The animation shows how various parameters (e.g. wind speed, number of blades) affect the rotor blade shape of a wind turbine. In the animation, several parameter sets can be changed. The result is displayed both as a curve and as a 3D model.
Instructions for Use
The windows can be enlarged or reduced by clicking on them, as with all animations.
The rotor of the wind turbine can be viewed from several predefined perspectives:
After starting the application, you can view the animation in fullscreen mode. To do so, click on “View” and then on “Fullscreen”:
To exit fullscreen mode, press the Esc key.
Explanation
The basis of the calculation is the so-called Betz formula. The Betz formula defines the blade depth as a function of the distance from the rotor hub. The animation uses NACA airfoil profiles, which are also actually used in the construction of some wind turbines.
The Betz formula can be represented as follows (Hein 2013):
\[ t(r) = \frac{8}{9} \cdot \frac{1}{Z} \cdot \frac{1}{C_a} \cdot \frac{1}{n} \cdot \frac{v_1^2}{\sqrt{\left(\frac{2}{3} v_1\right)^2 + \left(2 \pi \cdot r \cdot n\right)^2}} \]
All parameters can be changed in the table:
- Number of blades Z
- Lift coefficient Ca
- Design rotational speed n
- Blade length l
- Wind speed v in m/s
The lift coefficient is a parameter that can only be determined empirically or through simulation.
The design rotational speed determines whether the turbine is a fast runner with low torque or a slow runner with high torque.
Note: To display the curve, double-click on the 3D model.
In the animation, wind turbines with up to 9 rotor blades can be constructed, even though calculations show that turbines with 3 rotor blades have the highest efficiency. Wind turbines with more than 3 blades are still used today for special applications. One example is the operation of pumps. The limit of 9 rotor blades has animation-technical reasons, because the high number of polygons pushes the computing power of a normal PC to its limits.
Wind speed depends on local conditions. This value is obtained through measurements and statistical analyses.
Rotor blades are tested in wind tunnels not only for efficiency but also for noise emissions. The loudest areas are usually at the blade tip and can be made significantly quieter using serrated edges (“serrations”). Some manufacturers even experiment with owl-wing-inspired patterns because owls fly almost silently. Moreover, temperature and humidity influence the performance of a turbine more than one might think — cold, dense air provides more energy, warm, thin air less. Such effects are taken into account in modern simulations so that rotor blades operate optimally under as many conditions as possible.
Overview and Download
| Title | Construction of Rotor Blades for Wind Turbines |
| Target group | Teachers and presenters |
| Platforms | Microsoft® Windows® |
| Features | Fullscreen mode lossless magnification Supports large screens and projectors |
| License | Freeware |
| Download | Contact |
Contributors
C. Hein, S. Rikowski
Sources
- 3D engine for 3D model: Papervision3D 2.0
- Airfoil profiles (NACA 4412, 4418, 4421): http://www.ae.illinois.edu/m-selig/ads/coord_database.html
- Authoring tool (control elements included): Adobe Animate
- Hein, Christian (2013): [Untitled]. URL: http://www.unimuenster.de/imperia/md/content/fachbereich_physik/technik_didaktik/energietechnik_nutzung_windenergie.ppt [Last accessed: 18.02.2013].
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