Wave and Tidal Energy

Learn about the history of wave and tidal energy and how it works. Ocean waves are energy moving through water, usually from the friction of wind with the ocean surface. Tides are planetary-scale waves caused by the pull of the moon and sun on oceans. Tidal power has been used for over fifteen hundred years in Europe and around the Atlantic. Hundreds of tidal mills were in use during the 1800s. In France, a tidal generator has provided electricity since 1966. In England, Stephen Salter responded to the 1970s energy crisis with “Salter’s Duck,” a pioneering wave energy converter that has influenced WECs ever since. 

• Wave and tidal energy converters (WECs/TECs) use ocean energy to move turbines, pistons, or pumps that drive generators, producing electricity. Because water is so energy-dense, wave energy converters can usually capture multiple orders of magnitude more electricity than solar. For example, a wave converter captured 40,000 watts of electricity compared to a similarly sized solar converter that captured 150 watts.
• Recent advances in technology mean WECs/TECs could generate up to 10 gigawatts by 2030, a huge increase over 530 megawatts in 2020.
• Location is critical to wave and tidal energy. Tidal energy requires fast or large tides. Narrow channels between islands are often ideal. Scotland, Maine, Indonesia, and the Philippines all have high tidal energy potential. Wave energy works best where waves are large, fast, and have a long distance to travel, as in Portugal, the south coast of Australia, or the west coasts of the U.S. and Chile. 
• Tidal energy is highly predictable in timing, strength, and direction. Nearly all TECs use turbines, though they vary in how they are arranged and anchored in tidal currents.
• Ocean wave energy is highly variable. WECs vary as a result, with three main types: (1) oscillating water column WECs, in which waves surge into a tube to drive a turbine, which work well for onshore or near shore, such as WaveSwell; (2) oscillating body WECs, which utilize the motion of waves to create oscillating motions in two bodies having dissimilar masses and are designed for deeper water, such as SWEL Waveline Magnet or CalWave; (3) overtopping WECs, in which waves surge into and drain from a reservoir, such as WaveDragon.
• Wave energy can be incorporated into already existing structures such as piers and jetties. They can also be created as hybrid projects with offshore wind farms that can integrate WECs.
• Nearshore wave energy generation is more cost-effective than trying to capture more intense waves farther out.

Learn about the challenges the sector faces. WECs/TECs go through a demanding process from proof of concept through prototyping through open-sea testing, and finally, commercial-scale demonstration. All these stages require costly test sites and multiple stages of refinement, making the process of bringing them to market long and expensive. Without support, even robust, well-tested designs can be lost to market forces. Other challenges:

• The same water energy that powers WECs/TECs can destroy them, particularly high-energy waves.
• Salt water corrodes metals, and biofouling can slow turbines to a stop. WECs/TECs have to be maintained in the difficult marine environment, adding to their cost.  
• Scaling up and selecting the most energy-efficient designs for waves that can vary in size, speed, and direction is complex and costly.
• For many projects, permitting and the logistics of power grid tie-ins are a challenge.

Become an advocate for marine renewable energy. 

• Join an organization that works on wave and tidal energy projects. Pacific Ocean Energy Trust (POET) advocates for ocean energy in the U.S. Pacific Northwest. Although much of their focus is on wind energy, their research is relevant to wind and tidal energy.
• Write an op-ed. This example calls for increasing investment in wave energy in the United States. This one advocates for improved wave and tidal energy policy in Great Britain.
• Educate students and others on wave and tidal energy. Tethys has resources for students from elementary to college level. National Energy Education Development Program has a curriculum for U.S. grades 6–12.  

Consider a pilot wave or tidal project. Well-thought-out projects can provide backup energy or help remote coastal areas power their own microgrids, reducing or replacing the need for gas or diesel generators.

• In Igiugig, Alaska, a river current powers turbines that are similar to those used for tidal generation and compatible with the annual salmon run.
• For six years, the MeyGen pilot tidal turbines in the Orkney Islands have provided enough energy for approximately six thousand houses and are ready to scale up.
• Off the Tasmanian coast, a pilot oscillating column wave generator has powered homes on Kings Island for twelve months.
• Japan piloted a tidal turbine off the coast of Naru Island. Scheduled to generate for six months, it successfully provided energy for eleven months. Japan is also looking for a site to conduct a trial of a patented wave converter called mWave energy generation. 
• The Philippines are in the early stages of piloting a tidal project in the San Bernardino Strait that will provide twenty-four-hour power and enable all residents of Capul Island to get electricity.

Use existing test sites. Wave tanks and flumes can provide proof of concept for wave and tidal energy converters, but open-ocean tests are necessary to ensure that devices can stand up to real-world conditions.

• PacWave is a pre-permitted site on the Oregon coast for open-ocean wave energy testing.
• The Bourne Tidal Test Site is being established by MRECo as a permanent small-scale test site in New England. 
• EMEC has grid-tied open-sea test sites in the UK.

Use standards to guide siting, testing, and production through already-established processes and best practices. EMEC has standards for both wave and tidal energy conversion, from assessing energy resources through manufacturing.

Understand the permitting process. The costs associated with the permitting process for WECs/TECs are poorly understood, and the process itself can be confusing. Here is a guide to the regulatory framework for marine renewable energy around the world.

• Ocean Renewable Power Company found that understanding federal and state permitting, as well as environmental regulations, were essential for its tidal power project in Maine.
• Here is a toolkit from the U. S. Department of Energy to speed the development of marine energy.

