Renewable Energy Can Provide 80 Percent of U.S. Electricity in the next 30 years. The question is . . . which type of renewable energy will dominate the field, and how do the different types of renewable energy work toward that goal? In this article, I would like to discuss wave energy. Most of the earth is covered with water, producing a constant movement of waves. This movement is capable of creating a huge amount of energy, especially for countries that border on the oceans. Wave energy has the potential of delivering about 252 billion KWh per year along the U.S. coastline.

Waves are created by wind, which is produced when the sun heats the air, creating temperature differences across the Earth's surface. As the air circulates, it comes together as wind. Wind-driven waves, or surface waves, are created by the contact between wind and surface water. As wind carries across the surface of the ocean, the incessant disturbance creates a wave crest. These waves are found across the open ocean and along the coast. In addition, the gravitational pull of the sun and moon brings about waves, which are known as tidal waves.

The waves are converted into energy through turbines that are either placed on the surface or under the ocean. These turbines are activated by the force of water. They spin and produce energy, which is transmitted to the grid.  

Wave energy has numerous advantages since waves are plentiful and widely accessible. They can deliver virtually an unlimited source of energy without producing greenhouse gases. Many cities, which are close to coastlines, can decrease the cost of energy by bringing wave electricity to their customers. Besides low cost, wave energy does not produce damage to the land. Since ocean water is free, there is no need to purchase or build on land.

Another significant advantage of wave power is that it is easily predictable. The amount of energy wave power churns out can be easily calculated. Wave energy is consistent and much better at produce energy than other sources, which are dependent on the wind or sun.

A wave farm refers to the instrumentations placed in the high seas to successfully utilize wave power and adapt it to practical wave energy. These wave farms are referred to as Wave Energy Converters (WECs). Chile has the highest wave energy potential in the world. According to predictions, wave energy along Chile's coast can fulfill 24 percent of the country's energy demand in the summer and 26 percent in winter.

Photo: enel.cl

All sources of energy have drawbacks and wave energy is no different. The initial equipment and machinery needed is costly. Therefore, these devices must be placed in the areas with the strongest waves. Some areas of the world are not as suitable as other areas for wave energy.

Underwater disturbances that generate large waves very quickly can damage the machinery, such as earthquakes, landslides, or volcanic eruptions. The waves caused by these turbulences are called tsunamis. These waves roll on to the shore like a massive sea level rise. Also, some critics contend that these facilities can be a source of detriment to the marine ecosystem.

Technically operating a wave farm in the ocean is far more problematic than on land. Besides being more expensive, saltwater is a hostile environment for any type of device. In addition, the waves themselves present a challenge as they not only roll past a device but also bob up and down and converge from all sides in chaotic seas. This provides enticing opportunities for energy capture, but a challenge for optimum design.

There are eight potential types of wave devices. Riding the waves, an attenuator is a floating device which operates parallel to the wave direction while capturing energy from the relative motion of two arms as a wave passes.

A point absorber converts the motion of a buoyant top relative to the base into electrical power. It is a floating structure which absorbs energy from all directions through its movements at or near the surface of the water. 

Oscillating wave surge converters extract energy when an arm oscillates as a pendulum mounted on a pivoted joint in response to the movement of water particles within them.

Photo: energy.gov

An oscillating water column is a partially submerged, hollow structure, which is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves make the water column rise and fall, compressing and decompressing the air column. The trapped air flows to and from the atmosphere by a turbine, which has the ability to rotate regardless of the direction of the airflow, generating electricity.

Water is captured by overtopping devices as waves break into a storage reservoir. As the water is returned to the sea, it passes through a conventional low-head turbine which generates power. 

Photo: Wavedragon.net

The motion of the waves causes the sea level to rise and fall above submerged pressure differential devices, which are located near shore. The device induces a pressure differential in the device, which causes the alternating pressure to pump fluid through a system to generate electricity.

Bulge wave technology uses a rubber tube filled with water, secured to the seabed facing into the waves. A bulge is created as the water enters through the stern, and the passing wave triggers pressure variations along the length of the tube. As the bulge passes through the tube, it grows marshalling energy, which can be manipulated to drive a standard low-head turbine located at the bow, where the water then returns to the sea.

Photo: reuk.co.uk

Using a rotating mass, two forms of rotation are drawn on to capture energy, using the movement of the device, heaving and swaying in the waves. The motion drives either a weight or a gyroscope, moving an electric generator inside the device. 

The industry has made halting progress, with these designs. Even the experts agree that wave energy continues to be decades behind other forms of renewables. With large amounts of money and research required for the industry to even begin to catch up,commercial wave farms are not close to being feasible.

While wave energy is safe, clean and one of the preferred methods to extract energy, who knows what the future holds for this source of renewable energy.

The content & opinions in this article are the author’s and do not necessarily represent the views of AltEnergyMag

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