Ocean Waves & Electrical Energy

Have you ever asked yourself: where can we find more renewable energy? Humankind has found many ways to acquire this type of energy resource. I’m sure you have already heard of wind, hydro, geothermic, and solar energy, but have you ever thought about harnessing the ocean as wave energy? According to the Bureau of Ocean Energy Management, ocean waves have a lot of energy potential. In the measurement of terawatt hours/year (TWh/yr), just one unit of energy could supply approximately 93,850 average U.S. homes annually—the potential recoverable amount of resource that could be obtained from along the U.S. costal shelf edge is close to 1,170 TWh/yr. Potential recoverable energy refers to the energy gathered from regions that aren’t sensitive due to naval operations or environmental concerns and therefore can provide energy with little to no ecological distress [1]. This is still about 1/3 of the electricity used in the United States each year [1].

There are a few types of these “wave harnessing devices” in use or in the process of being made today, four of them suitable to be used on the Outer Continental Shelf, where the most energy can be harnessed. The first device is a Terminator. This contraption is angled perpendicular to the direction of the waves to capture or reflect its energy. Terminators can be on the shore, near shore, or even floating devices. These types of devices work because the water moves a column inside it to force air through an opening connected to a turbine, which generates power [1]. The power then is transported to the shore to be stored in a special type of facility. The second type of device is what is called an Attenuator. These are long, floating structures that are parallel to wave direction. Waves flex the joints between the segments, which are, in turn, connected to hydraulic pumps to generate power as the waves move across. A transformer will then connect a power line to the Attenuator that runs to a junction box on the seafloor. Finally, a subsea cable runs the electricity to shore where it can be stored in a power station, waiting to be used by homes, businesses, or facilities [1]. There has been a recent example of an attenuator in the United Kingdom; there are 10 floating flexible mooring devices in Lewis, Scotland in development by Pelamis Wave Power Limited. Pelamis Wave Power Linited is planning on connecting their device to the grid to supply energy to buildings in Scotland [4].

Another type of wave energy device is the Point Absorber. This type of device is a floating structure—like a buoy—inside of a fixed cylinder. It generates energy from the bobbing motion of the buoy-like structure in the cylinder caused by waves. This creates either electromechanical or hydraulic energy, which is converted to power stored on the coast. The last type of device is called an Overtopping Device. These contraptions are reservoirs that are filled by waves as they come, giving the holding unit a slight build-up of water pressure—somewhat like a dam. When the water buildup is released from the reservoir, it falls and turns hydro turbines and generates power [1].

There has been a more recent style of a wave energy-harnessing device, which is being constructed at the school of Berkley Engineering in California. An assistant professor of mechanical engineering at the school, Reza Alam, worked with graduate student Marcus Lehmann to build a device that harnessed wave energy in a unique way to the previously mentioned contraptions. Called the Wave Carpet, the goal is to have a device that could lay on the bottom of the seafloor where it would absorb the energy of the waves—just as a natural seafloor would. The device would have a flexible membrane that moves as a response to passing waves, collecting the energy from the wave (which is usually passed on into the mud that covers the seafloor) in the process. One of the problems that Alam and Lehmann ran into is the highly complex process of converting the wave energy into a useable power source. To counteract this obstacle, Alam and Lehmann came up with vertical double-action pumps that are fastened to the membrane. These pumps use the energy from the membrane to power a shore-based turbine that generates electricity [1].

Another problem that Alam and Lehmann faced was the simple fact that salt water is highly corrosive, to which they found a simple solution. The Wave Carpet is built of corrosion-resistant materials, and it operates submerged and at the floor of the ocean—far enough below the waterline so weather such as storms are less likely to turn waves into destructive forces that could destroy the machinery. The Wave Carpet is currently being built at a size of about 30” long by 30” wide by a range of 3-10” high, which makes it strong enough to withstand regular waves and, hopefully, waves that result from storms [1]. Nemaco has specialty Marine Epoxy Coatings available for their electrical casings to ensure quality and durability so that they can last as long as the wires they are protecting, connecting devices like these to the shore where the power can be stored and/ or used.

The Wave Carpet is only just one example of the many machines that are currently being designed and/ or implemented to obtain clean energy as an alternative to non- renewable resources such as coal and gasoline. These machines can even be placed or developed close to “load centers,” which are storage facilities for energy and power, to reduce transmission needs [2]. All of this energy could help to power necessary facilities desired by humans, such as desalination plants and sewage treatment facilities (and many more), to carry some of the load we create for the power grid. Hopefully, one day there will be more ways of harnessing renewable energy— such as ocean wave energy—to make way for a better future. Devices that harness ocean wave energy are meant to reduce the impact humans have on the environment so that we can look forward to a cleaner, brighter, and healthier future for not only ourselves, but the ecosystem around us as well.

[1] Bureau of Ocean Energy Management (BOEM). “Ocean Wave Energy.” <https://www.boem.gov/Renewable-Energy-Program/Renewable-Energy-Guide/Ocean-Wave-Energy.aspx>. March 29, 2019.

[2] Office of Energy Efficiency & Renewable Energy. “How are Ocean Waves Converted to Electricity?” April 19, 2017. <https://www.energy.gov/eere/articles/how-are-ocean-waves-converted-electricity>. March 29, 2019.

[3] Levy, Tomas W. Berkeley Engineering. “Making Waves: Turning Ocean Power into Electricity.” March 15, 2016. <https://engineering.berkeley.edu/2016/03/making-waves-turning-ocean-power-electricity>. March 29, 2019.

[4] The European Marine Energy Center LTD (EMEC). “Wave and Tidal Projects.” 2019. <http://www.emec.org.uk/marine-energy/wave-and-tidal-projects/> March 29,2019.