Harbor Branch seeks to tap Gulf Stream for electricity
STORY
Sometime in the next year or so, a test turbine will be deployed 20 miles offshore from Fort Lauderdale to explore whether it may someday be commercially feasible to tap the Gulf Stream and turn ocean energy into a source of hydropower that could illuminate millions of homes.
“The Gulf Stream has 30 times as much flow as all the rivers on the planet combined,” says Gabriel Alsenas, manager of a program at Harbor Branch and Florida Atlantic University aimed at extracting some of the almost inconceivable store of energy contained in the coastal current and plugging it into Florida’s electric grid.
At full commercial deployment, the first phase of tapping the Gulf Stream Alsenas and his colleagues envision could generate more electricity from an undersea field of turbines than the two nuclear power plants on Hutchinson Island.
The bladed turbines will operate similar to wind turbines, but receive a more powerful thrust than wind normally provides.
“We think you could get 2 to 3 gigawatts,” says Alsenas. A gigawatt is a billion watts. If the first array of Gulf Stream turbines achieves the high end of the goal it would exceed the output of the St. Lucie nuclear plants.
If the first field is successful, it could be followed by successive placements at intervals all the way up the East Coast to North Carolina, each generating a similar bonanza of pollution-free energy.
Full-scale power generation remains years in the future, but the FAU program is nearing a major milestone.
Deployment of the first test turbine will enable FAU and the dozen or so energy companies working on undersea turbine power to test and refine the complex technologies needed to channel ocean energy into usable electricity.
The substantial floating platform – called a mooring and telemetry buoy – the first turbine will be tethered to sits complete and ocean-tested on a steel rack in the Harbor Branch boatyard where the famous Johnson Sealink research submarines were built.
The components of the Ocean Current Research Turbine that will dangle from the buoy are awaiting assembly in an adjacent shop.
Alsenas, who received his undergraduate and graduate degrees in ocean engineering from FAU and has been working on the ocean energy initiative since he was a graduate student, says it is very satisfying to see the long-imagined, much-researched devices finally emerge from the minds of engineers into the real world of wind and waves.
“My graduate advisor was the professor who got the initial $5 million in funding,” he says. That was in 2007 and the Department of Energy cash went to create what was then called the Center for Ocean Technology.
The program, which relies on state and federal grants and contracts, has since evolved into the Southeast National Marine Renewable Energy Center, one of three national centers focused on extracting power from the oceans.
“The Hawai’i National Marine Renewable Energy Center focuses on wave energy and thermal energy conversion,” Alsenas says. “The Northwest National Marine Renewable Energy Center is developing wave and tidal energy technology. We use what we have locally, our regional resource, and focus on energy from ocean currents and thermal conversion.”
Thermal conversion creates electricity from the temperature differential between deep and surface ocean water, using condensation and evaporation of a gas/liquid such as ammonia to drive turbines.
The three national centers were designated by the Department of Energy. They do not aim to create commercial power generating systems. Instead they exist to help private companies develop the needed technologies, sort out environmental and regulatory issues and establish protocols and standards for an ocean energy industry that is just now being invented.
It is a complicated task, to say the least.
Here in Florida, Alsenas and his associates at the renewable energy center have to think about everything from coral reefs on the floor of the ocean where commercial underwater turbines will eventually be anchored to the effect of turbine fields on sea turtles and dolphins to the impacts on recreational boating, commercial shipping, submarines and the Gulf Stream itself.
The test berths require permits from a long list of state and federal agencies with an alphabet soup of acronyms. The agencies have never had to regulate this type of technology or activity before so they have to evolve along with the program, devising guidelines and setting standards.
“There is a balancing act on the environmental side,” Alsenas says. “On the one hand this is clean energy with no pollution. On the other we have to make sure turbines are anchored so they don’t impact coral beds and figure out how the fields of turbines may affect marine mammals.”
On the technology side, devices have to withstand years of submersion in salt water with low maintenance and be stable and efficient in changing ocean conditions.
But the electricity-generating potential off the Florida coast outweighs the problems, according to Alsenas.
“The Gulf Stream is unique,” he says.
The earth’s rotation swirls the water in ocean basins in a way that creates powerful currents along the east coasts of Brazil, South Africa, East Africa, Japan and Indonesia as well as Florida, but all of those currents are much more diffuse and changeable than the Gulf Stream, which is channeled through a vast submarine valley between Florida and the Bahamas that keeps it concentrated and steady.
“We are the lucky ones,” Alsenas says.
The Gulf Stream also has the advantage that the fastest water is relatively near the surface, making it easier to deploy and maintain turbines.
Juan Ponce de León was the first European to note the extraordinary power of the Florida current, which is what the Gulf Stream is called where FAU plans to deploy its devices. He noted in his journal that mariners who tried to sail against it found themselves carried backward, regardless of the strength of the wind.
The Gulf Stream was charted and named by Benjamin Franklin, that ever curious Founding Father, who worked with British and American ship captains to understand how the ocean river affected navigation to and from Europe.
The Gulf Stream is also uniquely suitable for thermal energy conversion, according to FAU documents.
In most places several thousand feet separate deep cold ocean water from warm surface water. Because of the Florida current and the shelf of land off Florida’s coast, cold and warm water are only about one thousand feet apart here, setting the stage for more efficient energy extraction than can be achieved elsewhere.
Because it is forging into uncharted technological territory, FAU’s ocean energy initiate is creating new knowledge all around it much like the space program.
By the time the first turbine generates electricity, much more will be known about the distribution of deep sea coral beds and marine mammals than was known before.
“We don’t know anything about what sea turtles do when they are out at sea,” Alsenas says. “So we are doing aerial surveys to count them and start to understand their at-sea behavior.”
On the technological side, SNMREC has created devices such as its Rotary Dynamometer, which allows energy companies to test their rotor designs against the force created by a motor programed from ocean data to mimic the flow of the Florida current.
FAU is also charting the current itself in greater detail and analyzing the physical properties of seawater in new ways to help create the most efficient possible turbines.
“I think getting the first turbine in the water will be a huge catalyst,” Alsenas says. “I believe it will generate a tidal wave of new interest and accelerate development of the technology.”
