Nov 29th XPlore- Kinetic Sculpture

Introduced transitioning from windpower project to Kinetic sculpture-

Wind turbine project should have showed that increasing the number of blades slows the speed of the rotor, but increases the amount of power that can be extracted from the wind-

see http://www.learnengineering.org/2013/08/Wind-Turbine-Design.html--

However, increasing the number or length of blades marginally increases efficiency, but results in other problems-

Effect of Number of Blades

As the number of blades in the wind turbine increases aerodynamic efficiency increases, but in a diminishing manner. When we move from 2 blades to 3 blades design efficiency gain is about 3%. But as we move from 3 blades to 4 blades design, efficiency gain is marginal.

Fig.1 Efficiency gain as number of blades in wind turbine is increased

As we increase number of blades, cost of the system increases drastically. Along with that mechanical design of blades also becomes a difficult affair. With more number of blades, blades should be thinner to be aerodynamically efficient. But blades with thinner portion at the root may not withstand bending stress induced due to axial wind load. So generally wind turbines with 3 blades which can accommodate a thicker root cross-section are used.

Fig.2 Wind turbine blades have got thicker root to withstanad huge bending moment induced

Blade Length

Next big factor affecting performance of wind turbine is length of the blade. As we discussed in first video lecture, power extracted by the wind turbine varies according to this equation. So it is clear that, a longer blade will favor the power extraction. But, with increase in blade length, deflection of blade tip due to axial wind force also increases. So blind increase in length of the blade may lead to dangerous situation of collision of blade and tower.

However, due to technical issues( loose rotor blades, etc.) this was not always clear.

Showed Design Squad video, 'Blowin in the Wind'



Students task will be to design a small prototype that shows what it will look like, then build a larger one that will both be artistic and produce power.

Discussed with Mr. P. whether a system that produces power can also be sculptural/artistic.

Showed Strandbeest Video:
https://www.youtube.com/watch?v=PuxtdylbwVs

Linkage Mechanism:
http://www.mekanizmalar.com/theo-jansen.html

Instructables:
https://www.instructables.com/tag/type-id/?sort=none&q=kinetic+sculpture