THE quest to derive energy from wind more efficiently may soon be getting some help from California Institute of Technology (Caltech) fluid-dynamics expert John Dabiri – and a shoal of fish.
Dabiri is head of Caltech’s Biological Propulsion Laboratory and has been “inspired” to consider optimal wind-turbine spacing by watching shoaling fish and analysing the hydrodynamic interference between the wakes of neighbouring fish.
“It turns out that many of the same physical principles can be applied to the interaction of vertical-axis wind turbines,” he said.
The biggest challenge with current windfarms is lack of space, whether on or offshore. Dabiri argues that, with help from the hydrodynamic principles that govern the intervals between each fish in a shoal and the use of vertical-axis turbines, that may change.
Vertical turbines – which are relatively new additions to the wind-energy landscape – have no propellers. Instead, they use a vertical rotor. Because of this, the devices can be placed in a denser pattern.
Caltech graduate students Robert Whittlesey and Sebastian Liska researched the use of vertical-axis turbines on small plots during a class research project supervised by Dabiri. Their results suggest that there may be substantial benefits to placing vertical-axis turbines in a strategic array, and that some configurations may allow the turbines to work more efficiently as a result of their relationship to others around them – a concept first triggered by Dabiri watching fish.
In current windfarms, all the turbines rotate in the same direction. But while studying the vortices left behind by fish swimming in a school, Dabiri noticed that some vortices rotated clockwise while others rotated counter-clockwise.
So he now 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 windfarms that place turbines neatly in rows. Whittlesey and Liska’s computer models predicted that the wind energy extracted from a parcel of land using this staggered placement approach would be several times that of conventional windfarms using horizontal-axis turbines.
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