Quite a while ago was the last mention by this weblog of VAWTs (Vertical Axis Wind Turbines). The post had some “Imagineering”, i.e., VAWTs in coastal or Great Lakes cities and resorts since they are safer and quieter*.
*Note: Units that spin on sealed bearings are nearly soundless, complying with municipal noise code restrictions for installations on apartment building complexes.”
The post cited certain product literature, which suggested wind directing strategies for easy adaptation to urban settings. And, because VAWTs are easier to erect and keep up, they are more affordable. In general, a VAWT will cost less than a HAWT “at all ranges of electrical output.”
San Francisco Treehugger Jaymi Heimbuch tells us that researchers at the California Institute of Technology (CalTech) have found ways to improve HAWT design by observing schooling fish. Design improvements “could yield as much as 10 times more energy from the same amount of space.”
Image via CalTech
“Wind turbine blades need a lot of room. If placed too close together, their efficiency drops because of the vortexes created as the blades turn.” Where land area is an issue, CalTech’s John Dabiri suggests vertical axis turbines as an alternative. By observing schooling fish, Dabiri believes his research team has found a better way to set up VAWT wind farms.
Fluid-dynamics expert John Dabiri uses bioinspiration for coming up with better solutions for water and wind energy. According to Dabiri, schools of fish offer a wealth of insight into setting up better wind farms using vertical axis turbines.
“I became inspired by observations of schooling fish, and the suggestion that there is constructive hydrodynamic interference between the wakes of neighboring fish,” says Dabiri, associate professor of aeronautics and bioengineering at Caltech. “It turns out that many of the same physical principles can be applied to the interaction of vertical-axis wind turbines.”
[W]hile studying the vortices left behind by fish swimming in a school, Dabiri noticed that some vortices rotated clockwise, while others rotated counter-clockwise. Dabiri therefore wants to examine whether alternating the rotation of vertical-axis turbines in close proximity will help improve efficiency. The second observation he made studying fish-and seen in Whittlesey and Liska’s simulation-was that the vortices formed a “staircase” pattern, which contrasts with current wind farms that place turbines neatly in rows.
Mother Nature Network states “The repeating vortices in an air stream around a body are relatively common. And it’s that same science that keeps schools of fish synchronized. It also reduces the total propulsive power needed per fish. In the field of fluid dynamics there have been well-developed models for simulating this phenomenon. This effect also reduces the fuel consumption of vehicles traveling in a platoon.”
With optimal placement, Dabiri thinks we could get 10 times more energy out of the same wind farm using vertical instead of horizontal turbines. A test of the fishy findings is underway with a pilot program called The Caltech Field Laboratory for Optimized Wind Energy (FLOWE). Two plots of land in the LA area will be home to six vertical turbines (three of which are provided by Windspire Energy) on mobile platforms, which will be moved around to test different configurations and discover the best patterns for wind farms.
“Our goal is to demonstrate a new technology that enables us to extract significantly more wind energy from a given parcel of land than is currently possible using existing methods,” says Dabiri. “We want to take advantage of constructive aerodynamic interference between closely spaced vertical-axis wind turbines. Our results can potentially make better use of existing wind farms, allow for wind farms to be located closer to urban centers-reducing power transmission costs-and reduce the size of offshore installations.”
“This project is unique in that we are conducting these experiments in real-world conditions, as opposed to on the computer or in a laboratory wind tunnel,” says Dabiri. “We have intentionally focused on a field demonstration because this can more easily facilitate a future expansion of the project from basic science research into a power-generating facility. Our ability to make that transition will depend on the results of the pilot program.”