Novel Mini-Turbine Arrays Stacey Chan, Mike Romanko, Jesse Greene, with Charles Williamson

Motivation

Urban environments contain high densities of wind energy that are inaccessible to large traditional wind turbines. By exploring vertical-axis wind turbines at the small scale, we can efficiently harvest wind energy from these constrained spaces. We developing fundamental knowledge about the fluid dynamics of the mini-turbines that has not yet been rigorously studied. The result will be a robust and radically new wind turbine that will blend engineering and art in the public setting.

Fundamental Blade Studies

Atkinson’s Center for a Sustainable Future

Objectives

• Increase Power Output. Optimize the power output of a single turbine with a comprehensive and previously unexplored study of the parameter space, including virtual shapes, offset pitch angles, and relative blade sizes.

• Rapid-Prototyping of Designs. Use our 3D printer and wind tunnel to rapid prototype and test radically new turbine designs and arrays.

• Optimize Positive Interference. Evaluate configurations of turbine arrays for constructive interference between turbines and take advantage of the omni-directionality of the turbines.

• Artistic Concepts. Encourage engineering

and art in a public display of aesthetically pleasing renewable energy harvesting systems. Potential locations include alleyways, rooftops, elevator shafts, tunnels, under bridges, between street lights, and even free-standing lattices.

Rapid-Prototyping

Interference Studies We intend to study the interaction between mini-turbines. Results to date suggest one can achieve positive interference, which increases energy density for a given area.

Co-Rotating Turbine Pair

Counter-Rotating Turbine Pair Surface-Flow mini-turbine array can be placed on vertical or horizontal surfaces

Broader Impact

Through-Flow mini-turbine array between walls in an alleyway

We are radically departing from classical blade designs by studying large c/D ratios, where c is the chordlength of the blade and D is the diameter of the turbine. The success of high c/D turbines largely depends on the camber of the blade, the “virtual shape,” and the offset pitch angle. Our preliminary tests show that larger blades extract an order of magnitude more energy than small blades! It is important in designing the blades to take into account the interaction of one airfoil’s wake on the performance on the other blades.

The power of rapid-prototyping allows us to print 3-D models quickly for testing designs in the wind tunnel at real operating conditions. We have combined techniques from 3D printing and machining to fabricate a flexible and thorough testing platform.

One possibility is to integrate a prototype array on Cornell campus! A public display of renewable energy acts as a permanent outreach tool, encouraging engineering, art, and future sustainability projects.

The result of this study would be a high-density energy harvesting technology, involving modular, exchangeable, inexpensive, lightweight devices, secured by tension cables. The success of this project will result in an increase of knowledge of the fundamental aerodynamics of mini-turbines and their interactions, and an increase of renewable energy in the urban environment.

Flow curvature causes the flow to “see” a different airfoil blade than what is physically there.

The wake from one blade will interact with the downstream blades.

Exploded diagram of testing platform and turbine

The rapid-prototyping process starts with (a) a

computer design. Next is printing the model from

a 3-D printer (b), and finally testing the

turbine in the wind tunnel at speed! (c)

Wind

(a)

(b) (c)

Energy harvesting using small-scale vertical-axis wind turbines for the urban environment

Sibley School of Mechanical and Aerospace Engineering at Cornell University October 2012

Physical Airfoil

“Virtual Airfoil”