Controllable Rubber Trailing Edge Flap To Reduce Loads On Wind Turbine Blades

SOURCE

ScienceDaily (Mar. 17, 2009) — The trailing edge of wind turbine blades can be manufactured in an elastic material that makes it possible to control the shape of the trailing edge. This will reduce the considerably dynamic loads that large wind turbine blades are exposed to during operation.

”Providing the blade with a movable trailing edge it is possible to control the load on the blade and extend the life time of the wind turbine components. This is similar to the technique used on aircrafts, where flaps regulate the lift during the most critical times such as at take-off and landing, "explains Helge Aagaard Madsen, Research Specialist on the project.
However, there is a difference. Whereas on aircrafts, movable flaps are non-deformable elements hinged to the trailing edge of the main wing, this new technique means a continuous surface of the profile on the wind turbine blade even when the trailing edge moves. The reason for this is that the trailing edge is constructed in elastic material and constitutes an integrated part of the main blade.
Robust design of rubber
In 2004 Risø DTU applied for the first patent for this basic technique of designing a flexible, movable trailing edge for a wind turbine blade. Since then there has been a significant development with regard to the project. By means of so-called "Gap-funding" provided by the Ministry of Science, Technology and Innovation and by the local Region Zealand it has been possible to develop such ideas into a prototype stage.
Part of the research has been aimed at the design and development of a robust controllable trailing edge. This has now led to the manufacturing of a trailing edge of rubber with built-in cavities that are fibre-reinforced. The cavities in combination with the directional fibre reinforcement provide the desired movement of the trailing edge, when the cavities are being put under pressure by air or water.
“In this project a number of different prototypes have been manufactured with a chord length of 15 cm and a length of 30 cm. The best version shows very promising results in terms of deflection and in terms of the speed of the deflection” says Helge Aagaard.
The size of the protype fits a blade airfoil section with a chord of one metre and such a blade section is now being produced and is going to be tested inside a wind tunnel.
The capability of the trailing edge to control the load on the blade section is going to be tested in a wind tunnel. This part of the development process is supported by GAP-funding from Region Zealand.
”If the results confirm our estimated performance, we will test the rubber trailing edge on a full-scale wind turbine within a few years” says Helge Aagaard.
Adapted from materials provided by Risø National Laboratory for Sustainable Energy.

New Design Means Cheaper, More Sustainable Construction

SOURCE

ScienceDaily (Mar. 11, 2009) — People are always looking for ways to make something less expensive and more environmentally friendly – and a team of researchers from North Carolina State University has figured out how to do both of those things at once when raising the large-scale buildings, such as parking garages, of the future.

More specifically, the researchers have figured out a way to use 30 percent less reinforcing steel in the manufacture of the concrete beams, or spandrels, used in the construction of parking garages – without sacrificing safety. Dr. Sami Rizkalla, one of the leaders of the research team, says they developed design guidelines that use less steel while maintaining safety and reliability. The new spandrel design "simplifies construction for precast concrete producers," Rizkalla says. In addition to using less steel, the new design cuts labor and manufacturing time in half – significantly decreasing costs.
Greg Lucier, a doctoral student at NC State who was also crucial to the research effort, says the new design guidelines include a significant margin for safety. For example, Lucier says the spandrels could handle two to three times the maximum weight they would be expected to bear. Lucier is also the lab manager of the Constructed Facilities Laboratory at NC State, which oversaw the testing of the new spandrel design.
The new design guidelines stem from a two-year project that was launched in January 2007, with support from the Precast/Prestressed Concrete Institute (PCI). PCI provided NC State with more than $400,000 in funding, materials and technical support over the life of the project.
The success of the project is already drawing interest from the concrete industry, with individual companies coming to NC State to get input on how to improve their products and manufacturing processes. For example, Rizkalla says, many companies want to collaborate with researchers at the Constructed Facilities Laboratory on research and development projects related to new materials, such as advanced composites, to be used in concrete products.
While researchers have published some elements of the research project, they will present an overview of the entire project – including new testing data – for the first time at the spring convention of the American Concrete Institute in San Antonio this month.
Adapted from materials provided by North Carolina State University.