Taiwan: Researchers Refine Small Wind Turbine Power Generation via 3D Printing

In the recently published ‘Small wind generation using complex airfoil turbine,’ researchers from Taiwan 3D printed a small wind turbine for small power generation in public utilities like streetlights.

The use of wind turbines continues to increase around the world, and as the researchers remind us—wind is an infinite source of power; however, its supply at a particular place and time is not always guaranteed. Variations in speed are a big reason for erratic power generated by turbines—of which there are two types: horizontal axis wind turbine (HAWT) and vertical axis wind turbine (VAWT). Historically, many researchers have attempted to refine turbine efficiency, especially those with smaller components. Variable pitch blades may solve torque issues, while the use of different blade angles increases power.

Force and velocity vector acting on the cross section of a VAWT blade.

Today, an affordable power generating system for cities that have lower wind—and unpredictably so—works well with fixed pitch blades and fixed angle of attack. For this study, the researchers recommend a turbine that acts on its own, using complex airfoil for the best performance between blades.

“The blades with airfoil shape are mounted to the struts of the three-blade H-rotor wind turbine in order to enhance the advantages of both vertical and horizontal axis turbine blades,” stated the researchers. “Both turbine blades are working on the same shaft to get maximum power from near-ground turbulent flows. The system design also considers how to reduce the drag of horizontal blades from hindering the rotation of vertical blades.”

With their new airfoil design, gusts from all directions can create better efficiency. Autodesk Flow Design was used for system simulation analysis. Ultimately, the researchers realized an ‘efficiency improvement’ of 15.3 percent.

Force and velocity vector acting on the cross section of a HAWT blade, θ⌢ is the tangential direction of the blade.

Experiments to evaluate the performance of the complex airfoil system were conducted with air deflectors in one instance, but not the other. Three different performance tests were given:

1. RPM of VAWT in various AoA conditions of the horizontal blades
2. Voltage output of VAWT in various AoA conditions of the horizontal blades
3. Cut-in speed of VAWT in various AoA conditions of the horizontal blades

Flowchart of the H-rotor complex airfoil VAWT design.

“In the case of adding the deflector to the tests considered as the working condition on the rooftop, there is an approximately 10 ~ 15% increase in performance,” concluded the researchers. “This means that the complex blade design is suitable for the use in near-ground wind conditions. In addition, wind tunnel testing reveals some unexpected aerodynamic effects that a down-force is derived to stabilize the wind turbine in operation.

“The merit of the complex airfoil will be useful for small utility wind power sets in urban use. In the experiment system, there are some defects to improve in future works: (1) improve the roughness of the blade surface that causes significant drag resistance, (2) improve rotation part friction to get better rotation efficiency, (3) introduce higher performance DC generator for suitable power output. A design criterion shall be established to approach the best design with predetermined specifications. Finally, the foundation of the VAWT set should be redesigned and modified to keep off rain or dust.”

3D printing is being used more often today in connection with the redesign of wind turbines, making them taller and more effective, creating designs for faraway countries like Nicaragua, and even finding ways to ward off animals like bats.

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