Wave Energy Technology





Prototype Pelamis Machine at EMEC in Scotland.

Prototype Pelamis Machine at EMEC in Scotland.

Wave energy technology harnesses the power of ocean waves to produce energy to benefit mankind. The technology is similar in theory to wind turbine generators or solar panels in that the collection is passive after the machinery has been emplaced. As wind passes over the surface of the water, waves are generated. Wave energy technology’s main limitation is that collecting energy from ocean waves efficiently requires constant waves that don’t surpass certain heights.

Humans have long dreamed of harnessing the raw power of the ocean, dating back to the late 18th century. Although water covers over 70% of the Earth’s surface, it’s potential as an energy source is only now being fully realized. Hundreds of patents for devices and methods to collect energy from waves have been filed in the past 200 years, but it was not until recently that the technology became economically feasible. The Gulf Oil Crisis of 1973 forced eminent scientists at universities the world over to reexamine alternative energy sources in search of one that was renewable and sustainable. Following the crisis the price of oil plummeted and interest in alternative energy sources waned. Due to once again rising oil prices and global warming mankind is once again intrigued by wave energy.

There are a few different manners in which energy can be harnessed from ocean waves. First, they must be installed either near the shore, offshore, or far offshore. Almost all wave energy collection equipment is meant to be installed on the surface of the water or just below. The exception to this is in certain offshore technology which can be as deep as 130 feet. The technology will differ further based on the type of energy it is being converted to, although most convert the wave power to electricity. Referred to as wave energy converters (WECs), there are three main types that are outlined below.

Terminator Wave Energy

Terminators are fixed in place perpendicular to the oncoming wave direction. Each terminator has two main components; one that is immobile and one that flows with the wave energy. Both pieces are vital to the operation, essentially operating as a piston in a vehicle engine would. The moving piece is pulled up and down by the waves, and as it rises, it compresses a substance (normally air), which is then expelled to drive a turbine. As the device draws back downward in concert with the falling crest of the wave, air is sucked back through the turbine, spinning it in the opposite direction. This type of terminator is referred to as an oscillating water column.

Another type of terminator is an overtopping device, which operates on a similar principle as other terminators. Instead of using pressurized air or oil to drive a turbine, water is utilized. A low wall is placed at the front of the device, and as waves pass over the top, they are then collected in a reservoir. Water continuously pools and is drained through the center of the device, where it passes through and spins a vertical turbine.

Attenuator Wave Energy

The second type of WEC are attenuators, which are placed parallel to the oncoming wave direction. Where terminators used turbines to generate power, attenuators rely on hydraulics. They are composed of multiple sections of floating tubes, which are attached together by hinges. Think of the manner in which subway cars are attached but instead of turning side to side, they pivot up and down in response to the waves. As the individual sections bob up and down hydraulic fluid is pumped into generators which then create electricity.

Point Absorber Wave Energy

The final WEC that will be covered are point absorbers and they are not limited to being placed a certain way in relation to the waves. They can absorb the energy of waves that come from any direction and convert that wave energy to electricity. Although there are many different ways that point absorbers can be constructed they all operate on similar principles. Essentially internal components are affected by the motion of waves and interact with each other in such a manner as to produce energy. The interaction can be in the form of electromechanical (such as opposing magnets) or hydraulic energy converters. Several point absorbers would be grouped together in a certain area and would transport their energy to a central point. In this configuration a large wave farm can be created simply by adding more “points” to the mesh.

Pros and Cons of Wave Energy Technology

The energy created by harnessing ocean waves is free. Beyond the initial cost of the devices and placement the waves do the work and no further major expenses are necessary for power to be generated. Even the maintenance and upkeep on the devices is nowhere near as expensive as other energy sources. Also the amount of energy that could be harnessed from ocean waves is staggering.

Much like any other energy source wave energy technology is not perfect. While the advantages made possible by this technology are remarkable there are some drawbacks as well. WECs cannot function without constant waves but also require safe wave size to prevent damage. This limits the placement to specific locations around the world. Similarly the energy created would not always be constant as the wind and wave strength is never the same from day to day. The cost of manufacture and placement is fairly steep as the devices are designed to function best in rough weather so up front costs are higher than some other energy sources. Along with the placement at or just below the waterline comes a danger to ships that are underway. The last considerable disadvantage is that the use of these devices may have an adverse impact on marine life where they are used if proper care isn’t taken during anchoring and operation.

Optimal Wave Generator Placement

So, where are some locations around the world with suitable conditions for harnessing wave energy? While certainly not all inclusive the following countries have the largest potential electrical capacity for wave technology with current technology.

  • Denmark
  • Northern Scotland
  • United Kingdom
  • Australia
  • South Africa
  • United States

Further research and development must be done before this technology is used with any major impact on the energy landscape. The possibilities are quite promising for wave energy technology. Imagine an offshore WEC powering a coastal desalination plant on the edge of a desert. This may be a reality sooner than you would expect.

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