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Changing Arctic

Researchers Fine-tune Mini-hydropower Technology in Effort to Field System in Villages

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Harnessing rivers to generate electricity …

University of Alaska Fairbanks researchers are helping develop small hydropower systems that don’t require building a dam but instead use a turbine anchored into a river to harness the flow of water to generate electricity for remote communities located far off the grid.

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Credit Tim Ellis/KUAC
Jeremy Kasper pulls his boat alongside barges where the river turbine is being tested. Kasper is director of Alaska Center for Energy and Power's Alaska Hydrokinetic Energy Research Center. He's also a research assistant professor at UAF's Institute of Northern Engineering.

But before that could happen, researchers like Jeremy Kasper with the Alaska Center for Energy and Power must solve problems that’ve held back development of so-called river hydrokinetic systems.

“There’s a lot of things involved in getting a turbine like this out in the water,” he said in an interview at the turbine test site along the Tanana River near Nenana. “And so we need to demonstrate that we can get these turbines out there for long periods of time.”

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Credit Tim Ellis/KUAC
The hydrokinetic turbine being tested by UAF in Nenana is suspended into the Tanana River from the middle of three platforms, at left. The bouy in the upper right marks the point where the barges are anchored to the river bottom. The debris diverter is located between the bouy and barges.

Kasper and his team have already solved one problem that’s plagued previous tests – protecting the turbine from being smashed by logs and other driftwood carried along by a river’s flow. The team last year designed and built a steel-frame “debris diverter” that shunts driftwood off to either side.

“Figuring out where things are going to go wrong, and how to prevent them -- that’s what’s we’re doing.”

Kasper says they’re now studying how to control fluctuations in electricity generated by the turbine that are caused by the variations in the river’s flow, which makes the turbine’s blades turn at varying speeds.

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Credit ABS Alaskan
The “eggbeater" design hydrokinetic turbine now undergoing testing at the Nenana site.

“The first thought was ‘Oh, it (turbine) is constantly spinning. It’s just a river. It’s constant,’” he said. “Well, it’s not. The power output of these things varies incredibly rapidly. Since they vary so much, it’s actually turning out to be fairly complicated to integrate them into the grid.”

He says researchers are developing a control unit that will stabilize the fluctuating output of electricity.

“Basically it takes the wildly varying voltage and current coming from the turbine and then conditions it, inverts it – turns it into an AC current.”

Kasper says the control unit is one of many technologies that’ll be required to make small hydrokinetic systems commercially viable and practical for such uses as powering remote communities.

Next week: The Alaska Hydrokinetic Energy Research Center conducts more precise testing on river turbines in its facility on the UAF campus.