Ocean waves contain a large amount of energy derived from the winds, so that the ocean surface can be seen as a huge wind energy collector.
On the other hand, The seas absorb large amounts of solar energy, which also contributes to the movement of ocean currents and waves. This energy, accumulated over long distances in the form of waves, can be harnessed to generate electricity using various technologies, collectively known as wave energy or wave power.
Waves are waves of energy generated by wind and solar heat, which are transmitted through the ocean surface. This movement involves both a vertical and horizontal displacement of water molecules. When we observe the passage of a wave, we see that the water does not move forward, but that the water molecules describe a circular orbit.
In a gentle swell, the water near the surface not only moves up and down, but also forward at the crest and backward in the trough, allowing this energy to be transformed into electricity. Water molecules describe a circular motion: They rise as the crest approaches, move forward with the crest, then down as it passes, and retreat within the trough of the wave.
These waves of energy on the surface of the sea, i.e. the waves, They can travel thousands of kilometers and store large amounts of energy, especially in regions such as the North Atlantic, where strong winds generate waves with an average energy potential of up to 10 kW per square meter of ocean surface. This resource is immense when the vastness of the oceans is taken into account.
Harnessing wave energy
Technology to harness wave energy began to be studied in the 1980s and has advanced considerably since then. It focuses on converting the vertical and horizontal movement of waves into wind or electrical energy. Among the most viable areas For the implementation of this technology, there are latitudes between 40º and 60º, where the winds generate constant waves with good characteristics for its use.
In this sense, several have been developed pioneering projects in Europe and other coastal regions, highlighting examples such as the one developed in the Canary Islands.
Currently, wave energy is being implemented in numerous countries, where results have been obtained excellent results in terms of electricity production. For example:
- In U.S., around 55 TWh per year come from wave motion, representing 14% of the country's energy consumption.
- In Europe, the figure is even higher, reaching 280 TWh per year.
Onshore wave energy accumulators
In some areas where winds such as those predominate, trade winds, a system of reservoirs can be installed to collect the water pushed by the waves. These dams must be elevated, between 1,5 and 2 meters above sea level, to allow the use of conventional hydroelectric turbines to release the water back into the ocean.
This system is feasible in areas where tides do not significantly interfere with the operation of the reservoir. In addition, in areas with particularly strong waves, offshore concrete blocks can be built concentrate the energy of a wave front in a relatively small area, which would increase the energy potential of the system.
Use of wave motion
One of the best-known technologies to take advantage of the movement of waves is the system of oscillating water column (OWC). This system consists of a structure that encloses a column of water in which air pressure is generated by the upward movement of the waves. This air is forced through a turbine to generate energy. This system also works in depression phases when the wave descends, allowing continuity in electricity production.
A successful example in this field is the Kaimei ship powered by compressed air turbines, jointly developed by the Japanese government and the International Energy Agency.
Innovative inventions
There are various devices that convert wave motion into energy. Some examples include:
- The Cockerell raft: a system of articulated rafts that take advantage of the movement of the waves to operate hydraulic pumps.
- Salter's Duck: It consists of a series of oval bodies that oscillate with the waves, each of which drives electrical generators.
- Lancaster University Airbag: a rubber tube that, with the waves, compresses air to move turbines.
Various technological solutions continue to be developed to take advantage of the up and down motion of waves.
Advantages and disadvantages of wave energy
Wave energy offers great advantages such as:
- Renewable and inexhaustible: taking advantage of a resource that will always be present in the oceans.
- Low environmental impact, except in certain cases where ground storage systems are implemented.
- Can be integrated into coastal infrastructure already existing.
But it also has disadvantages:
- Onshore or near-shore installations may have a strong visual and environmental impact.
- It is not predictable exactly, since the waves depend on the weather conditions at the time.
- Systems face technical complexities and operational problems due to the harsh conditions of the marine environment.
Wave energy presents a great potential and continued progress is being made to overcome the challenges still present in its large-scale implementation.