Ocean Energy

Scientists at UNC Coastal Studies Institute are testing new technologies that would harness the power of the ocean to create new sources of energy. Ongoing studies look at the energy potential and feasibility of generating energy from wind, waves, and currents.

WANCHESE - As North Carolina’s energy needs continue to grow, scientists and engineers are looking to the state’s vast coastline for renewable energy solutions. It’s an idea that makes a lot of sense, because North Carolina has the largest area of shallow coastline along the east coast. That could make tapping ocean energy much easier.

“A shallow coast is a good thing because right now, most of the structures for renewable ocean energy require less than a 100 meter water depth,” says Dr. Lindsay Dubbs, Research Assistant Professor at the University of North Carolina Coastal Studies Institute.

There are three goals in the search for ocean energy: support and expand the state’s renewable energy portfolio, create jobs, and expand economic opportunity. But while the ocean as a resource is plentiful and available thanks to the state’s long and shallow coastline, there are many questions surrounding marine hydrokinetic energy. That’s the renewable energy found in the movement of waves and currents.

The UNC Coastal Studies Institute is working with the engineering programs at North Carolina State Univeristy, University of North Carolina at Charlotte, and North Carolina A&T University, to answer several ocean energy questions.

Those questions include: just how much renewable energy can be harnessed in the ocean, what types of structures will be needed to collect the energy, and how difficult and expensive will it be to build those structures?

“All of those questions are key to whether we move forward with ocean energy, but don’t forget, we’re engineers, we can make anything stand up, we can build anything so it stays in place,” says Dr. Billy Edge, UNC-CSI Program Head for Ocean Engineering. “Those are all challenges, but it’s not an impossibility. However, with every challenge comes an expense and that expense is not going to be trivial.”

The results of ocean energy research so far have identified three types of energy that offer the most promise along the North Carolina coast. And if you have ever stood on the beach and watched and listened to the crashing surf, you won’t be surprised at some of the findings. The winds and waves that the Outer Banks are famous for have tremendous energy potential.

But here’s an energy source you might not consider.

One of the most intriguing ocean energy ideas is the concept of putting a giant turbine in the Gulf Stream, which runs about ten miles off the tip of Cape Hatteras in roughly 800 feet of water.

“It’s reasonably accessible and it is the largest and most consistent form of ocean energy,” says Mike Muglia, research associate at UNC-CSI.

The Gulf Stream current moves at about four knots, which is about four to five miles per hour.

“That doesn’t sound very fast, but don’t forget the laws of physics, which say the energy you get from a moving fluid is propotional to the density,” adds Muglia. "So, since the water is 1000 times as dense as air, you don’t need the water moving very fast to push a turbine. In fact, you get about the same energy from the water as you get from air if you put a turbine in the Gulf Stream.”

Scientists are combining data from land-based radar, which measures surface currents, with satellite images measuring water temperature to pinpoint the exact location of the Gulf Stream. Muglia is also designing an experiment in which a device sits on the ocean bottom and sends out sound waves towards the surface every ten minutes. As those sounds waves bounce off particles floating in the water, the device measures the Doppler shift, which will show how fast the current is moving.

Next comes wave energy. It does not appear the potential energy from waves would be as consistent as that from the Gulf Stream because waves can be large and small. However, early research shows wave energy is as good along the North Carolina coast as it is anywhere along the east coast.

There have been several experiments in wave energy conversion using what are called “surge devices.”

“A surge device is essentially a paddle that would be anchored to the bottom and be able to flap back and forth as the waves come by with the top of the structure very close to the water level," says Dr. Edge. “As the waves come by, it would flap back and forth and that would drive a turbine that would allow the power take off to generate energy.”

Those experiments show that depending on the coastline and the conditions, wave energy is very efficient. It generated roughly 10 kilowats of energy per meter. That’s enough energy to power about three houses. A string of the devices near the shore could power small communities.

That leaves wind power, which is probably the best-known form of renewable energy. But it presents a huge challenge. That’s because nobody wants to see a wind farm with hundreds of towers sitting off the coast and ruining the pristine view of the ocean.

To harvest the winds, turbines would have to be located far offshore, which makes it more difficult to get the power that is generated back to shore. It also means wind farm turbines must be strong enough to survive hurricane force wind and waves.

“So we would have to put those turbines, those wind farms, far enough offshore that we don’t interfere with the landscape,” adds Dr. Edge. “We can certainly do that, but when we do we expose ourselves to the currents and the waves, not to mention the extreme waves that are associated with storms.”

Because there are so many engineering challenges, researchers say it could be almost a decade before ocean energy can be tapped. In addition, there are also environmental challenges that must be overcome.

“We have to take into account that any of these methods of harvesting ocean energy would affect threatened and endangered species as well as protected species like marine mammals and the protected habitats along the coast,” adds Dr. Dobbs, as she looks about over the marshy coastline near the Institute labs in Wanchese. “Energy projects would also have to take into account the effects on current human uses of the ocean such as the state’s huge commercial fishing and sport fishing industry.”

There is also a huge diving community to consider.

No one denies that North Carolina needs to search for alternative energy sources and that the ocean is a good resource that could be tapped, but the reality is becoming clearer as to just how challenging that will be. It is easier to get to the ocean than to get energy from it.

Related Resources: