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 Gebäude­tech­nik 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.