Off the NC coast, researchers are testing how to use energy from ocean waves to make drinking water
It’s peak season at Jennette’s Pier in Nags Head. By 8 a.m., the pier is already lined with anglers and sightseers, and the waves below are alive with schools of fish.
Far out on the bright water, a white buoy marks the future location of a new addition to the pier: the test site for a machine designed to harness the energy of the waves to make clean drinking water.
The prototype “wave energy converter” is scheduled to be deployed in the last two weeks of August for a ten-day trial run. If successful, the machine could help provide emergency drinking water for coastal communities cut off from other resources.
The movement of the ocean – as waves, tides, or currents – represents a truly massive source of energy. Mike Muglia, the assistant director for science and research at the North Carolina Renewable Ocean Energy Program, will help launch the prototype later this month. He explained that the initial focus of the ocean energy program was “grid-scale” marine energy: how to tap into the tremendous power of the Gulf Stream to provide electricity to much of North Carolina.
But we’re a long way from grid-scale ocean energy, and Muglia maintained that, for now, wave power is most practical for more modest applications like the prototype.
“I happen to be a proponent of doing things small like this and figuring out how to do it first, before you build something giant,” he said. “And so that’s what we’re doing.”
The prototype could produce emergency drinking water or electricity
The machine itself is currently tucked underneath an overhang at the Coastal Science Institute on Roanoke Island about five miles from the pier. It looks surprisingly practical: a chunky white-and-blue inner tube supporting seven hundred pounds of sturdy gears, tubes, and cables.
A cable will run from a seafloor anchor up through a system of gears on the float. As the machine moves up and down with the waves, its movement relative to the cable will drive the gears. A module on the float can be switched out so that the motion either runs a generator to produce electricity, or powers a pump to drive seawater through a filter, making clean drinking water.
This wave energy converter, though small, could be used to produce drinking water for coastal communities in an emergency, explained Mike Remige, the director of Jennette’s Pier.
“Eventually, somebody could provide disaster relief to a place like Ocracoke Island, if it was isolated during a storm and had no fresh water,” he said. Remige looks forward to seeing how the prototype performs during the ten-day test run.
“I’m just really excited to see how much clean water they can produce in that amount of time,” he said.
Eventually, somebody could provide disaster relief to a place like Ocracoke Island, if it was isolated during a storm and had no fresh water.Mike Remige, director of Jennette’s Pier
In the future, wave energy could also be especially practical for providing power to devices far from land, like offshore radar scanners or autonomous underwater vehicles, according to Muglia.
If the system is ever to reach practical use, though, depends a lot on whether people will want it in their backyards.
Linda D’Anna is a research associate at the Coastal Studies Institute who focuses on human dimensions of the coast. D’Anna cautioned against overenthusiastic deployment, explaining that the ocean is already valued for other reasons that should be taken into account first.
“Other folks are using ocean space and ocean resources for some other purpose, whether that’s for fishing, or transport, or military, or they’re concerned about conserving space for wildlife and other species,” she said.
“There have been a lot of examples of getting so excited by the potential of the technology, and working so hard to figure that out, and then getting through that process and realizing, oh wait – someone’s already using this thing that we wanted to use, or someone’s valuing it for something else, like, we’re going to have neighbors!” D’Anna said. “What is the neighborhood we’re moving into?”
In these early days of ocean energy technology, figuring out how the neighbors feel about it is no easy task, she said. “It’s hard for people to tell you what they think of something when you can’t tell them what it’s like.”
Small-scale wave energy is unlikely to harm marine ecosystems
Another open question is how the wave energy converter will affect ocean ecosystems. No system of energy production is without consequences, and Lindsay Dubbs, research associate at the Renewable Ocean Energy Program at the Coastal Studies Institute, explained that even small-scale ocean energy devices can impact the ecology of their surroundings. But those impacts aren’t necessarily negative.
The wave energy converter, like anything put in the ocean, will almost immediately start to be colonized by marine life.
There are organic particles that stick to it, and then you have bacteria that come after that and algae,” Dubbs explained. ‘And eventually, you have kind of like a benthic [seafloor] habitat, but on the structure. And that habitat also attracts fish.”
For larger-scale ocean energy installations, or ones further out to sea, the ecological concerns become more serious and less known, Dubbs said.
“Whether you're talking about turbine blades, or you're talking about wave energy converters that are kind of moving in the waves, there has been concern that those would strike organisms. There's also entanglement risk from lines and cables.” But for small-scale deployments, she said, “all of the evidence thus far suggests that those effects are going to be minimal.”
Despite the many unknowns, Dubbs said that there are excellent applications for wave energy. “I think that it is important for us to consider all of our options,” she added. “We don't know what the impact of marine energy is going to be on marine systems. We know what the impact of fossil fuel-based energy is on marine systems.”
First, though, the wave energy converter has to survive the tremendous forces it’s intended to harness. It’s been tested in the ocean once before, but for less than 24 hours. The upcoming ten-day trial will help determine how robust it truly is, said Remige.
“A device that’s really only been put in the ocean environment once, you learn a lot about how it’s going to withstand the forces out there.” He added, “The ocean has a way of humbling you, very quickly.”
Muglia remains philosophical about the possibility the prototype could fail. “What we always say when we’re working in the ocean is – especially with one of these wave energy converters – is we’re going to put it out there and we’re going to break it. And then we’re going to learn from that.”