Hydrogen (H2) is a versatile fuel: it can be used as a fuel for fuel cell vehicles or for feeding into the natural gas network combined with the subsequent generation of electricity and heat using gas turbines, combustion engines or for fuel cells. Renewable generation of H2 is currently becoming increasingly important worldwide. H2 is synonymous with a sustainable energy supply that is largely based – and in the future will be entirely based – on renewable energy sources.

The research topics of electrolysis, Power-to-Gas (P2G®) and fuel cells are among the most important focal areas at ZSW – and hydrogen bridges these technologies.


Markus Jenne
+49 (0)731 95 30-821
Quality of hydrogen and refuelling


Dr. Ludwig Jörissen
+49 (0)731 95 30-605
New electrolysis technologies
Hydrogen as energy carrier

As a carbon-free fuel, hydrogen can make a major contribution to reducing greenhouse gas emissions and to climate protection.

The use of hydrogen in fuel cells increases energy efficiency and reduces pollutant emissions compared with furnace systems and/or combustion engines. Hydrogen is converted locally in fuel cells and is free of harmful emissions.

Storing one TWh of energy requires (see picture):

  • 5.5 million cubic metres of water in a pumped storage plant with a height difference of 83 m
  • 0.5 million cubic metres of air in a compressed air reservoir with approx. 50 bar
  • 0.017 million cubic metres of hydrogen at approx. 50 bar
  • 0.006 million cubic metres of natural gas at approx. 50 bar
Hydrogen for mobility
Hydrogen for rmobility.
Hydrogen for rmobility.

Alongside hybrid vehicles and pure battery-powered vehicles, e-mobility also includes electric vehicles, which generate their electricity themselves from the hydrogen in a fuel cell.

Fuel cell vehicles have a comparable range and take roughly the same time to refuel as petrol and diesel vehicles. A number of leading automobile manufacturers are currently launching fuel cell vehicles worldwide.

Interactive map of H2 filling stations: Clean Energy Partnership.

Interactive map of H2-stations.
Interactive map of H2-stations: https://cleanenergypartnership.de/kundenbereich/h2-tankstellen/
Hydrogen infrastructure
Hydrogen station at ZSW in Ulm.
Hydrogen station at ZSW in Ulm.

One requirement for the market introduction of fuel cell vehicles is the simultaneous establishment of a network of hydrogen filling stations and systems for generating and storing hydrogen.

Currently, studies are primarily focusing on the refuelling procedure and compliance with the hydrogen quality required for fuel cell operation. The present standard is refuelling with a hydrogen pressure of 70MPa in accordance with SAE J2601 and hydrogen quality in accordance with SAE J2719 / ISO14687.

ZSW, with its many years of experience in fuel cell technology and thus also in hydrogen use, is involved in a number of projects on the establishment of a European hydrogen infrastructure.

Water electrolysis

With the increasing availability of excess renewable electricity, the electrolytic decomposition of water is becoming an attractive option for hydrogen generation. There are three process principles available here, which differ in their choice of electrolytes. With alkaline electrolysis, potassium hydroxide solution is used as an electrolyte. Alkaline electrolysers have proven their applicability, robustness and load cycle resistance. The electrodes do not need any expensive precious metals. However, the power densities that can be achieved are limited. With PEM electrolysers, as with PEM fuel cells, acidic polymer electrolyte membranes are used as electrolytes. For this reason, they require the use of precious metal catalysts. PEM electrolysers generally achieve very high power densities. In addition, PEM electrolysers have been used successfully in load cycle operation. The third electrolyser technology uses a ceramic electrolyte at high temperatures. This generally achieves a significant reduction in the electricity required, but requires a heat source at a high temperature.

Current research topics on water electrolysis in the area of fuel cell fundamentals at ZSW include the development of new electrode microstructures based on nanomaterials.

For more information, see "systemic eletrolysis research".