Expertise for the Hydrogen Age

Ultimately, the goal is for the transport sector to forgo fossil fuels altogether. One approach well underway is electric mobility. Hydrogen-powered propulsion systems can complement this technology. In this case, hydrogen is either used to power a combustion engine or converted into electricity via a fuel cell. Hydrogen vehicles possess a number of advantages over electric vehicles. For example, they have an operating range of between 400 and 750 kilometers, greater than any current electric vehicle, and they only require between three and four minutes to refuel. There are currently 75 hydrogen filling stations in Germany, with a further 28 in the pipeline.

In Roadmap Gas, a project on behalf of the German Environment Agency (UBA), Fraunhofer ISI has investigated the role that hydrogen can play in a defossilization strategy. The results show that hydrogen is of importance principally in areas where it is difficult to make a direct use of electricity. This is true not only of the steel and chemical industries but also of heavy-duty transport by road and of shipping and aviation. A study by Fraunhofer ISE to compare CO₂ emissions of battery-powered, diesel, and hydrogen vehicles, which was conducted on behalf of H₂Mobility, came to a similar conclusion: for short trips and urban driving, battery-powered vehicles are preferable, but for distances over 250 to 300 kilometers, hydrogen vehicles perform better.

If hydrogen vehicles are to prevail, a proper infrastructure must be established. Here, too, Fraunhofer is contributing vital expertise. As far back as the 1990s, Fraunhofer IPA was working with Daimler, BMW and Aral to develop a refueling robot that could automatically refill a vehicle tank with a range of fuels, including hydrogen. More recently, Fraunhofer ISE has been exploring ways of transporting hydrogen without having to subject it to high pressure or low temperature. In a further project, Fraunhofer ISE is working with partners on the development of so-called liquid organic hydrogen carriers (LOHC), which simplify the transport of hydrogen and enable safer storage.

When hydrogen is used directly in fuel cell vehicles, the three major considerations are efficiency, safety and reliability. In the Eco-CC project, which is funded by the State of Saxony, Fraunhofer IWU is working with partners to develop a cost-effective and reliable concept for measurement and control. This will ensure that the system reaches its optimal operating parameters quickly and precisely. Researchers are also optimizing the load management system for the fuel cell and working to improve economy, efficiency and durability.

Instead of utilizing hydrogen to power fuel cell vehicles, gaseous hydrogen can also be used to produce liquid fuels via methanol as a platform chemical. Combustion of these fuels produces low levels of pollution and, on a well-to-wheel comparison with fossil fuels, reduces greenhouse-gas emissions by as much as 90 percent. As with ethanol used as an additive to gasoline, these oxymethylene dimethyl ethers (OME) can be mixed with diesel in order to produce a blended fuel. This type of power-to-liquid process makes sense primarily for applications in which hydrogen cannot be used to power the propulsion system – for example, in shipping and aviation. As such, Fraunhofer ISE covers the entire value chain for OME production. In addition, it builds plants on a pilot scale in order to develop the requisite process technology. These pilot plants are then scaled up in cooperation with industry – for example, in the BMBF-funded NAMOSYN project.

Hydrogen can also be used to power environmentally friendly marine propulsion systems based on a closed CO₂ cycle. Fraunhofer IKTS is a partner in the EU project HyMethShip, which features an innovative combination of membrane reactor, CO₂ capture system, storage system for CO₂ and methanol, and a hydrogen-powered combustion engine.

• Projekt HyMethShip

There are further applications for hydrogen in aviation other than as a feedstock for the production of synthetic kerosene. As the research project DIANA shows, one option is to use hydrogen as a direct fuel. In a BMBF-funded project in partnership with Diehl Aerospace and the German Aerospace Center (DLR), Fraunhofer IMM is developing a mobile source of power for use in catering trolleys on passenger aircraft. The power unit consists of a fuel cell powered by hydrogen that is produced directly from propylene glycol. The unit is used to generate electricity for the aircraft galley.

• DIANA project: Electrically autonomous galleys relieve engines and environment