WAVE ENERGY: HISTORY, HOW IT WORKS, ADVANTAGES, DISADVANTAGES - ENVIRONMENT - 2024

The wave energy or wave - power is the mechanical energy generated by the wave and which is transformed into electrical energy. It is the kinetic energy of water, produced by the energy of the wind in its friction with the surface of bodies of water.

This kinetic energy is transformed by turbines into electrical energy, being a renewable and clean energy. The history of the use of this energy dates back to the nineteenth century, but it is at the end of the twentieth century when it begins to boom.

Power of the waves. Source: Mostafameraji

Today there are a large number of systems proposed to take advantage of the forms of wave energy. These include wave oscillation, wave shock, or pressure variations under the wave.

The general principle of these systems is similar and consists of designing devices that transform the kinetic energy of the waves into mechanical energy and then into electrical energy. However, the design and implementation is highly variable, and can be installed on the coast or offshore.

Equipment can be submerged, semi-submerged, floating, or built on the shoreline. There are systems such as Pelamis, where the upward movement of the waves activates hydraulic systems by thrust that activate motors coupled to electric generators.

Others take advantage of the force of the waves when breaking on the coast, either by pushing hydraulic pistons or columns of air that move turbines (Example: OWC system, Oscillating Water Column).

In other designs, the force of the wave is used as it breaks on the shoreline to channel it and fill reservoirs. Subsequently, the potential energy of the stored water is used to move turbines by gravity and generate electrical energy.

Wave energy has undoubted advantages, since it is renewable, clean, free of charge and has a low environmental impact. However, it involves some disadvantages associated with the environmental conditions in which the equipment works and the characteristics of the waves.

The conditions of the marine environment subject the structures to corrosion from saltpeter, the action of marine fauna, high solar radiation, wind and storms. Therefore, depending on the type of system, working conditions can be difficult, especially in submerged or anchored offshore systems.

Likewise, maintenance is costly, especially in offshore systems, since the anchors must be checked periodically. On the other hand, depending on the system and the area, they can have a negative impact on boating, fishing and recreation activities.

History

It has its antecedents in the 19th century when the Spanish José Barrufet patented what he called "marmotor". This machine produced electricity from the vertical oscillation of the waves and was not commercialized until the 80s of the 20th century.

Barrufet's apparatus consisted of a series of buoys that oscillated up and down with the waves, driving an electrical generator. The system was not very efficient but, according to its inventor, it was capable of generating 0.36 kW.

Today there are more than 600 patents to harness the force of the waves to generate electrical energy. These can work by means of the force produced by the vertical oscillation or that generated by the impact of the wave on the coast.

How does wave energy work?

Pelamis converter in Peniche, Portugal. Source: Dipl. Ing. Guido Grassow

The operation of wave power systems depends on the movement that you want to take advantage of from the waves. There are floating or anchored systems onshore, which take advantage of the vertical oscillation of the water, while others capture the force of the shock of the waves on the coast.

Likewise, there are those that use the variation of pressure under the surface of the wave. In some cases, the kinetic energy of the waves allows the sea water to be stored and take advantage of its potential energy (gravity fall) to activate electric turbines.

In other systems, the mechanical energy of the waves produces movements of hydraulic pistons or air masses that activate hydraulic motors or turbines to generate electricity.

- Floating or anchored systems onshore

These systems can be semi-submerged or submerged and take advantage of the oscillating movement caused by onshore waves. Some systems use the force of the surface swell and others the deep movement.

Surface swell

There are systems of articulated segments, such as the Pelamis or "sea serpent", in which the waves move articulated modules that activate hydraulic motor systems coupled to electric generators.

Another alternative is the Salter Duck, where buoys fixed to an axis perform a pitching movement with the waves, also activating hydraulic motors. On the other hand, there is a whole series of proposals based on buoys whose oscillation also activates hydraulic systems.

Deep rocking motion

The Archimedean Wave Oscillator consists of two cylinders mounted in series on a structure anchored to the seabed. The upper cylinder has side magnets and moves vertically downwards with the pressure of the wave.

When the cylinder goes down, it presses on the lower cylinder that contains air and, as the pressure of the wave yields, the air pressure drives the system upwards. The oscillating movement in the vertical direction of the magnetized cylinder allows electricity to be generated by means of a coil.

Wave Dragon

It consists of a floating platform tied to the bottom with fins that allow it to receive the water moved by the waves, causing the structure to flood. The water accumulates and is then circulated through a central column through a turbine.

- Coastal systems

These systems are installed on the coast and take advantage of the energy generated by breaking waves. The limitation of these systems is that they only work on coasts with strong waves.

An example is the system designed by the Basque engineer Iñaki Valle, which consists of a platform anchored to the sloping coast with a magnet on rails. The wave pushes the magnet upwards, it descends by gravity and the movement induces a coil to produce electricity.

System

It consists of a system of plates that oscillate back and forth with the ebb and flow of the waves and this movement, by means of a piston pump, activates the electric turbine.

System of

In this case it is a question of floating plates anchored to the coast that receive the force of the breaking of the wave and activate a hydraulic system. The hydraulic motor in turn drives a turbine that generates electricity.

CETO system

It consists of a series of submerged buoys anchored to the seabed and whose oscillation activates hydraulic pumps that carry seawater to the coast. The pumped water activates a turbine to generate electricity.

Systems that harness potential energy

There are a number of systems that store seawater in tanks and then, by gravity, can activate Kaplan turbines and generate electricity. The water reaches the tanks driven by the wave itself as in the TAPCHAN system (Tapered Channel Wave Power System) or the SSG Wave Energy (Sea-wave Slot-cone Generator).

