Courtesy of Fraunhofer Institute for Applied Polymer Research IAP
These systems enable private households, businesses, or disaster relief organizations to set up a decentralized energy supply and use renewable energy efficiently.
The newly developed wind turbines start moving even in a light breeze. Wind tunnel tests show that the rotor begins to turn at a wind speed of 2.7 meters per second - a key requirement for the efficient use of wind power in regions with low wind conditions. The starting speed for comparable systems is four meters per second.
Weak Wind, High Efficiency
"Our goal is to use the power of the wind as effectively as possible to generate electrical energy," emphasizes Marcello Ambrosio, Head of Simulation and Design in the Polymer Materials and Composite PYCO research division at Fraunhofer IAP.
The lightweight construction experts at the Wildau site are taking a holistic approach to the development of the wind turbine: "We have optimized the aerodynamic design and the manufacturing process", explains Ambrosio.
High-Performance Rotor Blades
The result: the wind turbine achieves up to 450 revolutions per minute. With an output of 2500 watts at a wind speed of 10 meters per second, it is on average 83 percent more powerful than comparable systems on the market. The system achieves an efficiency of 53 percent. "Physically, a maximum of 59 percent is possible," says Ambrosio, classifying the measurement data from the wind tunnel test.
Raúl Comesaña M., Managing Director of the BBF Group, adds: "Efficient small wind turbines make an important contribution to an independent energy supply. As a project developer and construction company in the Berlin-Brandenburg region, we demonstrate with this project how end consumers and businesses can design decentralized energy generation individually and sustainably."
The rotor blades of the small wind turbine are constructed from two shells in a lightweight design. They are made of fiber composite materials. Compared to conventional designs, which are constructed with a foam core, the newly developed components are hollow inside. This construction method reduces the overall weight up to 35 percent. Fiber composites are produced by precisely laying fiber strips in a mold, which is then hardened using resins or other plastics to form a component.
Marcello Ambrosio and his team specially designed the mold for the rotor blades. The scientists use an industrial 3D printer that can print objects up to two-by-two meters in size. A modern Automated-Fibre-Placement system handles the placement of the fiber strips in the mold. This automated method ensures high quality, reduces overlaps compared to manual placement, and allows for smaller component dimensions.
A special laminate structure also ensures that the rotor withstands strong winds. "We designed the individual layers of the composite material so that the rotor blades can flex elastically in a storm and turn out of the wind," describes Marcello Ambrosio. This automatically reduces the rotation speed of the turbine and protects it from overload. Complicated control technology and elaborate mechanics can thus be avoided.
Five prototypes of the small wind turbine were recently delivered to the BBF Group to be installed at various locations. With this approach, the researchers and their development partner aim to find out how the position and height of the system affect performance. The next steps include further optimization of the rotors and the development of lightweight structures made of monomaterial - meaning chemically identical materials - instead of composite materials. Such components are easier to recycle and help improve the environmental balance of lightweight solutions.