Insights on Wave Power

Earth is a water-world. More than 70% of our planet’s surface is covered by an ocean that is ceaseless in motion. All of this motion – from surging tides, coursing currents, and rolling waves – produces what is known as hydrokinetic energy.

Ocean waves pack the strongest degree of power in the water-world, ranking the greatest in terms of levels of marine energy resource potential in the United States. For perspective: on the West Coast, wave energy has a potential of 250 TWh/yr, equivalent to 67% of the region’s net electricity generation in 2019, which is enough to power 23 million homes. CalWave is working to harvest and convert this energy into cost-effective and reliable electricity – but how are ocean waves converted to electricity, exactly? The process that begins with the sun:

1. Wind flows across the ocean and creates waves

Wave energy is, essentially, a condensed form of solar power produced by wind action. The sun heats up air at different places around the globe, which creates wind that blows over the ocean’s surface. Surface waves, like those that crash on a beach, are created by the wind. Ranging in size (from ripples to nearly 100 feet tall), waves can travel thousands of miles before they reach land with almost no energy loss.

2. Waves approach land

Ocean waves are essentially a large composition of water waves with different frequencies and amplitudes interacting with each other. On top of that, the height and length of individual ocean waves can be impacted by environmental influences such as seafloor shape and slope, and of course, the weather.

3. Waves encounter technology

Ocean waves are converted to electricity through wave energy converters, or WEC, devices. Full-scale WEC devices are typically expected to be anchored miles offshore in deep water where wave energy is strongest. WECs can extract energy from incident ocean waves via a multitude of different motion patterns and wave characteristics, and directionality influence what the ideal pattern to extract the most energy looks like.

Identifying the type of machine that can most-effectively do this work has been a key goal for the U.S. Department of Energy.

The Wave Energy Prize, an 18-month competition sponsored by the U.S. DOE, highlighted a variety of promising devices that advanced the energy capture potential of WECs. CalWave was recognized and awarded for our xWave device in this competition.

4. Technology convert waves into electricity

In short, a WEC device is a collective term for a machine that converts the incident ocean waves into usable energy such as electricity. There are many different proposed approaches to harness wave energy but a common approach is to extract the kinetic energy of a wave energy absorber via a suitable drivetrain, similar to a wind turbine’s drivetrain.

Ultimately the kinetic energy leads to turning a shaft connected to a generator and that motion creates electricity.

5.  Electricity is applied to the grid or other needs

Electricity from converted ocean waves is transported via export cables back to shore and could power swaths of coastal homes and businesses. In fact, developing just a third of the available wave energy near Pacific states with U.S.-made equipment could support 33,000 jobs and meet up to 30% of West Coast electricity demand. Wave energy is highly predictable and can be developed close to load centers to reduce transmission needs and ease integration onto the grid. Additionally, wave energy could power distributed applications in the near term, like desalination plants—which remove salt from salt water to benefit water-insecure communities and military bases.

Source: The U.S. Department of Energy, 2021.