NREL Team & HERO WEC Made Another OBX Visit in Spring 2024

Good waves aren’t just for surfers on the Outer Banks. They’re preferred by some engineers, too.

The National Renewable Energy Laboratory’s (NREL’s) hydraulic and electric reverse osmosis (HERO) wave energy converter (WEC) was once again deployed in the shallow waters off Jennette’s Pier on March 14. Met with a calm and beautiful day followed by a few days of good waves, a team from CSI collaborated with NREL engineers to set the hexagonal device in place and then left it to work its magic.

The raft-looking HERO WEC, initially a proof of concept for the U.S. Department of Energy’s Waves to Water Prize, is designed to produce desalinated water using energy from waves. The WEC uses either a hydraulic or electric power conversion system to desalinate seawater.

A simple illustration created at NREL depicts how the HERO WEC operates in both of its configurations.

During the first of two deployments this Spring, the hydraulic system was put to the test. Using the simple up-and-down motion of waves to create pressure, the device pumps ocean water through a hose and into a land-based reverse osmosis (RO) system, which then removes salt and other impurities from the seawater. Over the six-day deployment, the HERO WEC produced more than 300 gallons (or approximately 1300 liters) of freshwater. That’s enough water to fill about 2,575 water bottles.

“It’s always a pleasure to accomplish a challenging ocean deployment and recovery with the CSI and NREL teams. We always learn a lot from each other and continue to expand our rewarding collaborations,” states Dr. Mike Muglia, head of the Oceanography & Marine Hydrokinetic Energy Lab at CSI.

Due to an impending storm and in need of minor repairs, the HERO WEC was removed from the water on March 20. The WEC was successfully redeployed in the electric configuration on April 18th. The electric system uses the motion of the waves to engage an onboard rotary generator to create electricity. The electricity then travels through a subsea cable to charge a small battery system to power an onshore pump that draws water from the ocean and pushes it through the same reverse osmosis desalination system mentioned above.

Unfortunately, the pumps were turned off overnight on the 18th to allow the batteries to charge before replacing the desalination unit’s filters and membranes. Wave conditions that night were greater than expected, leading to a faster battery charge completion. Since the pumps were not on when this happened, the WEC no longer had a sufficient electrical load which caused it to move significantly more than if the pumps had been on.

Ultimately the WEC reached its limit numerous times causing the winch line to eventually snap. While this sounds catastrophic, the NREL data collection system was able to capture the motion and forces that the WEC endured, giving the NREL team valuable data for future iterations.

“After deploying the electric configuration in August 2022, we upgraded the system to convert and store energy more efficiently,” said Scott Jenne, NREL’s marine energy systems engineering and techno-economic lead and principal investigator for the wave-powered desalination project. “The upgrades added to the system proved very effective, but now the team is focused on making the system more robust”.

In the video above, the drive train- connected to the generator on the left and winch on the right- spins as waves pass below the device.

Moving forward the NREL team will continue to work closely with the CSI team to take the lessons learned from these deployments, along with CSI’s invaluable ocean experience, to design a second-generation prototype that can survive much more extreme conditions.

But why is NREL pursuing this work in the first place, and why did they decide to test in Outer Banks’ waters?

As impacts from climate change are increasingly felt all over the world, efforts to reduce greenhouse gas emissions and diversify the U.S. energy portfolio are in high demand. Wind and solar are well-known and tested renewable energy sources, but many also see the ocean as an untapped power source. NREL, CSI’s North Carolina Renewable Ocean Energy Program, and other public and private organizations recognize the potential in marine energy and are developing and testing new technologies to harness the power of the ocean. While the sector is still many years away from producing grid-scale energy, researchers and engineers are on a path to create devices for small-scale applications.

The HERO WEC is just one such example, and the NREL team has found that the northeastern NC coastal environment offers a well-rounded assortment of resources for this rather nascent technology. Not only is the area easily accessible and offers a suitable wave field, but there are also enough calm days between swells for deployments and on-the-water maintenance to occur. As it turns out, other sites with this combination of beneficial factors are much harder to come by than one might first think.

NREL’s partnership with the Coastal Studies Institute stems from their shared interest in marine energy development and CSI’s extensive deployment experience. CSI leads the North Carolina Renewable Ocean Energy Program (NCROEP) and is a founding member of the Atlantic Marine Energy Center (AMEC) under which Jennette’s Pier is a federally designated marine energy test site.

“Recent testing of the HERO WEC provides a tremendous opportunity to build on lessons learned for testing of marine energy technologies,” says NCROEP Director George Bonner. “Through our role with the Atlantic Marine Energy Center, we are excited about additional resources to support open ocean testing as well as taking advantage of the unique advantages Jennette’s Pier provides for education and stakeholder input as we advance responsible blue economy solutions.”

“We rely on CSI’s oceanographic and on-water expertise for these deployments,” said Jenne. “Operating in the ocean environment is challenging, and CSI can help us predict and overcome those challenges in ways that ultimately benefit NREL’s wave energy research.”

The CSI-NREL partnership is mutually beneficial and allows members of both teams to learn more about marine renewable energy device deployment logistics while forging a path forward together. Additionally, to foster further technological development, the NREL research teams publicly provide the information and data gathered through the HERO WEC project.

The preceding story first appeared in the Spring 2024 edition of CoastLines.