Water Power

When Gabriel Alsenas briefs Florida legislators on how much energy the Gulf Stream holds, he asks them to visualize it: “Imagine all the major freshwater rivers in the world, like the Amazon and the Mississippi, and their discharge into the world’s oceans. Multiply that water flow by 30, and you get what’s going by our shores every second.” Every. Second.

Alsenas is director of FAU’s Southeast National Marine Renewable Energy Center (SNMREC). In 2014, the U.S. Bureau of Ocean Energy Management tendered a five-year lease to SNMREC to develop a test site for technology that could generate energy from ocean currents like the Gulf Stream. Alsenas and his team fulfilled the terms of the lease on Oct. 23, when they demonstrated a turbine they designed and built using energy-capture technology patented by local industry leader Ocean Current Energy, LLC. It is the first modern turbine to generate electricity from the Gulf Stream in the Florida Straits off Palm Beach County.

The crux of Ocean Current’s technology is a coin-shaped disc that supports a rotor and rare Earth magnets. The interior contains the rotor, turned by rushing water. The outside holds the magnets, typically found in a generator. Eliminating the gearbox and shaft found on wind turbines makes repairs easier, increasing uptime. Two discs turning in opposite directions are coupled together, creating an equal and opposite force that allows the device to sit still as water rushes by. To generate utility-scale power, inverted funnels behind the discs create a negative pressure zone that sucks more water through the rotors. The devices will fly like kites, capturing the flow in the water column.

SNMREC was tasked with transforming Ocean Current Energy's technology into a turbine demonstrator that could produce energy from the Gulf Stream and validate the company’s claims. That included manufacturing the rotors, choosing the proper combination of magnets, designing the frame, testing the output, and assembling the machine without losing a finger. William Baxley, PE, SNMREC’s chief engineer, oversaw the delicate operations at FAU Harbor Branch Oceanographic Institute.

To speed up iterating suitable designs of rotors, they innovated a way to 3-D print them out in sections (their printers weren’t large enough to print out full-size rotors). They added epoxy for increased strength and structure, finally reinforcing the entire blade with metal rods. Then, they had to ensure the rotors worked.

“We created a unique platform to test the rotors by pushing different designs through the water at different speeds to simulate what the rotor would be doing at different flow speeds in the ocean,” Alsenas said. “Ours generated about 100 watts, like a bulb you might have in a floodlight.”

Additional analysis was carried out by James VanZwieten, Ph.D., affiliate researcher with SNMREC and assistant research professor at FAU’s civil engineering department. Modeling the efficacy of the funnels, he and his students identified a two- to four-fold increase in power.

In 2013, a study funded by the US Department of Energy found that the Florida section of the Gulf Stream alone could yield the equivalent of two to three nuclear power plants’ worth of energy. Including the energy that flows past the Carolinas, this could power about 15 million U.S. homes. “It’s huge, but that’s just a fraction of the amount of energy the Gulf Stream actually carries,” Alsenas said. “It’s a tiny, tiny piece of what our technology could tap into.”