Prospects for hydrogen in the German energy system

The focus of the paper concerns the current discussion on the contribution of the hydrogen economy to a "sustainable energy system". It considers whether advantages for the environmental situation and energy carrier supply can be expected from the already visible future characteristics of hydrogen as a new secondary energy carrier.Possible production paths for hydrogen from hydrocarbon-based, renewable or carbon-reduced/-free primary energy carriers are evaluated with respect to primary energy use and CO2 emissions from the fuel cycle. Hydrogen has to be packaged by compression or liquefaction, transported by surface vehicles or pipelines, stored and transferred to the end user. Whether generated by electrolysis or by reforming, and even if produced locally at filling stations, the gaseous or liquid hydrogen has to undergo these market processes before it can be used by the customer. In order to provide an idea of possible markets with special emphasis on the German energy sector, a technical systems analysis of possible hydrogen applications is performed for the stationary, mobile and portable sector. Furthermore, different "business as usual" scenarios are analysed for Germany, Europe and the World concerning end energy use in different sectors. The very small assumed penetration of hydrogen in the analysed scenarios up to the year 2050 indicates that the hydrogen economy is a long-term option.With reference to the assumed supply paths and analysed application possibilities, hydrogen can be an option for clean energy use if hydrogen can be produced with carbon-reduced or -free primary energy carriers like renewable energy or biomass. However, the energetic use of hydrogen competes with the direct use of clean primary energy and/or with the use of electric energy based on renewable primary energy. As a substitution product for other secondary energy carriers hydrogen is therefore under pressure of costs and/or must have advantages in comparison to the use of traditional energy carriers. (c) 2005 Elsevier Ltd. All rights reserved