Water-air column systems

In other cases, the force of the water driven by the waves is used to move a column of air that, when passing through a turbine, generates electricity.

For example, in the OWC system (Oscillating Water Column) the water in the wave flow enters through a duct and drives the indoor air. The air column rises through a chimney and passes through the turbine to go outside.

When the water retreats in the ebb of the waves, the air re-enters the chimney, moving the turbine again. This has a design that makes it move in the same direction in both flows.

Another similar system is the ORECON, where the oscillation of the water inside the chamber drives a float that in turn presses the air to pass through the turbine. This system works equally by moving air in both directions.

Advantage

Wave farm. Source: P123

Renewable energy

It is an energy from a virtually inexhaustible natural source such as ocean waves.

The energy source is free

The source of wave energy is ocean waves, over which no economic ownership is exercised.

Clean energy

Wave energy does not generate waste and the systems proposed up to now for its use do not generate relevant waste in the process either.

Low environmental impact

Any interference in the aquatic or coastal environment generates some environmental impact, but most of the proposed systems are low-impact.

Association with other productive purposes

Some wave power systems allow the extraction of sea water to carry out desalination processes and obtain drinking water, or for the production of hydrogen.

For example, those whose operation involves collecting and storing seawater on the coast, such as the TAPCHAN and the SSG Wave Energy.

Disadvantages

Most of the disadvantages are not absolute, but depend on the specific wave system we are evaluating.

Wave force and regularity

The rate of energy production depends on the random behavior of the waves in regularity and strength. Therefore, the areas where the use of this energy can be effective are limited.

The amplitude and direction of the wave tends to be irregular so the incoming power is random. This makes it difficult for the apparatus to obtain maximum performance over the entire frequency range and the energy conversion efficiency is not high.

Maintenance

The maintenance of the structures involved entails certain difficulties and costs, given the corrosive effects of the marine saltpeter and the impact of the waves itself. In the case of offshore and submerged facilities, the cost of maintenance is increased by access difficulties and the need for periodic supervision.

Climatic and environmental conditions in general

The structures for capturing wave energy and converting it into electrical energy are subjected to extreme conditions in the marine environment. These include humidity, saltpeter, winds, rains, storms, hurricanes, among others.

Storms imply that the device has to withstand loads 100 times greater than the nominal, which can cause damage or total damage to the equipment.

Marine life

Marine life is also a factor that can affect the functionality of equipment such as large animals (sharks, cetaceans). On the other hand, bivalves and algae adhere to the surface of the equipment causing significant deterioration.

Initial investment

The initial economic investment is high, due to the required equipment and the difficulties of its installation. The equipment needs special materials and coatings, hermetic and anchoring systems.

Impact on anthropic activities

Depending on the type of system used, these can affect navigation, fishing and the tourist attraction in the area.

Countries that use wave energy

Motrico Wave Power Plant (Spain). Source: Txo

Spain

Although the potential of the Mediterranean Sea is low in terms of wave energy, in the Cantabrian Sea and in the Atlantic Ocean it is very high. In the Basque town of Mutriku there is a power plant built in 2011 with 16 turbines (300kW power).

In Santoña (Cantabria) there is another wave power plant that uses 10 submerged buoys to take advantage of the vertical oscillation energy of the waves and generate electricity. In the Canary Islands there are several projects in order to boost wave energy due to the favorable conditions of their coasts.

Portugal

In 2008, the Ocean Power Delivery (OPD) company installed three Pelamis P-750 machines located 5 km off the Portuguese coast. These are located near Póvoa de Varim, with an installed capacity of 2.25 MW.

Scotland (UK)

OWC technology is being used on the island of Orkney, where a system has been installed since 2000 called LIMPET. This system has a maximum production of 500 KW.

Denmark

In 2004, a Wave Dragon type pilot project was installed in Denmark, its dimensions being 58 x 33 m and with a maximum power of 20 KW.

Norway

The installation of a plant for the SSG Wave Energy system in Svaaheia (Norway) is in progress.

U.S

In 2002, a pilot project for a Power Buoy device was installed in New Jersey, with an offshore buoy measuring 5 m in diameter, 14 m long and with a maximum power of 50 KW.

In Oregon, an SSG Wave Energy pilot plant was installed in the Port of Garibaldi. Likewise, in Hawaii they promote renewable energy sources and, in the case of Maui island, the main renewable source is wave energy.

References

1. Amundarain M (2012). Renewable energy from waves. Ikastorratza. E-Journal of Didactics 8. Revised 08/03/2019 from ehu.eus
2. Cuevas T and Ulloa A (2015). Wave energy. Conventional and Renewable Energy Market Seminar for Civil Engineers. Faculty of Physical Sciences and Mathematics, University of Chile. 13 p.
3. Falcão AF de O (2010). Wave energy utilization: A review of the technologies. Renewable and Sustainable Energy Reviews 14: 899–918.
4. Rodríguez R and Chimbo M (2017). Use of wave energy in Ecuador. Ingenius 17: 23-28.
5. Suárez-Quijano E (2017). Energy dependence and wave energy in Spain: the great potential of the sea. Degree in Geography and Spatial Planning, Faculty of Philosophy and Letters, University of Cantabria. 52 p.
6. Vicinanza D, Margheritini L, Kofoed JP and Buccino M (2012). The SSG Wave Energy Converter: Performance, Status and Recent Developments. Energies 5: 193-226.

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