concrete facing the ocean, on which the waves can slide to accumulate in the reservoir located between 1,5 and 2 meters above sea level.

This water could be turbined, allowing it to return to the sea, to produce electricity.

The rise and fall of the tides, in some areas where this technology would be applicable, are very small, so it will not produce any interference.

In coastal areas where the waves have a lot of accumulated power, the waves can be oriented by means of concrete blocks moored in the open sea, which can concentrate almost all the energy of a wave front 10 kilometers wide in a small area 400 meters wide.

The waves in this case would have a height of 15 to 30 meters when moving towards the coast, so the water could easily accumulate in a reservoir located at a certain height.

By releasing this water into the ocean, electricity could be produced using conventional hydroelectric equipment.

Use of wave motion

There are various devices of this type.

In the following image you can see one that has been practically used and that has given quite satisfactory results.

wave pressure and depression

It is a system for harnessing wave energy whose operation is quite simple and consists of the following:

  • The wave going up builds air pressure inside the closed structure. Exactly the same as if we press a syringe.
  • The valves "force" the air to pass through the turbine so that it turns and moves the generator, producing electrical energy.
  • When the wave goes down it produces depression in the air.
  • The valves again "force" the air to pass through the turbine in the same direction as in the previous case, with which the turbine resumes its rotation, moves the generator and continues to produce electricity.

This same principle was applied in the Kaimei ship powered by a compressed air turbine, a joint project of the Japanese government and the International Energy Agency.

The results of this project were very productive, although its use has not become widespread.

The same technology has recently been applied, but using large floating concrete blocks, in a project built in Scotland.

There are other devices that also convert upward and downward movement of the wave to produce electricity such as:

The Cockerell raft

This device consists of an articulated raft that bends with the passage of the waves, thus taking advantage of the movement to drive a hydraulic pump.

raft energy waves

Salte's duckr

Another better known is the Salter duck, which is made up of a continuous series of oval-shaped bodies that move alternately forwards and backwards, when “lashed” by the waves.

wave motion

The Lancaste University airbagr

The air bag consists of a 180 meter long reinforced rubber compartment tube. As the waves rise and fall, air is drawn into the compartments of the bag to drive a turbine.

The University of Bristol cylinder

This cylinder has a configuration similar to that of a barrel placed on its side that floats immediately below the surface. The barrel rotates with the movement of the waves, pulling chains connected to hydraulic pumps located on the seabed.

Direct use of wave motion

Have been tested other systems to directly utilize the upward and downward motion of the waves.

One of them, based on the movement of dolphins and whales, you can see it in this diagram.

dolphin simulation

The principle of operation is very simple and consists of the following:

  • When the wave rises and pushes a fin, which can be displaced between 10 and 15º.
  • Next, the fin reaches its end of travel and the wave continues to rise, here there is an upward push by the wave that the fin transforms into a push back.
  • Later, when the wave goes down, it moves the fin downwards and the same phenomenon occurs as in the previous case.

If the boat has systems of this type, it is propelled by the effect of the waves without consuming the slightest amount of energy.

The experimental tests of this system have been satisfactory, although as in the previous case, its use has not been generalized either.

Advantages and disadvantages of wave energy

Wave energy has great advantages on the table:

  • It is a source of renewable energy and inexhaustible on a human scale.
  • Its environmental impact is practically nil, if we except systems for accumulating wave energy on land.
  • Many coastal facilities can be incorporated into port complexes or other type.

Faced with these advantages it has Some disadvantages, some more important are:

  • Accumulation systems wave energy on land can have a strong environmental impact.
  • Is almost exclusively usable in industrialized countries, because a favorable wave regime is rarely found in the Third World; Wave energy requires high capital investment and a highly developed technological base that poor countries do not have.
  • Wave energy or waves cannot be predicted exactly, since the waves depend on the weather conditions.
  • Many the devices mentioned they still have functional problems and they are faced with complex technological dilemmas.
  • Coastal facilities have a great visual impact.
  • In offshore facilities it is very complex to transmit the energy produced to the mainland.
  • The facilities have to withstand very extreme conditions for long periods of time.
  • The waves have a high torque and low angular speed, which must be transformed into a low torque and high angular speed, used in almost all machines. This process has a very low performance, using current technologies.

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