About Wave Energy

There are numerous energy sources available today. Among these are wind, coal, and oil. However, the search for alternative energy sources continues (Darvor, 2015). This explains why Europe is investing billions of euros on the still-in-development field of nuclear energy. But not all energy comes from clean sources. In actuality, global warming poses a threat to life as we know it (Darvor, 2017). Climate change is the steady increase in global temperatures brought on by the release of greenhouse gases like carbon dioxide. Therefore, the world has been forced to look for other safer sources of energy (Darvor, 2015). This explains why Europe is pumping billion of Euros in pursuing nuclear energy which is still under development. However, not all sources of energy are clean. As a matter of fact, the world as we know it is under threat from global warming (Darvor, 2017). Global warming is the continuous rise of global temperatures due to the emission of greenhouse gasses such as carbon dioxide. Therefore, the world has been forced to look for other safer sources of energy (Darvor, 2017). This has led to the development of marine energy. There are two types of marine energy; mechanical and thermal energy. Thermal energy is generated from the oceans’ absorption of solar energy while mechanical energy is generated from tides and waves (Ocean Energy). This paper will discuss wave energy, how it is produced and some of its advantages and disadvantages.

As mentioned earlier, wave energy is generated from waves in the oceans. Waves are caused by wind blowing across the surface of the oceans (Whetzel, 2017). Before looking at how waves are formed, it is imperative to first look at how wind is generated. Wind can simply be defined as moving air. For air to move from one point to another, there has to be a difference in atmospheric pressure. Difference in atmospheric pressure can be caused by difference in air temperature from one point to another. When the sun heats up the air above ocean surfaces, the air increases in temperature and increases the atmospheric pressure. The high atmospheric pressure causes the hot air to move to areas of low temperatures. This is what is called wind. When moving air blows across the surface of the ocean, it transfers some of its kinetic energy to the water on the surface and the water just below it (Darvor, 2017). Kinetic energy is the energy possessed by moving bodies. This kinetic energy causes the water to move vertically and then horizontally in the direction of the wind resulting in what are called waves.

Waves carry kinetic energy. When tapped, this energy can be converted into electric energy. In the recent years, scientists have come up with numerous devices capable of harnessing wave energy into electric energy. These devices can be categorized into three groups, depending on their distance from the shore. The three categories are shore line devices, near shore devices and offshore devices. Shore line devices are devices that are located on the shore of the ocean. A good examples is the shore – based terminator. Near shore devices are devices that are situated a short distance from the shore (Ocean Energy). They are placed at a water depth of approximately twenty meters. Offshore devices are placed deep into the oceans (Wave Energy, 2017).

There are about eight devices that are used to convert wave energy into electric energy. These are; rotating mass, bulge wave, submerged pressure differential, overtopping terminator device, oscillating water column, oscillating wave surge converter, point absorber and an attenuator (Wave Devices, 2017). These devices, although they serve the same purpose, function differently (Ocean Energy). The attenuator for example is made of two arms connected by hinges and is placed on the surface of the ocean. The device captures the energy generated by the relative motion of the two arms. A point absorber is also placed on the surface on the ocean. It is made up of two main parts, one on the surface and the other on the ocean floor. The two parts are then connected by a shaft. Waves on the surface cause the top part to move up and down together with the shaft while the bottom part remains steady (Wave Devices, 2017). It then converts this vertical motion into electrical energy. The oscillating wave convertor is also made up of two parts. The top part takes the form of a square and is placed perpendicular to the direction of the wave. This causes it to move back and forth in the direction of the wave generating energy in the process. This energy is then converted into electric energy. The oscillating column works differently from the oscillating wave convertor. It is generally a hollow column enclosing a column of air above a column of water. When the waves hit its lower part, which is submerged below the surface of the water, they cause the enclosed column of water to move vertically pushing the air out of the column through a turbine. The turbine rotates in either direction as air moves in and out of the column generating electric energy (Wave Devices, 2017).

The overtopping terminator devise is the largest of them all. It is raised above the surface of the sea. When high waves develop, they manage to push water over the surface into a reservoir. The reservoir then directs the water through a turbine and back to the ocean below generating electricity in the process (Ocean Wave). The submerged pressure differential works in the same principle as the point absorber. The only difference is that it is fully submerged into the ocean. A bulge wave simply a hollow tube with a low head turbine in it placed on the surface of the water. When waves form, they push water into it forming a bulge. The bulge increases in size depending on the momentum of the wave and flows through a turbine to the other end of the tube generating electricity in the process. A rotating mass is more complex than the bulge wave. It is made up of a metal container in the shape of one half of a hemisphere. It is open on one side and closed in the other with a rotating mass in it. When waves get into the container, they rotate the rotating mass generating electricity in the process (Wave Devices, 2017).

Just like any other type of energy, wave energy has its own advantages and disadvantages. However, the advantages overshadow the disadvantages. For starters, wave energy is clean energy. This simply means that it does not pollute the environment through emission of greenhouse gases such as carbon dioxide. This is one of the reasons it is so popular.

Wave energy is also renewable (Wave Energy, 2017). This is because it is generated by winds blowing over the surface of the ocean. This means that it cannot be exhausted. Another advantage of wind energy is that it removes the dependency of fossil fuel such as coal and oil. This is in the end reduces pollution. Wind energy is also predictable and consistent especially because winds can be forecast days in advance (Wave Energy, 2017). Most wind energy devices are placed in the ocean meaning there is no soil erosion or digging on the shores during construction. Wave energy devices are easier to site than other kind of energy devises such as coal and oil plants which must be dug it the ground.

However, despite its many advantages, wind energy has its disadvantages too. For example, wave energy devices and plants have high installation and maintenance costs (Wave Energy, 2017). This is because they are easily destroyed or corroded by strong ocean waves which requires constant repairs and maintenance. Transmitting power from offshore plants and devices to the mainland requires long strong power cables that lie across the surface of the sea (Whetzel, 2017). This makes it very expensive. When wave energy devices are damaged, they may cause death of marine life due to maintenance fluids such as oil and grease. Wave energy is also not as consistent as other forms of energy because sometimes the weather is calm with weak or no winds at all. If there are no winds, then it means there are no waves meaning no power can be generated. Lastly, wave energy cannot be harnessed in all places around the world. It only works in areas frequented by strong winds meaning it is not readily available in most parts of the world.

In conclusion, we have seen that wave energy is caused by strong winds blowing across the surface of the earth. Wave energy is harnessed by devices such as rotating mass, bulge wave, submerged pressure differential, overtopping terminator device, oscillating water column, oscillating wave surge converter, point absorber and an attenuator. Some of the advantages of wave energy include environment friendly, predictable, renewable and easy to harness. Some disadvantages include; not readily available, expensive to maintain and limited to areas frequented by strong winds.

References

Wave Devices (2017). The European Marine Energy Centre. Retrieved from http://www.emec.org.uk/marine-energy/wave-devices/

Wave Energy (2017). Alternative Energy Tutorials. Retrieved from http://www.alternative-energy-tutorials.com/wave-energy/wave-energy.html

Whetzel. J (2017 April 25). How Is Wave Energy Used to Generate Electricity? Retrieved from

https://sciencing.com/wave-energy-used-generate-electricity-6499297.html

Darvor, H (2015 Oct 11). Ocean Energy. Our Energy. Retrieved from https://www.our-energy.com/ocean_energy.html

Ocean Energy. Bureau of Ocean Energy Management. Retrieved from https://www.boem.gov/Ocean-Wave-Energy/