Image: Fraunhofer IAP

Hydrogen power plant for the garden

In the future, private customers will produce hydrogen for their own use with small wind turbines. Lightweight construction experts from the Fraunhofer Institute for Applied Polymer Research IAP, the BTU Cottbus and an industrial partner are now developing the key technologies for this: small efficient rotors and safe tanks.

According to the Federal Environment Agency, private households today require around a quarter of the total energy consumed in Germany to generate electricity and heat. A good half of this energy is generated from natural gas and crude oil. In view of the worsening climate change, this balance is sobering. “Hydrogen produced from renewable energies will be much more suitable as an energy source in the future,” states Prof. Holger Seidlitz, lightweight construction specialist at the BTU Cottbus-Senftenberg and head of the “Polymer Materials and Composites PYCO” research area at the Fraunhofer Institute for Applied Polymer Research IAP in Wildau. Together with his team and a medium-sized company, he is currently approaching the future of hydrogen from two sides at the same time: On the one hand, he has his eye on the generation of electricity, which is needed for hydrogen production. To this end, the cooperation partners are currently developing a small and efficient wind turbine. Secondly, the team is working on the storage of the valuable gas. To this end, it is producing new types of hydrogen tanks made of fibre-reinforced composites.

Hydrogen for fuel cell and car

“The wind turbine will be designed so small that private individuals can also place such a plant in their garden,” explains Holger Seidlitz. “The hydrogen will then be produced on site in a small electrolyser and stored in the tank.” It would then power a fuel cell in the house, for example, which would produce heat and electricity at the same time. Owners of hydrogen cars, in turn, would be able to refuel their cars directly at home in the future. The strength of the concept lies above all in the fact that the entire system is small and yet very efficient, Seidlitz emphasizes. This starts with the wind turbine. The lightweight construction experts have designed a new propeller that already starts moving in a weak breeze. “Here in Lusatia, the wind blows much weaker than in northern Germany,” says mechanical engineer Marcello Ambrosio, who is overseeing the project at Fraunhofer IAP. “We have adapted the design of the rotor blades to this and reduced their mass by around 30 percent compared to conventional small wind turbines.” The Fraunhofer IAP recently added an industrial 3D printer that can be used to produce objects up to a size of around two by two meters. Marcello Ambrosio and his colleagues recently used it to complete a plastic mold for the production of their low wind rotors made of fiber composite. They were supported in this by the company EAB Geb√§udetechnik Luckau, which also specializes in lightweight construction.

Light and agile rotors

Fiber composites are manufactured by precisely placing fiber strips into a mold and then curing them with the help of a resin or other plastic to form the component. Often the laying is done by hand. At the Fraunhofer IAP, however, this task is performed by a modern automated fiber placement system that precisely places the reinforcing fibers in the mold. Ambrosio: “Unlike laying by hand, there are fewer overlaps here, so we can significantly reduce the dimensions.”

Another unique feature is that the rotor can withstand strong winds. The rotor blades are designed in such a way that they bend elastically in a storm and turn out of the wind. “This means that the system throttles the rotation speed on its own and does not take any damage,” says Holger Seidlitz. Complicated control technology and complex mechanics can thus be dispensed with. In the next few months, the rotors will be tested in the field. In comparison with conventional small wind turbines, they are to show what they are capable of.

Tank with built-in safety sensors

The second project, the production of hydrogen tanks, is also about lightweight construction technology. Classic hydrogen tanks for industry consist of large, pressure-resistant steel containers. For use in thousands of private households, however, lightweight tanks made of carbon fiber composites would be much more economical in terms of materials and easier to handle, and would offer particular advantages, especially for mobile applications. However, these must be very safe. Hydrogen must not be allowed to escape because it can form an explosive mixture with atmospheric oxygen. Here, too, the team from Lausitz offers an interesting solution. The tanks are made of carbon fiber strips that are wound onto a cylindrical body. Impregnated with synthetic resin, these then harden into a tank that can withstand many hundreds of bar of pressure. To detect leaks, the experts build sensors into the tank at the same time. “Currently, we are working with 3D printers that can process electrically conductive inks,” explains Marcello Ambrosio. “We work these directly into the fiber composite.” The researchers can even integrate small electronic components into the tank wall. This early warning system is an important prerequisite for future safe use by end customers.

Holger Seidlitz emphasizes that the research cooperation strengthens not least the region. “Lusatia is strongly influenced by structural change. I come from the region and find it important that we involve small and medium-sized enterprises in our research projects in order to build up continuous value chains here.” With the wind turbine and the tank, he is now combining two developments on site – renewable energies and hydrogen technology, – which will be of outstanding importance in the coming years.