Changing the Tides of the Climate Crisis
By: Brenna Cody
Tags: Wave And Tidal Energy, Global Warming, Renewable Energy, Climate Change Solutions, Climate Change

Wave Energy Status

Wave energy has yet to be used in a commercial setting, but it has potential to supply energy to remote areas. Despite this lack of development, wave energy is considered one of the most promising sources of renewable energy due to its consistency. Solar and wind energy have many variables that impact their reliability. Obviously, it’s not always windy and the sun isn’t always shining. As you are probably aware, however, waves are consistently crashing and moving, providing ample opportunity to capture motion energy.

While solar and wind energy are available 20 to 30 percent of the time, wave energy sites can be active 90 percent of the time¹. LIMPET 500, the first commercial wave plant, was installed in Scotland in 2000 and was successfully running for around 18 years. With 250 kW capacity, Islay LIMPET was a shoreline device in which waves drove air in and out of a pressure chamber through a turbine. A multitude of other turbine plants were built based on the LIMPET 500 design¹. Since powerful waves correlate to powerful winds, the most promising regions for wave energy are windy areas including Scotland and the West Cost of the United States. The World Energy Council estimated in 1993 that wave energy could meet up to 20 percent of the global energy demand. As with many forms of renewable energy, lack of prominence arises due to the economic preference towards fossil fuels. However, costs for wave energy technology have dropped, incentivizing companies to continue to compete with conventional power plants.

A very notable developed wave energy testing site is PacWave: formed in collaboration with Oregon State University and the US Department of Energy. Pac Wave is a test site for wave energy conversion technologies that is being developed off the west coast of Oregon. It is planned to contain twenty wave energy converters in four berths, and it will provide the ability to test at reduced costs and accelerate the improvement of wave energy technology. Each of the four berths will be connected to an onshore grid-connected station — which makes access to both the energy and technology easier. Ultimately, this testing facility will allow interested parties to prove technological performance in a variety of dynamic wave environments. This kind of testing will provide the opportunity to show viability, ways to reduce cost, and general advances in technology towards a manner of delivering power in a commercial setting. A test site such as PacWave is extremely important in the furthering of wave energy as a potential resource for the future of the United States and the world as a whole².

From Pac Wave Energy

Brief Overview of Wave Energy Technologies

One kind of technology, called an absorber, utilizes a buoy to extract energy from the rise and fall of waves. This energy is then converted into electrical energy by a generator as the vertical motion from the waves pumps one end of the absorber up and down. The advantage of this particular device is that it can absorb energy from wave movements in all directions.

Point Absorber Technology from onepetro.org

Attenuators are floating devices that are situated parallel to incoming wave direction. They consist of several segments which flex as the waves pass forward. At these flexing points, the motion created by waves is met with hydraulic resistance which pump fluid to drive hydraulic motors. These motors then power electrical generators.

Attenuator Technology from The European Marine Energy Centre

Oscillating Water Columns are enclosed structures that trap air between the water’s surface and a turbine at the top of the structure. In this structure, the waves essentially act as pistons, compressing and decompressing air that is trapped in the column. When a wave comes in and compresses the air, air is forced upwards, moving the turbine. And, as you might expect, when the wave moves out, air is drawn through the turbine again. This bi-directional motion drives a turbine generator to produce electricity.

Oscillating Water Column from US Army Corps of Engineers

Tidal Energy Status

Tidal energy is already supplying energy to coastal areas by harnessing tidal currents. Tidal technologies, specifically tidal barrages, are fairly well developed. Since accurate tidal forecasts are widely available, this particular form of energy is promising in its predictable nature.

An important implementation of tidal energy is the Roosevelt Island Tidal Energy (RITE) Project that was originally developed in 2012 and is estimated to be complete by 2022. With potential capacity up to thirty different 35kW Kinetic Hydropower Systems turbines, ten TriFrame mounts, 480-volt underwater cables from each turbine to five shoreline vaults, and other faculties for navigation and operation, this project is well on its way to become a reliable energy source. The turbines have three blades and can rotate as the direction of the tide changes. These turbines are installed 10 meters down in the strait that connects Long Island Sound to the Atlantic Ocean. When the water moves at a certain velocity, a generator turns on and electricity is able to be transferred through the underwater cables. In this particular instance, research and monitoring show that there aren’t significant negative ecological impacts from the turbines, though scientists continue to monitor bird and fish behavior as well as land erosion³.

In Massachusetts, the Muskeget Channel Tidal Case Study is another project developing tidal current renewable energy. With potential capacity of 5MW, enough electricity to generate energy for 1,500 homes every year, developers are hoping to expand that capacity of up to 20 MW. This energy would be enough to meet around 20 percent of the nearby city Edgartown’s energy demand⁴. The Channel is planned to home 14 turbines at a minimum depth of 100 feet.

Brief Overview of Technologies

Tidal Barrages (structures similar to dams) form tidal basins. Gates allow the basin to fill with water when the tide rushes in and then release the water through turbine systems when the tide goes out. By controlling the water flow and level, this creates a bidirectional opportunity to generate electricity.

