Why wave power could complement solar and wind

Waves off the coast of the U.S. could generate 2.64 trillion kilowatt hours of electricity per year — that’s about 64% of last year’s total utility-scale electricity generation in the U.S. We won’t need that much, but one day experts do hope that wave energy will comprise about 10-20% of our electricity mix.

“Wave power is really the last missing piece to help us to transition to 100% renewables, ” said Marcus Lehmann, co-founder and CEO of CalWave Power Technologies, one of a number of promising startups focused on building wave energy converters.

But while scientists have long understood the power of waves, it’s proven difficult to build machines that can harness that energy, due to the violent movement and corrosive nature of the ocean, combined with the complex motion of waves themselves.

“Winds and currents, they go in one direction. It’s very easy to spin a turbine or a windmill when you’ve got linear movement. The waves really aren’t linear. They’re oscillating. And so we have to be able to turn this oscillatory energy into some sort of catchable form,” said Burke Hales, professor of cceanography at Oregon State University and chief scientist at PacWave, a Department of Energy-funded wave energy test site off the Oregon Coast. Currently under construction, PacWave is set to become the nation’s first full-scale, grid-connected test facility for these technologies when it comes online in the next few years.

“PacWave really represents for us an opportunity to address one of the most critical barriers to enabling wave energy, and that’s getting devices into the open ocean,” said Jennifer Garson, Director of the Water Power Technologies Office at the U.S. Department of Energy.

At the beginning of the year, the DOE announced $25 million in funding for eight wave energy projects to test their technology at PacWave. We spoke with a number of these companies, which all have different approaches to turning the oscillatory motion of the waves into electrical power.

Of the eight projects, Bay Area-based CalWave received the largest amount, $7.5 million. 

A small-scale version of CalWave’s device, the xWave, recently returned after a successful 10-month deployment off the coast of San Diego.

“The device we’re testing at PacWave will be a larger version of this,” said Lehmann. The x800, our megawatt-class system, produces enough power to power about 3,000 households.”

CalWave’s device operates completely below the surface of the water, and as waves rise and fall, surge forward and backward, and the water moves in a circular motion, the device moves too. Dampers inside the device slow down that motion and convert it into torque, which drives a generator to produce electricity.

“And so the waves move the system up and down. And every time it moves down, we can generate power, and then the waves bring it back up. And so that oscillating motion, we can turn into electricity just like a wind…