Researchers Look at Tidal Turbines as Renewable Energy Source

May 15, 2018

Eben Franks of the Marine Renewable Energy Collaborative along the Cape Cod Canal.
Credit Sarah Tan / WCAI

With its rushing current and ever-changing tides, the Cape Cod Canal has become the country’s first test site for a new kind of renewable energy source. Researchers at the University of Rhode Island and the Marine Renewable Energy Collaborative hope that soon they'll be able to add tidal energy to the list of renewable energy sources, and the canal could be the place where companies test prototypes. 

Marine Renewable Energy Collaborative, the company behind the building of the canal's test site, built a platform that would house potential tidal turbines back in November. Currently, researchers are collecting different kinds of data about the canal, to inform turbine engineers. 

The platform is located under the Sagamore Bridge, about a hundred feet from shore. It looks like construction scaffolding under the bridge, but in another year or so, there may be a tidal turbine prototype spinning underneath. Eben Franks, the platform's project manager explained what they're doing out there. 

"Getting this current data, the water movement data, will be very helpful in attracting our first customer, we hope," he said.

On a visit out to the platform, Franks and his team of researchers from the collaborative collect data from their water height sensor and install a current speed profiler, a machine that looks like a turtle shell, which will record how fast the canal’s current runs underneath the platform. They affectionately call it Big Green.

"So we’re going to attach Big Green to the two pilings, and then launch it. Launching it just means we’re going to wrestle it off the bow into the water and hopefully it’ll sink and land upright," Franks said. 

The canal runs at a speed of about 4 knots, or 4 miles per hour, and the canal’s dynamic tides turn three times a day. The Cape Cod Canal is currently the only place in the United States where companies can test tidal turbine prototypes. There are test sites in Europe and Canada, but the canal is special because its currents are strong and predictable.

"It’s unique in many ways. The tides, as you can imagine, come and go a couple times a day. It’s much higher energy at the peak high tide, and that allows turbine developers to get a real look at what their turbines can do in a real-world situation," Franks said. 

And the Cape Cod Canal has an unusual feature.

"Most other canals where you have a place like that would either have some locks to change levels, or a dam already in place to create electricity, so you wouldn’t just have a free-flowing canal with a tide," boat captain Corey Katz said. 

The idea of using a turbine to harness the energy of the canal’s tides isn’t new; back in the 90s, a similar project was attempted in the canal, but it couldn’t generate enough interest to become an actual test site. But John Miller, director of the marine collaborative, said that with the increased profile of wind energy today, tidal energy could be the perfect complement.

"So while there’s less tidal and wave energy than there is wind, they provide nice complements to the wind," Miller said. "When the wind isn’t moving, the waves are still moving, the tides are still moving."

That, and tides aren’t as fickle as wind.

"And another thing about tidal energy is, it’s incredibly predictable. You can predict tides for a hundred years. Wind energy is probably predictable on the order of hours, tides on the order of days," he said. 

The future of tidal turbines is still a few years behind wind power developments, and according to Miller, it'll be five or more years before people start hearing about turbines generating energy underwater. But as interest in renewable energy of all kinds ramps up, he hopes that tidal turbines will be able to fit into the mix as well.

"If you have a lot of wind turbines offshore, and they're on platforms, why can’t you put wave devices on those platforms?" he asked. 

On May 16, the collaborative will be holding a conference to invite turbine developers to partner with them to place a test turbine in the canal. By the fall, Miller said they hope to have a tidal turbine prototype in the water and operating.