Include monitoring for environmental effects. WECs/TECs can impact ocean ecosystems and marine wildlife. Although one study suggests that the environmental impact of small-scale WECs and TECs is low, and one long-term study showed no negative effects, long-term monitoring is essential. WECs and TECs can serve as artificial reefs or fish-aggregating structures, which are known to create habitat. However, tidal turbines can kill fish and disturb wildlife. 

Consider hybrid wind-wave projects or using existing infrastructure. Hybrid wind-wave systems combine offshore wind turbines with WECs on a shared platform, optimizing renewable energy production at a single location. Integrating wave energy converters such as turbines into breakwaters is feasible and may improve breakwater performance.

• Floating Power Plant has tested a hybrid wind-wave grid-connected project, the Poseidon P37, in Denmark. It is a floating, rotating platform that supports a wind turbine and four integrated paddle-style wave energy converters (WECs).
• Pelagic has successfully tested a prototype W2Power floating wind-wave platform that supports two wave turbines and a series of hydraulic pumps that capture wave energy.
• Noviocean’s prototype floating WEC is planned to also support solar on its deck.
• Singapore is researching a hybrid of offshore solar, wind, wave, and tidal energy that can make the project footprint small and provide continuous energy generation. It would use modular floating solar platforms that can also integrate wave and tidal energy converters and wind.

Involve local stakeholders in the planning process. Scotland’s Fishing Liaison with Offshore Wind and Wet Renewables Group has published a Best Practices document for offshore energy developers to work with fishers. It can serve as a model for working with other groups as well.

Join a trade association. National Hydropower Association's Marine Energy Council in the U.S. promotes technologies and related services to harness clean, renewable power from significant untapped marine energy resources.

Consider nature-inclusive design to build habitat into structures. Designing for nature and climate can reduce environmental harm, increase biodiversity, and improve fisheries, and it is more cost-effective the earlier it is included in the design process.

• TenneT, an offshore grid developer in the Netherlands, has identified opportunities for nature-inclusive features for grid platforms, such as fish hotels and oyster reefs. 
• The University of Wageningen in the Netherlands has an extensive catalog of nature-inclusive possibilities for wind platforms, some of which may apply to wave and tidal anchors.
• Letting seaweed and mollusks grow on some wave energy converters might make them more efficient.

Partner with wave and tidal energy converter producers to pilot grid-tied projects. The last stage of bringing WECs/TECs to market is testing them while tied into the grid. While installing cable and managing variable ocean energy is challenging, WECs/TECs can also complement wind and solar. Working ocean energy can be a point of community pride.

• Bangor Hydro Electric (now Versant Power) partnered with Ocean Renewable Power Company to pilot the TidGen Cobscook Bay Tidal Energy project. 

Research open questions in wave/tidal energy production. Life-cycle analyses, environmental impacts, socioeconomic impacts, costs, grid integration, installation and operational procedures, and regulatory affairs are all issues that are understood mainly on small scales and case-by-case bases. More research is needed to enable the industry to mature. Data on small-scale development is promising, but much more is needed. 

• A study of a small-scale CalWave deployment assessed the risk of entanglement with anchor lines, collision, noise pollution, electromagnetic field disturbance, and discharge or spill and found all to be minimal; monitoring wildlife showed it to attract fish without harming wildlife.

Tidal Power 101 (2 mins.)

Why Wave Power Isn’t Everywhere Yet: A History (12 mins.)

How Waves Could Power a Clean Energy Future (15 mins.)

NREL's Marine Energy Research: Advancing a Clean Energy Future (2 mins.)

Wave Power Could Be Energy’s Next Big Leap (15 mins.)

Can Underwater Turbines Work? Tidal Power Explained (12 mins.)

U.S. Dept of Energy, Powering the Blue Economy (3 mins.)

NREL Cook Inlet Research: Turning the Tide for Renewables in Alaska (6 mins.)

Tidal Energy Could Be Huge—Why Isn't It? (12 mins.)

Cobscook Bay Tidal Energy Project 2012 (12 mins.)

Solar, Wind, and Wave (12 mins.)

Wave and Tidal Energy, edited by Carlos Soares and Matthew Lewis

Ocean, Tidal and Wave Energy: Power from the Sea by Lynne Peppas

“The Promise and Pitfalls of Wave Power” (Earth Island Journal)

Are Tides and Waves the Missing Piece of the Green Energy Puzzle? (Grist) 

“Wave Energy Machines on Australian South Coast Would Slash Renewable Energy Costs” (Guardian)

“The Motion of the Ocean Could Be the Next Big Source of Green Energy” (Medium)

Ocean Wave Energy Converters: Status and Challenges

Wave-Energy Devices Might Affect the Natural Environment

Ocean Renewable Energy Development in Southeast Asia: Opportunities, Risks and Unintended Consequences

This Matters: Waves Of Power Creation: How Tidal Energy Is the Next Potential Renewable Source (16 mins.)

Into the Blue: Will Wind and Tidal Energy Power Our Homes in the Future? Dr. Michela De Dominicis and Dr. Charlotte Williams (18 mins.)

The Project: Is There a Future for Wave Power?  (23 mins.)

Making Waves: Renewable Energy, Queen Elizabeth Prize for Engineering (25 mins.)

Crowd Science: Wave Power (27 mins.)