US researchers team up to collect and share experimental data on vertical-axis tidal turbine

Researchers from the National Renewable Energy Laboratory (NREL) and the University of New Hampshire have partnered up to develop tools and collect data on the operation of vertical-axis tidal turbine in an effort to accelerate the development of tidal energy industry.

Vertical-axis tidal turbine in the Piscataqua River's site (Courtesy of NREL/Photo by Casey Nichols)
NREL's research engineer Aidan Bharath (Courtesy of NREL/Photo by Dennis Schroeder)
NREL’s research engineer Aidan Bharath (Courtesy of NREL/Photo by Dennis Schroeder)

NREL’s research engineer Aidan Bharath has teamed up with the University of New Hampshire’s Living Bridge project, a ‘smart bridge’ that runs on clean tidal energy, which is able to facilitate studies of a real-world tidal turbine beneath New Hampshire’s Portsmouth Memorial Bridge.

Collaborating with the University of New Hampshire’s team, Bharath and his NREL researchers will perform a crucial job for the project where they will design and build tools to collect the data needed to understand how well this turbine is operating.

Outfitted with sensors that monitor the bridge’s structural health as well as weather, traffic patterns, and the Piscataqua River flowing beneath it, the bridge is a kind of living laboratory to study bridge structures, the latest sensor designs, and renewable energy technologies.

Vertical-axis tidal turbine in the Piscataqua River's site (Courtesy of NREL/Photo by Casey Nichols)
Vertical-axis tidal turbine in the Piscataqua River’s site (Courtesy of NREL/Photo by Casey Nichols)

The experimental tidal turbine installed in the river not only powers those sensors – it also provides clean energy to raise and lower the bridge, allowing boats to pass through, and even powers a few homes nearby.

The bridge uses a vertical-axis tidal turbine, which are less common, so there are gaps in prior research and data available to understand how they work.

Bharath said: “The project was a rare opportunity to both understand these turbines and collect and share data with the wider industry. It’s way too expensive to build several prototypes of these turbines, throw them in the water, and test them individually.”

Therefore, the team is relying on a less risky way to evaluate new ideas using numerical models.

But even numerical models – which meld physics and mathematics to estimate how designs are likely to function in the real world – are not perfect, according to NREL.

To make their models more accurate, Bharath and the NREL team must compare their numbers to actual experimental data. To get that valuable data, Bharath and his team are improving the custom-made Modular Ocean Data Acquisition System, which has been collecting and sharing live data on the device’s performance.

With the tidal energy device back in their lab in Colorado, the team is adding sensors to measure how much strain tidal forces put on the blades. Once the device is back in the water, those sensors will wirelessly send data to a larger data collection system on a platform above the surface before transmitting it to the cloud where it is stored for future access.

Because wires can get tangled and salt water can be corrosive, the team built custom components – like slip rings that collect data from the rotating blades – to accommodate these challenges.

But until the turbine is reinstalled under Memorial Bridge, the uncertainties on the system’s performance remain, according to NREL.

“It’s been a fairly complicated build, and definitely a learning experience because we’re trying to do all of this in a cost-effective way while also adhering to NREL’s standards for quality assurance. It’s been a fun and big challenge for our designers,” Bharath said.

Bharath’s goal is to have the system gather data on the tidal turbine for two consecutive weeks (enough time to experience the full range of potential tidal stream velocities).

The team is also using the opportunity to test how well different glues and protective coatings survive on the underwater blades.

“There’s a lot that can be done and needs to be done because there are still so many unknowns out there,” Bharath noted.

Eventually, this data set will be added to the US Department of Energy’s Marine and Hydrokinetic Data Repository so anyone can access it. The data can also improve current marine energy models, like OpenFAST, and help marine energy developers hone their designs.

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