Tiny turbines help Iowa researchers test wind

Iowa State engineers are mini-wind turbines to study how hilly terrain and turbine placement affect power production. (Photo courtesty Iowa State University.)

What is this? A wind farm for ants? (Zoolander reference. Sorry, I couldn’t resist.)

Engineers at Iowa State University in Ames are using tiny, 10-inch wind turbine models to test how hills, valleys and turbine placement can affect the power output of wind farms.

The project started after Hui Hu, an associate professor of aerospace engineering, noticed that there’s little data about how uneven terrain affects wind turbine generation.

It is well known that it does. When we wrote about wind forecasting in October, WindLogics CEO Mark Ahlstrom explained how topography and the placement of turbines relative to each other are important variables for predicting generation.

“The challenge is that a turbine is taking energy out of the wind flow,” creating a wake behind it, Ahlstrom said. “And so depending on exactly how those turbines are lining up that day relative to the wind directions, you’ll get very different power output at every turbine that’s downwind.”

Hu and his research team created turbines that are perfect 1:320 scale reproductions of standard, 80-meter diameter wind turbines. They’re now setting them up and running experiments with them in Iowa State’s Aerodynamic/Atmospheric Boundary Layer Wind and Gust Tunnel.

The goal is to give the wind industry better data about how wind moves across hilly terrain, and hopefully some insights on how to improve turbine placement and wind farm design.

“These studies are telling us things we didn’t know before,” Hu said in a news release. “And this will help optimize the design of wind turbine layouts with consideration of the terrain.”

The turbines have sensors mounted on the base to measure wind load and actually include mini generators inside to measure power production. The team also plans to used particle image velocimentry, a technique that involves using a laser and camera to document the flow of particles around the models.

Preliminary results suggest that, on flat terrain, wind “wakes” extend behind a turbine a distance six times its diameter. Other turbines in that wake lose 13 percent of their power production. The wind recovers more rapidly on hills, they’ve found.

“That means you can put wind turbines closer together in hilly terrain,” Hu said.

The research is being supported by a three-year, $300,000 grant from the National Science Foundation and a two-year, $100,000 grant from the Iowa Alliance for Wind Innovation and Novel Development.

The Iowa State researchers are illustrating wind "wakes" using particle image velocimetry.

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