Tidal Barrage Technology from National Geographic

Tidal Turbines function similarly to wind turbines. They have blades that rotate from the power of tides which then turn a rotor to power a generator.

Tidal Turbine Technology from National Geographic

Tidal Fences have vertical axis turbines that are mounted in a row (or fence) on the sea floor. Similar to tidal turbines, the rotation of the vertical turbines caused by water generates electricity.

Tidal Fence Technology from Our World of Energy

Obstacles

Since the goal of renewable energy is to minimize negative impacts on the environment, a large concern with wave energy is the potential for endangering marine ecosystems. Particularly since oceans are already victims of climate change, a system that is designed to mitigate the negative effects of the climate crisis should not inflict harm. Therefore, close government and scientific regulation and monitoring are imperative to the success of marine energy.

Devices, particularly ones with rotor blades or any other moving parts, can pose threats to marine life. Additionally, since noise is a component to some marine energy devices, the impact of underwater noise must be monitored as anthropogenic sounds can be dangerous to animals. Due to a general lack of implementation of tidal and wave energy, there is consequently little research on the effects of these energies on the ecosystems with which they would interact. In general, however, animal behavior may change when machines are introduced into their habitat, so a key aspect of developing these technologies is preliminary research and monitoring of marine life behaviors.

Another common argument against marine energy is the aesthetic, or lack thereof. Similar to pushback against wind turbines, the technology involved in ocean energy isn’t appealing to the eye — it could disrupt the beauty of the natural environment and impact local tourism and appreciation.

Also prohibiting the development of Wave and Tidal energy is the general cost of the technological development required for the devices. The high cost mainly originates from the engineering necessary to build and install the various devices as well as the associated power plants⁵. Despite investments in marine energy, technological development has been very slow which is a difficult obstacle to overcome. But as with all technology, with further research and time, costs will go down and these energy sources can become more widely used.

One last key aspect to discuss regarding potential obstacles is the amount of upkeep and maintenance required for any sort of devices that reside in the ocean. The ocean is known to reclaim things that are left in its ecosystems for long periods of time, so both design and maintenance must be considered with this in mind. A budget must account for both the extra specialty required to account for marine degradation as well as the upkeep necessary to keep the technologies functioning as long as possible.

Place in Our Future

Specifically for the United States, scientists estimate that upwards of 2.64 trillion kilowatt hours of energy exists in waves off the coasts⁶. That number equates to around 64 percent of the US’s electricity generation in 2018. For reference, only 17 percent of the United States’ energy generation came from clean energy. If we can tap into the ocean’s energy, even just half of the theoretical yield, the US could conceivably run on around 50 percent renewable energy. This is just from waves⁷.

Incorporating tidal energy, the US Department of Energy estimates that certain regions of the US coasts can harness enough tidal energy to help meet the goal of generating 80 percent clean energy by 2035.

At the current rate of investment and technological development, it could be years before US citizens can rely on tidal and wave energy as large-scale energy contributors. However, if serious action is taken by the US government to provide incentives and funding for these energy sources, we could start to tap into the large energy sources that surround our continent.

In particular, the comparison to wind energy is a huge inventive for marine energy as a power source. Water is around 835 times denser than air, which essentially means that 3-knot current would contain kinetic energy equal to that of a wind of 100 miles per hour. As a whole, over the next thirty years, ocean power is estimated to reduce fossil fuel usage by 1.4 gigatons⁶.

Before large scale development of wave and tidal energy can occur in most countries around the world, governments need to understand the implications of ocean energy so that they can ensure proper mitigation of negative environmental impacts. In many case studies that are currently occurring, scientists and developers are closely monitoring the ecological impacts of their technology on surrounding marine life and habits. Overall, the potential for wave and tidal energy as future sources of renewable energy is vast. With time and development, these two forms of energy could prove to be reliable and large contributors to the global demand for energy. As renewable sources, tidal and wave energy can reduce the use of fossil fuels and mitigate the effects of climate change to ensure a safe planet for future generations.

Bottom line, the time for action is now. Realistically, it was many decades ago. This means that our action needs to be even more impactful and prioritized. Wave and Tidal energy have promise, but they cannot act alone. Other renewables, personal lifestyles choices, and government action must also be at the forefront of our efforts to combat climate change. It is critical that people aren’t intimidated by the concept of renewable energy. In order to reach this level of familiarization, renewable energy must be a central topic of communication. It is imperative that you discuss these ideas with your family members and your peers. The most effective course towards progress is through policy, so advocating for implementation of renewable energies through your local representatives is a way for everyone to understand the intensity of their need.

These conversations can be tough, often because the concept of “fixing the earth” can be quite daunting. It can help to have a potential solution or two as talking points or reassurances that there is some hope. Perhaps, now your talking points can be Wave and Tidal Energy.

To find more information about Marine Energy in the United States, look towards the US Energy Information Association (wave and tidal). For more global information: the United Nations WOA Chapter 22 Draft.