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Project Summary

The HyBlade project developed a single-component blade profile made of high-strength steel sheeting for rotors of smaller wind turbines. Reliable production techniques were used such as CNC bending to produce the preform and hydroforming for producing the final geometry. This process guarantees the high level of profile dimensional accuracy by means of calibrating, one of the essential prerequisites for good aerodynamics and a high level of rotor energy output. Finally, the very efficient process chain makes it possible to produce even larger blades with much more complex geometries.

The first step was working out a detailed strategy that not only evaluated the potential flow profiles, but also the benefits and downsides of potential production processes. Then, the blade was laid out based upon studies on the impact of various geometric parameters (blade width and length, material thickness and internal reinforcement), the appropriate load spectrum and basic considerations on material selection. It was possible to design the blade or a complete rotor based upon these findings that were studied afterwards in terms of its structural integrity under load and in operation by means of simulation. Something that had an important role to play were the considerations on the rotor's fatigue strength over the envisioned 20 years of operation.

Beyond the clarification of structural issues, extensive studies were launched. This not only discovered the rotor's optimum aerodynamic operating point and appropriate dimensions of blades the rotor. It also delved into the arrangement of several rotors in groups. One promising approach was the three-cornered arrangement of counterrotating pairs of rotors in a hexagonal structure. Furthermore, the variation of the turbine spaces made it possible to obtain area energy output much greater than state-of-the-art. Unfortunately, it was not possible to obtain a final answer to the question as to what maximum size a hexagon should have due to the extremely complex aerodynamic relations and impact "from above" into the hexagon of air flowing in (that could not be determined in the framework or the project.

The section of the project delved into applying the theoretical results found in the first section. Several actual tools and demonstrators were built with the knowledge from them along them with a detailed interpretation of the production process. It was not only the proof that the process chain is suitable and the feasibility of the blade, but also focusing on the field test of a real rotor. For instance, a metallic rotor made during the project was exchanged for a commercially available one and tested on a test field at the Belgian coast under real conditions. The findings here suggest that the blades' weight empty was not the crucial criterion for the layout especially with small and medium-size wind turbines in relation to their much larger counterparts, which is why the thickness of the material is no longer as important when laying out the blades and metals are competitive alternative materials. That means that the objective of the 79EBR (IWU) and 120279 (VUB) research project (i.e., developing and hydroforming manufacture of competitive metallic blade profiles for vertical axis wind turbines) was achieved in the framework of this project.

Rotor

Fig.: Detailed picture of the primer lacquered HyBlade rotor with steel blades at the field test

Literature

Pröhl, Marco; Troyer, Tim de: HyBlade - Hydroformed blades for meshes of vertical axis wind turbines (EFB-Forschungsbericht, 422).

Poster: EWEA 2014 in Barcelona, Spain   >>> Download (You are not authorised to download.)


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