Here at Ocean Conservancy, we know the ocean provides powerful solutions to the climate crisis. Often, that conjures up images of rotating wind turbines rising up from the sea. Offshore wind energy is a growing source of renewable energy in Europe and East Asia, and it is taking off along U.S. coasts. But there is another renewable energy source just over the horizon—wave energy.
What is wave energy?
Waves are created when wind blows over the ocean, moving water molecules at its surface, creating ripples and, eventually, waves. Waves can then drive generators that produce electricity using devices called wave energy converters (WECs).
Engineers around the world have been trying to harness the power of waves into electricity for at least 200 years because of their capacity as a large, predictable and renewable energy source. Wave energy potential exists along every coast although it is greatest in windy areas along the western edges of continents. Just ten percent of the potential wave energy in the continental United States would supply electricity to 13 million homes.
Before we dive deeper into wave energy, I want to clarify one thing: When speaking of “wave energy,” we are not talking about capturing power from ocean currents or tides—those are slightly different types of marine renewable energy that are also currently being researched. Now, let’s dive in.
What does wave energy look like?
Waves are complex and operate in turbulent environments and multiple categories of WECs along with even more specific prototype and experimental designs that exist to generate electricity. Some, like the point absorbers, attenuators and wave surge converters pictured below, use the water to directly push and pull pistons, hydraulic rams or rotary electrical generators to produce electricity. In fact, the first commercial-scale offshore WEC device to sell electricity to a national grid was a 150-meter-long attenuator produced in 2008 off the coast of Portugal. Use of this device, however, was shut down within two months of opening due to technical problems. Other WECs, like the oscillating water column example below, use the waves to drive compressed air through turbines above the water level to generate electricity.
Point absorber WEC
© Al Hicks, NREL
Attenuator WEC
© Al Hicks, NREL
Oscillating wave surge WEC
© Al Hicks, NREL
Oscillating water column WEC
© Al Hicks, NREL
Still many more examples exist as industry engineers have yet to coalesce around a cost-effective and efficient design that can withstand various ocean conditions. While some companies have been able to sell electricity from waves to local grids, commercial WECs remain costly, very small in scale and exist in only a few locations in the world.
Where would we see wave energy?
Wave energy will likely take off where it holds the most promise for certain communities and applications.
At a small-scale, wave energy could power individual devices at sea. Underwater drones, stationary pieces of scientific equipment or marine internet-connected devices could benefit from a renewable energy supply from waves.
Requiring more electricity, remote coastal and island communities must often use small, diesel-powered generators. Many of these communities want to move past these polluting fuel sources, particularly when prices are high. But renewable energy sources such as wind and solar might be too intermittent or sparse to rely on. Waves, however, constantly crash near the shore, offering more stable electricity production.
The proximity of waves to communities can reduce the need for long transmission lines as well. In the United States, almost 40% of the population (127 million people) lives in coastal counties. Much of their electricity is produced far inland, making wave energy and its reduced infrastructure needs an attractive alternative. Utility-scale wave energy production is likely decades in the future, but small-scale wave farms could boost energy resilience sooner by kickstarting larger power grids out of blackouts caused by storms or providing power for emergency communications.
If utility-scale wave energy does take off, it could also complement wind and solar projects in two ways: It could provide electricity when the sun is not shining, or the wind is not blowing. In addition, wind and solar sometimes produce more electricity than is needed at a specific time, so large batteries are used to store that excess power for later. These batteries are expensive and their critical mineral components are currently in tight supply. Wave energy could offset these needs by providing a consistent baseload power, wind or no wind, day or night.
Wave energy in the United States
Interest and infrastructure for wave energy are slowly growing in the United States. Multiple wave energy development companies have tested their new devices inside artificial wave tanks and are looking to jump into ocean trials. Since 2015, the U.S. Navy has been hosting WECs in Hawaii at one of the few open-ocean, grid-connected wave energy test sites in the world, and the Department of Energy is constructing another larger facility in Oregon that might host WECs in late 2023. Having two sites with monitoring capabilities and different real-world wave conditions will greatly speed up wave energy development.
What are the environmental impacts of wave energy?
In all honesty, so few WECs have been successfully deployed in the ocean that more studies are needed to determine the long-term impacts to the neighboring environment and communities. In addition, WEC designs vary widely, making specific studies less broadly applicable. The Hawaii and Oregon test sites mentioned above will help to bridge those information gaps particularly by monitoring for noise, water chemistry, electromagnetic fields and the alteration of water and sediment flow. Leaking hydraulic fluids and the possible creation of artificial reefs from the WECs will also need investigation.
What’s next for wave energy?
The possibilities for wave energy seem to be as wide as the ocean. The growing interest in ocean renewables, coupled with the additional Oregon testing site coming online soon, gives us hope for another viable clean energy option. So, stick around as we watch the horizon for what happens next!
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