German researchers have paved the way for decentralised renewable energy by developing a lightweight, small wind turbine capable of generating electricity even in the gentlest breeze.
The system, developed by the Fraunhofer Institute for Applied Polymer Research (IAP) in collaboration with the BBF Group, combines advanced aerodynamics with fibre-composite engineering to achieve remarkable efficiency at low wind speeds.
The small wind turbine in lightweight design. Image: Fraunhofer IAP.
While conventional small wind turbines typically need wind speeds of around four metres per second to start rotating, the novel rotor begins spinning at a mere 2.7 metres per second.
This means that it can operate efficiently in regions where wind conditions have long been considered too weak for viable energy generation.
“Our goal is to use the power of the wind as effectively as possible to generate electrical energy,” Marcello Ambrosio, head of simulation and design in the institute’s polymer materials and composite (PYCO) research division, revealed.
Wind power innovation
Wind tunnel tests revealed that the turbine can reach up to 450 revolutions per minute and deliver a power output of 2,500 watts at a wind speed of about 10 metres per second.
This is roughly 83% more powerful than comparable systems currently on the market. In addition, the turbine’s efficiency reaches 53%, approaching the theoretical maximum of 59% set by Betz’s law.
“Physically, a maximum of 59% is possible,” said Ambrosio. “We have optimised the aerodynamic design and the manufacturing process.”
Raúl Comesaña M, left, BBF Group’s managing director, and Marcello Ambrosio, head of simulation and design in the polymer materials and composites research division at Fraunhofer IAP. Image: BBF Gruppe.
Raúl Comesaña M, BBF Group’s managing director, emphasised the importance of efficient small wind turbines for achieving 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 decentralised energy generation individually and sustainably.”
The secret behind the system’s great performance lies in its rotor blades, which are constructed from two shells in a lightweight design. They are also made of fibre composite materials.
These are produced by precisely laying fibre strips in a mold, which is hardened using resins or other plastics to form a component. Compared to conventional designs, which are built with a foam core, the newly developed components are hollow inside. This reduces their overall weight up to 35%.
The team specially designed the mold for the rotor blades. The scientists used an industrial 3D printer that can print objects up to two-by-two metres in size.
Using a modern Automated Fiber Placement (AFP) system, they precisely laid the fibre strips into the mold. This fully automated process ensured great quality, minimised overlaps compared to manual placement, and enabled the production of more compact, lightweight components.
“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,” Ambrosio said in a press release.
A special laminate structure allows the rotor to withstand strong winds. When wind speeds rise, it automatically slows the turbine’s rotation, protecting it from overload. This built-in feature eliminates the need for complex control systems.
Five turbine prototypes were delivered to the BBF Group for testing at different sites to assess how location and height affect performance. The team now plans to refine the rotors and develop recyclable monomaterial structures to enhance sustainability.